Rectoverb 50 cut out / cat scratch

[user 41014]

Only recently have I given the tremoverb a look but never really paid attention to the rectoverb/tremoverb. Are the two twins with different feature sets or different amps?

I grabbed one because of the burled hardwood, pics very soon, even with scratches and nicks. At 24 1/32" it's one of the widest if not widest chassis I've seen. I really don't think many if any mesa's are swap-able into this cab so it may be rectoverb only- we'll see.

I briefly tried the amp out and it was cutting out in both channels and had a scratch like someone was moving scratchy pots or close to and there was a hum. Something not right. But I was getting good tone, even overdrive from P90's on the front end and the original tone tubby single driver.

To pull the chassis the back and grill (5 drywall screws from the back) had to come off.

Two things struck me when I got the chassis out besides what a pain in the ^&^ it is to change tubes even tho I like tube shields on all preamp tubes; but the back needs to come off to do it comfortably. 1st is all the pre's are russo Mullards. Brief excitement when I saw Mullard was dashed quickly by seeing "made in". I've seen @tbonesullivan state V3 and V4 in a tremoverb have cathode follower triodes so this seems the low having fruit- do V3 and V4 of the rectoverb also have cathode followers?

I'm going to roll a good tube thru but I couldn't find cathode follower positions for this amp on a search.

Finally as I was putting the amp in a safe place so as to a watch a hockey game my fingers on a power socket made a click revealing a loose socket. I'll have to check in the daylight if it is just chassis screws or what is going on but that can't be good for the longevity of the pin connections in that state.

 

[user 41014]

As for the loose power socket it was the ceramic part rattling. I pulled the board and cleaned the pin sockets. I used a continuity test rocking the ceramic to see if there was a weak solder connection but found none on either socket.

It might be hard to see but some of those pin sockets were stretched out especially at the ends. I tightened them up. I tightened the board back to the chassis snug enough to hold the ceramic part tight.

For testing it's going into a OS 4x12 loaded with 12L's.

BAMM! POW! WOW!

Completely cleaned the sound up. I didn't think pin sockets could account for all the noise but there it is.

 

[user 41014]

1st up was channel two.
Easily able to dial in good tones. No problems whatsoever.

Channel one however brought out an issue that was like using a slow gear pedal if my signal didn't have enough attack from the pick. I couldn't help but wondering about cathode heaters not being warmed up and the signal warming the tube enough to come through. Or possible I was riding one of the pots too low.

Back to channel two I quickly found a good teen spirit tone and then dialed in BOC's dominance and submission. Very happy with CH2.

It was harder for me to recreate the slow gear effect back on Ch1 so maybe the tubes were a little warmer if the cathode follower tubes theory is correct. I'll check pre tubes next.

Heads up on any of these singles with the footswitch jack underneath next to the single TRS footswitch jacks on the back:
The part of the pcb for the underside jack is hanging there like a diving board. Don't use much pressure pushing/pulling the cable in/out and if in there a dab of electrical grade silicone to the chassis might be advisable to give it a little support.

 

[bandit2013]

1st up was channel two.
Easily able to dial in good tones. No problems whatsoever.

Channel one however brought out an issue that was like using a slow gear pedal if my signal didn't have enough attack from the pick. I couldn't help but wondering about cathode heaters not being warmed up and the signal warming the tube enough to come through. Or possible I was riding one of the pots too low.

Back to channel two I quickly found a good teen spirit tone and then dialed in BOC's dominance and submission. Very happy with CH2.

It was harder for me to recreate the slow gear effect back on Ch1 so maybe the tubes were a little warmer if the cathode follower tubes theory is correct. I'll check pre tubes next.

Heads up on any of these singles with the footswitch jack underneath next to the single TRS footswitch jacks on the back:
The part of the pcb for the underside jack is hanging there like a diving board. Don't use much pressure pushing/pulling the cable in/out and if in there a dab of electrical grade silicone to the chassis might be advisable to give it a little support.

Just on the photo of the preamp board, it appears that the center area is discolored for some reason or another. The one electrolytic cap at the top of the diamond array looks wet just above the capacitor. Was the PCB flooded from a leaking capacitor? The change from green to brown is a sign of contamination or something etch the solder mask on the PCB. Either that, something has leached into the layer substrate, delamination of prepreg material or thermal overload in that general area are what is the main culprit for the discoloration. Just thought I would mention it. Could have been some damage from before you got it?

 

[user 41014]

Just on the photo of the preamp board, it appears that the center area is discolored for some reason or another. The one electrolytic cap at the top of the diamond array looks wet just above the capacitor. Was the PCB flooded from a leaking capacitor? The change from green to brown is a sign of contamination or something etch the solder mask on the PCB. Either that, something has leached into the layer substrate, delamination of prepreg material or thermal overload in that general area are what is the main culprit for the discoloration. Just thought I would mention it. Could have been some damage from before you got it?

Don't tell me Nichicon 10K's go south too!!!!!

You got some good eyes.

With the Mark IV's infamous brown radial 10k's I think it is fair that if you see a blob around a group of 10k radials there should be immediate concern.

Is that what you are looking at?

If so I'll get some better pics up because there is a trace with an unusual blob shape on one side but straight on the other heading for the power tubes and then hangs a right toward the PT.

 

[user 41014]

Anyone can have a bad batch but I have faith in Nichi.

 

[bandit2013]

This is the discolored area of concern. The dark area above the one cap next to the preamp tube socket does have suspect shape. This could be a shadow based on lighting conditions. The brown or tan discoloration of the PCB material is a sign of thermal degradation. This also includes the copper foil around the square ceramic resistor (I assume that is what it is). Surface does not appear to be blistered on the top side or burned from using a heat gun that is commonly used to remove large surface mount components. I have such at work for doing repair, investigations and assembly of prototype products. The components do not look suspect and the solder lands look ok but that does not mean this amp did not have a catastrophic failure in this area considering all of the diode rectifiers at the center. You also have a row of smaller electrolytics on the left and the 4 larger ones to the right.

All electrolytic capacitors can vent their fluids. It is what happens when the applied voltage sustained in the component is far beyond the capacity, electrolyte begins to boil and outgassing is a result. They also have weak points in the metal body to blow out vs explode. When a cap explodes it is more of a mess than a leak. As for this discolored area, it is not clear what is the source. It could have been beer or other foreign fluids that found its way into the amp. Take another look at this area, it may just be due to reflections if the solder mask is still shiny and it is just a photographic ghost or something the camera imaging chip picked up that is not actually there.

Also, the thick trace that couples the cathodes of the two diodes in the middle of the 6 diode array almost looks like it had lifted or separated from the board surface. If it is not a shadow and is actually lifted, that would be a heat related issue. For all I know, it could just be lighting on this image. If you used a flash, this can happen too.

As for the band, Nichicon is a good and reliable brand of capacitor if the correct part was used in that part of the circuit. Matching or exceeding the basic specifications of the original like rated hours, ripple current, voltage rating, etc.