Customer had this unit stored away for years and wanted to use it again, but found it wasn’t working properly, making an awful buzzing sound.
This Akai 4000DS MkII is a nice machine but in a bit of a state perhaps was in a damp area, had to clean a good portion of switches (particularly the head tape selector above the head block) and things just to get a bit of sense out of it (otherwise awful noise and no sensible output of either channel).
Clearly needs a good mechanical overhaul (dried up sticky grease removal and relubrication etc) and a few bad transistors replacing which was suspected to be causing the remaining buzzing noise on the left channel.
Pinch roller has some chunks out of it (quite odd, almost like it was left in play against the capstan, however only the areas above/below the central 1/4″ tape path!) – it may be substantially ok, can’t tell until after putting a tape on. May get away with the existing belts too.
Old sticky grease cleaned up and replaced with SuperLube synthetic grease with PTFE:
Idlers removed, cleaned and lubricated
Capstan and pinch roller bearings oiled Mobil DTE light, sticky tape auto shutoff lever stripped of old grease, lubricated and refitted
Once mechanically sound (the cleaned-up chunky pinch roller was actually ok, no adverse effect!), attention was moved to the electronics – found bad 2SC458 transistors on the preamp board (notorious for oxidation-related noise problems) – only 2 measured bad causing the noise, but replaced all 6 anyway with KSC1815.
Then all adjustments/alignments were then made according to service manual, (clutch tension, pinch wheel pressure, head adjustments, speed checked, freq. response, SNR, PB amp levels, EQ, Recording Bias, amp levels etc)
Wow and flutter and THD within spec.
Capstan belt still very good condition but replaced counter belt. Gave the unit a cleaning and polish and looking good!
Final test, all good and customer very happy it was brought back from the dead 🙂