Hi everyone!
I'm in the midst of rebuilding my amp, mainly because of some minor hissing but also because I'm exchanging the potentiometers to less sensitive ones, as well as trying to get the LM49170 to work stable.
I am trying to fulfill some or all of AndrewT's items in his earlier post. I have added one rectifier per channel, which means I now have a total of 4 in the amp. This is to achieve the "pseudo dual mono" construction.
Each channel has it's own 2 rectifiers and capacitor bank. From the center of the bank I have a 0V wire down to just in fron of the amp. To that wire is connected the three GND's, RCA ground (isolated from chassis, offcourse) and speaker return. That "star node" is decoupled to chassis by R||C (will add diods later).
When I fired it up my house fuse blew (slow blow 10A), but the slow 6.3A fuse in the chassis socket is fine. If I unhook the rectifiers, the toroid can be turned on.
Any help is appreciated, as always.
Best regards,
/Bo
I'm in the midst of rebuilding my amp, mainly because of some minor hissing but also because I'm exchanging the potentiometers to less sensitive ones, as well as trying to get the LM49170 to work stable.
I am trying to fulfill some or all of AndrewT's items in his earlier post. I have added one rectifier per channel, which means I now have a total of 4 in the amp. This is to achieve the "pseudo dual mono" construction.
Each channel has it's own 2 rectifiers and capacitor bank. From the center of the bank I have a 0V wire down to just in fron of the amp. To that wire is connected the three GND's, RCA ground (isolated from chassis, offcourse) and speaker return. That "star node" is decoupled to chassis by R||C (will add diods later).
When I fired it up my house fuse blew (slow blow 10A), but the slow 6.3A fuse in the chassis socket is fine. If I unhook the rectifiers, the toroid can be turned on.
Any help is appreciated, as always.
Best regards,
/Bo
Bo, you might ad that you parallel those two floating ground supplies on one singel (two secondary windings) transformer.
Yes very interesting if someone have a point.
Yes very interesting if someone have a point.
I'm not sure what you mean by "parallelling the floating grounds",
Ragnwald. Yes, I have only one trafo with two secondary windings.
These windings are feeding both left and right channels dual rectifier
bridges in parallell. The two 0V that builds from the rectifiers are not
connected, unless you count the decoupling to chassis (one for each
channel). Here is a picture that will hopefully clarify matters a little:
Full size picture
As you see, neither the rca's nor the speaker returns are connected
to the star grounds yet. The speaker protection PCB:s are not
connected either. Actually, the above picture was taken when I tested
with just the toroid connected (which works fine). Perhaps I should
try one channel at a time?
Best regards,
/Bo
Ragnwald. Yes, I have only one trafo with two secondary windings.
These windings are feeding both left and right channels dual rectifier
bridges in parallell. The two 0V that builds from the rectifiers are not
connected, unless you count the decoupling to chassis (one for each
channel). Here is a picture that will hopefully clarify matters a little:
An externally hosted image should be here but it was not working when we last tested it.
Full size picture
As you see, neither the rca's nor the speaker returns are connected
to the star grounds yet. The speaker protection PCB:s are not
connected either. Actually, the above picture was taken when I tested
with just the toroid connected (which works fine). Perhaps I should
try one channel at a time?
Best regards,
/Bo
use a light bulb tester!!!!!!!!!
check that the light bulb is off when only the transformer is connected to mains.
Then add one pair of rectifiers. and test.
Add the other pair of rectifiers and test.
Add one bank of smoothing and test.
get an idea of the procedure?
check that the light bulb is off when only the transformer is connected to mains.
Then add one pair of rectifiers. and test.
Add the other pair of rectifiers and test.
Add one bank of smoothing and test.
get an idea of the procedure?
AndrewT said:
Yep, got it!
I'll connect a light bulb in series with the mains out (from the softstart). Then I'll perform the above steps, one by one. Or should the bulb tester be added before the AC socket?
Thanks for helping out!
/Bo
PS. Any thoughts on using four rectifiers with a single toroid? DS.
bypass the soft start when using the light bulb.bomellberg said:
The relay across the ballast may not pull in when on lowish voltage from the bulb and this will confuse all readings you might want to take.
four rectifiers to create two separate PSUs is no problem. The isolation is not nearly as good as using four secondaries but it works better than a pair of single rectifiers and a common zero volts from the centre tap.
Your light bulb tester should consist of:-
A plug top to connect to the wall socket outlet.
A bulb holder to take a variety of tungsten filament incandescent bulbs.
A socket output where you plug in the equipment take requires to be tested. It's an extension lead with a bulb in the Live line.
Awesome! Thank you very much Andrew. By tungsten I assume you mean normal light bulbs and not the new low-energy ones. Tungsten translate to Volfram in Swedish, which is what the glowing wire inside the bulbs are made of.
Best regards,
/Bo
Best regards,
/Bo
OH NO !!!
Don't tell me we are going to get into a discussion of the sonic qualities of various lightbulbs now.
Don't tell me we are going to get into a discussion of the sonic qualities of various lightbulbs now.
We are discussing building (and testing, etc.) Jan's LINX Amp, not Nelson's ZenLite Amp...
AndrewT showed up an important thing, NTC vs PTC.
Back to topic... I still have 6 unpopulated LINX boards 🙁
I built a bulb tester and tried it out, both before and after the softstart.
The picture below is taken without the softstart involved. Just the toroid and nothing else (secondaries not attached to anything). And yes, the bulb is connected in series, not in parallell, so any light is a result of something drawing amps after the bulb.
The bulb is lit up quite much. Is the toroid itself pulling this much current? The voltage across the primary winding is 165 Vac. Perhaps this is normal?
Should I investigate this further or can I use the 165Vac to compare with as I connect the rest of Andrews list?
Best regards,
/Bo
The picture below is taken without the softstart involved. Just the toroid and nothing else (secondaries not attached to anything). And yes, the bulb is connected in series, not in parallell, so any light is a result of something drawing amps after the bulb.
An externally hosted image should be here but it was not working when we last tested it.
The bulb is lit up quite much. Is the toroid itself pulling this much current? The voltage across the primary winding is 165 Vac. Perhaps this is normal?
Should I investigate this further or can I use the 165Vac to compare with as I connect the rest of Andrews list?
Best regards,
/Bo
Hi,
disconnect everything from the transformer and test it alone.
Connecting either the dual secondaries or the dual primaries out of phase can result in excess and possibly damaging heat in the transformer.
If all is OK the bulb should be out and the voltage at the transformer >=95% of mains voltage.
disconnect everything from the transformer and test it alone.
Connecting either the dual secondaries or the dual primaries out of phase can result in excess and possibly damaging heat in the transformer.
If all is OK the bulb should be out and the voltage at the transformer >=95% of mains voltage.
Well, the picture was taken with nothing but the transformer connected. Also, the secondaries are not connected to anything.
I'm beginning to think there is something wrong with the transformer. The datasheet doesn't say anything about open loop current, but 165Vac doesn't seem right.
The only thing that is different from before is that I have added ~30 cm of shielded wire from the socket to the primary wires.
Best regards,
/Bo
I'm beginning to think there is something wrong with the transformer. The datasheet doesn't say anything about open loop current, but 165Vac doesn't seem right.
The only thing that is different from before is that I have added ~30 cm of shielded wire from the socket to the primary wires.
Best regards,
/Bo
strip it all apart so that you have just a transformer in front of you.
Measure the resistance of each winding.
Measure that all the windings are isolated from each other.
Connect all the secondary and all the primary wires into separate terminals of an insulated terminal strip.
Power up one primary through the bulb and measure the voltage across the single primary.
Measure the voltage at the other three pairs of outputs. The other primary will be at very high voltage so be VERY CAREFUL.
Now disconnect that primary and power up the other primary through the bulb.
Repeat the measuring. If both primaries are good they should be isolated and should generate the same voltage in the other open circuit windings.
Come back and post your 8 voltage readings.
Measure the resistance of each winding.
Measure that all the windings are isolated from each other.
Connect all the secondary and all the primary wires into separate terminals of an insulated terminal strip.
Power up one primary through the bulb and measure the voltage across the single primary.
Measure the voltage at the other three pairs of outputs. The other primary will be at very high voltage so be VERY CAREFUL.
Now disconnect that primary and power up the other primary through the bulb.
Repeat the measuring. If both primaries are good they should be isolated and should generate the same voltage in the other open circuit windings.
Come back and post your 8 voltage readings.
OK. Measuring done. Here are the results. Oh, and I only have a single primary winding.
Resistances:
Primary: 2.0R
Secondary Gn-Rd: 0R1
Secondary Bn-Bu: 0R1
None of the three windings have connection to any of the other.
Voltages: (with bulb)
Primary: 165.2Vac
Gn-Rd: 31.4Vac
Bn-Bu: 31.4Vac
This means there is 65Vac over the bulb. The bulb is a 60W, so its resistance should be 230^2/60 ~ 880 ohms. Perhaps this lamp is no good as a bulb tester?
Best regards,
/Bo
Resistances:
Primary: 2.0R
Secondary Gn-Rd: 0R1
Secondary Bn-Bu: 0R1
None of the three windings have connection to any of the other.
Voltages: (with bulb)
Primary: 165.2Vac
Gn-Rd: 31.4Vac
Bn-Bu: 31.4Vac
This means there is 65Vac over the bulb. The bulb is a 60W, so its resistance should be 230^2/60 ~ 880 ohms. Perhaps this lamp is no good as a bulb tester?
Best regards,
/Bo
The more I think about it, with an ideal transformer (without ANY losses) shouldn't the bulb be as lit as possible? I mean, if there are no losses, the primary winding would act as a short, which in effect would be just a switch to the bulb.
I read on another 800VA transformer that it had up to 45W+3.8W in magnetic and thermal loss.
I think, when you measure the transformer only, the less Vac you have over the primary winding, the better.
Best regards,
/Bo
I read on another 800VA transformer that it had up to 45W+3.8W in magnetic and thermal loss.
I think, when you measure the transformer only, the less Vac you have over the primary winding, the better.
Best regards,
/Bo
bomellberg said:
Do you know that "tung" = heavy in Swedish and "sten" is stone or pebble in swedish
=> heavy stone 🙂- Status
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