Hi jacquesl,
That Marantz has multiple taps for the primary. A single winding for the lamps. The only winding that can be used for the amp section is the one connected to the big bridge rectifier. The other winding is for the preamp section and could never supply enough current to a power amp.
I can not tell from my schematic what the transformer windings look like for sure (split there).
-Chris
That Marantz has multiple taps for the primary. A single winding for the lamps. The only winding that can be used for the amp section is the one connected to the big bridge rectifier. The other winding is for the preamp section and could never supply enough current to a power amp.
I can not tell from my schematic what the transformer windings look like for sure (split there).
-Chris
hi anatech
Your not wrong about that but i cant use that power source becuase it dont have a negative voltage it only have a positive and ground = 0v line
U see
U cant power a amp with only + source and 0v source you need +source, - source and 0v source so I must probaly take that transformer out and put mine in 35+35 centertap and connected it up to the poweramp section and preamp as well and see wat will happen.
Your not wrong about that but i cant use that power source becuase it dont have a negative voltage it only have a positive and ground = 0v line
U see
U cant power a amp with only + source and 0v source you need +source, - source and 0v source so I must probaly take that transformer out and put mine in 35+35 centertap and connected it up to the poweramp section and preamp as well and see wat will happen.
Yeah! I come back from Paris today!
I will start to work on that Marantz soon...
This thread is starting to be a permanent discussion on the Marantz 1060. But not on how good it sounds, just to repair that thing and to get it to work.
I will start to work on that Marantz soon...
This thread is starting to be a permanent discussion on the Marantz 1060. But not on how good it sounds, just to repair that thing and to get it to work.
Giaime, please don't make me have to edit your posts for bad language again. It gets me very annoyed...
Oh, sorry... it was that word... I'm Italian and I only know basic english, I don't completely understand some slang terms, and by reading them on other forum I use them here, but I didn't believe it was a bad word. Please excuse me it will never happen again.I feel very embarassed... you say it's not the first time... Sorry
As promised today I worked on the amplifier...
Here it is:
I soldered four long wires to the bias-check resistors (R747 and 748 if I remember well) to easily check the current. I turned the DMM on 200mV scale and plugged the unit on.
The channel that measured 80mv (read some of my previous posts) now measured 90; I turned down the bias pot and I obtained 170mV from a side, and 25mV on the other side. I suppose that the 25mV is the one... no more adjust range (original bias pot, perfectly working btw). But that's too high: the service manual says 7.5mV and a diy fellow (destroyerx) suggested me from 10 to 25mV. I don't know who to believe!
Even on 25mV it scares me: that reading is 25 as soon as the unit is plugged on, then it starts to raise rapidly (about 0.5mV every second). When I reached 50mV I thought it was better to shut everything off.
And now the more dramatic part: the other channel (the one with the open diode) measured about 3mV on EVERY bias pot setting, then it starts to lower, and it reachs 0.0mV in about 15 seconds. 😕
What is going on on that amp? Yes I know that the bias should be adjust when the transistors are warm enought, but:
1) for the 25mV channel, if that's true, I should read that the q.current drops as the outputs are getting warmer (thermal compensation), but it does the opposite.
2) for the 0mV channel, shouldn't I read a high reading with the unit cold and a lower one after a while?
Please tell me what's wrong in my arguments.
(hoping that the thermal compensation is doing it's work: the diodes are fully functional and mounted firmly to the heatsink in their original place with a thin film of fresh silicon grease...)
Here it is:
I soldered four long wires to the bias-check resistors (R747 and 748 if I remember well) to easily check the current. I turned the DMM on 200mV scale and plugged the unit on.
The channel that measured 80mv (read some of my previous posts) now measured 90; I turned down the bias pot and I obtained 170mV from a side, and 25mV on the other side. I suppose that the 25mV is the one... no more adjust range (original bias pot, perfectly working btw). But that's too high: the service manual says 7.5mV and a diy fellow (destroyerx) suggested me from 10 to 25mV. I don't know who to believe!
Even on 25mV it scares me: that reading is 25 as soon as the unit is plugged on, then it starts to raise rapidly (about 0.5mV every second). When I reached 50mV I thought it was better to shut everything off.
And now the more dramatic part: the other channel (the one with the open diode) measured about 3mV on EVERY bias pot setting, then it starts to lower, and it reachs 0.0mV in about 15 seconds. 😕
What is going on on that amp? Yes I know that the bias should be adjust when the transistors are warm enought, but:
1) for the 25mV channel, if that's true, I should read that the q.current drops as the outputs are getting warmer (thermal compensation), but it does the opposite.
2) for the 0mV channel, shouldn't I read a high reading with the unit cold and a lower one after a while?
Please tell me what's wrong in my arguments.
(hoping that the thermal compensation is doing it's work: the diodes are fully functional and mounted firmly to the heatsink in their original place with a thin film of fresh silicon grease...)
Hi Giaime,
Believe the service manual every time .(period) That is unless you have a service bulleton that says different.
The bias current will normally rise slowly with temperature on most products. Set the bias after idling and readings are stable unless the manual says differently. (There's the manual again)
The low bias channel is reacting to the rising heatsink temperature. Normal behaviour. The bias current is to low, something is likely open leaving the bias transistor on and no adj. on the pot. I would check the protection transistors on that channel (H705,706,707,708) for leaky or short. Also check diode H715,716 for short or resistance. I assume you've checked the 470R resistors R731,732,733,734 for open.
The channel with high bias. Either the voltage drop across H005,006 is too high or you may have high resistance in the pot contacts. Another thing to check is leaky caps C729,730. Possibly too much current in the vas. Try to power the unit up at a lower AC voltage or with a DC power supply, 35~40VDC should do it.
-Chris
Believe the service manual every time .(period) That is unless you have a service bulleton that says different. The bias current will normally rise slowly with temperature on most products. Set the bias after idling and readings are stable unless the manual says differently. (There's the manual again)
The low bias channel is reacting to the rising heatsink temperature. Normal behaviour. The bias current is to low, something is likely open leaving the bias transistor on and no adj. on the pot. I would check the protection transistors on that channel (H705,706,707,708) for leaky or short. Also check diode H715,716 for short or resistance. I assume you've checked the 470R resistors R731,732,733,734 for open.
The channel with high bias. Either the voltage drop across H005,006 is too high or you may have high resistance in the pot contacts. Another thing to check is leaky caps C729,730. Possibly too much current in the vas. Try to power the unit up at a lower AC voltage or with a DC power supply, 35~40VDC should do it.
-Chris
Hi Chris! Thank You for help.
The Protection transistors are all good, also H715, 16, 17,18 are all good.
470R resistors are fully functional, and they haven't drifted.
I measured all the pots and get normal operation on them, no contact resistance or whatsoever. Also the two diodes H005,006 measure good.
But... where are C729 and C730? I see them on the schematics but I can't find them on the board. I suppose they're little ceramic orange ones... the ones I found measured good: off-scale resistance on 2Mohm scale (that's good, isn't it?)
Where are those capacitors?
The Protection transistors are all good, also H715, 16, 17,18 are all good.
470R resistors are fully functional, and they haven't drifted.
I measured all the pots and get normal operation on them, no contact resistance or whatsoever. Also the two diodes H005,006 measure good.
But... where are C729 and C730? I see them on the schematics but I can't find them on the board. I suppose they're little ceramic orange ones... the ones I found measured good: off-scale resistance on 2Mohm scale (that's good, isn't it?)
Where are those capacitors?
Hi Giaime,
Those should be the ones. Normally mounted on the foil side. Something is wrong still. Make sure the transistors are installed correctly and are the correct part.
-Chris
Those should be the ones. Normally mounted on the foil side. Something is wrong still. Make sure the transistors are installed correctly and are the correct part.
-Chris
You mean... on the opposite side of the PCB? I think I remember 2 small caps in there... I'll check.
For the transistor pinouts, it is the same on the 2 channels, so if it is wrong they should behave similarly. Instead they show 2 opposite behaviours....
Yes the drivers are not the proper replacement of the originals, they're right for voltage, current and Pd but, as said, their hfe is quite different from the originals... I'm starting to think that the 25mV biased channel is allright, but as the hfe of the drivers is well distant from the correct one, the bias pot might not have enought adjust range for them... It is safe to leave that channel at 25mV? It seems to me a bit too much, because the manual says to bias at 7,5mV, and destroyerx said from 10 to 25mV...
See you soon!
For the transistor pinouts, it is the same on the 2 channels, so if it is wrong they should behave similarly. Instead they show 2 opposite behaviours....
Yes the drivers are not the proper replacement of the originals, they're right for voltage, current and Pd but, as said, their hfe is quite different from the originals... I'm starting to think that the 25mV biased channel is allright, but as the hfe of the drivers is well distant from the correct one, the bias pot might not have enought adjust range for them... It is safe to leave that channel at 25mV? It seems to me a bit too much, because the manual says to bias at 7,5mV, and destroyerx said from 10 to 25mV...
See you soon!
Hi Giaime,
Normally an amplifier is biased from 10 to 25 mA. Some run around 50mA per device and special cases may run hotter 100mA and above. In this case, 7.5 mV across 0.24R gives you a bias of around 31 mA. I wouldn't run it much higher.
It is possible that gain differences may require a resistor value adjustment. However, there is something wrong. Another set of eyes may help you out.
I wish it was on my bench as I know I could get it running. Pay attention to base - emitter voltages. Could you measure and list those indicating the transistor number? That may help us do some troubleshooting.
-Chris
Normally an amplifier is biased from 10 to 25 mA. Some run around 50mA per device and special cases may run hotter 100mA and above. In this case, 7.5 mV across 0.24R gives you a bias of around 31 mA. I wouldn't run it much higher.
It is possible that gain differences may require a resistor value adjustment. However, there is something wrong. Another set of eyes may help you out.
I wish it was on my bench as I know I could get it running. Pay attention to base - emitter voltages. Could you measure and list those indicating the transistor number? That may help us do some troubleshooting.
-Chris
Yes, I'll try to post some measurements, but you know they're not easy since the solder side of the PCB is facing the heatsink... and I wouldn't run the amp without the board attached to the heatsink (I will lose thermal compensation). I will see what I can do (don't expect nothing in a day or two; I'm a little busy with school this period... just finished my one-tube radio... 😀 )
Hello Folks!
I just re-checked everything. I found the two little capacitors under the board, and I believe that are the misterious C729/30. I desoldered a leg of each one and tested them. Both measured infinite resistance on the highest scale. So they are good.
I also checked every possible solder joint, and also the little wires that link the board to the output transistors and checked for good contact between the socket and the tranny.
Checked for contacts in the bias and balance pots, and they work fine. The only thing I noticed is that the thermal compensation diodes (H005 and H006) read a different junction voltage: the one on the 25mV channel reads circa 1800mV, the other (on the 0mV channel) reads 1200mV. Is that strange? Is it because I overheated it in consequence of the repair work I attempted to fix it's leg (that was broken very close to the unit)? And does it matters that I've replaced H714 on the 0mV channel(I touched it and it broke into pieces) with a 1N4002? the other one (H713) is still original...
When you think you have finished... there's always something that's going to happen! 🙄
I just re-checked everything. I found the two little capacitors under the board, and I believe that are the misterious C729/30. I desoldered a leg of each one and tested them. Both measured infinite resistance on the highest scale. So they are good.
I also checked every possible solder joint, and also the little wires that link the board to the output transistors and checked for good contact between the socket and the tranny.
Checked for contacts in the bias and balance pots, and they work fine. The only thing I noticed is that the thermal compensation diodes (H005 and H006) read a different junction voltage: the one on the 25mV channel reads circa 1800mV, the other (on the 0mV channel) reads 1200mV. Is that strange? Is it because I overheated it in consequence of the repair work I attempted to fix it's leg (that was broken very close to the unit)? And does it matters that I've replaced H714 on the 0mV channel(I touched it and it broke into pieces) with a 1N4002? the other one (H713) is still original...
When you think you have finished... there's always something that's going to happen! 🙄
Hi Giaime,
Okay, if H714 was blown, then R730 cannot be trusted (replace it). H006 is defective also. What else did you replace in this channel?
Check R737 on the 25mV channel.
-Chris
Okay, if H714 was blown, then R730 cannot be trusted (replace it). H006 is defective also. What else did you replace in this channel?
Check R737 on the 25mV channel.
-Chris
Hello Chris! R730 (the bias pot) has already been replaced when H714 was replaced. You say I have to replace H006, but how? That part seems to be very hard to find... and I'm so unsure about the possibility to string 3 diodes in series and place them on the heatsink... if you think it will work I will try...
In this channel I replaced (like in the other one) the protection transistors (all check good) with BC639/640, the H703/704 with 2N1974 (all I can find in metal can case), some 220ohm and 10ohm resistors (don't remember which). Also all electrolytics, the big 0.24ohm resistors (with 0.25 ohms ones, I couldn't find 0.24), other than, obviusualy, the output transistors with 2N3442... And H714 with a 1N4002.
If the problem is H006, I can replace it with single diodes... but I don't know if it will work. Also what about a bigger value pot for the bias (so I can lower the bias in the working channel)? 1k will do?
In this channel I replaced (like in the other one) the protection transistors (all check good) with BC639/640, the H703/704 with 2N1974 (all I can find in metal can case), some 220ohm and 10ohm resistors (don't remember which). Also all electrolytics, the big 0.24ohm resistors (with 0.25 ohms ones, I couldn't find 0.24), other than, obviusualy, the output transistors with 2N3442... And H714 with a 1N4002.
If the problem is H006, I can replace it with single diodes... but I don't know if it will work. Also what about a bigger value pot for the bias (so I can lower the bias in the working channel)? 1k will do?
Hi Giaime,
Okay, try the triple diode string. Possibly some varnish will insulate it but allow more temperature sensitivity.
With the high bias channel, you need lower resistance. The bias network "hangs" between the two driver bases. The lower the voltage drop, the less bias current there is in the drivers and outputs. It is possible that the voltage drop is too high in the original part. In that case, try two diode drops. Alternatively, stick in a vbe multiplier that you've seen in a couple threads. That might be a better solution as the parts are then easy to get. You will have to play with some values, but that's half the fun! The transistor in the vbe multiplier is in contact with the heatsink.
You know, the amp is basically fixed. You are only playing with a bias issue now.
Carry on!
-Chris
Okay, try the triple diode string. Possibly some varnish will insulate it but allow more temperature sensitivity.
With the high bias channel, you need lower resistance. The bias network "hangs" between the two driver bases. The lower the voltage drop, the less bias current there is in the drivers and outputs. It is possible that the voltage drop is too high in the original part. In that case, try two diode drops. Alternatively, stick in a vbe multiplier that you've seen in a couple threads. That might be a better solution as the parts are then easy to get. You will have to play with some values, but that's half the fun! The transistor in the vbe multiplier is in contact with the heatsink.
You know, the amp is basically fixed. You are only playing with a bias issue now.
Carry on!
-Chris
- Status
- Not open for further replies.