Blaupunkt CR-4096 AM/FM/Cassette playing speed too fast

[jcoda95]

I have a Blaupunkt CR-4096 am/fm/cassette radio from the 70's.  Everything works except the cassette motor is playing the cassettes too fast.  I've opened up the unit looking for a potentiometer and no luck.  There are four pots on the back, but when tweaked don't adjust the speed.

Anybody have any thoughts on how to adjust the speed of the motor?

Thanks,
Jeff

[Zoli]

Given the age of the unit, the motor most likely has centrifugal speed control(internal to the motor) with stuck contacts.
For more/better help, try Tapeheads.

[jcoda95]

Thanks. I appreciate the guidance.

[David_AVD]

Something else to check is that the pinch roller is really in proper contact with the capstan shaft. If not, the take-up reel might be just pulling the tape through as fast as it can manage.

[jcoda95]

Can the pinch roller be adjusted by any of the four pots on the back of the unit?

So far have not been able to find a service manual?

Thanks for the help,
Jeff

[floobydust]

Some cassette motors have a built-in electronic speed regulator. Some are external power transistor/board and extra wires for the tach.
Look very very closely at the back of the motor, in the holes and see what they are about. Sometimes there is an adjustment trimpot.
With the older centrifugal weights speed regulators contacts can get stuck. I'm suspicious there are no capacitors outside this motor.

You can measure the motor speed or listen if it changes with a change of say 12-14V power, that will tell you if it is just regulating fast, or no regulation at all. I have taken motors apart and done surgery when desperate.

I am finding those grey electrolytic capacitors are drying up as well, so make sure the motor has clean power.

[jcoda95]

Appreciate the info. This gives me some add’l direction on what to check out.

Thank you,
Jeff

[Uunoctium]

tl;dr


https://www.ebay.de/itm/115734307368?

[jcoda95]

I just purchased this!  Thank you for sending this link. The overall response from you and the other members has been extremely helpful. Very happy to have found this blog.

[jcoda95]

Any thoughts on finding belts for this model!

[Uunoctium]

this chinese seller offers a lot of pinch rollers and transmission belts for cassette decks. Packed in lots of 50 or 90 pcs with different diameters
https://www.ebay.de/str/chocalaestore

[Stray Electron]

  At one time there was a series of radio repair manuals that were being printed for repair shops by the name of Sam's Photo Facts or something close to that.  Each book typically covered about five models and there were hundreds of volumes published.  There is a very good chance that one of the volumes covers your model.  Do some looking around on the net and see what you can find.

   FWIW about fifteen years ago I passed up a set of about 170 the books because they would have literally filled up a closet! 

[bostonman]

A 70s cassette that plays too fast? You got quite lucky because I had a car that was five-years-old and it played fast.

I brought it to one or two repair places, but they never fixed it. Eventually I upgraded the stereo system so the issue never got resolved.

[floobydust]

OP, you know the little circuit board the motor connects to, is the speed controller. I don't see a tachogen for feedback so it must be motor back-EMF?
The board has a trimpot to adjust motor speed. But if yours is way fast then the power transistor could have shorted.

How I used to calibrate speed, is record a test tone say 10kHz on a cassette deck that I know has correct speed, musicians can tell right away if pitch is off.
Then put the cassette in the deck and adjust speed until a freq. counter reads correctly.

[Jeff eelcr]

Belts, PRB Projejtor Recorder Belt Co.
SAMS Photofacts, AR Radio Series.
Jeff

[FIXITNOW2003]

the 4 adjusters on the back are ferrite cores for radio alignment , often there was a small hole in top off motor with a speed adjuster bellow

[jcoda95]

I have made a speed adjustment using that pot. Not much left to adjust further.

There was a link on this thread for a NOS motor, , but it was the wrong part.

Looking for a cross ref for an alt motor if it exists.

I’ve slowed it down by ear and now hear wow and flutter.

I have a new belt coming, so we’ll see if that resolves things.

Thanks,
Jeff

[David_AVD]

If the speed can still be adjusted, it's unlikely that the motor is faulty.

The fast speed could be a mechanical issue, hence my suggestion to check the pinch roller is actually engaging fully.

It could also be the belt riding up on the edge it the motor pulley instead of being in the middle, or residue from an old belt wrapped around it (increasing the effective diameter), etc.

[jcoda95]

Good info.  Once the new belt arrives, I'll see what that reveals.

Thanks,
J

[tunk]

No experience with this, but could it possibly be a bad solder joint or a damaged resistor?

[jcoda95]

Appreciate the info.

Thanks