# Supersonic 22 reverb



## J-75 (Jul 29, 2010)

I acquired a used SS 22 which has a reverb that is extremely weak, almost unnoticeable. I tested the 12AT7 - it passed. I'm wondering if there could be something physical in the delay line hardware that could be at fault. Is that possible, or would issues in that area simply result in go versus no-go symptoms?
Do the supersonic models characteristically have weak reverb? I could remove the delay line to check it out, but how would I test it other than just continuity?


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## jb welder (Sep 14, 2010)

First, is it weak if you have the amp set up for a clean sound?
It's worth looking in the tank for a broken spring or wire etc., but yes, they are usually dead or alive.
Disconnect tank and measure resistance at the in and out jacks of the tank. Post results as well as the number stamped on the tank.


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## J-75 (Jul 29, 2010)

It's an Accutronics 64063, resistance: 2.5 ohm IN, 212 ohm OUT, measured at ends of the unplugged leads.


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## jb welder (Sep 14, 2010)

That's the right tank and those resistance numbers are good.
Another quick test to try: disconnect the 'out' at the tank end. Touch the tip of the rca plug with your thumb. Do you get a big hum if you turn up the reverb knob (amp on clean ch.)?


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## J-75 (Jul 29, 2010)

jb welder said:


> That's the right tank and those resistance numbers are good.
> Another quick test to try: disconnect the 'out' at the tank end. Touch the tip of the rca plug with your thumb. Do you get a big hum if you turn up the reverb knob (amp on clean ch.)?


I disconnected the output wire at the tank, and got an increasingly loud response as I turned up the 'Reverb' control from zero while touching the tip.


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## jb welder (Sep 14, 2010)

Hmm. Still a question of 'is it loud enough' relative to the signal. The hum should have been very loud when the reverb control got to high settings.
If you give the amp a good shake with the reverb control set at say, halfway, do you get a loud crashing of the springs? Or just audible?


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## dtsaudio (Apr 15, 2009)

I see what you're on to JB. It does sound like the receiving end is not working properly
Check V4 (12AX7). It could also be in the switching. There are two JFET transistors that actually short out the reverb signal. One may be faulty. 
It could also be just a lousy reverb. With Fender you never know☺


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## J-75 (Jul 29, 2010)

jb welder said:


> Hmm. Still a question of 'is it loud enough' relative to the signal. The hum should have been very loud when the reverb control got to high settings.
> If you give the amp a good shake with the reverb control set at say, halfway, do you get a loud crashing of the springs? Or just audible?


I would say the hum was quite loud with reverb pot maxed out. The crashing test was definitely loud with reverb set at half way.


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## J-75 (Jul 29, 2010)

dtsaudio said:


> I see what you're on to JB. It does sound like the receiving end is not working properly
> Check V4 (12AX7). It could also be in the switching. There are two JFET transistors that actually short out the reverb signal. One may be faulty.
> It could also be just a lousy reverb. With Fender you never know☺


I just tried swapping out V4 with a brand new AX7 - no change.
The tubes in this amp look like it hasn't been used much. They all look new - the power tubes (GT's) don't show any signs of heat on the labels.


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## cboutilier (Jan 12, 2016)

Could be a bad coupling cap on the tube.


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## jb welder (Sep 14, 2010)

dtsaudio said:


> I see what you're on to JB. It does sound like the receiving end is not working properly
> Check V4 (12AX7). It could also be in the switching. There are two JFET transistors that actually short out the reverb signal. One may be faulty.


Yep, it was those Fet's I was wondering about. Lo and behold they have one on the drive side too (Q10), unusual for Fender.
@J-75 if you want to take a gamble, snip out Q10. It's just a mute so you don't get a pop through the reverb at turn-on or when engaging reverb. If it goes bad, it will kill or weaken the drive to the reverb, like you have.
If clipping it out doesn't solve the problem, you can replace it later if desired. If it solves the problem, you can use as is, or replace if desired.


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## J-75 (Jul 29, 2010)

jb welder said:


> Yep, it was those Fet's I was wondering about. Lo and behold they have one on the drive side too (Q10), unusual for Fender.
> @J-75 if you want to take a gamble, snip out Q10. It's just a mute so you don't get a pop through the reverb at turn-on or when engaging reverb. If it goes bad, it will kill or weaken the drive to the reverb, like you have.
> If clipping it out doesn't solve the problem, you can replace it later if desired. If it solves the problem, you can use as is, or replace if desired.


I haven't pulled the chassis yet, but before I do, I'm wondering how I'm going to locate Q10. The only pictorials I've found so far are too blurred to identify the component's location. Can we use a coordinate reference, or what do you suggest?


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## jb welder (Sep 14, 2010)

J-75 said:


> I'm wondering how I'm going to locate Q10. The only pictorials I've found so far are too blurred to identify the component's location. Can we use a coordinate reference, or what do you suggest?


Straight back from Gain2 pot, near C72.










https://www.thetubestore.com/lib/thetubestore/schematics/Fender/Fender-Super-Sonic-22-Schematic.pdf


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## J-75 (Jul 29, 2010)

I snipped one end of Q10. Tight proximities make it really hard to access/get a snipping tool under. The reverb seems to be better, but not like what some other amps can provide.
I think I'm not going to pursue it any further as I have some other amps with a richer reverb. Thanks to you guys for helping me out.


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## jb welder (Sep 14, 2010)

J-75 said:


> I snipped one end of Q10. Tight proximities make it really hard to access/get a snipping tool under. The reverb seems to be better, but not like what some other amps can provide.


As long as the lead you snipped was *not* the one on the right when looking at the flat face. Clipping that one would not help.
In the pic above, you would want to clip the one closest to the top of the pic (nearest to R141).
I can't say I've heard one so I don't know how the reverb compares to the classic fender amps. In case it was more than 1 cause of the issue, sometime try swapping out the 12AT and V4 again. I think you said you tried the 12AT on a tester, sometimes they (testers) miss faults.


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## J-75 (Jul 29, 2010)

Yep, it's the one on the right that I cut - it was the most accessible. There is a ribbon buss strapped down, with a lot of turn-outs, looming over the opposite side of the FET, pretty much blocking access to cutting it. The FET is mounted very close to its PC board with little exposure of its leads. I managed to poke a soldering iron, with a fine tip, laterally and diagonally against the more exposed end lead, while barely touching the middle lead. It was enough to melt their joins and pull up that side of the FET enough to expose that end lead. I could then get the jaw points of a small diagonal cutter on that terminal.
I re-assembled the amp after having tried it out without significant improvement. If and when I decide to give it another shot, should I just un-solder and remove the FET?
Meanwhile, I have a new 12AT I'll try. Thanks again for your time and thought.


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## jb welder (Sep 14, 2010)

Yes, just unsolder and remove. But if it has any wiggle room at all, try rocking it back and forth until it breaks off it's leads.
Or crush it with pliers and clip the leftovers.  I say that as it is a cheap part and not worth trying to re-use. Any method that will remove it without having to pull the board will save you a lot of headaches.


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## J-75 (Jul 29, 2010)

jb welder said:


> Yes, just unsolder and remove. But if it has any wiggle room at all, try rocking it back and forth until it breaks off it's leads.
> Or crush it with pliers and clip the leftovers.  I say that as it is a cheap part and not worth trying to re-use. Any method that will remove it without having to pull the board will save you a lot of headaches.


OK, I'll do that when I have an opportunity to get back into it. Thanks again.


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