Fender DSP 90, champion 110 and similar

Nice little budget amps with a range of built in effects.  Seem to suffer from intermittent sound loss and cutting out.   The PCB are plagued with bad joints around ribbon cables, regulator  U10, and although I have not seen it the numerous large resistors and caps.

Also recently saw one making g a terrible humming or buzzing noise.  No signal was coming through at all. Current draw on the amp was about right so quickly able to link to open circuit power supply filter capacitors. Replaced, resoldered and glued into position and amp will be good as gold for another ten years minimum.

Fender Deluxe Reverb

My friend Roger’s lovely 1972 Fender DR suffering with smoking front panel looking like a scene out of spinal tap.

Took it apart, powered it on and . . . all fine.  So what’s  the problem – nothing, it’s fine.  Left it on for a while – then fireworks. Bang . .  .Bang – bits of electrolytic capacitor all over the place and that curious, quite pleasant smell.

So replaced the caps, and with a meter measured the anode HT voltage, I got worried.  Those caps are rated at 500v but the HT is way higher, more like 560vdc – how can this be – is it normal?

So, after a bit more research I reckoned that the rectifier tube could be gone, or breaking down.  Replaced it and watched the anode voltage carefully as it was wound up on the variac – this time with protective glasses.

The voltage is still high, think about 520vdc, but Fender Deluxe reverb’s do run hot.  I regret not choosing 600vdc caps as they are just as easy to get hold of. However once the amp is being played the power supply sag will lower the HT voltage to perhaps lower than the rating of the caps.  If so all well and good. The amp has been giggied a  few times since being fixed and is running well.  It sounds absolutely awesome really clean, sounds like a bell and very detailed.  I do think that Fender might make the best amps.

Moral of the story – play safe on cap voltage.