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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 19th Nov 2020, 10:57 pm   #21
Uncle Bulgaria
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Default Re: Uher CR 240 adjustments - operating point and hub tension

Having followed Lawrence's flip-flop through, it turned out C703 wasn't keeping it on because it was 4.7µF rather than 10µF. Presumably it was discharging before the next pulse came through. Changing this and re-instating the 2.2µF as C704 means the tape continues to the end properly. Hurrah!

However, there's still the extreme warbling flutter which has appeared in the couple of months since I was last working on this. I have changed the belts in the last couple of years, since I've owned the deck. Could they have gone already? The tape path has been cleaned, but I haven't disassembled or lubricated any of the hubs or the pinch roller bearing. There is nothing mentioned about this in the service manual.
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Old 20th Nov 2020, 6:33 am   #22
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Default Re: Uher CR 240 adjustments - operating point and hub tension

I've had the belt assembly out and checked over it all, cleaning everything again, with nothing wrong there. It looks like the pinch roller has decided to give up the ghost in the last few months, bizarrely. It now struggles to play at all, and the speed is all over the place. Pre-recorded tapes are very slow, and a TDK90 refuses to move.

Is there anything I can do to check it's the pinch roller before sending it off to the States? Should the capstan be polished or rough - is there anything I can look for there?
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Old 20th Nov 2020, 10:11 am   #23
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Default Re: Uher CR 240 adjustments - operating point and hub tension

Capstan shaft should not be rough.

If it was OK previously you would be fairly unlucky if it is the pinch roller, what is its condition like ?

Have you checked by lowering the cassette mechanism (with cassette not in) that the pinch roller is consistently moving forward correctly and making good contact with the capstan shaft and the pinch roller rotation then OK when Play selected ?
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Old 20th Nov 2020, 11:06 am   #24
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Default Re: Uher CR 240 adjustments - operating point and hub tension

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Having followed Lawrence's flip-flop through, it turned out C703 wasn't keeping it on because it was 4.7µF rather than 10µF. Presumably it was discharging before the next pulse came through. Changing this and re-instating the 2.2µF as C704 means the tape continues to the end properly. Hurrah!
Bit early in the morning for me so I haven't had my gallon of focusing coffee yet but on the schematic and board layout I'm looking at C703 is shown as 4.7uF?

Lawrence.
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Old 20th Nov 2020, 11:46 am   #25
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Default Re: Uher CR 240 adjustments - operating point and hub tension

On the SDS supplied drawing that shows the Hall effect sensor/magnet (as opposed to the photo diode/transistor shown on online drawings) C703 is shown as 10uF, so maybe Uher changed the value to suit the newer sensor arrangement or maybe it was found that 4.7uF was not optimum anyway.

David
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Old 20th Nov 2020, 11:52 am   #26
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Default Re: Uher CR 240 adjustments - operating point and hub tension

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On the SDS supplied drawing that shows the Hall effect sensor/magnet (as opposed to the photo diode/transistor shown on online drawings) C703 is shown as 10uF, so maybe Uher changed the value to suit the newer sensor arrangement or maybe it was found that 4.7uF was not optimum anyway.
Cheers, that would explain it, a production change to suit.

Is that versions schematic available online without having to sign up/register for it?

Lawrence.
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Old 20th Nov 2020, 11:56 am   #27
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Default Re: Uher CR 240 adjustments - operating point and hub tension

Not to my knowledge, we had to purchase it as a hard copy from SDS.

David
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Old 20th Nov 2020, 12:00 pm   #28
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Default Re: Uher CR 240 adjustments - operating point and hub tension

Cheers.

Lawrence.
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Old 20th Nov 2020, 12:04 pm   #29
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Default Re: Uher CR 240 adjustments - operating point and hub tension

When I get my scanner repaired (one of many ongoing repair jobs) I will scan that section.

David
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Old 20th Nov 2020, 12:08 pm   #30
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Default Re: Uher CR 240 adjustments - operating point and hub tension

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When I get my scanner repaired (one of many ongoing repair jobs) I will scan that section.
Thanks David, that would be good.

Lawrence.
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Old 20th Nov 2020, 12:17 pm   #31
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Default Re: Uher CR 240 adjustments - operating point and hub tension

In the mean time photo attached.

David
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Old 20th Nov 2020, 2:30 pm   #32
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Default Re: Uher CR 240 adjustments - operating point and hub tension

Thanks Dave, I've saved that to file now.

Lawrence.
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Old 20th Nov 2020, 3:26 pm   #33
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Default Re: Uher CR 240 adjustments - operating point and hub tension

Thanks for that, David - I thought I'd posted that very section some posts ago because it's indeed different in the versions available online. My apologies!

I was considering getting a big scan and duplication done of all the fold-out service information I got from SDS once that sort of outfit is open again, both for spares and for uploading them somewhere as it has been very confusing for me working from a dodgy PDF before I got the originals. With, as it turns out, relatively significant variations from model to model!

I have had some success with roughing up the roller and reducing the roller pressure by bending pin 'H'. Tapes now play, though with still audible flutter. Far less than before though, and certainly exacerbated by the fact I'm listening for it. The capstan had some discolouration that looked like incipient rust, so I gave it a light touch up with wet and dry. If it's supposed to be polished, I'll try giving it some brasso on a cotton bud as it rotates.

Hilmar Krueger of Uher Service offers me a new roller for €27, saying the old one has to be sent back after. I've not asked yet, but that implies they're rebuilding old ones so it won't be a decayed 'NOS' one from store. Perhaps this is a better route than Terry's Rubber Rollers as it will be the right size and specification

Fast wind is peculiar. At least one slows to walking pace when approaching the end of FF. In general, winding seems far slower than I imagine it should be. A commercial tape is by far the fastest, presumably because there's only enough tape for the album so there's less tension on average to overcome.

TDK90: FF through whole tape takes 3:30. REW through whole tape takes 2:50 with a noticeable increase in speed towards the end of rewinding, and a noticeable decrease towards the end of fast forward.
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Old 20th Nov 2020, 7:02 pm   #34
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Default Re: Uher CR 240 adjustments - operating point and hub tension

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Set up my CR 240 6.6V setting for operating voltage to the left edge of the green field on the left VU meter, it was way off around -10dB, had to adjust the R 1001 trimmer fully clockwise to just about get it to reach the left edge.
After some investigation found that I was not on battery box contact "I" due to misreading the fuzzy PDF schematic and also making an assumption that it was battery/power adapter input voltage.

After looking at the clear schematic saw my error and then correctly monitoring contact I, was then easily able to adjust the VU meter reading. With 6.6V at contact I, my power supply output was 8 volts.
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Old 20th Nov 2020, 7:18 pm   #35
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Default Re: Uher CR 240 adjustments - operating point and hub tension

Did some FFD and RWD timings using a TDK90.

Did it initially at min battery voltage setting (using external power supply) as per above Post.

RWD and FFD were both quite slow and very similar around 4 mins 5 seconds on average. Speed generally was pretty consistent end to end and power supply drain averaged around 240mA.

Took the power supply to its maximum voltage of 20 volts so as to be similar to the 24 volt output of the Z131 power adapter and started to repeat fast wind timings but had to abort (they would have been quicker) as the Uher power supply regulator was getting really hot.

I had still not bolted the Uher power supply regulator to the case, it ran fine like this at the lower external power supply voltage but obviously not happy at 20 volts.

Struggling at the moment to find where I have put the regulator mica insulator and associated fixings both for the regulator and the other fixing on the power supply board. Thought I would find them fairy easily but after looking through around 30 component storage trays looking difficult
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Old 20th Nov 2020, 10:41 pm   #36
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Default Re: Uher CR 240 adjustments - operating point and hub tension

Thank you for making the effort on that, David. Perhaps they are just slow! I would have thought they'd want to minimise battery drain by getting the winding over quickly rather than grinding it out over minutes.

My regulator gets warm as well. If you need a washer and insulating sleeve, I had to buy some for when I first got mine and was completely befuddled by why it cut out when I bolted the BD241 to the case, having never heard of these washers before! As I only needed the one, I have spares.

The pinch roller is soft and pliable, but taking it off the metal sleeve shows there's some cracking on the edges when it's compressed. I haven't got anything to compare it to, though, nor experience. As the belts are OK and the motor electronics are as balanced as I can get them, it's any of the pinch roller, the capstan, or the clutches. Unless the motor having a slight underlying sine wave could cause it. I lean towards the pinch roller because of the pressure adjustment with pin H having such an effect. It does seem peculiar it could just happen when out of action for a short while though, after 40 years! Perhaps I knocked pin H during some other work without realising, and bent it, increasing the pressure?
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Old 21st Nov 2020, 1:46 am   #37
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Default Re: Uher CR 240 adjustments - operating point and hub tension

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Thanks for that, David - I thought I'd posted that very section some posts ago because it's indeed different in the versions available online. My apologies!
Did not see it, you did post several new schematic scans on my 240 Thread but those did not cover the Hall effect area.

David
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Old 21st Nov 2020, 1:49 am   #38
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Default Re: Uher CR 240 adjustments - operating point and hub tension

Thank you for the offer of the parts, I may come back to you on that.

I am feeling more confident that I should be able to find them because I also cannot find the control knobs and other parts, they must all be together somewhere.

David
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Old 21st Nov 2020, 12:54 pm   #39
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Default Re: Uher CR 240 adjustments - operating point and hub tension

For comparison fast wind timings I checked the times on my ITT SL 530 mono cassette recorder (using the same TDK90 tape), which were obviously visually quicker.

Both FFD & RWD were consistently around 2 minutes 38 seconds end to end, so quicker than the Uher, this was done with a mains connection, not yet checked with batteries.

David
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Old 21st Nov 2020, 6:40 pm   #40
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Default Re: Uher CR 240 adjustments - operating point and hub tension

Checked ITT on batteries with identical fast wind times as when mains powered.

Previous reference to TDK90 should have read Maxell90.
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