4 issues to be addressed on my 1990 Red Knob Twin

[jalexquijano]

First of all, i would like to express my gratitude to the members who have been helping me troubleshoot my recently ebay purchase of a 1990 used Fender the twin aka Red Knob Twin. However, after playing the amp for more than 40 minutes yesterday after replacing the 1st input Jack, i am really pleased with the results but still notice the following issues which need to be solved:

1. If playing the amp on the clean channel with a Gibson les paul, SG or 335 (humbucking), the sounds comes out a Little bittle overdriven and not fully clean. With a single coil telecaster or strat it sounds cleaner. Could the amp be suffering from a change of electrolytic caps which i am still waiting to arrive.

2. If i switch to the overdrive channel, and i dime the gain full and start raising the volume over 6 you can hear a high pitch squeal. Could one of the preamp tubes be microphonic or damaged?

3. Reverb does not actívate until i raise the knob over 4. If i dime it fully then a feedback is reproduced.

4. I have some potentiometers that are working but the shaft is bent. Do you think there is a posible way of straighten them? or should i just swap them?

Hope someone can point out the solutions for these remaining issues.

[The Dude]

...... Could the amp be suffering from a change of electrolytic caps which i am still waiting to arrive......

I'm not sure what that means. Are you running the amp with some caps missing? If that's the case, you can't expect the amp to work normally until they're installed.

[g1]

1) Do you have the humbucking guitar at full volume? If so, and you are picking hard, it may be normal. You may have to back off the guitar volume a bit with humbuckers to stay clean.
2) It could be a microphonic preamp tube, but it could be normal too. When it squeals like this, does turning off the guitar volume make the squeal go away?
Is this a realistic setting you would actually use? (gain full, volume 6)
3)The reverb tanks in these amps were prone to feedback, especially if reverb turned up full. But if there is no reverb till the knob is set to four, there could be something wrong. Have you looked inside the tank? A dirty or defective reverb control might do this as well.
4)It is very easy to break the bent shafts trying to straighten them. Many of the pots in this model are no longer available, expecially the ones with the pull switches. If you can still turn them, I would use it like that. Otherwise, make sure you can still get the part before you try to straighten the shaft.

[Justin Thomas]

If you are not running the amp still with the old electrolytic caps and some of those ARE bad, it is very possible that some of your oscillations and strange noises are indeed caused by failing caps. Bad electrolytic caps can cause ALL SORTS of problems. The tricky part is, how do you know if they're bad? Usually trying a new one is the quickest way to find out...
(Just going on all the threads about oscillating Hot Rods with failing caps here...)

Justin

[jalexquijano]

All caps are in place. No caps missing just starting to replace them!

[jalexquijano]

1) Do you have the humbucking guitar at full volume? If so, and you are picking hard, it may be normal. You may have to back off the guitar volume a bit with humbuckers to stay clean.
2) It could be a microphonic preamp tube, but it could be normal too. When it squeals like this, does turning off the guitar volume make the squeal go away?
Is this a realistic setting you would actually use? (gain full, volume 6)
3)The reverb tanks in these amps were prone to feedback, especially if reverb turned up full. But if there is no reverb till the knob is set to four, there could be something wrong. Have you looked inside the tank? A dirty or defective reverb control might do this as well.
4)It is very easy to break the bent shafts trying to straighten them. Many of the pots in this model are no longer available, expecially the ones with the pull switches. If you can still turn them, I would use it like that. Otherwise, make sure you can still get the part before you try to straighten the shaft.

3) Dirty or defective reverb control?? What do you mean?? The reverb potentiometer could be dirty or worn? I already checked the tank and its an original accutronics made in USA with its three springs perfectly assembled. Reverb does not go in until i turn the knob to 4. Please advise.

THis amp is working nice. I just want to get these last issues sorted.