Blues Jr tube-board fix with epoxy

[nuke]

The world is awash in Blues Juniors, and many of them are broken.

The most common failure is the tube socket board, broken traces on the EL84 sockets. The factory board is a cheap piece of single-sided junk. The amp is fabricated as a single board, then the speaker jack and tube socket board snaps off and it all goes into the chassis.

The most common thing I see is mechanical failure of the board. Three pins of an EL-84 are "no-connects" and Fender put the tiniest of donut-pad lands on the board to hold these three pins. Look at the board, wiggle the EL84 and you'll almost always see the 3 no-connect pins wiggling loose, broken away from the PCB.

That's one-third of the mechanical strength gone, and pretty soon, the plate and screen break away too.

There are aftermarket replacement tube socket boards, and they're better, double-sided and plated through-hole. If the board is a mess, just replace it.

However, if you catch it early, and no one has been there to slag solder all over the broken traces, there is a fix that appears to last a long time.

I desolder and clean out the three NC pins, clean them thoroughly, and fill the hole and epoxy the no-connect pins to the board. This provides a lot of mechanical stability to the socket, preventing further damage to the active traces. If there is any wiggle on any of the active pins, run a #22-AWG solid jumper into the pin's hole and back to the ribbon cable.

Here's a typical situation, wiggling the tube reveals the three no-connect solder boards were completely detached from the board. The plate pin solder pad is partially broken away on both tubes (between two NC pins) and solder cracks are evident on the other pins.

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The sockets are desoldered showing the no-connect donuts were completely loose. I don't normally completely desolder, but did for the photos. I use a Hakko 808 desoldering tool, electric vacuum pump on a trigger. Makes fast work of desoldering circuit boards.

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After fully cleaning the board, 5-minute epoxy is introduced into the holes for the no-connect pins, worked in to just fill the hole and secure the pin to the circuit board. Use just enough to secure the pin, don't get it into the socket itself.

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Repair the fractured foils with a jumper wire after the epoxy is set. Insert the solid wire into the hole with the pin, then solder it securely. I like to use a little mildly-activated flux on the socket pins to be sure they wet up with the solder.

Be sure to thoroughly clean the PCB of rosin. High-voltage circuits must be scrupulously clean.

I've found this fix to hold up well for the long term. I can't say I ever see the Belton sockets fail, just the solder/foil coming loose. It is a bit radical to permanently glue a socket in. You needed to change the socket later, snip the three epoxied pins off, unsolder the rest and drill the glue out. Bt you should probably just change the board at that point to a better one.