'97 LM6100 bias

marshalltsl said:
I need a coffe. Then I toke a look on my 1/2w resistors.
Thanks so much AMS!
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Què és la tensió nominal de C219 i C220? Els condensadors tenen una potència de 250 volts? Els condensadors han de tenir una tensió de 400 volts o superior.

What is voltage rating of C219 and C220 ?
Is the capacitors 250 volt rating?
The capacitors should be 400 volt or higher voltage rating.

6100 coupling.png
 
marshalltsl said:
Tomorrow I will do more tests. I tryed 4K on R213. Just -46v dc.
Thanks a lot AMS!
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Aquest amplificador 6100 té una història de dificultat de biaix. Sí, crec que és un error de fabricació en el disseny. Tothom que va intentar esbiaixar-los: els tubs surten calents. Però hi ha almenys 2 maneres de corregir els problemes de tensió de biaix.

Podeu canviar R213. Feu més petita la resistència. Podeu canviar C211 i C 212. Aquests condensadors d’acoblament alternatiu són originàriament de 47 N, però es poden canviar a 68N o 100N. Aquest canvi de condensador també augmentarà la tensió de biaix per fer que l’amplificador sigui més fresc.

R214, R215 es pot canviar de 56K a 82K, que també ajudaria a augmentar el voltatge per parcialitat ... només una idea.

O, l’ampliador es pot canviar a EL34, que requereix 10 volts menys de biaix. Però no estic segur que EL34 s’ajusti a l’armari. EL34 pot ser massa alt per adaptar-se a la caixa.

Es requereix temps i esforç per obtenir una tensió de biaix de 50 volts de corrent continu en el pin 5, però crec que podeu tenir èxit si ho intenteu.

Anglès
This amplifier 6100 has a history of bias difficulty.
Yes I think it is a factory mistake in the design.
Everybody who tried to bias it - the tubes come out hot.
But there are at least 2 ways to correct the bias voltage problems.

You can change R213. Make the resistor smaller.
You can change C211 and C 212. These AC coupling capacitors are originally 47N but they can be changed to 68N or 100N.
This capacitor change will also increase the bias voltage to make the amp cooler.

R214, R215 could be changed from 56K to 82K which would also help increase the voltage for bias....just an idea.

Or, the amp can be changed to EL34, which requires 10 volts less bias.
But I'm not sure that EL34 will fit inside the cabinet. EL34 may be too tall to fit inside the box.

It is some time and effort to get -50 volt DC bias voltage on pin 5, but I think you can succeed if you keep trying.

6100 bias boost.png
 
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Thanks AMS. I remember when I installed 6L6 on this amp years ago. I had 21 mV per tube with the trim pot on low side. I think something it's wrong on It. I removed the trim bias pot to test It days ago. It was ok. Maybe C211 or C212 loose some capacity. The amp sounds great. No strange noises on it.
 
I tryed 3K2 on R213. Pin 5 it's -46,1. The amp works. The amp sounds amazing, very good. I disassembled 4 times in one week. I'm not going to disassembled it any more. I'm tired, lol. I have 20W of dissipation in the tubes. It's ok.
Thanks a lot AMS. I know it's really dificult repair an amp if you can't see It.
 
Amp Mad Scientist said:
If the speaker load is wrong, it will draw too much current.

If the filter caps are going bad C209 C210 it can draw too much current.
But it is not often that the filter caps go bad.

What I'm thinking is that there may be a defect in the circuit board....
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Could be. I bought used in Italy years ago. It was working but when you turned on the stand-by switch you listened a Big noise. Pom! I replaced all filter caps. I solved the bomb noise. I saw it had burn tracks from power board when I did It I. Those are fixed. But the bias was ok.
 
marshalltsl said:
Could be. I bought used in Italy years ago. It was working but when you turned on the stand-by switch you listened a Big noise. Pom! I replaced all filter caps. I solved the bomb noise. I saw it had burn tracks from power board when I did It I. Those are fixed. But the bias was ok.
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Pot ser que l’aïllament entre les vies del circuit s’estigui trencant.

Si ja heu substituït C209 C210, i continua caient massa tensió al circuit de biaix.

Originalment, la tensió de biaix havia de ser de 50 cc.

It might be that the insulation between the circuit tracks is breaking down.
If you already replaced C209 C210, and it is still dropping too much voltage in the bias circuit.
Originally the bias voltage was supposed to be - 50 DC.
 
Amp Mad Scientist said:
Pot ser que l’aïllament entre les vies del circuit s’estigui trencant.

Si ja heu substituït C209 C210, i continua caient massa tensió al circuit de biaix.

Originalment, la tensió de biaix havia de ser de 50 cc.

It might be that the insulation between the circuit tracks is breaking down.
If you already replaced C209 C210, and it is still dropping too much voltage in the bias circuit.
Originally the bias voltage was supposed to be - 50 DC.
Click to expand...

I don't replaced c209 c210. Now the amp works great. I hope It stay ok for many years to come. Thanks AMS for your patience.
 
marshalltsl said:
I don't replaced c209 c210. Now the amp works great. I hope It stay ok for many years to come. Thanks AMS for your patience.
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Proveu de substituir C209 i C210. Per això, el biaix no funciona correctament.
Aquests condensadors no fallen molt sovint, però encara és possible.

Try replacing C209 and C210. That might be why the bias is not working correctly.
These capacitors do not fail very often, but it is still possible.
 
Amp Mad Scientist said:
Proveu de substituir C209 i C210. Per això, el biaix no funciona correctament.
Aquests condensadors no fallen molt sovint, però encara és possible.

Try replacing C209 and C210. That might be why the bias is not working correctly.
These capacitors do not fail very often, but it is still possible.
Click to expand...
I will do It. Now I want have fun with the amp. These days it's my favorite.

C209 C210 are class x caps. I don't have It. I need order It. Can I replace It with no class x caps? Where can I order It? Just I can find It on Ebay. They are expensive.
Thanks
 
marshalltsl said:
I will do It. Now I want have fun with the amp. These days it's my favorite.

C209 C210 are class x caps. I don't have It. I need order It. Can I replace It with no class x caps? Where can I order It? Just I can find It on Ebay. They are expensive.
Thanks
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C209 C210 són condensadors electrolítics regulars. No classe X. Els condensadors poden ser massa vells. Però, com he dit, no sabem si aquest és el problema. Potser ho sigui.

C209 C210 are regular electrolytic capacitors. Not Class X.
The capacitors might be too old.
But as I said, we don't know if this is the problem. Maybe it is.
 
Hi
I just disassembled the amplifier. C209 is out of tolerance. I will change both C209 and C210. Then I will re-install the original resistors.
AMS ! Thank you so much for the help!
You are the master of the amplifiers.
 

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