Right hand channel output transistors BDV 65B and BDV64B shorted and took out 0.22 ohm emitter resistors which very quickly went open circuit. NOS ST brand BDV parts acquired and fitted to the dead channel, along with new 1W wirewound resistors Always wise to check output for DC offsets etc before connecting to speaker and […]
Bang and Olufsen Beomaster 5500 amplifier blown channel Read More »
This was one of the more unusual repairs (if there is such a thing) – tractor mower JCB D20/50 dead in the water, nothing working, was playing up but now doesn’t do anything, main pc board module failure suspected. Was potted in silicone, so scraped off the bottom (came away quite easily as the whole
JCB/Countax D20-50 lawnmower main pcb/computer module Read More »
This lovely example of 70’s Japanese workmanship came in with no output. Turns out +57V and -57V rail rectifiers (double-diodes D501 and D502) one had gone short circuit, and taken out both 2.2 ohm R501/R502 1/8W fusible resistors. As these were now unobtainium (CO8P-1 and CO8P-1R) they were temporarily replaced with 1/8W and couple of
Technics SU-3500 powers up but no output Read More »
Customer asked to check state of valves in case they needed replacement and a quick check over everything else, plus a rattle… Very impressed by the build quality: Valves recommended to be replaced after 5000 hours use, am seeing no degradation or need to change at this stage: However a couple of minor issues were
Avalon VT737SP valve compressor checkup/service Read More »
No power, fuse blown, found mosfet switching transistor shorted in PSU section, perhaps due to a power spike, and usually other stuff blows, but could be lucky and only be that… Mosfet (STB36NM60ND) was a pig to get out as not much space and the heatsink soldered to the board, but a combination of hot
Peavey Mini Max class D bass amp dead Read More »
Dishwasher was not heating up, element had continuity and relay was clicking but no power getting to element. Relay contacts worn out: Replacement Omron relay ordered and fitted Then after replacing the board back in the machine to test, discovered the ULN2003A IC had subsequently failed, so this was also replaced and everything back in
Baumatic dishwasher not heating Read More »
Intermittent crackling noise – which proved to be quite elusive… There was some aluminium shielding tape which exhibited a little noise when amp module was moved slightly, so made a better connection to that, also found a dry solder joint and replaced NE5532 op-amp. And whilst in there, gave all the sliders and pots a
Dynacord BS412 Bass Amp Read More »
