EL34 Grid Stopper resistor

[ca7922303]

Do you have say 100k resistor at hand ?

Yes, what to do with it?

[ca7922303]

Do you have say 100k resistor at hand ?

There is a distortion trim pot on main preamp board, could that be causing issue?

[ca7922303]

There is a distortion trim pot on main preamp board, could that be causing issue?

I placed a 100k resistor where your blue and green marks were at and it had no effect on the (0.00 ohms) reading.

[catalin gramada]

Hey, between blue and green points was just a link wire as much I can see. Put 100k between jack at orange wire solfer and blue point. You will inject some nfb directly from 16 ohm tap in this way. Maybe it help to stabilise. Power on the and see if still oscillate

[ca7922303]

Hey, between blue and green points was just a link wire as much I can see. Put 100k between jack at orange wire solfer and blue point. You will inject some nfb directly from 16 ohm tap in this way. Maybe it help to stabilise. Power on the and see if still oscillate

Thought I had 100k, it's actually 100 ohms 1/2 watt, and I've got some 10k 1/2 watt, some 5 watt cement resistors 470 ohms and 4.7k 5 watt cement resistors. Should I try any of these or I'll see if I can find some locally if not then order online.

[Chuck H]

I'm pretty sure g1 was onto something when THIS was discovered:

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

So the presence control doesn't work either because the control it broken or not connected OR... The feedback loop is disconnected or faulted somehow.

[ca7922303]

I'm pretty sure g1 was onto something when THIS was discovered:



So the presence control doesn't work either because the control it broken or not connected OR... The feedback loop is disconnected or faulted somehow.

I pulled presence pot and it tested good out of circuit, reinstalled it, still no presence.

[ca7922303]

I pulled presence pot and it tested good out of circuit, reinstalled it, still no presence.

Went ahead and tried a 10k 1/2 watt and there's a definite volume increase, less distortion when I'm plugged into 16 ohm jack only. Will get 100k ohm 1/2 watt locally. What's best way to make all output jacks work 4/8/16? Thanks.

[ca7922303]

Found a 147k resistor, installed it and even more volume increase, less distortion, but still oscillating and red plating.

[ca7922303]

Hey, between blue and green points was just a link wire as much I can see. Put 100k between jack at orange wire solfer and blue point. You will inject some nfb directly from 16 ohm tap in this way. Maybe it help to stabilise. Power on the and see if still oscillate

Got some 100k ohm 1/2 watt resistors locally and have one installed now. Same condition, volume increase, less distortion, about the same amount of oscillation and red plating.

[catalin gramada]

Did you tried to pull v5 out to see if osscilate? Oh you said the volume increased with 100k feedback resistor? then your wires to power tube inputs should be reversed. It is possible those wires to be reversed by mistake ? hope you used 100k from orange wire to blue point without those link on board you removed( blue-green)

[ca7922303]

I've got a signal generator and PC based oscilloscope if someone could help me trace this issue down? Thanks.

[ca7922303]

Did you tried to pull v5 out to see if osscilate? Oh you said the volume increased with 100k feedback resistor? then your wires to power tube inputs should be reversed.hope you used 100k from ora ge wire to blue point without those link you removed blue-green

Removed V5 and only oscillates on channel 2. Does not oscillate on channels 1 & 3.

[ca7922303]

Did you tried to pull v5 out to see if osscilate? Oh you said the volume increased with 100k feedback resistor? then your wires to power tube inputs should be reversed. It is possible those wires to be reversed by mistake ? hope you used 100k from orange wire to blue point without those link on board you removed( blue-green)

Here's what I've got. No link between your blue and green points.

[ca7922303]

Did you tried to pull v5 out to see if osscilate? Oh you said the volume increased with 100k feedback resistor? then your wires to power tube inputs should be reversed. It is possible those wires to be reversed by mistake ? hope you used 100k from orange wire to blue point without those link on board you removed( blue-green)

What are you saying I need to do with the power tube input wires? Can you point me in the right direction with that? Thanks.