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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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15th Apr 2018, 6:42 pm | #1 |
Retired Dormant Member
Join Date: Apr 2018
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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 |
15th Apr 2018, 7:00 pm | #2 |
Heptode
Join Date: Aug 2009
Location: Worthing, Sussex, UK.
Posts: 659
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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. |
15th Apr 2018, 7:28 pm | #3 |
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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 |
15th Apr 2018, 8:54 pm | #4 |
Dekatron
Join Date: Mar 2008
Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.)
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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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15th Apr 2018, 8:59 pm | #5 |
Retired Dormant Member
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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 |
16th Apr 2018, 11:49 am | #6 |
Octode
Join Date: Jul 2006
Location: Perth, Western Australia
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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. |
16th Apr 2018, 1:17 pm | #7 | |
Octode
Join Date: Dec 2017
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Re: Uher 4000L slows and wows near end of reel
Quote:
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16th Apr 2018, 2:07 pm | #8 |
Dekatron
Join Date: Mar 2008
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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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16th Apr 2018, 8:59 pm | #9 |
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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 |
16th Apr 2018, 10:59 pm | #10 |
Tetrode
Join Date: Dec 2016
Location: Huddersfield, West Yorkshire, UK.
Posts: 50
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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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17th Apr 2018, 7:42 pm | #11 |
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Join Date: Apr 2018
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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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17th Apr 2018, 11:37 pm | #12 |
Tetrode
Join Date: Dec 2016
Location: Huddersfield, West Yorkshire, UK.
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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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17th Apr 2018, 11:46 pm | #13 |
Tetrode
Join Date: Dec 2016
Location: Huddersfield, West Yorkshire, UK.
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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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18th Apr 2018, 5:40 pm | #14 |
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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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19th Apr 2018, 8:07 pm | #15 |
Dekatron
Join Date: Mar 2008
Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.)
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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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19th Apr 2018, 8:18 pm | #16 |
Dekatron
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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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20th Apr 2018, 6:10 am | #17 | ||
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Re: Uher 4000L slows and wows near end of reel
Quote:
Quote:
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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20th Apr 2018, 2:25 pm | #18 |
Dekatron
Join Date: Aug 2006
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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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20th Apr 2018, 3:58 pm | #19 |
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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 |
20th Apr 2018, 5:07 pm | #20 |
Banned
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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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