7% slower speed what to do?

[xchg.ca]

Hi guys,

I have H/K CD-401 never paid attention to it's speed, but recently acquired speed test tape from duplication.ca
and turned out to be that its about 7% slower !
I used Tek 2252 scope with Frequency meter function as well as HP/Agilent 5315A Universal Counter to double check on replay frequency and I was surprised that instead of 3150Hz I was reading ~2950Hz (on both), which is about 7% slower
Tried to press pinch roller against capstan and pull it slight away to see it this has any effect on speed - it has no effect ( trying to analyze if pinch roller is bad )

Wondering if I need to replace belts or this is sight of other problem(s)?

 

[benricci]

Pop the case open and see if you can locate a small trim pot for the motor speed. If your belts are fine, this might just be an easy twist of a small flat-head screwdriver. I'm not 100% familiar with your exact model, but that's where I'd start.

 

[zedex]

If it has a sankyo transport the trim pot would be inside the motor. Small hole on the back. Make sure you use an insulated screwdriver(jewelers flat blade). Just wrap a thin strip of elec tape around the screwdriver shaft so it doesn't short on the motor housing.

 

[Bone Yard]

Feel your belt while it's open, they can get hard and slip on the pulleys.

 

[xchg.ca]

Thank you guys, Indeed it was a motor with little hole and a flap, I have ceramic screwdriver and I used it.
Thing is it is very hard to get precise, you have to do like super-duper tiny adjustment in order to get 3150..... I still can get it right, +/- 20 with just single touch on the scredriver
Belt seems to be OK

 

[zedex]

lol. yup. I let the deck run a bit and like you say the tiniest touch changes the speed. Just keep at it,and you will get it close.

 

[BilboBaggins]

Yes, that is the way to do it. In my case, I had an Aiwa M700B that was too slow even after adjusting, so with nothing to lose, I let a few drops of deoxit flow in to the pot housing and moved it back and forth. I was able to adjust my speed after.

 

[zedex]

Those pots are so sensitive,i get it close. And to get it right on i just flex the skin on my fingers while holding the screwdriver and i can get it right on the money. If i actually try turn the pot and feel it turn, its too far.