6G15 Fender reverb unit noise on startup

[Stevewdewitt]

I am troubleshooting a fender 6g15 from around 1993. It has the cream colored board. I replaced the electrolytic capacitors, cleaned the pots, jacks, and sockets. Tried replacing all tubes. It sounds fine after an initial 5 seconds of static on startup and shutdown. Has anyone ever heard of this issue? I can't imagine that his is normal. I have never worked on a standalone reverb unit.
thanks in advance,
Steve

[Esquirefreak]

Sounds like a poor solder connection somewhere. Possibly heat related?

/Max

[Latole]

Did this problem exist before all the work you've done ?  IMO yes,  please confirm .

Burn On / OFF switch contacts ? Use jumper to put ON , not the toggle lever.
One or more ground solder could be the cause too

Successful troubleshooting depends on a good knowledge of many details; static noise as the only information can be vague if you don't hear it yourself.
Replacing the filter caps seems pointless and has nothing to do with the noise.

One or more ground solder could be the cause.

[Latole]

circuit board

[Stevewdewitt]

I will check the switch. That is a great suggestion. Could be a ground solder also.

I replaced the filter caps because of the initial issues. It was non-stop crackling, bacon frying, humming. That issue is now gone. The unit is 30 years old.
All that is left to resolve is the startup noise. It was a good thing to replace the 30 year old caps.

[Stevewdewitt]

Bypassing the switch didn't help. I will check the ground connections.

[Esquirefreak]

I'd also check the tube sockets. Wiggle the tubes gently and listen for pops/statics. After that I'd chopstick every component and connection to check for bad solder joints.

/Max

[Latole]

I will check the switch. That is a great suggestion. Could be a ground solder also.

I replaced the filter caps because of the initial issues. It was non-stop crackling, bacon frying, humming. That issue is now gone. The unit is 30 years old.
All that is left to resolve is the startup noise. It was a good thing to replace the 30 year old caps.

30 years is not old , not old enough to replace filter caps.
I repair a lot of amplifiers (and all kinds of equipment) that are 50-60 years old and still have good filter caps.
Filter caps is the only name that comes to mind for those not trained in electronics for any amplifier problem.

But I understand that you have no choice but to replace parts that are still good, quite by chance.

Cracking stop because of the new solders you do on power supply circuit/ filter caps.

[Willabe]

30 years is not old , not old enough to replace filter caps.
I repair a lot of amplifiers (and all kinds of equipment) that are 50-60 years old and still have good filter caps.

Yes it is.

They may still work at 30, but, they have degraded in performance. And I'm definitely pulling 50 to 60 year old caps, wouldn't even think about it, they're gone, to risky to keep them.     

[Stevewdewitt]

I will check the switch. That is a great suggestion. Could be a ground solder also.

I replaced the filter caps because of the initial issues. It was non-stop crackling, bacon frying, humming. That issue is now gone. The unit is 30 years old.
All that is left to resolve is the startup noise. It was a good thing to replace the 30 year old caps.

30 years is not old , not old enough to replace filter caps.
I repair a lot of amplifiers (and all kinds of equipment) that are 50-60 years old and still have good filter caps.
Filter caps is the only name that comes to mind for those not trained in electronics for any amplifier problem.

But I understand that you have no choice but to replace parts that are still good, quite by chance.

Cracking stop because of the new solders you do on power supply circuit/ filter caps.

I can tell you with 100% assurance that the new solders didn't resolve the issue. It is good that you have an opinion. You might want to keep it to yourself if it is not helpful.

[tubeswell]

A bit of pink noise at startup and shutdown isn’t uncommon with tube amps. (From changing voltage across slightly noisy load resistors being amplified in the signal path. Gator clip a 0.1uF 600V film cap from each plate to ground -one stage at a time- to find out which stage(s) might be producing the noise. Seeing as how it’s a 6G15, twiddle the knobs to find out if the noise occurs when the level control is dry or wet)

[HotBluePlates]

... I will check the ground connections.

As you do this, keep in mind the next-to-last paragraph of the Theory of Operation here.

R22 (15Ω), R23 (15Ω), CR5, and CR6 are all used to separate circuit-ground from chassis-ground, to break the inevitable ground-loop that forms between the Reverb Unit and the amp when both have 3-prong cords.

The original Fender amps & Reverb Unit had 2-prong cords, and ground-loops completed by the power cords weren't an issue.