Arcam_A38_Amplifier

Problem:    Current source failure, transformer failure caused by regulator
Solution:   Lots of work, replace transformer, regulator, transistors and passives
Brand: Arcam
Cost new:   £1450
Cost of fix: £30
Age: 15
Success?:   Yes

What a mammoth repair! This amplifier came into the repair cafe and was a piece of art in terms of the layout of the board!

The customer brought it in and said that they turned it on one day and heard a bang, and then refused to turn on ever again. Looking at the board there were some visible heating marks on the back of the board where something had gotten very hot. Then there were a few passives and some transistors that had popped that were part of the constant current source for the amplifier.

Annoyingly Arcam didn’t provide the schematic for this version, but I could find schematics for a previous model that had the same regions and operations as this one so that helped a lot! Turns out the 5V LDO signal that goes to the front panel to turn on the device wasn’t present, so following that back it turned out the LDO itself was dead, which had resulted in a short between the 5V and GND, causing the smaller transformer that chopped up the mains failed and blew the winding insulation! Replacing the transformer, the LDO and the diodes in that area got me 5V back!

Then it came to replacing the components that had popped in the current source and they weren’t too difficult to do. Very fiddly having to partially reverse engineer the schematic and compare against a version that was a couple of models older! A very satisfying fix resulted in this beefy amplifier getting a new life, and maybe a few more years out of it before something else goes…