Uher CR240 play problem

[cassetter]

Hi - I have a Uher CR240 which has a problem that when I press PLAY, plays for 2 seconds and then stops. The cassette will continue playing if I hold the PLAY switch in the right position.

What I assume is a linked issue is that the fast forward and rewind only function for approximately 2 seconds unless I hold the PLAY switch to the right also.

Has anyone seen this behaviour before? I am thinking it may be something to do with the mechanism that checks for a stopped tape or maybe an electrical component issue with the circuit on the ‘toggle’ PLAY switch

[Nickthedentist]

Hello and welcome.

It sounds like the automatic stop is being triggered.

This thread may help: https://www.vintage-radio.net/forum/showthread.php?t=190776

[Uncle Bulgaria]

Welcome! I second Nickthedentist. In this instance, it sounds as though the belts are OK, or at least working enough to play when the joystick is held.

Is it new to you? Have you had it working before? Was there anything that happened to cause this new behaviour?

There are several variants of auto-stop on these, depending on when it was made. My surmise is that you have one with strobed clutch wheels like the attached, which rely on reflected light being detected in pulses. The picture's from a CR 210, but the parts are the same. If the photodetector is not illuminated, the machine thinks the reels are not rotating, therefore it's the end of the reel, and it stops the tape. Any problems in this area will result in the symptoms you describe.

If you remove the clear plastic access panel on the top of the case, above the cassette well, you will be able to peer in and see whether you have the strobed reels. What is the serial number?

How competent are you feeling? Have you done things like this before? What equipment do you have? Uhers are well made and nicely put together, but these machines fit so much into a small space that they have an awful lot of tiny, solid core wires which are very easy to fracture (ask me how I know...)

[cassetter]

Hi - thanks for the posts. I have been away and unable to check the reels until recently. They are not the strobed type, but they are rotating when I turn the machine on. I replaced the belts a few years ago and they appear to be OK - it does play when I hold the 3-way switch in ‘start’.

Do you know how the auto-stop works on my machine?

The serial number is: 1624 022330

I am fairly competent - not so good on modern ICs so small you cannot see them, but the Uher is more traditional components!

[Uncle Bulgaria]

I'm sorry - I didn't get notified about this post. My guess is that you have the Hall effect sensor on the take-up clutch. See DMcMahon's photo in post #17 of the thread linked above. It's the sensor reading the thick grey collar around the spindle. I've had a quick look at a couple of my CR 240s and 1624 008922 has a strobed wheel, while 1624 019614 has a Hall effect sensor. Compare with the PDF circuit diagram I got from somewhere online where the earlier board 800 has been crossed out and the updated circuit drawn in.

Take the top off and it's easy to see what's happening by making the machine think a cassette is inserted as per the attached snips from the service manual.

[Michael Maurice]

You have to see what is happening at MP1. You will need a scope for that. you need to check for pulses at that point, rotating the reel by hand should be enough to get the pulses. I'm in London if you need help.