Agressive glue should positively be avoided.
I read that vintage amps from Sansui suffer from such a case.
Contemporary PCB makers suggest neutral silicon, because it exudes no "dangerous" compositions.

I have used SMP glues (sylyl modified polymers) that exsude alcohol (ethanol or methyl) upon curing.
The companies seemingly like to shroud their compositions in mystery, so we might meet anything like "silane-modified polymers, modified-silane polymers, MS polymers, silane-terminated polymers (STP), MS Hybrid, Hybrid, Polyoxypropylene, or "silane terminated polyether (STPE)" . These might work.

Exact product names are futile because every country has their own.

A sure sign is that the glue needs moisture to cure.
SMPs tack like hell and stay flexible.

I do add strain relief, even if I don't carry the gear around, because I permanently refine my gear, although for my purposes I have found better ways than glueing.

Last day I had to repair an amp, and many companies use this stiff ribbon cable. If you flex them often enough, they break. If you anticipate extensive problem locating sessions, then glueing may be a wise thing.

I have read some threads, and people indeed use silicon glue & sealant for that purpose, however, stock household silicon exudes acetic acid, which can become a problem soon. There is a "neutral curing" silicon, preferably exuding alcohols, that is used for electronics.

Silicons have the disadvantage of, once opened, curing in the dispenser quickly, so when you want to use it a few weeks later, its cured...

I've got a squealing issue in a 76 deuce 240t. It only happens when plugged into the series input. When the gain is turned up past 7 or 8 on the normal channel the amp begins to squeal. It does this regardless of the gain setting on the effects channel. The gain can even be turned all the way off on the effects channel and as soon as you go past 7 or 8 on the gain on the normal channel, the squealing starts. Also, the guitar volume has to be on 10 for the squeal to happen. It also does this even when the amp is in standby mode because I can see the squeal on the scope when the amp is in standby which makes me think its isolated to the preamp of the normal channel. The squeal is also showing up in the effects channel with the gain all the way off for that channel. But if there was an issue with a component causing squeal in the normal channel preamp, why wouldn't the same problem show up when plugged into the normal input, as I stated it only squeals in the series input. I've checked voltages on all the transistors and everything is close to the schematic. Anyone have any ideas?

Quote from: aquataur on April 17, 2026, 04:33:06 AMIn older SS amplifiers, particularly Hi-Fi units, but also instrumental amps, they used to glue large components with some white-ish glue, very flexible, tacking like hell. Also, wires were glued to the PCB where the joined the PCB, for a strain relieve. It does not look like hot melt glue.

I could never find out what this was.
Sometimes you have to replace a worn-out cap. It is not easy to remove the glue, but it appears not so easy to find a comparable glue to secure it again too.

How do you guys do that?

Honestly, I never add strain relief glue because I don't gig my gear or ship it to customers since it is just for me.  If I were to add glue, I would probably use silicone - same stuff you use for sealing around bathtubs etc.  It is normally good for up to 400F (verify on the tube you are buying), sets up fairly quickly, lasts practically forever, and is very strong.

Unsure what was used at the factory though - but I do know the stuff you are talking about and am curious myself if anyone happens to know.

In older SS amplifiers, particularly Hi-Fi units, but also instrumental amps, they used to glue large components with some white-ish glue, very flexible, tacking like hell. Also, wires were glued to the PCB where the joined the PCB, for a strain relieve. It does not look like hot melt glue.

I could never find out what this was.
Sometimes you have to replace a worn-out cap. It is not easy to remove the glue, but it appears not so easy to find a comparable glue to secure it again too.

How do you guys do that?

Where did you measure the 8V?  The 30V should go to pin8 of the op amp.  As you mentioned, if the op amp was only getting 8V I don't think you would hear the tank output but I guess it's possible.
Like Phatt said, check the resistance at the input jack of the reverb tank.  Broken wires inside the tank are the most common cause of reverb issues, especially when the amp gets tossed around/abuse.

Any kind of ground issue or ground loop will give you 50Hz hum, so a poor ground scheme could also be the source of your hum.

It looks like D10 is a 30V 500mW zener, RD-30EB

Just think of it as a 2 ohm speaker in series with a 4 ohm speaker. 2 ohms will increase the output wattage. 4, 6 or 8 ohms will reduce overall wattage. I guess you could throw a crossover into the mix and use mid-high speakers to add more flavors. The idea of what it sounds like is subjective to your preference. The other factor is understanding how wattage affects each speaker or sets of speakers. It's best to evenly distribute the power output between speakers that have the same impedance and wattage limitations. So if you have an 100 watt amp and 2 speakers rated @ 50 watts each then you are good. Say you have one 75 watt speaker and the other is 25 watts it is not recommended. Mismatched speaker impedance can cause performance issues with the overall speaker load distribution. Any way you want to do it, it's best to balance the load across the speakers equally. I am sure there are some creative ways to do this!!

As fate would have it, I was called that part of the rehearsal space was to be cleared. I liberated the Special 212 from the bondage of those unworthy.

I found that they had no clue what to do with all the controls. Also, they have trodded over the footswitch cable, and excerted the connector to some heavy stress.

It took me a few hours to find the crack in one of the tracks.
Where are the times when connectors on amps were indestructible...

Apart from that, the interior of the amp looks very tidy, almost empty compared to what you expect by glancing at the schematic.

It would not be exactly my wettest dream to have to exchange one of the pots, but it is doable.

The 'verb pan is defective, output coil is ruptured. This is one of the accutronics that use plugs. I ordered a replacement from MOD. This is soldered.

These amps appear very rugged throughout (it is a silver stripe btw.)

I can understand that people shy away from them, because maybe one is asked to read a manual , but I dare saying that if you had to play a gig without anything else on you, having one of those amps would not be the worst thing that could happen. You'd have to harness the thing though...