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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 25th Jul 2020, 2:54 pm   #21
DMcMahon
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Default Re: Uher CR 240 AV Cassette Recorder

Thank you for your inputs and offers of photo's etc. The bent tab I referred to in Post 2 is on the underside of the cassette lift/carrier, when I refitted it, it checked out OK so I did not attempt to straighten it.

From your photo my top piece does indeed look bent, will look at this a little later.

One other thing that improved after refitting the cassette lift (apart from getting correct retraction of heads when cassette goes down) is that when cassette is pushed in around 3/4 it now correctly is mechanically pulled in fully, before one had to fully push in it manually.

Have just connected up an external power supply (the Farnell 30/2 I recently purchased from westcliffe) but very disappointingly the CR 240 is still dead (external PSU is good) so more fault finding required. This is not the easiest of units to work on.

David

Last edited by DMcMahon; 25th Jul 2020 at 3:03 pm.
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Old 25th Jul 2020, 3:03 pm   #22
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Default Re: Uher CR 240 AV Cassette Recorder

Quote:
Originally Posted by Uncle Bulgaria View Post

the yellowish passivated part shouldn't interfere with the cassette.
I noticed during my work on replacing the belts that there is a spring on the top right front of my cassette lift (in photos 2 and 3 of Post 2) but in the Service manual the spring is shown fitted on the right side of the cassette lift, i.e. not at the top.

Do not think too important as should do the dame job in either position, I can see on my lift, a hole and indentation where spring should fit as per drawing.

I see on your photo there is no spring at the top so I guess yours is in correct location on the right hand side.

David
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Old 25th Jul 2020, 3:12 pm   #23
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Default Re: Uher CR 240 AV Cassette Recorder

Great! That over-cam spring device on the cassette holder is brilliant. Unfortunately I've lost the spring that held the tape door shut - is there any chance you can post a picture so I can attempt to make another? I bet it's on the floor somewhere and I'll find it in a year's time...

I feel like this is the one unit I can offer something back for all the great help I've had from the forum in answer to my stupid questions, as I've spent so much time with it in pieces that I almost understand some of it. Thus I'd be glad to help if I can.

I had trouble with the ribbon cable going from the power supply board to the motherboard. Some of those solid wires were broken, so I slit the ribbon into its constituent wires and tested each for continuity. I was also missing the mica washer from behind the BD241, so it was grounding out on the chassis.

Have you checked the pins on the internal battery compartment? They are in various clever configurations that engage depending on whether the Z131 or rechargeable pack or C cells are inserted. I had some pieces that had work-hardened and broken off, so they didn't project enough to make contact with the Z131 outputs.

If you're running it from the DIN power input then you've bypassed that, of course.

Then the outputs from the power board (600) can be checked as they're all labelled with the voltages they should have on the circuit diagram.

I've attached a string of photos of this part of my diagram in case it's clearer than the one you're working from. They go from the Z131 right to left, so you should see how they link together. If the forum has compressed them too much, I'll scan it in and send you a Dropbox link.

My biggest trouble with this was the very thin solid core wires breaking, and having to jumper motherboard cracks. I'd be very thorough with testing for continuity along the power rails, as I found dry joints as well as the aforementioned broken cables, and never would have spotted them if it weren't for methodically tracing what should be connected.

Addendum: mine is a CR 240 Dolby, not AV, but I think most of the circuitry is very similar. The SDS pack of drawings I got included the Hall sensor for the spindles that was correct for my model rather than the light trap on the PDF I was working from previously, for example.
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Old 25th Jul 2020, 3:24 pm   #24
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Default Re: Uher CR 240 AV Cassette Recorder

Quote:
Originally Posted by Uncle Bulgaria View Post
Great! That over-cam spring device on the cassette holder is brilliant. Unfortunately I've lost the spring that held the tape door shut - is there any chance you can post a picture so I can attempt to make another? I bet it's on the floor somewhere and I'll find it in a year's time...

I feel like this is the one unit I can offer something back for all the great help I've had from the forum in answer to my stupid questions, as I've spent so much time with it in pieces that I almost understand some of it. Thus I'd be glad to help if I can.

I had trouble with the ribbon cable going from the power supply board to the motherboard. Some of those solid wires were broken, so I slit the ribbon into its constituent wires and tested each for continuity. I was also missing the mica washer from behind the BD241, so it was grounding out on the chassis.

Have you checked the pins on the internal battery compartment? They are in various clever configurations that engage depending on whether the Z131 or rechargeable pack or C cells are inserted. I had some pieces that had work-hardened and broken off, so they didn't project enough to make contact with the Z131 outputs.

If you're running it from the DIN power input then you've bypassed that, of course.

Then the outputs from the power board (600) can be checked as they're all labelled with the voltages they should have on the circuit diagram.

I've attached a string of photos of this part of my diagram in case it's clearer than the one you're working from. They go from the Z131 right to left, so you should see how they link together. If the forum has compressed them too much, I'll scan it in and send you a Dropbox link.

My biggest trouble with this was the very thin solid core wires breaking, and having to jumper motherboard cracks. I'd be very thorough with testing for continuity along the power rails, as I found dry joints as well as the aforementioned broken cables, and never would have spotted them if it weren't for methodically tracing what should be connected.
Many thanks for the schematic sections (and suggestions), they are much better than the fuzzy PDFs, can actually make out the infamous Ein-Ausschalter

My trap door spring is missing also, when I got the unit I thought the trap door was also missing but it popped out when I removed the cassette lift.

Yes have checked the pins and those little switch contacts on the battery compartment, all test OK. Currently have got the external power supply connected directly to the +24V & 0V pins. I have not yet tried the AutoRadio DIN power input, need to make up suitable cable.

David
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Old 25th Jul 2020, 3:35 pm   #25
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Default Re: Uher CR 240 AV Cassette Recorder

I realised it was the other sheet that has the drawings of the boards themselves so you know what pin numbers the circuit diagram refers to. However, I've discovered that a PDF I have of the AV is clear enough to see these drawings, so it's attached if you haven't got that one. I did reach a stage where I was able to know each connector pin number with the motherboard either way up!

All together now: "All those wasted hours...!"

Good luck.
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Old 25th Jul 2020, 4:58 pm   #26
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Default Re: Uher CR 240 AV Cassette Recorder

Thank you Uncle Bulgaria, I had found that one.

Have now got the unit to power up (hooray). Found that no voltage was getting through to the On/Off switch and that there was no voltage at wire 623 (which connects out to the On/Off switch via wire 608) which is shown as common contacts I/II.

Had voltage at wire 622 which connects to contact IV and contact IV is supposed to switch through to contacts I/II when the Z131 power adapter is fitted.

Because I am not currently using the Z131, the switch contact is not being made from IV to I/II but by manually pressing the little switch there was still no power. Found that contacts I and II are not common/commoned up until the Z131 is inserted.

There is a third contact (non live) on the face of the Z131 (in addition to the +24 volt and 0V contacts) that bridges contacts I & II, so by manually pressing the little switch and manually shorting contacts I and II (simulating insertion of the Z131) able to get power on using the external power supply.

While I have the power supply connected I will do a few quick functional checks, have to be careful though as I have no heatsink on the BD 241 power transistor.

I know all about wasted hours !
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Old 25th Jul 2020, 5:38 pm   #27
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Default Re: Uher CR 240 AV Cassette Recorder

A supply from the autoradio input would normally rely on switch contacts 15 & 16 making when the plug is inserted.

Lawrence.
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Old 25th Jul 2020, 6:24 pm   #28
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Default Re: Uher CR 240 AV Cassette Recorder

Yes agreed, indirectly referenced that in Post 19 but did not state that the actuated contacts with DIN plug in are 15 and 16.

David
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Old 25th Jul 2020, 8:05 pm   #29
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Default Re: Uher CR 240 AV Cassette Recorder

I didn't have a PSU when I was repairing mine, so had to do everything with the Z131 inserted (it always falls out when you have to get under the motherboard...sigh...). At least it meant that the relevant switches were all depressed!

Check the nylon push switches that link to the buttons on the front if you have intermittent operation. You can slide them out after pushing out the little nylon pin at the back which prevents them from being pushed out of the front panel when the buttons are released. I had to manufacture a new Record switch as mine had cracked. It seems the pressure of that nylon pin banging up against the back edge of the contact tunnel had overstrained the fabric of the switch.
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Old 25th Jul 2020, 8:58 pm   #30
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Default Re: Uher CR 240 AV Cassette Recorder

Did some quick functional checks, FFD and RWD work well. Initially Play did not work at all (no movement), could see that the Pinch Wheel was nowhere near the tape/capstan shaft.

After a bit of delicate playing with the Pinch Wheel mechanism it is now working well, seemed like it was jammed up.

No sound on Playback though, this maybe because it is stuck in Record mode because the Record red LED is lit all the time. At the beginning of the thread the Record LED was going on and off under control of the Record push button, so something has subsequently changed.

Noticed that the green On LED goes off and the yellow Play LED lights when in Play mode, does not sound correct, but maybe it is ?

The BD 241 power transistor soon warms up without a heatsink so I will refit the power supply board and go back to the Z131 power adapter operation before starting looking at Record LED always being on now.

David
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Old 25th Jul 2020, 9:40 pm   #31
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Default Re: Uher CR 240 AV Cassette Recorder

I have a yellow 'on' and a green 'play'. Yes, only 'play' lights when in playback. Record should only be accessible with the joystick in 'stop' mode. Otherwise the metal fixing visible in my photo above prevents the switch from being depressed as there's a slotted gate behind it which is only disengaged by the joystick being pushed up.

I had trouble with the playback solenoid not pulling in the roller, but it seems you've sorted that.

The record switch, in common with the others, has alternating upper and lower contacts which bridge two of three possible contacts in the tunnel it runs through. These contacts come through to the bottom of the motherboard where they're visible as a series of parallel lines of pins. Either the switch is broken and some parts are covering the 'depressed' contacts when they should be contacting the 'open' two. You can check this with the cover off by checking for continuity between the pairs, which are numbered on the circuit diagram, and accessible to meter probes between the plastic fins of the contact tunnels.

For example, Dolby on my unit is operated by S(witch)1, with one channel (pin 513 on the Dolby board 500) on pins 4, 5 & 6 of S1, with the other (pin 527 of board 500) on 43, 44 & 45.

It could just be dirty.

I may be teaching you to suck eggs, but it took me a while to work this out because I wasn't familiar with the notation, or following the switch contacts around the board. As you seem to be experienced with Uhers, this could be entirely unnecessary, in which case my apologies and I don't mean to patronise!

Edit: Included my sketch of the record switch's layout, and which pins do playback and which record. It helped me to draw this out when I was working out what should have continuity in each position.
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Old 25th Jul 2020, 10:54 pm   #32
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Default Re: Uher CR 240 AV Cassette Recorder

Yes I got the colours mixed up, yellow for On and green for Play, good to know that the On LED going off in Play is normal.

The Operation of the Record switch did not feel correct and after a few operations it fell apart, broken off near the end like your photo !
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Old 25th Jul 2020, 11:27 pm   #33
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Huge bore! I made a new switch from two strips of copper-clad board. I filed down one side of each strip to thin them down, then stuck them together back to back with epoxy. I etched them to have the same contact shape as the original switch (having measured the separation between the contacts on the tunnel and original switch), then filed out the slot for the metal latch mechanism and the slot for the knob. The hole for the limit pin that stops the switch from pulling through the contact tunnel was marked and drilled after I'd fettled all the contacts to work at the same point (by checking for continuity in the guessed 'in' and 'out' positions between the three possible contacts on the tunnel).

Note that the contacts don't make contact with the central strip - each contact bridges its two contacts on the tunnel independently, and the central strip seems to be a hangover from the manufacturing process. Initially I thought the whole strip was one contact and spent ages trying to work out why my new switch wasn't working, before having to file away the copper between each contact!
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Old 25th Jul 2020, 11:49 pm   #34
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Default Re: Uher CR 240 AV Cassette Recorder

Wow that sounds like a task and a half, gives me a headache just thinking about it

Am I correct to think that to access/see the rest of the broken switch I will have to strip it down again, removing the flyhwheel (s) and head electronics assembly ?
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Old 26th Jul 2020, 12:43 am   #35
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Yes, it was something I put off for a long time, fearing it would be difficult. However, in the end it was easier than changing the belts, I just thought it onerous because I had never etched copper board before. My switch is my first attempt and it's pretty ropey but it does the trick!

You shouldn't have to remove anything beyond the pull-out boards from their motherboard pins. The Record switch is a little underneath the heads assembly, but not inaccessible. I found replacing the belts such a trial that I avoided removing any of that assembly again.

Use some small pliers to press out the nylon pin from the rear end of the switch strip that's attached to the knob, then with the face-plate off you can use a probe or screwdriver to lever away the metal gate enough to pull the switch out from the front. The knob is pressed or glued on. I think I had to snap it off and drill away the remainder of the switch strip from inside the back of the knob. The knob had an internal bar that created the alignment with the slot in the end of the strip.

The metal latch can be extracted from the middle of the nylon switch strip and retained (once you've measured its location). I have a DWG I made and a pencil templet, which I used as a mask to colour in the etch with, but if you want to go this route it would be good to have a second opinion on the dimensions. Despite all my checks and double checks, when I glued the knob back on to my new switch it was proud of the other knobs! Most annoying.
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Old 26th Jul 2020, 10:12 am   #36
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Default Re: Uher CR 240 AV Cassette Recorder

Once again thank you for all the detailed information. Good that rest of the record switch can be accessed without doing a big strip down, was not looking forward to the big strip down again, found it quite an ordeal to be honest.

You are not teaching me to suck eggs, far from it. Your fix to me sounds really difficult (but elegant) but I think it might be beyond my capabilities to successfully implement, for me personally the switch repair sounds more daunting than doing the big strip down again .

I need to have a serious (probably quite long) think about it and possible ways of tackling it. First job will be to strip down the rest of the broken switch and understand better (from the hands on) your detailed description of the various little switch parts.

It is a little similar (but more complex) to my broken Radio/Micro push button switch on my Uher Variocord 63S which is another job I need to get back to after a few months not looking at it any further.

On the 63S it is quite a lot simpler (but still not easy) as it is only the end of the operating shaft that has broken off (the contact section of the shaft is OK) first attempt at glue repair failed. Tried to get a new/replacement switch but could not find anything suitable with correct pin spacing apart from paying a fortune for a switch from the USA

The Pinch Roller now (after freeing it up) moves into position mechanically (the same as the heads) when the cassette lift goes down, I do not think the Playback relay is now having any effect on the roller position but I think the relay did move the roller originally (but nowhere near the tape) before playing with the mechanism. So this is something I will probably have to revisit later.

David
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Old 26th Jul 2020, 2:00 pm   #37
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Default Re: Uher CR 240 AV Cassette Recorder

Good luck!

Here's a picture of the top of mine, with all the plug-in boards out (and the metering board which I took out to access some dodgy tantalums on the motherboard beneath, but which I wouldn't recommend doing as realigning that ribbon cable from underneath is a nightmare!) Anyway, not necessary for the record switch. The piece I'm calling the 'switch tunnel' is the long red object at the bottom.

I thought this might make the operation clearer, as you can see from the switch at the top (where the 'tunnel' is separated into two pieces, next to the volume control) that the nylon pin that prevents the switch strip and knob coming out of the front panel is hard up against the rear of the right-hand tunnel piece.

I must have already removed the one from the record switch as you can see the end of the switch strip poking out from the record tunnel, but there's no nylon pin in it.

When I rebuilt it, I used a short length of wire in a friction-fit hole drilled through the copper-clad board to perform the same action.

If you make a switch, it's easy enough to test it without all the latching paraphenalia, as it can slide in from the front and you can work out where the record and play positions are by nudging it in and out until the lights come on.

That was how I discovered which of my etched contacts needed filing off as they were, for example, causing continuity between the front, middle and rear of a certain three adjacent contacts instead of the middle and rear for 'record' and front and middle for 'play'.

I'm sure it will make sense once you've got your hands on. With the 'speaker unplugged I just worked on it with the moveable boards out and the Z131 in, as that showed up everything to do with the mechanicals and switch operation.
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Old 26th Jul 2020, 2:08 pm   #38
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Default Re: Uher CR 240 AV Cassette Recorder

Yes that is a great help thank you, I now clearly understand what the switch tunnel and nylon pin is.

David
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Old 27th Jul 2020, 1:43 pm   #39
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Default Re: Uher CR 240 AV Cassette Recorder

Contacted SDS Germany to see if they hold stock of the push button switches but unfortunately they do not. They say a common problem and that Super glue repairs do work.

I was thinking of trying Super glue first but am not very confident of being successful.

David
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Old 27th Jul 2020, 2:25 pm   #40
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Default Re: Uher CR 240 AV Cassette Recorder

Yes, I went through that rigmarole. There were a couple on eBay when I was doing mine, but very pricey and I thought must surely suffer from the same stress problem and would fail in the same way. I couldn't get glue to hold, as I found that the stress of releasing the switch, where the latch unlocks and the spring bangs the stop up against the tunnel simply caused the end of the switch strip to crack off again.

If you've made a PCB before, the method I used will be very easy. I only found it difficult because I had no experience of etching so was rather fearful of getting it right. If you look at the tunnel you'll see there's quite a lot of leeway between the contacts (and the existing switch doesn't look like the manufacturing tolerances to punch the strip into the nylon were the closest) so it's eminently 'fettleable'.

If you're really desperate, I could try making one from my templet again for you. It might spur me on to improve!
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