K-960 cassette deck knocking sound issue

[bennybee]

Hi, I got this deck for its dbx capability which my K-950 (alas sold long ago) didn't have. The seller replaced the capstan belt, but after receiving it I soon ran into FF and REW problems, so I replaced the idler tyre. After that I happily closed the deck only to discover that the machine often suddenly stopped in Play mode, piling up tape behind the cassette window because the capstan (of course) kept turning. Flexing the left side board (power & control print?) caused interruptions of the power to the reel motor. After (long) investigation I found several bad contacts where the legs of some components moved up and down in their print holes. Repaired that and now the deck runs solid, but there's a faint, dull knocking sound approx. every 2 seconds in Play mode, which resonates inside the unit when thevolume is turned down. Can't be the motor I guess, maybe related to the counter? Any ideas please?

 

[clinic-audio]

Hello
Did you check every capacitors on the board (vertically ) on the left side of the unit ? I have refixed plenty of those and own a lot today
Do you have service manual ?

 

[bennybee]

hi Clinic, thx for yr reply. Yes, I replaced a few caps which were obviously leaking or ad corroded legs. There were also a couple of leaking caps on the main board in the 'power supply' section near the left edge of the print.
I tested some more this morning and found that the sound appears to be coming from the right spindle , and every now and then the hesitating knocking sound is preceded by a faint zipping squeekie. The 'knock' sounds like missing/skipping a tooth on a cog and can be felt with the fingertip on the tip of the right spindle. There is no knock in Play mode without cassette, nor in FF mode.
Leaving the machine in Play mode with cassette for a while, eveything goes quiet after a few minutes though.
I don't have the SM and I am no technician... so any help is ver appreciated. thanks.