Here’s some photo’s from a recent repair of a VOX Night Train amplifier.

The amplifier was producing no sound.

Curiously the HT voltage on the first pre-amp valve was only 95 VDC, way below spec.

I removed the valves and the HT on the first valve stage was still only 95 VDC. On further investigation I found that there was only 10k of resistance from the HT to ground on the first valve, ie something was shorting to ground.

Finding the problem was an interesting exercise.

The filter cap was removed, tested and given a clean bill of health.

I then traced the HT circuit around the PCB, NOT helped by the brown gunge liberally spread over the board.

After mucho careful scraping I found resistors R23 and R24, which lie over a PCB track with HT on it.

On lifting these resistors from the board, the resistance to ground was unmeasurable, and of further inspection, you could see that there was a short between R24 and the PCB track underneath.

I replaced R23 and R24 with 1W MF resistors (all I had in the relevant values), and stood them off from the PCM trace to avoid any arcing/ shorting in future.

Here are some photos from the inside of a Peavey Classic 30 that I recently repaired.

The amp was brought in making a ton of crackling noises and was cutting out intermittently.

It had been looked at previously by someone who had concluded that the PCB had absorbed moisture (not possible), and had tried to cure this problem by removing the PCB and baking it for 5 hours! Suffice to can this didn’t cure the problem.

Anyhow, looking at the inside of the Classic 30 we can see why many techs don’t like working on them. The PCB snaps into 3 sections that are folded around, with the pots and jacks connected to the top panel and the valve sockets on the bottom.

Worse the 3 sections are connected together with jumper wires.

To change a component on the board requires that the board is removed from the chassis, and unfolded. Once the repair has been performed the PCB is refold around and inserted into the chassis. This is quite an involved process and each time you unfold the refold the PCB assembly you risk breaking the links or their solder joints.

Not a great design, although I expect this was the only way the amp can be as compact, and in their favour Peavey amps do seem to be pretty reliable.

Anyhow, on removal of the PCB I found a couple of dry joints and a broken wire link.

Dry Joint 1.

Dry joint 2.

Broken wire link.

I resoldered the joints , replaced the wire link and this cured the problems when the amp was reassembled.