60's Ampeg Reverberocket II (GS-12-R) Reverb Not Working - Advise Needed

[Wittgenstein]

Thanks for the tips. I was digging through my tools yesterday and found an old signal generator that I bought a few years back that will be perfect for this. I did remove the suspect 10K 7W resistor and it is definitely broken open. Ordered a new 10K resistor and a couple 6U10 tubes to swap in.

[Randall]

I use an iPod that I installed some 40Hz, 400Hz, and 1KHz tones on for a signal generator.

[Wittgenstein]

Update: Finally received and installed the replacement 6U10 tube and 10K 10W resistor and for the first time I was able to hear the reverb, but it was stuck permanently on. I found that the ground wire going to the back of the reverb pot was barely hanging on and after some fresh solder it was fine. I also replaced the 20uf electrolytic coming off the power tubes (appeared to be bulging out on the positive side) for a new higher voltage one. The amp could still use some loving: new electrolytic caps, three prong cord and death cap removed, and possibly a new 7199 tube. I ended up giving back to the owner however as he was only looking to have the fuse fixed and did not want to spend much / any money, but I could not in bring myself to give it back before fixing the reverb and footswitch. I just charged him what I spent in parts, about $20, and suggested he spend the extra $60-$120 (depending on if the tubes are bad) to upgrade the rest when he has some money to throw at it.

A couple of questions:
Occasionally the amp without any input would start to make a strange crackle and popping noise that would sometimes build louder and louder, but if you just gave the amp a little bump, it would go away. Any thoughts what could cause this?
I did not have a chance to remeasure the voltages after installing a working tube, but below are the voltages I took with the old tube and new 10K resistor. I noticed a few of the values are pretty low compared to the schematic. Do you think this is do in part to the 610U being bad?



Values in parentheses are the suggested voltages shown on the schematic.

V1 - 12AX7
Pin 1 (170V) - 142V
Pin 3 (1.4V) - 1.4V
Pin 6 (160V on, 260 off) - 108V on, 176V off
Pin 8 (1.7V on 3.5V off) - 1.2V on, 3.5V off

V2 - 6U10
Pin 2 (60V) - 87V
Pin 3 (3.7V) - 3.5V
Pin 4 (9V) - 11V
Pin 5 (155V) - 105V
Pin 6 - 1.6V - 1.0V
Pin 9 - 4V
Pin 10 (250V) - 239V

V3 + V4 - 7199's
Pin 1 (240V) - 238V
Pin 2 (115V) - 46.4V
Pin 3 (50V) - 37.9V
Pin 6 (1.8V) - 2.3V
Pin 8 (50V) - 47.8V
Pin 9 - 15V

B+ on schematic
1st cap (360V) - 366V
2nd cap (355V) - 360V
3rd cap (340V) - 350V
4th cap (280V) - 302V

[Wittgenstein]

I recently was able to borrow this amp again for a little while and I wanted to try and fix it up a bit more. I'm still having the same troubles that I listed above, but I plan on going through it this weekend with a signal tracer and will be sure to post the new pin out voltages. I am putting off changing all the electrolytics as I do not have the money at this time.

[cyclone]

I recently was able to borrow this amp again for a little while and I wanted to try and fix it up a bit more. I'm still having the same troubles that I listed above, but I plan on going through it this weekend with a signal tracer and will be sure to post the new pin out voltages. I am putting off changing all the electrolytics as I do not have the money at this time.

I did a similar amp recently'64 r12r reverberocket factory updated to compactrons and 7868's, three schematics pasted on top of each other! Crazy mods and looked like factory work, amp was from NYC.

One of the 7 watt resistors was open, and about 12 coupling caps were leaky. They were all pink molded ones, all the Wimas were good. I tested them and the electrolytics with a sprague to5 at rated voltage.

Big electrolytics were all fine. Hope that helps! You should be able to test the 3 triodes for function in the 6u10, 6c10 with just voltage checks. Aes had 6u10's in stock for cheap last I checked

[Wittgenstein]

Thanks cyclone that gives me a good place to start looking. After getting to play around a bit more last night on it, it seems that most of the issues are coming from the tremolo stage.

[Wittgenstein]

Update: New Caps but Microphonic Tube?



So I had a chance to go through and change out all the electrolytic capacitors and replace the fried optocoupleand it definitely sounds better, however when I play certain notes on the guitar with the amp up decently loud, it shakes the cab in just the right frequency to vibrate the 7199 tube which causes a terrible noise (flubby, buzzy, and even like white noise). If I have someone hold the 7199 tube with their hand to reduce vibration while I play the same note there are no problems.

Is this just a bad tube that has gone microphonic? I checked the tube socket itself to make sure the pins were tight and that there were no cold solders / loose wires.

Also I notice when the reverb unit is on, I was picking up a local radio station. I thought there was a RF snubber to prevent this? Is this a sign of possible bad grounding or is this normal?

[Leo_Gnardo]

when I play certain notes on the guitar with the amp up decently loud, it shakes the cab in just the right frequency to vibrate the 7199 tube which causes a terrible noise (flubby, buzzy, and even like white noise). If I have someone hold the 7199 tube with their hand to reduce vibration while I play the same note there are no problems.

Is this just a bad tube that has gone microphonic? I checked the tube socket itself to make sure the pins were tight and that there were no cold solders / loose wires.

Also I notice when the reverb unit is on, I was picking up a local radio station. I thought there was a RF snubber to prevent this? Is this a sign of possible bad grounding or is this normal?

Have you cleaned the pins on that 7199? Touch up soldering on its socket in case a lead isn't properly attached. 7199 do make this sort of racket sometimes, and good luck finding a replacement. They are scarce and quiet ones scarcer yet. Could rewire the socket to take I think 6U8 or find an adapter, I think Antique has these. There's another equivalent tube in function but not pinout, can't remember at the moment, but I'm sure someone will mention it.

One of my customers had RF problems and bought himself a 2-pack of interference filters at Radio Shack. These are blocks of ferrite encased in plastic housing and can be arranged to suppress RF on whatever wire's bringing it in. Don't have the part number but it was @ 7 then, probably 10 bucks or so now. They look clumsy but worked a charm for him. Plus the snap on snap off feature lets you try them in a couple of locations on the amp so you can assess maximum effect and park 'em there.

[Wittgenstein]

Have you cleaned the pins on that 7199? Touch up soldering on its socket in case a lead isn't properly attached.

I did check the socket, cleaned the pins, re soldered all the pins as well as the eyelets the corresponding wires ran to to check for loose connections.

One of my customers had RF problems and bought himself a 2-pack of interference filters at Radio Shack. These are blocks of ferrite encased in plastic housing and can be arranged to suppress RF on whatever wire's bringing it in.

Thanks for the tip. Any suggestions on where to try attaching these to? I would assume the screen on v1?

[Wittgenstein]

Update: Fixed and sounding great!

Just wanted to post an update on this Reverberocket to report that it is finally finished. The first used / NOS 7199 phase inverter I swapped in seemed to eliminate all the microphonic troubles, however it still made a woshing, almost like a wave on the ocean, sound with the volume cranked. The new phase inverter also seemed to smooth out the sound of the amp.

I assumed after trying new tubes, that this woshing sound was due to a leaky caps letting current back through, so today I finally got around to changing out the coupling caps for new Malory caps, as well as swapping out the old power cord to a 3-prong cord. Now the amp sounds AMAZING. It sounds especially nice with the tone when you crank it to 7 or 8 with the reverb set to 6 and with slow tremolo. Now to give it back to the rightful owner for more abuse and gigging.


More photos here (Flickr)


Recap:
Fixed broken fuse holder - Powered on but had issues
Complete cleaning inside and out (tube sockets, tube pins, jacks, pot cleaner, steel-wool, simple green, etc...)
Fixed leather handle (stripped threads) - glued in toothpicks and reattached
Fixed non-working reverb - new 10W wire-wound and adjacent caps, new tube, and broken ground to foot-switch (always on)
All new electrolytics - made a huge improvement, but still had woshing sound
Fixed intermittent tremolo - new optocoupler
Replaced faulty / microphonic 7199 phase inverter tube - made another huge improvement but still woshing sound
All new coupling caps - sounds great, no more woshing sound
2 to 3-prong power cord conversion - removed death cap and seemed to quiet the hum a tiny bit


Old gut shot:


New Gut Shot