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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 7th Dec 2021, 3:53 pm   #1
OldTechFan96
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Default Sanyo Cassette Deck Trouble

I'm busy working on a Sanyo cassette mechanism from a mid '70s music centre and I'm having a few issues.

I have done all of the usual deck servicing, cleaning rubber parts etc. The original drive belt was 'boiled' in the microwave and refitted. With the boiled belt installed, there was not enough torque for the deck to function properly.

I bought a variety pack of belts and fitted a suitable one. PB, FF and RW did work, but were not perfect.

I timed how long it took for the deck to FF and RW a standard TKD D90 tape.

FF to the end: 4:48. Around about the 3 minute mark the deck had slowed and started to 'chug' (a sort of stop, start movement).

RW to the beginning: 3:15. This time seems slow to me but the the speed of the RW was consistent and did nit bog down.

During normal playback, the tape eventually slows and stops when the tape is nearly finished.

Does the above suggest that there is not enough torque, even with the new belt? Maybe the the voltage supplied to the motor/deck is too low? I think the motor is fed via a voltage regulator.

Any thoughts would be much appreciated!
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Old 8th Dec 2021, 7:35 am   #2
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Default Re: Sanyo Cassette Deck Trouble

I can't give specifics but I would place the deck in FF with no cassette inserted and check that the supply spool brake is fully released (supply spool free to spin).

For playback slowing again check to see if there could be brake issues and/or excessive back tension. Again make sure the supply spool is not tight. Back tension means it will not free spin, that is normal and correct, but it should not be tight.

The motor actually looks like it might be an old mechanical governor type with little bob weights (unless you know differently) fitted internally to break the current flow into the windings when correct speed is reached. These often had tremendous torque compared to the weedy transistor regulated variety that became the norm.

If it is electronically regulated then you need to do the usual sort of checks. You should feel the motor 'maintain speed' if you lightly load the pulley with a finger.
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Old 8th Dec 2021, 12:12 pm   #3
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Default Re: Sanyo Cassette Deck Trouble

Morning Mooly,

Both spools spin freely and are not hindered by the brake.

When the spools are touched during PB, FF or RW, they stop instantly. If I pinch the motor pulley it also stops straight away. The motor seems to provide little torque.

The motor is electronically governed. Removing the cap around the motor reveals a two transistor circuit that connects to the speed adjust pot.

I wonder I this is a voltage issue?

Pin 3 on connector CP8 supplies a voltage to the deck motor. With the connector removed 9.8V was measured on pin 3. This later fell to 9.65V. The voltage for the motor is supplied via a mains transformer secondary, so I'll have a look at that.

I'm not sure if this is a 9V or 12V motor. I can't see an info sticker. 53.12.8 and 70351-0 is stamped on the motor housing. I suppose the 12 could be a clue.

The service manual does not tell me anything useful.
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Old 8th Dec 2021, 12:27 pm   #4
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Default Re: Sanyo Cassette Deck Trouble

If the motor will not withstand even light finger touching on the rotating pulley then it is suspect.

Trace the motor wires back and measure the supply voltage on and off load.

These motors with a simple transistor regulator work on back emf and a simple feedback system. It is effective within limits and you should certainly 'feel' the motor pulley trying to maintain speed as you add a little finger friction to it.

These things used to be pretty universal and cost a couple of pounds. CW or CCW (clockwise/counter clockwise) and 6, 9, and 12 volt type. Standard fittings and I think from memory 2400 rpm.
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Old 8th Dec 2021, 1:11 pm   #5
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Default Re: Sanyo Cassette Deck Trouble

I've been doing some load/off load measurements (from pin 3 of CP8) and I suspect that that the motor regulation has failed.

Off load the motor is supplied with 9.5V. When any of the functions are selected the voltage drops as low as 7V. With a cassette installed the voltage drops as low as 6.7V. RW is responsible for the biggest drop.

I'll remove the motor and see what can be done.
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Old 8th Dec 2021, 2:29 pm   #6
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Default Re: Sanyo Cassette Deck Trouble

Forget that... let me look again
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Old 8th Dec 2021, 2:32 pm   #7
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Default Re: Sanyo Cassette Deck Trouble

I've removed the cassette motor and have been testing it with a bench top PSU. I gave the speed adjust pot a small squirt of switch cleaner.

Out of circuit, the motor has plenty of torque when pinched.

The PSU has been connected to the input to the regulator circuit and I have connected a DMM across the output. The output of the regulator connects directly to motor.

With no load the regulator provides 3.88V to the motor. When a load (finger pressure) is applied to the motor the voltage supplied to the motor increases. The greater the load, the higher the voltage supplied to the motor.

The above, to me, suggests that the regulator is working as it should.

Am I right here?
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Old 8th Dec 2021, 2:33 pm   #8
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Default Re: Sanyo Cassette Deck Trouble

Me going cross eyed... it was the pin 3 of CP8 bit.

Check C102 by substitution. Bridging with another is fine. You can get an idea of motor current by measuring the voltage across the 10 ohm under load.
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Old 8th Dec 2021, 2:36 pm   #9
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Default Re: Sanyo Cassette Deck Trouble

What you are measuring sounds correct. The motor voltage as measured across the commutator will increase with loading.

C102 could be favourite and less likely, the half wave rectifier D101. Make sure the 10 ohm is good.
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Old 8th Dec 2021, 4:39 pm   #10
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Default Re: Sanyo Cassette Deck Trouble

Check and double check the obvious things.
Is that counter belt loose? It should be, yours looks quite tight.
Roughen up the contact surface of the spooling idler tyre.
Drop of light oil on spool/spindle shafts and motor top bearing.
Check replacement main belt is thick enough, ISTR 1.2 x 1.2mm. And above all, not too tight.

I have service several of these Sanyos, they used the same mech in dozens of music centres. Usually the above gets them going.
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Old 8th Dec 2021, 7:31 pm   #11
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Default Re: Sanyo Cassette Deck Trouble

I've removed the counter belt and so far, everything is working as it should! PB, FF and RW work at a consistent speed with no chugging.

Auto stop is working on PB. I don't think this deck supports auto stop on FF and RW. The manual only mentions auto stop in the context of PB.

The time to FF and RW a C90 tape is now down to about 2:30 a side. How long should this take?

I'll install a more suitable belt soon.

Thanks to Mooly and Ben for the help!
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Old 8th Dec 2021, 8:27 pm   #12
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Default Re: Sanyo Cassette Deck Trouble

Pleased to hear its getting there I'm not sure how long it should take tbh and I can't remember now what an average sort of speed was on the decks I've had. It sounds a little on the slow side but then again maybe not...

https://www.youtube.com/watch?v=h-GcJk91lr8
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Old 8th Dec 2021, 9:31 pm   #13
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Default Re: Sanyo Cassette Deck Trouble

I have reinstalled the original counter belt and things are working as they should.

Looking online, 1:30 crops up a few times.

The next test would be to check the record function.
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Old 9th Dec 2021, 9:54 am   #14
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Default Re: Sanyo Cassette Deck Trouble

Great news!
Have you also lubricated the spool tables and motor? This is important if you want to improve rewind, etc.
Also roughen up the take up spool table's rubber rim.

These are fairly crude mechs, so no autostop in rewind, and no locking FF.
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Old 9th Dec 2021, 7:16 pm   #15
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Default Re: Sanyo Cassette Deck Trouble

I've been able to lubricate both spools and the top bearing of the motor. The take up spool was removed and I was able chuck it in a drill. I lightly smoothed it over with 3000 grit paper and a spray of platenclene. All of the other rubber parts were in good order after a clean up with a cotton swap and plattenclene.

The pinch roller worked fine, despite being shiny. This was treated with 400 grit paper and platenclene.

The auto stop was a little bit intermittent. After a slight adjustment the AS worked 25/25 times with four different tapes.

PB seems to work as it should. I have spent very little time listening to cassettes which means I am not too sure what to expect quality wise. In fact, I have probably spent more time working on decks than listening to them!

The deck is back in its cabinet. I'll test the record side of things later with some Poundland tapes I bought in 2016. They are the only blanks I have.
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Old 10th Dec 2021, 12:06 am   #16
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Default Re: Sanyo Cassette Deck Trouble

OK.
Don't expect much from the poundland tapes, any tape of that late era is likely very poor. There was a discussion on this somewhere.
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