Sony TC161-SD Motor Run Cap
 

Dear All,

I would be grateful for a bit of advice about a motor run cap on a Sony TC161SD cassette deck.

The cap is a dual capacitance component (0,6uF and 0,4uF) switched by an internal 50/60Hz rocker switch. At the 50Hz setting the two capacitances are connected in parallel.

My motor is running slow (about one tone in pitch) and I suspect the run cap, having read various helpful threads on this forum. The belts are new.

My best guess (using a variety of meters) is that capacitance is between 20% and 30% high. ESR readings look OK.

Is this enough to cause a very slight speed reduction and sluggish rw/ff function? Or should I look elsewhere?

Thanks for any advice.

Re: Sony TC161-SD Motor Run Cap
 

There's no harm in trying a new one, they cost very little, maybe a few pounds.

Re: Sony TC161-SD Motor Run Cap
 

I would look at the belts..

Re: Sony TC161-SD Motor Run Cap
 

Assuming you are only going to use it on 50Hz you could save a bit by just getting a 1uF Run capacitor and fitting it in the 50Hz position and remove the 2 old capacitors.

Cannot easily find a schematic but wondering if it has electronic speed control with adjustable capstan speed.

David

Re: Sony TC161-SD Motor Run Cap
 

Thanks, all.

David, unfortunately there is no speed control. Speed is derived from 50/60Hz.

So, would this do the trick?

http://www.capacitorc.com/uploads/CBB61.pdf

Described as a 450 VAC motor run cap and readily available.

Re: Sony TC161-SD Motor Run Cap
 

You say the belts are new, but are they a bit tight. That can be a cause of running slow.
Might also be in need of lubrication on pulleys/motor etc.

Re: Sony TC161-SD Motor Run Cap
 

I have used the CBB61 Motor Run capacitors, they are good.

Re: Sony TC161-SD Motor Run Cap
 

Thanks,

I see that standard tolerance for motor caps seems to be ±5% which suggests that my presumed +20% to +30% readings might be a problem.

Kemet do a 1uF C87 series motor run cap that is a perfect fit and I can do away with the internal frequency switch wiring and just run on 50Hz.

Looks like it would outlast the Chinesium CBB61 by miles.

The belts, as far as I can tell, are correctly tensioned, but I might try a few drops of sewing machine oil into the motor.

Re: Sony TC161-SD Motor Run Cap
 

By replacing the motor run cap, I was able to improve the playback speed but it's still half a tone flat on commercially recorded tapes rather than a whole tone. Unfortunately, I have perfect pitch, so that won't do.

The aluminium Kemet version wouldn't fit, so I went with the CBB61 1uF device as recommended by David. Capacitance was well within 5% of its stated value.

As the motor sits across the mains supply, there's no provision for speed adjustment.

The belts are new and not overly tight, so I can only think that the motor/pulleys need lubrication.

Re: Sony TC161-SD Motor Run Cap
 

Given that you are sensitive to deviations from absolute pitch, you might be better served by a cassette player with the variable speed feature. The recordings themselves played back at exactly 1.875 inches per second are not guaranteed to play at exact concert pitch, or the pitch at which the music was performed.

Re: Sony TC161-SD Motor Run Cap
 

Maybe it is worth measuring the time for a fixed length of tape to be processed, so the speed can be calculated? If it is not correct, maybe the factor it is out will be significant, highlighting the issue?

Re: Sony TC161-SD Motor Run Cap
 

In this case it's not simply whether the Sony is running at the correct speed but the fact that the owner has "perfect pitch". Some musicians have excellent pitch memory. Recordings played off speed can annoy them.

When a cassette was recorded off speed/off pitch, it will be off when played at the correct speed but will sound correct when played at the same (incorrect) speed at which it was recorded. Many better quality reel to reel and cassette decks have a variable speed control on the front panel.

Re: Sony TC161-SD Motor Run Cap
 

A semitone is 6%, well out of tolerance for a decent pre-rec on a high quality deck, I'd have said. I think there's some drag somewhere...

Re: Sony TC161-SD Motor Run Cap
 

I'd agree - worth checking if any brake bands are being released / held off correctly - springs can lose tension over time .

From memory , wasn't the 161 SD a dual capstan deck , with one capstan slightly bigger than the other to tension the tapes across the heads ? maybe I'm thinking of a different machine .

I have a TC-209SD here which has been in storage for many years - the capstan is seized , so that although the motor turns valiantly , nothing happens - I need to strip down , clean , lube - when I get around to it !

Re: Sony TC161-SD Motor Run Cap
 

Gents,

Thanks for taking the time to reply.

One side of a TDK C90 tape took exactly 51 mins to get to the end of the reel, so even allowing for more than the nominal amount of tape, that's out of tolerance by some margin.

I will dive back in and check the brake band and anything that may be slowing it down.

Derek - it is a dual capstan deck with one capstan slightly larger than the other. I presume they're in the right configuration!

Re: Sony TC161-SD Motor Run Cap
 

Yes dual capstan. I have one but from memory it has a fair bit of hum in the audio playback which seems to be a design issue. It was probably more prevalent in these early decks using an AC motor too close to the playback head. With mine I considered modding by adding mumetal shielding around the motor but as these motors tend to run fairly hot and need their own cooling fan the idea of restricting the cooling seemed risky. So there it sits in the cupboard...

Re: Sony TC161-SD Motor Run Cap
 

If they were the wrong way round ( should be the one on the right , next to take up spool that has the larger diameter ) then more tape would be fed in than taken out and you would end up with some slack .