Customer said their LK-1 “wasn’t behaving right” (pops/clicks between channels) so asked me to take a look.
Several faults found (including some not noticed/mentioned by customer) on preamp board, including dead BC212L transistor shorted in the MC input (LH channel dead/buzzing), a faulty analogue switch IC DG309CJ causing popping switching to/from tuner input amongst other issues:
Replaced a couple of green LEDs on front panel (one leaky, causing crosstalk with TP2 channel – oddly, as is involved in the analogue switching circuitry) – I’d had a bag of these tiny ‘SMD’ style LEDs from Greenweld surplus about 30 years ago thankfully, a perfect drop-in replacement!
Found all the 22uF 50v caps were bad, so those were also scheduled for replacement:
Front panel NiCd backup battery was just about starting to leak, so replaced with holder and CR2032 protected against charging with a small diode, and service reliability modifications performed according to manual:
DG309CJ’s socketed, awaiting replacement:
Then onto the LK-2 power amp of which there were a few service updates and some obvious component replacement needed :
New power resistors fitted per service manual (and couple of bulging caps replaced, along with some more 22uf 50v casualties – must have been a ‘bad batch’):
Repeated same for the other channel.
All tested fine now, fully restored and lovely working order ready to give another 40 years’ service. 🙂
Bag-o-bits – expired parts from power amp and preamp, and its front panel:
