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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 15th Apr 2018, 6:42 pm   #1
ckbrooks
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Default Uher 4000L slows and wows near end of reel

I’ve just acquired a UHer 4000L. It works fine apart from when the reel gets quite near the end, the speed seems to slow down a tad and there’s a bit of wow. It perfect near the start of the reel.

What’s the best way for me to adjust and fix this?

Thanks for your kind help!

clive
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Old 15th Apr 2018, 7:00 pm   #2
JohnBHanson
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Default Re: Uher 4000L slows and wows near end of reel

Typically this is caused by a drive belt stretching - only solution is to replace drive belt.

another possibility though is that the supply voltage is low so the motor cannot generate enough touque.
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Old 15th Apr 2018, 7:28 pm   #3
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Default Re: Uher 4000L slows and wows near end of reel

Thank you John. The belts looked okay so I haven’t replaced them, but I will do so immediately now, based on your reply!

The machine is running on D cells at the moment, but they are very new, so I don’t think it’s probably that. I got no power supply with the machine, but I notice the original ones were 6v 50ma, and so I’ve ordered a new psu with these specs from eBay. Do you think that will work if I fit the right plug? I don’t suppose you know the correct two pins to connect up to by any chance do you?

Thanks for everything so far!

Clive
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Old 15th Apr 2018, 8:54 pm   #4
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Smile Re: Uher 4000L slows and wows near end of reel

Hi,
The PSU for the Uher 4000-L doesn't plug into the machine. Rather, it fits into the space vacated by the four 'D' cells and connects via two studs to the battery contacts of the two outermost cells. The marks that indicate which way the cells fit should indicate which is positive, and which is negative.
There is a white plunger in the battery box that is operated by fitting the PSU in place, but not by the cells. I'm not certain exactly what this does apart from preparing the machine to work from the PSU.
Hope this is useful.
Cheers, Pete
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Old 15th Apr 2018, 8:59 pm   #5
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Default Re: Uher 4000L slows and wows near end of reel

Hi,

I was rather hoping to use a cheap modern power supply and connect it to the socket on the side of the machine. Any thoughts?

Clive
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Old 16th Apr 2018, 11:49 am   #6
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Default Re: Uher 4000L slows and wows near end of reel

There could be various causes for the slowing towards the end of a reel. It could be caused by hardening of the rubber tyre that is bonded to the flywheel. The drive pulley can start to lose grip because the tyre has hardened. Sometimes removing the flywheel and carefully roughing up the surface of the rubber with suitable abrasive paper can help.
To check for this try carefully, temporarily increasing the pressure of the motor pulley onto the tyre. If the speed stabilises it suggests the problem is there.
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Old 16th Apr 2018, 1:17 pm   #7
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Default Re: Uher 4000L slows and wows near end of reel

Quote:
Originally Posted by Tractorfan View Post
The PSU for the Uher 4000-L doesn't plug into the machine. Rather, it fits into the space vacated by the four 'D' cells and connects via two studs to the battery contacts of the two outermost cells. The marks that indicate which way the cells fit should indicate which is positive, and which is negative.
There is a white plunger in the battery box that is operated by fitting the PSU in place, but not by the cells. I'm not certain exactly what this does apart from preparing the machine to work from the PSU.
There was another option as well, you could fit a 6 volt lead acid battery that was the same size as the PSU. This was then charged from the PSU which was plugged into the machine. This may be the reason for the plunger switch, to prevent attempting to charge dry cells.
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Old 16th Apr 2018, 2:07 pm   #8
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Smile Re: Uher 4000L slows and wows near end of reel

Hi,
Ah, I'd forgotten about the lead-acid battery option . I had another look at the PSU and it has a 5-pin DIN socket which may connect via a cable to the machine to recharge said battery.
Cheers, Pete.
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Old 16th Apr 2018, 8:59 pm   #9
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Default Re: Uher 4000L slows and wows near end of reel

Thank you all for the kind advice. I’m waiting for drive belts to arrive and I will also check the flywheel as suggested.

Regards

Clive
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Old 16th Apr 2018, 10:59 pm   #10
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Default Re: Uher 4000L slows and wows near end of reel

I have a 4400, stereo 4 track version. I use a modern wall wart 7.5v smps power supply which cost less than £10 sourced on the internet. All you need is to solder the lead to the correct pins on a 5pin din plug. When inserted it disconnects the batteries to prevent charging. The internal accumulator pack depresses a switch to allow charging if fitted. I cant remember which pins on the din to use, I'll open up mine and repost later.
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Old 17th Apr 2018, 7:42 pm   #11
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Default Re: Uher 4000L slows and wows near end of reel

Thank you very much indeed. I’ve ordered PSU and also the correct 6 pin din ready. When you’ve let me know the wiring for the two battery cables and I’ve completed it, will it be safe for me to leave my alkaline D Cells in the machine when I use my power supply? Also, will the PSU, when it’s attached, cancel out the battery power?
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Old 17th Apr 2018, 11:37 pm   #12
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Default Re: Uher 4000L slows and wows near end of reel

Quite correct, it is a 6 pin one. Looking at the inside of the plug, to which you will solder the wires, negative is the centre pin and positive is the middle outer pin, no.3. My psu is actually 6v, but 7.5v is ok as the Uher has a zener diode to drop the voltage a tad. I think the idea of 5 batteries is just to give a bit of headroom, 7.5v on standard cells. Of course NiCads are only 1.25v, so 5 will give 6.25v. The metal din plug body acts on a tab to disconnect the C cells from the circuit, so as long as that bit works it is ok to leave the dry cells in place. Might be worth checking it works though.
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Old 17th Apr 2018, 11:46 pm   #13
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Default Re: Uher 4000L slows and wows near end of reel

BTW, I have a 4000L which is basically a donor, bought for £10 as it had a better condition lid and I needed the meter innards to rebuid one of my dud meters. Any 4000 specfic bits you might need? Heads for example? I'll probably want to hang on to all the transistors, once tested as spares however!
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Old 18th Apr 2018, 5:40 pm   #14
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Unhappy Re: Uher 4000L slows and wows near end of reel

Thank you very much indeed for the kind offer. My machine seems to be in good shape, so I don’t think I need any parts. The depressing thing isn’t that I have just this minute replaced the belts with new ones, but the fairly severe wow at the end of a reel is still there exactly as before. It’s fine at the beginning of the tape and barely noticeable in the middle if at all. Everything else seems perfect. Should I try to abrade the flywheel (and how does that come off) or is there anything else that I could try first. I am sure it must be easily solvable by someone who knows!
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Old 19th Apr 2018, 8:07 pm   #15
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Smile Re: Uher 4000L slows and wows near end of reel

Hi,
These Uhers have quite a sophisticated motor control with a poly-phase system and feedback speed regulation. The motor in mine wouldn't start if it came to rest in certain places due to one duff AC188 driver transistor out of the three.
I'm thinking that, perhaps, one the three AC188s in yours may be weak and causing poor torque.
Just a thought.
Cheers, Pete.
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Old 19th Apr 2018, 8:18 pm   #16
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Default Re: Uher 4000L slows and wows near end of reel

Does your Uher have the self-tensioning guide next to the supply spool, which regulates the pay-out of tape by applying a brake when the tape becomes slack and releasing it when under tension, or is that just a feature of the later models?
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Old 20th Apr 2018, 6:10 am   #17
ckbrooks
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Default Re: Uher 4000L slows and wows near end of reel

Quote:
Originally Posted by Tractorfan View Post
I'm thinking that, perhaps, one the three AC188s in yours may be weak and causing poor torque.
Just a thought.
Thank you. If I can’t fix it mechanically I will certainly look into this solution.

Quote:
Originally Posted by julie_m View Post
Does your Uher have the self-tensioning guide next to the supply spool, which regulates the pay-out of tape by applying a brake when the tape becomes slack and releasing it when under tension, or is that just a feature of the later models?
Mo, it doesn’t have that guide. However, I notice that under the removable to plate there is a screw adjustment for the take up spool tension. Could that perhaps have become a bit weak over the years so that when it reaches the end of a full spool it struggles a bit?

I checked the friction on the driving wheel and that seems to me to be okay. I also added a single spot of oil to the centre bearing. Problem still remains when at the very end of the tape,

The other possible issue is when recording from the line in and setting the meter correctly, the recording still sounds a bit distorted on playback. Also, the monitoring level of the incoming sound through the speaker is far lower than the resultant playback level.
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Old 20th Apr 2018, 2:25 pm   #18
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Default Re: Uher 4000L slows and wows near end of reel

In my experience , wow near the end of tapes is caused by two things:

1. Bad pinch roller. Any loss of suppleness here will mean it can't poull the tape smoothly any more.

2. Problem with capstan motor or electronics, capstan belt.

Excess backtension or drag on the supply side will also give these symptoms.

Try some rubber restorer on the pinch roller in the first instance. Do NOT go adjusting tensions, etc. as these are unlikely to have shifted and doing this will just mask the real problem.

The take up drive should have no effect on the playback speed. If you momentarily stop the TU spool in playback the tape should carry on playing OK. If it doesn't - see above ;-)
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Old 20th Apr 2018, 3:58 pm   #19
ckbrooks
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Default Re: Uher 4000L slows and wows near end of reel

Thank you very much indeed. I cleaned the pinch roller with alcohol but have done nothing else with it. Do you know where I could source the rubber restorer that you mention in the UK? Is it safe to put it on the pinch roller? It won’t deform it will it?

Alternatively, are new pinch rollers available?

I’ve changed the belts so they should be fine.

Thanks for everything so far

Clive
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Old 20th Apr 2018, 5:07 pm   #20
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Default Re: Uher 4000L slows and wows near end of reel

Friction in the feed spool? Is there a felt brake catching? Any resistance in the feed spindle will be worse when it turns faster at the reel end.
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