My SS22 starts feeding back a high single tone if the verb is above 4. I've put 3 different new tubes in the reverb slot and 2 NOS and it just keeps running away.

99% of the night I'm never above 2 on the verb so it's not much issue, but a couple of times a night I need to crank it up for an effect and all I get is feedback.

Since microphonic tube seems to be ruled out, where do I look next?

Does you amp still under warranty ?
If yes, bring it back to the 7ender dealer.

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Tissan

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This could be another tube than the reverb tubes, An other tube wich is microphonic. Try to tap it with a choptstick to hear it.

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English is not my mother tongue , I do my best

I had it in my studio last week and chopsticked it to death. Actually it won't feedback in my studio....only on gigs. So it's annoyingly intermittent.

If you can Kyle, take it back.

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Life...... It's sexually transmitted and always fatal

Too late, besides I love that amp for the 4 gigs a month I use it. I know an authorized Fender tech a couple of hours away. I'll give him a ring. I was just hoping it was some type of recognized or reported issue besides microphonics.

Kyle, is this a used unit? How is the reverb tank mounted onto the cab? I sometimes see tanks mounted directly onto the wood with wood screws. This sometimes leads to great reverb & sometimes leads to amp succeptible to feedback with reverb "on."

I don't know where on the Net or in which book, but some amp tech (pretty famous) said like 20 years ago, that bolting the tank directly onto the cab improves the reverb tone. It does seem to increase the reverb sensitivity. But, sometimes to the point of bad things happening.

+100 BMW2002Ti

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English is not my mother tongue , I do my best

Interesting.....it's in the standard bag with cardboard and screwed onto the bottom of the cab.

The bag is screw on the bottom on the amp . The reverb tank itself is loose in the bag.

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English is not my mother tongue , I do my best

I googled around a bit and found a lot of people having the issue due to the coupling of the tank or tank/bag and the cabinet. Most cleared it up by using some type of rubber cushion between the 2. I'll give that a shot. I'm using it again this Sunday so I'll know soon enough.

mine had a skinned wire in the reverb tank that was shorting out. Very small wires and was quite hard to find the culprit. But after looking with a bright light and going over every bit of the wires and the contacts, I saw it - just part that was nicked, showing bare wire. So sometimes i had reverb sometimes not, or it would start getting very faint.
i fixed the wire and so far no issues
I do know that if the contact is completely broken you will get a loud sqeel though~

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My reverb sounds like crap..not the fender ztyle at all. Alos hums as volume incresses.

I bought a brand new SS22 and it was delivered to me in the original packaging, and it had a squealing reverb problem. At first I thought it could be a microphonic tube, and tapped on them, but tubes did not appear to be the problem. So after reading your posts, and googling and reading other's similar problems (not only with the SS22, but with other amps, I decided to open the reverb tank. When I examined the insides I found that one of the rubber grommets (there are two), one had the post that prevents too much movement, was stuck between the grommet and the hole in the tank. This not only limited the movement of the reverb (giving a weak reverb), but must have caused most of the squeal. I thought I had fixed the problem entirely, but after I screwed everything back together I still had some squeal at 7-8+ on the reverb knob. I then removed the bag again and isolated the tank and vinyl bag with a small piece of foam under the bag, and not screwing in the screws completely tight (enough to keep it in place, but with no squeal - determined by tapping on the tank and turning up the reverb knob. I also added plastic standoffs (spacers) under the screws between the bag and bottom of the cabinet, and this took care of the problem entirely. I can turn the reverb all the way up and tap on the amp, and get reverb sounds, but no squeal.

When I had my SS22 I fixed my squealing reverb simply by replacing the cheap chinese RCA cable from the amp to the reverb pan.