Help My GK 400RB

[Eekum]

So I have ran into an issue with my amp. It is the GK 400RB and I love this thing. However, a couple days ago I was playing and it started making this weird crackling/fuzzing sound at the end of notes. It’s not super loud but it’s loud enough to where you definitely notice. My girlfriend even asked me what the noise was and she knows nothing about amps/basses/etc. It never did that before. I thought it was the cab at first so I switched out cabs and got the same results. I tried using two other instrument and speaker cables cables and that didn’t help. I tried using 2 different basses and it continued. I changed outlets I was using, tried using a power strip/surge protector. I even took the rig over a couple cities to my friends house and had the same results. Does anyone know what this could be?

 

[ljazz]

Corrosion in the effects loop jacks? Try a patch cable from the send to the return. If that fixes it, try some deoxit in a quarter inch plug, and insert it a few times into the jack's.

 

[Eekum]

Corrosion in the effects loop jacks? Try a patch cable from the send to the return. If that fixes it, try some deoxit in a quarter inch plug, and insert it a few times into the jack's.

After tinkering with it some more I noticed that the boost knob was scratchy when I turned it. I turned the boost all the way off and the other noise went away. I then sat there and rotated the boost knob back and forth for about 5 minutes. Now the noise is completely gone and so is the scratchiness from the knob.

Would it be wise to still get some deoxit for the boost knob in case the problem comes back?

 

[ljazz]

If it stopped, I'd probably leave until it came back. What year is it?

 

[Bill Whitehurst]

Sounds like you have it covered.
If it comes back and repeating the rotating process
doesn't work again, then Deoxit.

 

[Kro]

Would it be wise to still get some deoxit for the boost knob in case the problem comes back?

No. IME deoxit on amp pots is a bad idea. They pack them with grease that protects the components.

Using deoxit flushes that protective grease out. It might help in the short term, but in the long term it does more damage than anything else. This is a reason why loose knobs are often a red flag when looking at used gear.

The first thing to do is exactly what you did - give it a few turns and let it work its way clean. I'm glad it's working better - I expect it to stay that way for quite some time.

 

[Eekum]

If it stopped, I'd probably leave until it came back. What year is it?

It is a series II, so somewhere in the mid 80's to early 90's. I think...

No. IME deoxit on amp pots is a bad idea. They pack them with grease that protects the components.

Using deoxit flushes that protective grease out. It might help in the short term, but in the long term it does more damage than anything else. This is a reason why loose knobs are often a red flag when looking at used gear.

The first thing to do is exactly what you did - give it a few turns and let it work its way clean. I'm glad it's working better - I expect it to stay that way for quite some time.

Sounds good. Thanks for the insight.

 

[ljazz]

I have a series one from Jan '90. I had it cleanup and recapped a couple of years ago. I love it! Best solid-state amp of all time!