Fender super sonic 22 no reverb?

[swaffy101]

Good afternoon!

So picked up a fender super sonic 22 combo (used) yesterday. I tested the amp at the guys house the reverb wasn’t working but figured I could fix it.
The reverb gets splash back when I tap the tank, so I assume the “return” is working.
Well I ran through the usually trouble shooting stuff: rolled the tubes with known good ones, tested the tank and switched the tank with a known good one, checked RCA cables and swapped to make sure, cleaned all connections, took amp out of the cabinet checked for loose connections on the PC board to the reverb transformer, checked continuity everything looks to be ok.

I’m stumped. I googled and checked every forum I could find stating the same problem and I got nothing. Most “fixes” were the 12ay7 or dirty sockets, but nothing regarding still getting splash when tapping the tank or rocking the amp.
Any ideas?

[B Ingram]

... picked up a fender super sonic 22 combo ... the reverb wasn’t working but figured I could fix it.
The reverb gets splash back when I tap the tank, so I assume the “return” is working.
Well I ran through the usually trouble shooting stuff: rolled the tubes with known good ones, tested the tank and switched the tank with a known good one, checked RCA cables and swapped to make sure, cleaned all connections, took amp out of the cabinet checked for loose connections on the PC board to the reverb transformer, checked continuity everything looks to be ok.

I’m stumped. I googled and checked every forum I could find stating the same problem and I got nothing. Most “fixes” were ...

Forums are bad about suggesting "Fixes" rather than showing "how to troubleshoot."

The Supersonic 22 schematic shows a muting circuit associated with the Footswitch and U2-B (Pins 5, 6, 7 of a 4560 opamp). There are voltages indicated on the schematic for each state of the Reverb switch on the stock footswitch.

At this point, you would go inside the chassis, measure the voltage around the 12AT7 (to determine whether it & the reverb transformer are likely working), then use the Reverb button on the footswitch to check voltages in the switching circuitry & associated FETs to verify they are not shunting signal that should pass in to the 12AT7 to drive the reverb tank.

[swaffy101]

First thank you for the reply!

I’ll dive into that tomorrow when the kids are at school. I’m not super knowledgeable when it comes how circuits work and tracing schematics but I like learning. Again thank you for helping I greatly appreciate it!

Dan

[Stevem]

If you have or can get a female rca to male 1/4” adapter you can run the send of the reverb into another amp.

If you get no signal which I bet is the case then the small pan drive transformer is likely bad.

Another way to go is to hook that send output up to a speaker since what that whole send side of the reverb circuit is really is a 1 watt 8 ohm amp.

[swaffy101]

If you have or can get a female rca to male 1/4” adapter you can run the send of the reverb into another amp.

If you get no signal which I bet is the case then the small pan drive transformer is likely bad.

Another way to go is to hook that send output up to a speaker since what that whole send side of the reverb circuit is really is a 1 watt 8 ohm amp.

1/4” directly into the front of another amp?

Are you referring to the reverb transformer or the transformer inside the reverb pan?

[Stevem]

Yes, run the send output right into another amp.
Just keep the volume on your 22 down low and the same for the amp your feeding the signal into, in fact use the number 2 input if the other amp has such .

I am talking about the transformer in the amp because you said you tested the two coils in the pan and they where not reading open.

[swaffy101]

Ok cool I’ll give that a shot! Thank you for giving me some ideas for trouble shooting.

[swaffy101]

TP 48 is measuring -13.5 reverb on and 13.9 reverb off. I’m assuming that is with into the tolerance range (+15/-15). So it is switching, which I can definitely hear the hiss with reverb on and it drop significantly when off.

TP 25 is measuring 47 mVAC (49mVAC)

TP 26 is measuring 7 VDC (+7.35)

I was second guessing myself on the reverb pan. So I remeasured the send and I’m getting 1.5 ohm which is supposed to be 8 ohm. However both my reissue twin and super reverbs measure the same and they work great. On the fender website for that model pan it covers most of the amps them make. The super sonic has the “mod” brand version stock. I have watched a few videos on how to measure and I’m doing it right.

Also when I measure TP 27 I’m getting 0.003 VAC (30 mVAC)
I’m lost in the sauce. Is the reverb transformer bad or the pan? What other test points should I measure?

[swaffy101]

Yes, run the send output right into another amp.
Just keep the volume on your 22 down low and the same for the amp your feeding the signal into, in fact use the number 2 input if the other amp has such .

I am talking about the transformer in the amp because you said you tested the two coils in the pan and they where not reading open.

Ok I gave this a try, return from the reverb tank to rca-1/4 adaptor, into low input of jcm 800. No sound.

[Stevem]

Not the send from the tank which I am assuming you mean the output from the tank, am talking about the send from the amp which would go to the RCA jack marked input on the pan.

Resistance wise the input to the pan should read .9 ohms and the output side about 200.
The input of that pan is said to be an impedance of 8 ohms and the output 2250 ohms impedance.

What do you have for voltage on V3 pin one, blue wire from reverb drive transformer and also on the red wire of the transformer?

[swaffy101]

Not the send from the tank which I am assuming you mean the output from the tank, am talking about the send from the amp which would go to the RCA jack marked input on the pan.

Resistance wise the input to the pan should read .9 ohms and the output side about 200.
The input of that pan is said to be an impedance of 8 ohms and the output 2250 ohms impedance.

What do you have for voltage on V3 pin one, blue wire from reverb drive transformer and also on the red wire of the transformer?

I ran the rca from the red rca input on the cassis to the low input of the jcm 800. I only heard static from the 800 but can hear the guitar clearly through the super sonic cab.

Pin 3 blue wire I get 418 VDC and 1.21 VAC
Red wire I get 417 VDC and 1.25 VAC

I removed the red and blue from the spade connections and measured 73 ohms, green and black measured 1.4 ohms.
I have not found a spec on the resistance for the transformer to compare the results to.

[Lauri]

I removed the red and blue from the spade connections and measured 73 ohms, green and black measured 1.4 ohms.
I have not found a spec on the resistance for the transformer to compare the results to.

Primary resistance on the reverb transformer should be somewhere around 1000 ohms. Looks like the primary winding has shorted.

[Stevem]

Yup, that reverb pan driver trans has a shorted primary.

[swaffy101]

Thank you! I’ll get one ordered today. I’ll update when the new one is installed.

Thanks,
Dan

[Stevem]

I just worked on a silverface SR last night and the primary side of the transformer check out at well over 1100 ohms.