Short reply now, it is a new day already.... long come later.
Yesterday FedEx delivered the 4pc of RC4580 opamps and 4pc TLE206 opamps, listed my TI as compatible with NJM4558. Both produced very similar oscilation noise, so, no help. Probably not THAT compatible...
So, I got the idea that I can make the opamps to run with like 10k load. That mean put a resistor 12k parallel to the 50k pot = 10 or 9.6k load resistance for opamp.
I tried it for center channel first and the noise it did really limit a lot the oscilations for center channel, but only at given volume, so I tried it for all channells and it make matters a LOT worse after power-on, but in just a short while 10 - 15 sec the noise deacrease to level witch is very nice.
Still noisy, but much more enjoayble. now.
I also tried bump the capacity of C7 & siblings from the 12pF to 330pF, but no change. Maybe it is even slighly worser now...
Maybe the grounding is not perfect and the voltage supply suxx too? Dunno.
Yesterday FedEx delivered the 4pc of RC4580 opamps and 4pc TLE206 opamps, listed my TI as compatible with NJM4558. Both produced very similar oscilation noise, so, no help. Probably not THAT compatible...
So, I got the idea that I can make the opamps to run with like 10k load. That mean put a resistor 12k parallel to the 50k pot = 10 or 9.6k load resistance for opamp.
I tried it for center channel first and the noise it did really limit a lot the oscilations for center channel, but only at given volume, so I tried it for all channells and it make matters a LOT worse after power-on, but in just a short while 10 - 15 sec the noise deacrease to level witch is very nice.
Still noisy, but much more enjoayble. now.
I also tried bump the capacity of C7 & siblings from the 12pF to 330pF, but no change. Maybe it is even slighly worser now...
Maybe the grounding is not perfect and the voltage supply suxx too? Dunno.
I can give you some 4558...
...sorry, I only see this thread now.
I have several 4558 in old boards that I keep for recycling parts.
If you still need them, I can pull them out and send them to you.
No guarantee that they work, though. I'll unsolder them carefully and you get them for free, so if it's still interesting, let me know.
I'll need your postal address.
Cheers,
gp
_
...sorry, I only see this thread now.
I have several 4558 in old boards that I keep for recycling parts.
If you still need them, I can pull them out and send them to you.
No guarantee that they work, though. I'll unsolder them carefully and you get them for free, so if it's still interesting, let me know.
I'll need your postal address.
Cheers,
gp
_
yangsmm - recommend LM4562? Too late. I already use them in both my X-Fi and my Genius SW-5.1 HT. In first case with good results, in other case with terrible ones.
Probably my fault, tough.
dietcoke - could you please give me a example schematic of circuit in witch the LM4562 fail miserably, but other opamps (and please mention witch ones you are tried) works well/satisfactory?
I would love to know more.
I still think the AD8599 is probably the best opamp for audio... Not tried YET in my speakers, as it is only made as SOIC NARROW version, so... gotta get it soldered first into the DIP8 sockets...
anatech -
I agree. Where we start with?
True. There is only one ground in the opamps PCB circuit and it looks like it is same as the signal ground - if by that you mean it being connected to the shielding on the cables...
What to do there? Add a own thick wire back to the PSU PCB on back of the amp?
One more thing. The whole amp is connected by two pins main outlet only. So, there is no reall ground connection to the mains ground, to witch should be all the metal back base connected as well, as the ground in the circuit... wait a minute, that would also somewhat undermine the transformator voltages separation from the mains... or I'm wrong there?
Unfortunately, this is not possible. I miss the
1) original opamps
2) original CapXon/Su'scon caps
The rest was once restored to the original state with no change on behaviour.
I can't, but that does not matter. I think I rather stand the clicks on X-Fi drivers turn on and off (as well when changing audio mode) much rather that I like my signal get distorted. And even a relay contacts add some noise... I use 6 channels anyway, that is a hell lot of relays ... impossible, IMHO.
Very true. LM4562 is MUCH faster opamp. Hence it probably oscilate much easier that AD8599, for example Not to mention it much likely pick up hi-frequency noises from air... AD8599 is much slower, much more suitable for audio, IMHO.
unclejed613 - I took your advice. C7 & spol. changed from 12pF to 330pF ones. Noise get worser...
So I added these 12k resistors from each opamp output to ground to make them loaded at like 10k (12k in parallel to 50k - the pot) and things is much nicer now. The noise is bearable now, tough I think with 12pF it was better a bit...
Neverless 330pF did not cure the problem.
dietcoke -
Yes, I did. I wote on bad caps and terrible voltage regulation/stabilization. The PCB, for example, under R11 and R12 is VERY MUCH dark by all the heat they produced...
pilli - DIP8 NJM4558? Then thanks a lot for your efforts, and you got a PM. I gladly try them out, tough I start to sucpect that there is something else entirely wrong...
WoW!
NJM4558 operating current - 3.5mA typical ; 5.7mA maximum.
What worry me is, that I can't find in the LM4562 spec what current it draw
trodas: LM4562 - Dual High Performance, High Fidelity Audio Operational Amplifier
But there I find: http://www.head-fi.org/forums/f6/stax-srm-001-mod-thread-277049/#post3536731
That the LM4562 draw 5-6mA/amp - but it is double amp (10 - 12mA) and that is true, when "amplifier current draw when using 3.7V lithium batteries"...!!!
While using +/- 12V voltages, then we talking probably a hell of more current!
I see the guy claiming that LM4562 draw notably more that others - (whole amp= 500m ) while with TL082 it is just whole amp current draw is 320mA.
So instead of the stuuupid R11 and R12 resistors and nonexisting D4 and D5 Zener diodes (they are NOT present in reality!) I slap a 7812 and 7912 regulators there and we see what happnen then.
With the TO-220 package, they should do about 1000mA, so heatsinks is probably not yet required
Work in progress update
I used L7812CV and L7912CV from STMicroelectronics in TO-220 to make better and nicer the +/-12V voltage supply for opamps. Luckily, I check the datasheets.... the 7912 is NOT like the 7812 - eg. pins view from top is INPUT, GROUND, OUTPUT - the damn 7912 is GROUND, INPUT, OUTPUT...!!!
And I'm NOT use ANY resistor now Recommended caps near these regulators are 0.33uF on input and 0.1uF on the output minimal. I used 1uF SMD ceramic on the input, and 0.1uF on the outputs of both ones. Soldered almost directly on the L7812 and L7912 legs.
Replaced C49 from the cursed 10 000uF CapXon to Samxon KM - also 10 000uF, but 25V only, as it is only 16V on the cap top.
Replaced C112 from bad cap Su'scon 1000uF 10V to Panny FM of same capacitance and voltage.
But damn! Brum is not gone... even the voltages going to the opamps are now very nice, a -11.96V and 11.95V - VERY close, very nice... but the amp play now MUCH louder, so the resistors are obviously overhelmed with the replacement opamps current, so, this was a good change...
Sadly no other changes. The amp still produce a lot of brum at start, and it slowly get away... as things heat up or what the hell...
Time to revert most modifications in the opamps stage back to what things way. I keep the voltage filtering and new regulation as well, as the quality caps, but put back the C7 & spol. caps of 12pF values as that sound best and most quiet, IIRC.
I consider the C117 & spol., but I would like it to keep off.
I remove all the 12k resistors added on all the opamps outputs to ground.
I put back C9 & spol.
But if that does not fix things up, well... I'm out of ideas
Probably my fault, tough.
dietcoke - could you please give me a example schematic of circuit in witch the LM4562 fail miserably, but other opamps (and please mention witch ones you are tried) works well/satisfactory?
I would love to know more.
I still think the AD8599 is probably the best opamp for audio... Not tried YET in my speakers, as it is only made as SOIC NARROW version, so... gotta get it soldered first into the DIP8 sockets...
anatech -
I agree. Where we start with?
True. There is only one ground in the opamps PCB circuit and it looks like it is same as the signal ground - if by that you mean it being connected to the shielding on the cables...
What to do there? Add a own thick wire back to the PSU PCB on back of the amp?
One more thing. The whole amp is connected by two pins main outlet only. So, there is no reall ground connection to the mains ground, to witch should be all the metal back base connected as well, as the ground in the circuit... wait a minute, that would also somewhat undermine the transformator voltages separation from the mains... or I'm wrong there?
Unfortunately, this is not possible. I miss the
1) original opamps
2) original CapXon/Su'scon caps
The rest was once restored to the original state with no change on behaviour.
I can't, but that does not matter. I think I rather stand the clicks on X-Fi drivers turn on and off (as well when changing audio mode) much rather that I like my signal get distorted. And even a relay contacts add some noise...
I use 6 channels anyway, that is a hell lot of relays ... impossible, IMHO.Very true. LM4562 is MUCH faster opamp. Hence it probably oscilate much easier that AD8599, for example
Not to mention it much likely pick up hi-frequency noises from air... AD8599 is much slower, much more suitable for audio, IMHO.unclejed613 - I took your advice. C7 & spol. changed from 12pF to 330pF ones. Noise get worser...
So I added these 12k resistors from each opamp output to ground to make them loaded at like 10k (12k in parallel to 50k - the pot) and things is much nicer now. The noise is bearable now, tough I think with 12pF it was better a bit...
Neverless 330pF did not cure the problem.
dietcoke -
Yes, I did. I wote on bad caps and terrible voltage regulation/stabilization. The PCB, for example, under R11 and R12 is VERY MUCH dark by all the heat they produced...
pilli - DIP8 NJM4558? Then thanks a lot for your efforts, and you got a PM. I gladly try them out, tough I start to sucpect that there is something else entirely wrong...
WoW!
NJM4558 operating current - 3.5mA typical ; 5.7mA maximum.
What worry me is, that I can't find in the LM4562 spec what current it draw
trodas: LM4562 - Dual High Performance, High Fidelity Audio Operational Amplifier
But there I find: http://www.head-fi.org/forums/f6/stax-srm-001-mod-thread-277049/#post3536731
That the LM4562 draw 5-6mA/amp - but it is double amp (10 - 12mA) and that is true, when "amplifier current draw when using 3.7V lithium batteries"...!!!
While using +/- 12V voltages, then we talking probably a hell of more current!
I see the guy claiming that LM4562 draw notably more that others - (whole amp= 500m ) while with TL082 it is just whole amp current draw is 320mA.
So instead of the stuuupid R11 and R12 resistors and nonexisting D4 and D5 Zener diodes (they are NOT present in reality!) I slap a 7812 and 7912 regulators there and we see what happnen then.
With the TO-220 package, they should do about 1000mA, so heatsinks is probably not yet required
Work in progress update
I used L7812CV and L7912CV from STMicroelectronics in TO-220 to make better and nicer the +/-12V voltage supply for opamps. Luckily, I check the datasheets.... the 7912 is NOT like the 7812 - eg. pins view from top is INPUT, GROUND, OUTPUT - the damn 7912 is GROUND, INPUT, OUTPUT...!!!
And I'm NOT use ANY resistor now
Recommended caps near these regulators are 0.33uF on input and 0.1uF on the output minimal. I used 1uF SMD ceramic on the input, and 0.1uF on the outputs of both ones. Soldered almost directly on the L7812 and L7912 legs.Replaced C49 from the cursed 10 000uF CapXon to Samxon KM - also 10 000uF, but 25V only, as it is only 16V on the cap top.
Replaced C112 from bad cap Su'scon 1000uF 10V to Panny FM of same capacitance and voltage.
But damn! Brum is not gone... even the voltages going to the opamps are now very nice, a -11.96V and 11.95V - VERY close, very nice... but the amp play now MUCH louder, so the resistors are obviously overhelmed with the replacement opamps current, so, this was a good change...
Sadly no other changes. The amp still produce a lot of brum at start, and it slowly get away... as things heat up or what the hell...
Time to revert most modifications in the opamps stage back to what things way. I keep the voltage filtering and new regulation as well, as the quality caps, but put back the C7 & spol. caps of 12pF values as that sound best and most quiet, IIRC.
I consider the C117 & spol., but I would like it to keep off.
I remove all the 12k resistors added on all the opamps outputs to ground.
I put back C9 & spol.
But if that does not fix things up, well... I'm out of ideas
Work in progress update
I removed all the 12k resistors added on all the opamps outputs to ground.
I put back C9 & spol. deblocking caps.
Caps C41 & C42 are now nice Nichicons VR 4700uF 35V suxxkas.
Caps C47 & C48 are now Rubycon XYF 1000uF 16V, taken from one old PSU for DVD player, looks genuine and sure better that Su'scons
Replaced R89 and D8 (near C26, top right part of schematics, close to the front L/R repros) with a L7805 regulator, 1uF ceramic on input (16V cap and the voltage there as well) and 100nF on the output. PCB under R89 was very much darker, so I consider that as safe replacement. Also the output was like 5.3V and not 5V as it should be.
Resulting changes.
Removing the 12k resistors increased the noise level to the before-known situation. Not good, not cool. Caps have no change on the subject, only the C64 seems to put the bass line under control (it was weird, overblown and just blurred before...).
I regret removing the resistors and I planing on puting them back to battle the noise.
Still weird.
It still act kinda weird. When I power the amp up, it lack the before-mod strong SUB kick, but very shortly a strong (oscilating?) noise come from all speakers, and it slowly fade (as things heat-up?) to more acceptable levels. Weird at least. Still lack caps to do complete recap and starting to fear the caps was not the issue, as from the main power caps only C37 & C39 remain as original bad caps...
Futher testing.
I'm somewhat confused that when I power the amp on my balcony, where I solder and work on it, there is no noise from the subwoofer. It might not be even when I power it on with all the speakers, because they simply produce too much noise, that I can't be sure about that. I'm sure about all the 5 other channels, tough.
So first I power the suxxka w/o my PC/watercooling pump nearby and so on. No change.
Then I got idea. I unplug the PCB with the opamps from the rest of the amp. That way, only the output stages are "in game" and they should be very quiet, no noise, as it was before? Right?
Well, wrong.
SUB and CENTER seems dead-quiet, but these L, R and RL, RR channels are full of - wait a minute - MUCH stronger noise that WITH the opamps (and resistors on their inputs to ground!) ...!
What I think of that?
I strongly beginning to suspect that when I at first connected the ceramic 10uF caps to the wrong opamps pins (1 and 7 to ground for all the there opamps), it has consequences. The oscilating noise was unbearable, true... So that lead me to question the TDA7269A amps.
CENTER and SUB use different amps, but the L, R and RL, RR channels use the two TDA7269A ones. What if they are somewhat damaged, so they produce the noise all-by-itself? It is normal that amp produce so strong noise when not connected to any source? I doubt that, and at least CENTER and SUB are fine then.
Their voltage filtering caps (C41 & C42) are quality new Nichicons from Digikey now, so... can't be a issue there.
This would ALSO explain the noise in SUB and CENTER channel too. These channels are interconnected by R109, R111, R156 and R157, so the noise CAN get there by this way.
It would ALSO explain why the resistors helped to battle the noise. Of course opamps does NOT need so low load, but if the noise come the other way, then these quiet it down for obvious reasons. 12k is reasonably low, so it helped...
I think I should remove the R109, R111, R156 and R157.
If that kill the noise from CENTER and the very little noise from the SUB, then these TDA7269A are damaged and replacing them fix the problem. Higher quality parts drop-in replacement (okay, I willing to add few components as well, but the basic pinout has to be the same) suggestion welcome.
I removed all the 12k resistors added on all the opamps outputs to ground.
I put back C9 & spol. deblocking caps.
Caps C41 & C42 are now nice Nichicons VR 4700uF 35V suxxkas.
Caps C47 & C48 are now Rubycon XYF 1000uF 16V, taken from one old PSU for DVD player, looks genuine and sure better that Su'scons
Replaced R89 and D8 (near C26, top right part of schematics, close to the front L/R repros) with a L7805 regulator, 1uF ceramic on input (16V cap and the voltage there as well) and 100nF on the output. PCB under R89 was very much darker, so I consider that as safe replacement. Also the output was like 5.3V and not 5V as it should be.
Resulting changes.
Removing the 12k resistors increased the noise level to the before-known situation. Not good, not cool. Caps have no change on the subject, only the C64 seems to put the bass line under control (it was weird, overblown and just blurred before...).
I regret removing the resistors and I planing on puting them back to battle the noise.
Still weird.
It still act kinda weird. When I power the amp up, it lack the before-mod strong SUB kick, but very shortly a strong (oscilating?) noise come from all speakers, and it slowly fade (as things heat-up?) to more acceptable levels. Weird at least. Still lack caps to do complete recap and starting to fear the caps was not the issue, as from the main power caps only C37 & C39 remain as original bad caps...
Futher testing.
I'm somewhat confused that when I power the amp on my balcony, where I solder and work on it, there is no noise from the subwoofer. It might not be even when I power it on with all the speakers, because they simply produce too much noise, that I can't be sure about that. I'm sure about all the 5 other channels, tough.
So first I power the suxxka w/o my PC/watercooling pump nearby and so on. No change.
Then I got idea. I unplug the PCB with the opamps from the rest of the amp. That way, only the output stages are "in game" and they should be very quiet, no noise, as it was before? Right?
Well, wrong.
SUB and CENTER seems dead-quiet, but these L, R and RL, RR channels are full of - wait a minute - MUCH stronger noise that WITH the opamps (and resistors on their inputs to ground!) ...!
What I think of that?
I strongly beginning to suspect that when I at first connected the ceramic 10uF caps to the wrong opamps pins (1 and 7 to ground for all the there opamps), it has consequences. The oscilating noise was unbearable, true... So that lead me to question the TDA7269A amps.
CENTER and SUB use different amps, but the L, R and RL, RR channels use the two TDA7269A ones. What if they are somewhat damaged, so they produce the noise all-by-itself? It is normal that amp produce so strong noise when not connected to any source? I doubt that, and at least CENTER and SUB are fine then.
Their voltage filtering caps (C41 & C42) are quality new Nichicons from Digikey now, so... can't be a issue there.
This would ALSO explain the noise in SUB and CENTER channel too. These channels are interconnected by R109, R111, R156 and R157, so the noise CAN get there by this way.
It would ALSO explain why the resistors helped to battle the noise. Of course opamps does NOT need so low load, but if the noise come the other way, then these quiet it down for obvious reasons. 12k is reasonably low, so it helped...
I think I should remove the R109, R111, R156 and R157.
If that kill the noise from CENTER and the very little noise from the SUB, then these TDA7269A are damaged and replacing them fix the problem. Higher quality parts drop-in replacement (okay, I willing to add few components as well, but the basic pinout has to be the same) suggestion welcome.
But it is this opa2132 a dual-amp?
And you sure this is the opamps? Remember, the L, R and RL, RR channels oscilate badly w/o the opamps connected at all!
Anyway, this is a little attempt to show how the amp behave on power on and power off/on by remove control. Turn the volume up to get an idea what I hear now all the time...
http://www.youtube.com/watch?v=iiPEJ2KgnQk
And you sure this is the opamps? Remember, the L, R and RL, RR channels oscilate badly w/o the opamps connected at all!
Anyway, this is a little attempt to show how the amp behave on power on and power off/on by remove control. Turn the volume up to get an idea what I hear now all the time...
http://www.youtube.com/watch?v=iiPEJ2KgnQk
opa 132 single
2132 double
4132 quad
I can not say that the opamps are the route of your problem.. likely you didsomething else too... but there will be an improvement makeing that swap... provided all other errors are replaced.
the 4558s I replaced was from 1978... THATS how old a design it is...
2132 double
4132 quad
I can not say that the opamps are the route of your problem.. likely you didsomething else too... but there will be an improvement makeing that swap... provided all other errors are replaced.
the 4558s I replaced was from 1978... THATS how old a design it is...
That is also probably quite possibly why it is so big problem to get them now Anyway, I was thinking more like AD8599 as rhe final opamp, once the problem is found and cured. Are the OPA2132 made in a DIP8 version, so unlike the AD8599 I did not need solder the opamp into a empty DIP8 socket, so I can use it?
One nice user pointed out, that the brum is not like 5 - 6kHz, but rather 100Hz!
Now when I yesterday at night read this, I was like... wow! Why I never thing about blown-out rectifier from the initial failure when I place the ceramics wrong on the wrong opamps legs and the whole thing oscilate unbearably loudly!
WoW!
Even the slovak moder of these amps suggested replacing these rectifiering diodes with higher rated ones - so I was like - yea, that has to be it, you got it!
So, luckily, I have 10 pcs of these 6A diodes 50V ( http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=6A05-TPMSCT-ND ) so I get right to it today. Took 8 pcs of them, yes, they are HUGE, and started with the B3 rectifier block, powering the TDA 7269A for the L, R and RL, RR channels. And... no change. Then I exchanged the rectifier block B1, powering the noisy center speaker and... no change at all.
Damn. And it looked so so promising...
Few scope ripple measuring on the amp.
C37, C39 - 69.9 - 70mV AC ripple (+19, -19V on them)
C41 - 41.5mV AC ripple (+29V)
C42 - 38.9mV AC ripple (-29V)
C49 - 31.2mV AC ripple (+16.2V)
C45 - 0.6 - 0.7mV AC ripple (+12V)
C46 - 0.6mV AC ripple (-12V)
C26 - 0.8mV AC ripple (+5.04V)
opamps IC6, 7 and 8 (+/-12V powered) on each 4 nd 8 pins has 0.9mV AC ripple
opamp IC9 (+15.8V powered) has ripple 30.2mV on pin 8...! 100Hz ripple too, BTW.
(still the sub seems to be quiet - at least very much, compared to the cursed center...)
The center is weird anyway. At some point only the center speaker was noisy (not the L/R, RL/RR ones) and then I measured what is ON the speaker anyway and found this:
CENTER speaker - 8.23V DC (!) and 6.4mV AC ripple, noisy. Weird.
RIGHT speaker - 0.2mV DC, 0.9mV AC ripple, quiet.
Errata
I don't know how I made it happen, but my previous statement that the L/R and RL/RR speakers only made strong noise (much stronger that with opamps board presend) when the opamps board is disconnected was FALSE.
When I unplugged today just the signal wires, all of them, the amp was quiet. In all channels. At least on balcony and when I have only one testing speaker that I just connect to different outputs...
What I like is that this somewhat confirm my determination to remove them - eg. I was right about them being unnecessary and possibly even bad for the sound...
What I did not like is, that this mercilessly kill my idea about how the terrible noise is spreading to other channels... damn
Reducing the noise.
Since the 12k resistors in parallel to the main 50k pot surpressed the noise nicely to notably lower levels, I tought that I "quiet" at least the center. So from the output of C61 to the ground, I added the 12k resistor as before. And quess what. No notable change. Since before I had these resistors where w/o the cap, then I put it, next time, on the C61 input, not on the oputput - so it will be directly on the opamp, not only after the cap.
This, together with the very high DC offset (8V?!) is sure a good hint to where to get the source of the problem, however... no luck. On the opamps outputs are very low AC ripple levels. VERY low...
Making better ground for the opamps PCB.
As part of attemt to cure the noise, it was suggested to make the grounding of the opamps PCB better. So, I took a nice, strong wire (originally a PC PSU black wire) and SOLDERED it to the ground on the opamps PCB as well, as on the back PSU/amps section.
So upon diassembling, I need to unsolder it from the PCB first.
No change at all. Sadly.
Attempt to cure the 30mV AC ripple in IC9 opamp voltage supply.
First I thought that the ceramic 10uF 16V Murata cap must be dead, so I desolder it from under the opamp and check and... it is fine. About 11.5uF capacity. So I solder it back and added another 10uF 16V Murata SMD ceramic cap on the legs of the added Samxon GC 470uF 16V cap shown there: http://img357.imageshack.us/my.php?image=geniussw51htcapaddedbk9.jpg
(on the very same pic you can clearly see, that the resistors R109, R111, R156 and R157 are not present)
Still, adding another ceramic does not fix the voltage at all, still about 30.2mV ripple there, in clear contrast to the 0.9mV ripple on other there opamps. Why is that, well, I don't know.
From the ripple measuring on the power caps it is clearly visible that the C37/C39 give almost twice the ripple the new caps show. Su'scon caps are crappy bad caps, that is why. However the 30.2mV ripple on the 10 000uF Samxon KM 25V cap is present all the way to the CENTER amp - TDA 7360.
I wonder why the Samxon GC did and the ceramic caps not help to make the voltage cleaner. This is beyond my understanding. Perhaps the better choice there will be some "softer" caps, that are also optimized for lower frequency, like Samxon KM or RS, or GF, or GK, or GT... Just not the superfast super-low-ESR ones.
Perhaps time to try the Panny FM there, if they works so well on the other there opamps?
I don't know.
Anyway, I was thinking more like AD8599 as rhe final opamp, once the problem is found and cured. Are the OPA2132 made in a DIP8 version, so unlike the AD8599 I did not need solder the opamp into a empty DIP8 socket, so I can use it?One nice user pointed out, that the brum is not like 5 - 6kHz, but rather 100Hz!
Now when I yesterday at night read this, I was like... wow! Why I never thing about blown-out rectifier from the initial failure when I place the ceramics wrong on the wrong opamps legs and the whole thing oscilate unbearably loudly!
WoW!
Even the slovak moder of these amps suggested replacing these rectifiering diodes with higher rated ones - so I was like - yea, that has to be it, you got it!
So, luckily, I have 10 pcs of these 6A diodes 50V ( http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=6A05-TPMSCT-ND ) so I get right to it today. Took 8 pcs of them, yes, they are HUGE, and started with the B3 rectifier block, powering the TDA 7269A for the L, R and RL, RR channels. And... no change. Then I exchanged the rectifier block B1, powering the noisy center speaker and... no change at all.
Damn. And it looked so so promising...
Few scope ripple measuring on the amp.
C37, C39 - 69.9 - 70mV AC ripple (+19, -19V on them)
C41 - 41.5mV AC ripple (+29V)
C42 - 38.9mV AC ripple (-29V)
C49 - 31.2mV AC ripple (+16.2V)
C45 - 0.6 - 0.7mV AC ripple (+12V)
C46 - 0.6mV AC ripple (-12V)
C26 - 0.8mV AC ripple (+5.04V)
opamps IC6, 7 and 8 (+/-12V powered) on each 4 nd 8 pins has 0.9mV AC ripple
opamp IC9 (+15.8V powered) has ripple 30.2mV on pin 8...! 100Hz ripple too, BTW.
(still the sub seems to be quiet - at least very much, compared to the cursed center...)
The center is weird anyway. At some point only the center speaker was noisy (not the L/R, RL/RR ones) and then I measured what is ON the speaker anyway and found this:
CENTER speaker - 8.23V DC (!) and 6.4mV AC ripple, noisy. Weird.
RIGHT speaker - 0.2mV DC, 0.9mV AC ripple, quiet.
Errata
I don't know how I made it happen, but my previous statement that the L/R and RL/RR speakers only made strong noise (much stronger that with opamps board presend) when the opamps board is disconnected was FALSE.
When I unplugged today just the signal wires, all of them, the amp was quiet. In all channels. At least on balcony and when I have only one testing speaker that I just connect to different outputs...
R109, R111, R156 and R157 are NOT even present in reality, much less connected. Same as, for example, the Zener diodes D7 and D8 drawn in dashed line box, are not present in reality in the amp, the resistors R109, R111, R156 and R157 are not present at all.
What I like is that this somewhat confirm my determination to remove them - eg. I was right about them being unnecessary and possibly even bad for the sound...
What I did not like is, that this mercilessly kill my idea about how the terrible noise is spreading to other channels... damn
Reducing the noise.
Since the 12k resistors in parallel to the main 50k pot surpressed the noise nicely to notably lower levels, I tought that I "quiet" at least the center. So from the output of C61 to the ground, I added the 12k resistor as before. And quess what. No notable change. Since before I had these resistors where w/o the cap, then I put it, next time, on the C61 input, not on the oputput - so it will be directly on the opamp, not only after the cap.
This, together with the very high DC offset (8V?!) is sure a good hint to where to get the source of the problem, however... no luck. On the opamps outputs are very low AC ripple levels. VERY low...
Making better ground for the opamps PCB.
As part of attemt to cure the noise, it was suggested to make the grounding of the opamps PCB better. So, I took a nice, strong wire (originally a PC PSU black wire) and SOLDERED it to the ground on the opamps PCB as well, as on the back PSU/amps section.
So upon diassembling, I need to unsolder it from the PCB first.
No change at all. Sadly.
Attempt to cure the 30mV AC ripple in IC9 opamp voltage supply.
First I thought that the ceramic 10uF 16V Murata cap must be dead, so I desolder it from under the opamp and check and... it is fine. About 11.5uF capacity. So I solder it back and added another 10uF 16V Murata SMD ceramic cap on the legs of the added Samxon GC 470uF 16V cap shown there: http://img357.imageshack.us/my.php?image=geniussw51htcapaddedbk9.jpg
(on the very same pic you can clearly see, that the resistors R109, R111, R156 and R157 are not present)
Still, adding another ceramic does not fix the voltage at all, still about 30.2mV ripple there, in clear contrast to the 0.9mV ripple on other there opamps. Why is that, well, I don't know.
From the ripple measuring on the power caps it is clearly visible that the C37/C39 give almost twice the ripple the new caps show. Su'scon caps are crappy bad caps, that is why. However the 30.2mV ripple on the 10 000uF Samxon KM 25V cap is present all the way to the CENTER amp - TDA 7360.
I wonder why the Samxon GC did and the ceramic caps not help to make the voltage cleaner. This is beyond my understanding. Perhaps the better choice there will be some "softer" caps, that are also optimized for lower frequency, like Samxon KM or RS, or GF, or GK, or GT... Just not the superfast super-low-ESR ones.
Perhaps time to try the Panny FM there, if they works so well on the other there opamps?
I don't know.
Done.
Update.
From one nice French guy (thanks, pilli!) I recieved todays a evenlope containing four NJM 4558 DIP8 opamps. As soon as I civilize their legs, I test them. I probably put back all he original caps (the ceramic ones, 100pF C7 & siblings and C117 & siblings.
I also place the 12k resistor BEFORE the cap on the center speaker, if that help me more.
Futher to do, I measure the DC offsets on the amp outputs (on the speakers) ... The 8V DC offset measured on the center speakers disturb me...
Update.
From one nice French guy (thanks, pilli!) I recieved todays a evenlope containing four NJM 4558 DIP8 opamps. As soon as I civilize their legs, I test them. I probably put back all he original caps (the ceramic ones, 100pF C7 & siblings and C117 & siblings.
I also place the 12k resistor BEFORE the cap on the center speaker, if that help me more.
Futher to do, I measure the DC offsets on the amp outputs (on the speakers) ... The 8V DC offset measured on the center speakers disturb me...
Work-in-progress report.
Todays I tried again to kill the cursed noise, and, well... What I did was that I put back the C117 & siblings and changed the C7 & siblings to the original 100pF value.
Then I moved the 12k resistor that was quieting a bit the noise from center speaker from the output of the C6 to the input of the C6.
Then I tried to fix the high ripple on IC9 opamp. While others (IC6 - 8) enjoy only 0.9mV ripple, thanks to the regulators and caps, this one is suffering at 32mV of ripple. I know, I know, power supply ripple rejection >80dB fix that, but I still did not quite like it. So... so the filtering cap Samxon GC 470uF 16V I changed the 1000uF 16V Panny FM and also added an another 100nF ceramic cap before the Panny FM one. On the bottom of the Panny FM cap is another 10uF Murata 16V X7R SMD cap and the last 10uF SMD Murata is on the opamp leg 8 against ground.
Ripple get lowered to 27mV
Next move - add a toroid L filter coil in the IC9 input voltage. I will kill the ripple on IC9, somehow!
Then I tried the another opamps I get on my hands in meantime. A big thanks to French user pilli from diyaudio forums for sending my 4pcs of the NJM4558 opamps.
So I put these original opamps into the almost identical circuit, and quess what. NOISE! Still the same, or... maybe even louder one. Damn!
This confirming my belief that something must be damaged, somehow, when I placed the ceramic caps wrongly... because there was now not a significant difference between the circuit before I touch it, and now.
Yes, the diodes on most of the power supply lines are now 6A, yes many caps are replaced for better ones, yes the 10uF CapXon bad caps are replaced with 22uF Elna RFS audio caps... but that it is. No other change. Well, okay, except these regulators providing clean voltage!
I also tried the OPA 2132 opamps todays. Same terrible noise. Definitively no opamps change could cure that, I'm affraid.
Opamps outputs voltage/ripple/frequency on no audio output from X-Fi
-------------------------------------------------------------------------
CENTER: -5,8mV DC, 18,6mV AC 33kHz
RL: -3.0mV DC, 34mV AC 83kHz
L: -1.8mV DC, 7.9mV AC 1.6kHz
R: -1.8mV DC, 8.1mV AC 1.8kHz
RR: -3.0mV DC, 33.8mV AC 81kHz
SUB, first stage (IC8 pin 7): -7.2mV DC, 73.7mV AC 111kHz
SUB, second stage (IC9 pin 7): 7.45V DC, 9.6mV AC 0Hz
Interesting, huh?
My X-Fi is a bit into the negative voltages, so that could be the source of them:
X-Fi output DC offset measuring with LM4562 opamps
---------------------------------------------------------------
L: -190mV DC, 10mV AC
R: -174mV DC, 10.2mV AC
RL: -210.2mV DC, 10.1mV AC
RR: -204.7mV DC, 10mV AC
CENTER: -209.5mV DC, 10mV AC
SW: -231.9mV DC, 10.2mV AC
X-Fi output DC offset measuring with AD8599 opamps
---------------------------------------------------------------
L: -219mV DC, 9.5mV AC
R: -205mV DC, 9.8mV AC
RL: -209mV DC, 9.7mV AC
RR: -205mV DC, 9.3mV AC
CENTER: -210mV DC, 9.6mV AC
SW: -232mV DC, 9.7mV AC
Conclusion - X-Fi opamps stage design does produce the -200mV DC offset. That probably can be cured by just increasing the positive opamps supply voltage from 5V to 5.2 or 5.4V ...
But the second stage of the SUB with the 7.45V is kinda interesting one. I did not pretend that I understand the circuit. If someone can, please... explain.
I also again measured the voltages/ripple on the speakers.
CENTER: 8V DC, 36mV AC 70kHz (next measuring show 13mV AC, 12kHz)
RL: -122mV DC, 100mV AC 110kHz
RR: -125mV DC, 105mV AC 112kHz
L: -183mV DC, 86mV AC 119kHz
R: -158mV DC, 42mV AC 70kHz
I was a hell lot worried about the 8V DC on center speakers, but davmax is saying that this is normal, since the TDA 7360 is in bridge configuration and hence on pins 8 and 4 should be about half of the powering voltage, witch is almost 16V (very close to it) and half from that is 8V, so, it is okay then.
Nothing still does not explain the noise.
Moving the 12k quieting resistor on the C61 input seems to INCREASE the cursed noise. AND change it - before the move, most of the noise come from center. Now the noise from L/R speakers overshadow the CENTER noise, witch is sort of bad... definitively worser that before. The resistor had to go back on the C61 output.
What if the output amplifiers are somewhat damaged and sending the oscilations back to their inputs...? Could that be a result from the misplaced ceramics 10uF caps?
How to explain that the amp is quiet when only single speaker and output by output is connected to it to check the silence, when the opamps are disconnected?
How to explain the terrible noise w/o opamps from L, R, RL and RR speakers when connected? And quiet center and sub at the same time?
Damn, I'm lost.
Todays I tried again to kill the cursed noise, and, well... What I did was that I put back the C117 & siblings and changed the C7 & siblings to the original 100pF value.
Then I moved the 12k resistor that was quieting a bit the noise from center speaker from the output of the C6 to the input of the C6.
Then I tried to fix the high ripple on IC9 opamp. While others (IC6 - 8) enjoy only 0.9mV ripple, thanks to the regulators and caps, this one is suffering at 32mV of ripple. I know, I know, power supply ripple rejection >80dB fix that, but I still did not quite like it. So... so the filtering cap Samxon GC 470uF 16V I changed the 1000uF 16V Panny FM and also added an another 100nF ceramic cap before the Panny FM one. On the bottom of the Panny FM cap is another 10uF Murata 16V X7R SMD cap and the last 10uF SMD Murata is on the opamp leg 8 against ground.
Ripple get lowered to 27mV
Next move - add a toroid L filter coil in the IC9 input voltage. I will kill the ripple on IC9, somehow!
Then I tried the another opamps I get on my hands in meantime. A big thanks to French user pilli from diyaudio forums for sending my 4pcs of the NJM4558 opamps.
So I put these original opamps into the almost identical circuit, and quess what. NOISE! Still the same, or... maybe even louder one. Damn!
This confirming my belief that something must be damaged, somehow, when I placed the ceramic caps wrongly... because there was now not a significant difference between the circuit before I touch it, and now.
Yes, the diodes on most of the power supply lines are now 6A, yes many caps are replaced for better ones, yes the 10uF CapXon bad caps are replaced with 22uF Elna RFS audio caps... but that it is. No other change. Well, okay, except these regulators providing clean voltage!
I also tried the OPA 2132 opamps todays. Same terrible noise. Definitively no opamps change could cure that, I'm affraid.
Opamps outputs voltage/ripple/frequency on no audio output from X-Fi
-------------------------------------------------------------------------
CENTER: -5,8mV DC, 18,6mV AC 33kHz
RL: -3.0mV DC, 34mV AC 83kHz
L: -1.8mV DC, 7.9mV AC 1.6kHz
R: -1.8mV DC, 8.1mV AC 1.8kHz
RR: -3.0mV DC, 33.8mV AC 81kHz
SUB, first stage (IC8 pin 7): -7.2mV DC, 73.7mV AC 111kHz
SUB, second stage (IC9 pin 7): 7.45V DC, 9.6mV AC 0Hz
Interesting, huh?
My X-Fi is a bit into the negative voltages, so that could be the source of them:
X-Fi output DC offset measuring with LM4562 opamps
---------------------------------------------------------------
L: -190mV DC, 10mV AC
R: -174mV DC, 10.2mV AC
RL: -210.2mV DC, 10.1mV AC
RR: -204.7mV DC, 10mV AC
CENTER: -209.5mV DC, 10mV AC
SW: -231.9mV DC, 10.2mV AC
X-Fi output DC offset measuring with AD8599 opamps
---------------------------------------------------------------
L: -219mV DC, 9.5mV AC
R: -205mV DC, 9.8mV AC
RL: -209mV DC, 9.7mV AC
RR: -205mV DC, 9.3mV AC
CENTER: -210mV DC, 9.6mV AC
SW: -232mV DC, 9.7mV AC
Conclusion - X-Fi opamps stage design does produce the -200mV DC offset. That probably can be cured by just increasing the positive opamps supply voltage from 5V to 5.2 or 5.4V ...
But the second stage of the SUB with the 7.45V is kinda interesting one. I did not pretend that I understand the circuit. If someone can, please... explain.
I also again measured the voltages/ripple on the speakers.
CENTER: 8V DC, 36mV AC 70kHz (next measuring show 13mV AC, 12kHz)
RL: -122mV DC, 100mV AC 110kHz
RR: -125mV DC, 105mV AC 112kHz
L: -183mV DC, 86mV AC 119kHz
R: -158mV DC, 42mV AC 70kHz
I was a hell lot worried about the 8V DC on center speakers, but davmax is saying that this is normal, since the TDA 7360 is in bridge configuration and hence on pins 8 and 4 should be about half of the powering voltage, witch is almost 16V (very close to it) and half from that is 8V, so, it is okay then.
Nothing still does not explain the noise.
Moving the 12k quieting resistor on the C61 input seems to INCREASE the cursed noise. AND change it - before the move, most of the noise come from center. Now the noise from L/R speakers overshadow the CENTER noise, witch is sort of bad... definitively worser that before. The resistor had to go back on the C61 output.
What if the output amplifiers are somewhat damaged and sending the oscilations back to their inputs...? Could that be a result from the misplaced ceramics 10uF caps?
How to explain that the amp is quiet when only single speaker and output by output is connected to it to check the silence, when the opamps are disconnected?
How to explain the terrible noise w/o opamps from L, R, RL and RR speakers when connected? And quiet center and sub at the same time?
Damn, I'm lost.
trodas said:
...sorry, I looked at the entire thread, but I didn't quite understand all the details.
May I ask to start from the beginning, and move by little slow steps?
We're talking of an "active speakers" system, right?
Which includes amplifiers (duh!) that use that TDA chip.
Now, this circuit with the op-amps, is it part of the original amplifier?
How many TDA's do you have?
They're stereo, I think so how are the five channels amplified?
Is there any of the TDAs that you can trust as being fully functional?
(that's to see if the problem doesn't come from there, as you cirectly suspect)
(more later)
_
http://www.youtube.com/watch?v=iiPEJ2KgnQk
Listening to your video
this is no doubt HUM.
The reason can often be some ground-loop.
A ground-loop is when we have 2 ground connections between same 2 GND points.
One could be via the PCB 0 Volt connection wire
and the other can be via some signal cable ( the shield is = GND ).
Some way the AC mains ripple ( 100 Hz / 120 Hz, 2x50 Hz or 2x60 Hz )
enters input of your circuit .. via the GND, the ground rails.
At input it is amplified by the Opamps and goes to output and speakers.
I would check all ground rails/wires and how signal cables are attached.
Listening
to your videothis is no doubt HUM.
The reason can often be some ground-loop.
A ground-loop is when we have 2 ground connections between same 2 GND points.
One could be via the PCB 0 Volt connection wire
and the other can be via some signal cable ( the shield is = GND ).
Some way the AC mains ripple ( 100 Hz / 120 Hz, 2x50 Hz or 2x60 Hz )
enters input of your circuit .. via the GND, the ground rails.
At input it is amplified by the Opamps and goes to output and speakers.
I would check all ground rails/wires and how signal cables are attached.
pilli said:
trodas,
I have to apologize, I hadn't followed the links in your first post, so I hadn't seen the other thread about this, where you had put the schematics and everything.
For troubleshooting purposes, I would still test the channels as much as possible one by one, hoping to find a situation where you don't have the hum.
Listening to the youtube you posted reminds me of the debugging of an amplifier I had built, where ground cables connections were causing a noise very similar to yours. Implementing a real star configuration solved the problem.
This has indeed already been suggested here.
But then, did your mods change anything in the ground routing...?
I think I found the bug - now just get a spare transformator for the Genius SW-5.1 HT to test this!
Many people from the very beginning suggested ground loop problems. I was investigating the PCB, the wires... well, everything. Despite many any many hours and days spent on the relatively simple circuit I was not able to find any wrong conenction, wire or so. Much less on the seriously made grounds there. Regardless, yesterday I got a idea. I heard the transformator has fuses included INTO his body (!).
So, what about if, when I at the start wrongly connected 10uF SMD caps on the IC6 - 8 opamps oputputs/-inputs caused, as I put it, "unbearable noise" ... I don't know what you guys are make off when someone say "unbearable noise", but believe me, it was so noisy, that is was unbearable as I put it. Now that could cause the meltdown in the transformator, because believe me or not, that was not something (considering the decibel levels) you experience on the concert of rock band - that was MUCH louder, it was as I put it - unbearable... seems the repro and the TDA circuits make it, but the transformator give up.
When I saw how thick the cooper wires are, well, I said to myself - this is impossible. The TDA must be melted well before these wires give up. But still, since the transofmer is connected to the rest of the circuit (except for the AC mains) by connectors - I unpluged it and measured the voltages.
I had a hard time explaining this to my friend (or ex-friend?) Davmax who told me that I'm crazy, however... I better draw what I measured to explain it better:
I marked the wirings by the Gretz bridges labels where they will go then in the complete schematics:
Now as you guys probably agree, the B1 wirings should NOT have shown any voltage against the middle of B2 wiring, UNLESS connected to the Gretz bridges and PCB itself. It should "hang in air" and did not show significant voltage. But because it does, I bet that somewhere inside of the transformator a solder was melted, when the ouput was so crazy high thx for my mistake and hence I bet that this cause shortcut somewhere...
By looking what all the B1 wirings powering and seeing that all these circuits behave weirdly since then - I think I found the bug. It is NOT the fuses, I checked:
So, who know, where to get a transformator from bad Genius SW-5.1 HT subwoofer? The type precisely go as follows:
CTP-10311U-2
INPUT-AC 230v/50Hz
OUTPUT-AC 28VCT/2.4A & 12v/1A & 40VCT/1.2A
TEMP FUSE M330F
TYPE FUSE 3.15A/250V
Anyone?
PS. pictures of my mods for your viewing pleasure:
My modification for the better opamps power +/-12V - instead R11/D4 and R12/D5 are L7812 and L7912 used:
Exchanging the diodes for 6A ones - you can also see added filtering by 1000uF 16V Panny FM cap for the CENTER TDA 7360 amp withch reduced the noise significantly!
Situation around TDA 7296 - SUB channel, caps almost all changed to Panny FC, for audio are used Elna RFS and added 2x 330uF 35V Panny FM for better voltage cleaning and support
Powering of the L, R and RL, RR channels are getting better diodes too, in the back you see added two Panny FM 470uF 25V caps, in fround Panny KG 0,1uF and L7805 instead of resistor and Zener diode for 5V...
Second from these L, R and RL, RR channels - again two Panny FM 470uF 25V caps, in front you can see added C83 cap that marketing removed and that is used to filter the mute voltage.
L, R and RL, RR channels still using the main caps as Su'scons (Samxon 6800uF 25V caps did not made it yet)
Bottom of the PCB - how I added these two L7812 and L7912 regulators for the +/-12V opamp power - holes after them are ready for 1N4001 diodes
The bottom way of adding the filtering caps for the TDA 7269A amps L, R and RL, RR channels
Bottom look at added L7805 regulator instead R89 and Zener diode D8
Many people from the very beginning suggested ground loop problems. I was investigating the PCB, the wires... well, everything. Despite many any many hours and days spent on the relatively simple circuit I was not able to find any wrong conenction, wire or so. Much less on the seriously made grounds there. Regardless, yesterday I got a idea. I heard the transformator has fuses included INTO his body (!).
So, what about if, when I at the start wrongly connected 10uF SMD caps on the IC6 - 8 opamps oputputs/-inputs caused, as I put it, "unbearable noise" ... I don't know what you guys are make off when someone say "unbearable noise", but believe me, it was so noisy, that is was unbearable as I put it. Now that could cause the meltdown in the transformator, because believe me or not, that was not something (considering the decibel levels) you experience on the concert of rock band - that was MUCH louder, it was as I put it - unbearable... seems the repro and the TDA circuits make it, but the transformator give up.
When I saw how thick the cooper wires are, well, I said to myself - this is impossible. The TDA must be melted well before these wires give up. But still, since the transofmer is connected to the rest of the circuit (except for the AC mains) by connectors - I unpluged it and measured the voltages.
I had a hard time explaining this to my friend (or ex-friend?) Davmax who told me that I'm crazy, however... I better draw what I measured to explain it better:
I marked the wirings by the Gretz bridges labels where they will go then in the complete schematics:
An externally hosted image should be here but it was not working when we last tested it.
Now as you guys probably agree, the B1 wirings should NOT have shown any voltage against the middle of B2 wiring, UNLESS connected to the Gretz bridges and PCB itself. It should "hang in air" and did not show significant voltage. But because it does, I bet that somewhere inside of the transformator a solder was melted, when the ouput was so crazy high thx for my mistake and hence I bet that this cause shortcut somewhere...
By looking what all the B1 wirings powering and seeing that all these circuits behave weirdly since then - I think I found the bug. It is NOT the fuses, I checked:
An externally hosted image should be here but it was not working when we last tested it.
So, who know, where to get a transformator from bad Genius SW-5.1 HT subwoofer? The type precisely go as follows:
CTP-10311U-2
INPUT-AC 230v/50Hz
OUTPUT-AC 28VCT/2.4A & 12v/1A & 40VCT/1.2A
TEMP FUSE M330F
TYPE FUSE 3.15A/250V
Anyone?
PS. pictures of my mods for your viewing pleasure:
My modification for the better opamps power +/-12V - instead R11/D4 and R12/D5 are L7812 and L7912 used:
An externally hosted image should be here but it was not working when we last tested it.
Exchanging the diodes for 6A ones - you can also see added filtering by 1000uF 16V Panny FM cap for the CENTER TDA 7360 amp withch reduced the noise significantly!
An externally hosted image should be here but it was not working when we last tested it.
Situation around TDA 7296 - SUB channel, caps almost all changed to Panny FC, for audio are used Elna RFS and added 2x 330uF 35V Panny FM for better voltage cleaning and support
An externally hosted image should be here but it was not working when we last tested it.
Powering of the L, R and RL, RR channels are getting better diodes too, in the back you see added two Panny FM 470uF 25V caps, in fround Panny KG 0,1uF and L7805 instead of resistor and Zener diode for 5V...
An externally hosted image should be here but it was not working when we last tested it.
Second from these L, R and RL, RR channels - again two Panny FM 470uF 25V caps, in front you can see added C83 cap that marketing removed and that is used to filter the mute voltage.
An externally hosted image should be here but it was not working when we last tested it.
L, R and RL, RR channels still using the main caps as Su'scons (Samxon 6800uF 25V caps did not made it yet)
An externally hosted image should be here but it was not working when we last tested it.
Bottom of the PCB - how I added these two L7812 and L7912 regulators for the +/-12V opamp power - holes after them are ready for 1N4001 diodes
An externally hosted image should be here but it was not working when we last tested it.
The bottom way of adding the filtering caps for the TDA 7269A amps L, R and RL, RR channels
An externally hosted image should be here but it was not working when we last tested it.
Bottom look at added L7805 regulator instead R89 and Zener diode D8
An externally hosted image should be here but it was not working when we last tested it.
maybe not an open fuse, but what about windings shorted together?
with everything disconnected and no power applied, check for continuity between B1 and B2. if you have anything there (like 100 ohms or less) then you have windings shorted together, and that's your problem. if there's nothing there (10k or more) then do careful resistance checks of the windings themselves. from ground taps to each end of a winding should be almost exactly the same. if not, you might have a shorted winding, which would seriously unbalance your AC going into the rectifier bridges, causing excessive ripple.
with everything disconnected and no power applied, check for continuity between B1 and B2. if you have anything there (like 100 ohms or less) then you have windings shorted together, and that's your problem. if there's nothing there (10k or more) then do careful resistance checks of the windings themselves. from ground taps to each end of a winding should be almost exactly the same. if not, you might have a shorted winding, which would seriously unbalance your AC going into the rectifier bridges, causing excessive ripple.
Weird thing. I did that measuring already. I wonder, where the voltage against the middle B2 wiring point ever come from, when these wirings SHOULD be separated.
And quess what. There is no connection between any wire going OUT from the transformator and any of the B1 wires. (wait a minute, I did not check the AC input, but that is crazy...)
The B2 and B3 wirings behave exactly as I would expect. They are like 1.5 ohms each completely and like 0.7 ohm from each middle point to the end one. Exactly as it should be. But the B1 remaining not connected by anything else. It has like 1.8 to 2 ohms but not connected to anything.
Exactly as it should be.
Weird thing (an unbelievable one) is, where the voltage is getting between the B1 ends and the B2 middle (and perhaps other points too, not measured yet, amp is in operation...) ...
That is what I expect to be the problem.
I gotta re-done the measurings, when I re-open the amp for another recap.
And quess what. There is no connection between any wire going OUT from the transformator and any of the B1 wires. (wait a minute, I did not check the AC input, but that is crazy...)
The B2 and B3 wirings behave exactly as I would expect. They are like 1.5 ohms each completely and like 0.7 ohm from each middle point to the end one. Exactly as it should be. But the B1 remaining not connected by anything else. It has like 1.8 to 2 ohms but not connected to anything.
Exactly as it should be.
Weird thing (an unbelievable one) is, where the voltage is getting between the B1 ends and the B2 middle (and perhaps other points too, not measured yet, amp is in operation...) ...
That is what I expect to be the problem.
I gotta re-done the measurings, when I re-open the amp for another recap.
The subject of the thread could then change to "CTP-10311U-2: where to find them"
...what you could try is to find transformers, even separate ones, that deliver what you need, that is:
28VCT/2.4A
12v/1A
40VCT/1.2A
As usual, in my basement I'd find enough to cover what you're looking for. Old VCRs have voltages/currents similar to those, but unlikely to be all on one trafo.
I'd be glad to give them to you, but these would be heavy and I cannot send them for free like the opamps (was just a letter stamp...)
Maybe you know somebody with a "dump in his basement"?
A place to find old VCRs/trafos for free?
Then that would be ugly and cumbersome, because you'd have more than one transformer, primaries in parallel. But for the benefit of testing I've done that before, and you know how it goes, the "nice box" never gets built...
Cheers,
pilli
_
...what you could try is to find transformers, even separate ones, that deliver what you need, that is:
28VCT/2.4A
12v/1A
40VCT/1.2A
As usual, in my basement I'd find enough to cover what you're looking for. Old VCRs have voltages/currents similar to those, but unlikely to be all on one trafo.
I'd be glad to give them to you, but these would be heavy and I cannot send them for free like the opamps (was just a letter stamp...)
Maybe you know somebody with a "dump in his basement"?
A place to find old VCRs/trafos for free?
Then that would be ugly and cumbersome, because you'd have more than one transformer, primaries in parallel. But for the benefit of testing I've done that before, and you know how it goes, the "nice box" never gets built...
Cheers,
pilli
_
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