EL34 Grid Stopper resistor

[catalin gramada]

Can you point me to nfb wire? Thanks

One moment. The injection poi t is at r34/r44/c16 junction. The nfb track in on the board, I see the output Jack's age soldered directly to board...

[ca7922303]

One moment. The injection poi t is at r34/r44/c16 junction. The nfb track in on the board, I see the output Jack's age soldered directly to board...

I see r34/r44, don't see c16/output jacks age on board.

[catalin gramada]

C16 should be between red mark and yellow mark. The red marked joint is the point of nfb injection in you circuit. Further you have a blue and green Mark's what I consider should be 100k nfb resistor solder points. You need to check somehow to be sure. Unfortunately you cannot broke the link without lifting the board as I see. The brutal crude intervention without lifting the board suppose to cut the track on board and to restore eventual with a wire link. I cannot recommend that, I have to think some else...till than do a cleaning with a tooth brush. I see some which seems solder rest between v6 pins

[ca7922303]

C16 should be between red mark and yellow mark. The red marked joint is the point of nfb injection in you circuit. Further you have a blue and green Mark's what I consider should be 100k nfb resistor solder points. You need to check somehow to be sure. Unfortunately you cannot broke the link without lifting the board as I see. The brutal crude intervention without lifting the board suppose to cut the track on board and to restore eventual with a wire link. I cannot recommend that, I have to think some else...till than do a cleaning with a tooth brush. I see some which seems solder rest between v6 pins

Checked the two points between red and yellow marks and getting(OL) again. Point near blue and green marks is a capacitor that was changed and trace was damaged. Had run a mound of solder to connect cap leg to trace. It does show continuity up and down line from cap.

[catalin gramada]

Check again in those points red and yellow, I posted the pic again. You should have the 100n cap in those position

[catalin gramada]

Also check green and blue in the top of the marks not at the bottom. I drawin by a mobile phone sorry

[ca7922303]

Check again in those points red and yellow, I posted the pic again. You should have the 100n cap in those position

Changed DMM, red and yellow points(99.2nF)
blue and green points(0.0 ohms)
Rechecked 1st red and yellow points below P20(20.7nF).

[ca7922303]

Changed DMM, red and yellow points(99.2nF)
blue and green points(0.0 ohms)
Rechecked 1st red and yellow points below P20(20.7nF).

C36(20.7nF)

[catalin gramada]

Man, I.m sorry but don't see any way to isolate nfb. You may take off those 100k which is on the other side of board or cut the tracr board between red and blue mark....

[catalin gramada]

Sent a new pic with blue and green points to measure

[g1]

I think maybe catalin wants to disconnect NFB to check OT phasing?
If so, maybe this is easier. The amp has a presence control. Is it working in the normal direction, or is it reversed? As you turn it up, the sound should get brighter.
(I'm assuming amp still works properly at lower volume settings)

[ca7922303]

Sent a new pic with blue and green points to measure

Blue and green points(0.00 ohms).

[ca7922303]

I think maybe catalin wants to disconnect NFB to check OT phasing?
If so, maybe this is easier. The amp has a presence control. Is it working in the normal direction, or is it reversed? As you turn it up, the sound should get brighter.
(I'm assuming amp still works properly at lower volume settings)

The amp is not at full volume, but does work at lower volumes, but just noticed the presence control has no effect on brightness or volume

[Chuck H]

the amp is not at full volume, but does work at lower volumes, but just noticed the presence control has no effect on brightness or volume

bing bing bing bing!!!!

[ca7922303]

I think maybe catalin wants to disconnect NFB to check OT phasing?
If so, maybe this is easier. The amp has a presence control. Is it working in the normal direction, or is it reversed? As you turn it up, the sound should get brighter.
(I'm assuming amp still works properly at lower volume settings)

So with presence not working, should I desolder one leg each of c16/c36 or something else? Thanks.