Gotcha. I have also heard that these amps often do this due to dirty OT connectors and pins. I am going to clean those, and if that doesn't work Ill start pulling tubes. (I can do this with the amp on, eh?) Thanks Wave!!
Rotus,
I did not think the fault would be in the reverb section, however I know what it's like when you think it could be! So the easiest way is to eliminate it!
As suggested by Wavebourn if you remove each tube from input to out at some point the noise should stop (as long as it's not in the output section).
Watch for any tubes with red plates if you do this. You may have a leaky coupling cap! Let us know what happens with V1, V2, V3, removed in sequence. Remember to replace each one before removing the next! If you just take them all out one at a time the HT may rise due to reduced load!
Regards
M. Gregg
I did not think the fault would be in the reverb section, however I know what it's like when you think it could be! So the easiest way is to eliminate it!
As suggested by Wavebourn if you remove each tube from input to out at some point the noise should stop (as long as it's not in the output section).
Watch for any tubes with red plates if you do this. You may have a leaky coupling cap! Let us know what happens with V1, V2, V3, removed in sequence. Remember to replace each one before removing the next! If you just take them all out one at a time the HT may rise due to reduced load!
Regards
M. Gregg
Last edited:
So M. the main reason I am pulling tubes is to see if the noise stops. And if I get some red plating then we have an issue with the coupling cap.
I will. The thing that sucks is that I dont have an o-scope, then I wouldnt have to worry about damaging the speaker.
So quick update. I cleaned the pins to the OT and there is A LOT less static. There is still some though. I think that I had a ton of loose connections in this bad boy. I am going to do the ol tube pull once the amp cools down.
Do you guy think I should clean the Main transformer pin also, or do they normally not cause any issues?
Do you guy think I should clean the Main transformer pin also, or do they normally not cause any issues?
Power off at each change!
The next thing you can try is to remove two of the output tubes. You have to keep the output balanced so try removing V6 & V7 first see if the fault is still there! If it is put them back and pull V4 & V5. If you get any instability power off straight away! Watch for red plates! Don't leave it on long!
Regards
M. Gregg
M. I tried pulling out V4 and V5, then V6 & V7 and no crackling. This amp actually doesnt produce any signal sound at all when only two tubes are plugged in. I know that some amps can be run with only two power tubes, but with this amp for some reason I have no signal at all making it to the speakers.
Wavebourn, I had corrosion in my tube jacks and they felt loose. I removed the old ones and replaced them for $12.00 and still the same crackling.
Wavebourn, I had corrosion in my tube jacks and they felt loose. I removed the old ones and replaced them for $12.00 and still the same crackling.
Yes sir I have two full sets of tubes, and the fresh sockets are installed. Funny thing is that when my brand new set of JJ 6l6gc are in there then it takes the amp a little longer to quiet down. No matter which tubes are in place, even mix and matched, there is always the issue.
That means tubes are innocent. If fresh sockets are installed they are innocent...
What else left?
Carbon comp resistors in screen grids?
Are you adjusting the volume pot or tone stack when this happens? If so it may be a characteristic of the circuit. Even without adjustment the pots can make noise during power up.
I've got a guitar amp that does this and I determined it is because on power up the caps that power the section driving the tonestack and volume pot are slow to charge (long RC time constant). So the voltage at the plate of the tube slowly comes up, which puts current through the coupling caps (dv/dt is ac to a cap) into the tonestack pots and volume pot.
Pots are noisy with dc current flowing though them.
I've got a guitar amp that does this and I determined it is because on power up the caps that power the section driving the tonestack and volume pot are slow to charge (long RC time constant). So the voltage at the plate of the tube slowly comes up, which puts current through the coupling caps (dv/dt is ac to a cap) into the tonestack pots and volume pot.
Pots are noisy with dc current flowing though them.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.