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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 17th Jul 2023, 1:20 am   #1
Karl T 01
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Default Grundig TK 141

Hi, I'm new to the forum and to the world of reel to reel tape recorders. I recently bought a Grundig TK 141. Replaced the belts and did a clean up of the heads etc. The machine played well for a few days but then the motor appeared to slow down and struggle to rotate the capstan. From what I've researched it seems it may be the run capacitor. I'm not familiar with electronics and I'm looking for help in identifying the run capacitor. Any help would be greatly appreciated. Thanks in advance, Karl.
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Old 17th Jul 2023, 8:55 am   #2
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Default Re: Grundig TK 141

Welcome to the Forum Karl.

The motor in the TK 12X/14X series is a combined motor/mains transformer and does not have a run/start capacitor. It is very unlikely this has failed.

The mains power to the motor/transformer is fused by a 630mA 20mm glass fuse, there are also 2 other fuses but these are on the output side of the transformer for the DC power supply circuitry.

If the drive belt to the motor was overly tight it possibly could stop the motor from rotating.

So first check the 630mA fuse and if OK then slip the belt off the motor pulley to see if the motor then runs. If no good then it is time to use a test meter (if you can do it safely) to check that the mains supply is getting to the recorder and to the motor wiring.

David

Edit update - If the Function Selector lamp is illuminated then this indicates that mains power is good and that the 630mA fuse is good.

Last edited by DMcMahon; 17th Jul 2023 at 9:14 am. Reason: Update
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Old 17th Jul 2023, 9:10 am   #3
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Default Re: Grundig TK 141

With the motor pulley drive belt removed it should be easy to manually rotate the motor and when powered the motor pulley then should spin at fairly high speed. If all OK but the motor struggles when the belt is refitted then either the belt is too tight or there is too much friction with the flywheel. It should be easy to manually rotate the flywheel when the belt is removed from the motor pulley.

Do Play, Fast Forward Wind and Rewind all struggle ?

David

Last edited by DMcMahon; 17th Jul 2023 at 9:15 am.
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Old 17th Jul 2023, 11:07 am   #4
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Default Re: Grundig TK 141

Is it possibly a tape sticky-shed problem? I wonder if Karl_T01 has cleaned the heads, tape guides, capstan and pinch wheel with IPA (Iso-Propyl Alcohol) since the problem showed itself?
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Old 17th Jul 2023, 2:14 pm   #5
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Default Re: Grundig TK 141

Be aware that these motors have a thermal “clutch”. In the event of overheating the solder melts allowing the motor to free wheel ignoring the obstruction.

Peter
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Old 17th Jul 2023, 2:23 pm   #6
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Default Re: Grundig TK 141

Yes a good point from Steve above, if the tape (s) being used suffer from Sticky Shed Syndrome (SSS) then the whole tape path could fairly quickly get coated with horrible sticky tape oxide debris which can play serious havoc with the tape control system.

David
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Old 17th Jul 2023, 2:26 pm   #7
Karl T 01
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Default Re: Grundig TK 141

Quote:
Originally Posted by DMcMahon View Post
Welcome to the Forum Karl.

The motor in the TK 12X/14X series is a combined motor/mains transformer and does not have a run/start capacitor. It is very unlikely this has failed.

The mains power to the motor/transformer is fused by a 630mA 20mm glass fuse, there are also 2 other fuses but these are on the output side of the transformer for the DC power supply circuitry.

If the drive belt to the motor was overly tight it possibly could stop the motor from rotating.

So first check the 630mA fuse and if OK then slip the belt off the motor pulley to see if the motor then runs. If no good then it is time to use a test meter (if you can do it safely) to check that the mains supply is getting to the recorder and to the motor wiring.

David

Edit update - If the Function Selector lamp is illuminated then this indicates that mains power is good and that the 630mA fuse is good.
Thanks for the swift reply and for the suggestions. I tested all the fuses for continuity using a multimeter. All bulbs working. I'll remove the belt next and see if there's any difference.
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Old 17th Jul 2023, 2:53 pm   #8
Karl T 01
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Default Re: Grundig TK 141

Thank you all for the swift replies and suggestions. I tested the fuses for continuity using a multimeter all are working. I took the belt of the pulley, doesn't seem to have made any difference. The motor is turning slowly and about a third of the way around it speeds up slightly and slows again. This is happening on every rotation in rewind. It's doing the same thing in the stop position but showing signs of speeding up a bit more than in rewind, (to normal speed) . It then slows down a lot, (almost stops), for a couple of rotations and this process continues to repeat. The motor also seems to generate heat quite quickly. Would a drop of oil have any effect on the motor? I did put one drop on the top of the motor pulley as I thought it would make it's way down the shaft to help it move more freely, this was before I found out that grease goes below the bearing plate which I have since applied grease to. I cleaned the heads, guides and capstan with 99.97% Isopropyl Alcohol after I replaced the belts about a week ago. I'll do that again.
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Old 17th Jul 2023, 3:22 pm   #9
Karl T 01
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Default Re: Grundig TK 141

I'm now wondering if the drop of oil would cause the drive shaft to slip in the motor?
The motor also sounds a bit louder since it stopped turning properly.
I'm thinking that the motor may need to be removed and cleaned.
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Old 17th Jul 2023, 6:14 pm   #10
Karl T 01
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Default Re: Grundig TK 141

I tried to post a message but it doesn't seem to have posted.
I tried taking the belt off the motor pulley. The motor ran slow but sped up for about a third of the rotation. When I was cleaning the machine I put a couple of drops of oil on the main belt pulley thinking it would make it's way down the shaft to lubricate the besring. I'm tnlhinking it may have gotten into the drive shaft and maybe this is why the motor is running as it is, (slowing and speeding up). I'm looking at removing the motor and giving the shaft a clean. Does this sound like a reasonable diagnosis?
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Old 17th Jul 2023, 8:35 pm   #11
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Default Re: Grundig TK 141

Quote:
Originally Posted by Karl T 01 View Post
I tried to post a message but it doesn't seem to have posted.
Your first five posts have to be approved by a moderator before they become visible on the forum.

Cheers

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Old 17th Jul 2023, 9:01 pm   #12
Karl T 01
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Default Re: Grundig TK 141

I posted a video on YouTube of the motor pulley if this is of any help. Thanks
https://youtu.be/ho38ngjGlts
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Old 17th Jul 2023, 9:03 pm   #13
Karl T 01
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Default Re: Grundig TK 141

Quote:
Originally Posted by Cobaltblue View Post
Quote:
Originally Posted by Karl T 01 View Post
I tried to post a message but it doesn't seem to have posted.
Your first five posts have to be approved by a moderator before they become visible on the forum.

Cheers

Mike T
That's great thanks Mike
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Old 17th Jul 2023, 10:50 pm   #14
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Default Re: Grundig TK 141

Very strange!

It almost looks as though the armature has become detached from the shaft and is just catching onto it every so often.

You'll have to remove the motor to verify what's going on with it.
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Old 18th Jul 2023, 9:27 am   #15
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Default Re: Grundig TK 141

Yes very strange indeed, I would not think that the motor assembly itself has a hard fault.

Examine it mechanically and check the wiring connections to it, make sure there is 240V mains voltage across it.

David
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Old 18th Jul 2023, 1:31 pm   #16
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Default Re: Grundig TK 141

Quote:
Originally Posted by Karl T 01 View Post
All bulbs working.
As the motor is also the power transformer for the electronics, I guess that "all bulbs working" would indicate normal operation in this respect, although if it were me I'd be checking and verifying that all voltages were correct and that nothing was unduly loading any of the supply lines. The thermal clutch that Reelman mentions in post #5 may be worth considering - it's not something I'm personally familiar with on these motors.

I thought I might have a 141 in my "collection", but when I checked late last night it seems I've just got the 121 and 126, both very similar to the 141, particularly the 121, other than they're both 2 track rather than 4 track machines. It was a bit of a task to dig them out, but having done so I decided to give them both a bit of a run, seeing as how they hadn't been touched for a few years. The 121 was a bit sluggish at first, but soon picked up and played well.
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Old 18th Jul 2023, 1:35 pm   #17
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Default Re: Grundig TK 141

Wondered if could simulate the motor problem by operating my TK 146 (basically the same as TK 141) on low mains voltage using Variac.

Brought the mains voltage up from zero slowly, at around 115V the motor started rotating/spinning (not at full speed) and the spin speed slowly increased as the voltage was increased until upto maximum speed was reached around 170V. Between 115V and 170V there was not a lot of torque on the motor and fairly easy to stop the motor rotating by tightly holding the motor pulley. Above 170V the torque rapidly increased and then impossible to stop the motor spinning by trying to hold the pulley.

All tests were done with all 3 drive belts fitted. At all times when the motor was spinning the motor was smooth and quiet in operation.

David
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Old 18th Jul 2023, 6:06 pm   #18
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Default Re: Grundig TK 141

Quote:
Originally Posted by Karl T 01 View Post
The motor also seems to generate heat quite quickly.
On my TK 146 the black body of the motor assembly gets pretty hot to the touch after at least 5 minutes of running.

David
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Old 18th Jul 2023, 6:30 pm   #19
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Default Re: Grundig TK 141

I think unlikely to be your issue but see Post # 1 of this linked Thread -

https://www.google.com/url?client=in...orlZIBhkZrpuNW

This references the motor pulley slipping on the motor shaft, just wondering if your motor problem could be similar, i.e. the motor is rotating OK but the pulley is slipping, on your video cannot see it clearly enough to see if the motor shaft is spinning properly.

David
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Old 18th Jul 2023, 6:54 pm   #20
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Default Re: Grundig TK 141

The motors on these recorders have bearings which are "self aligning". Try a few gentle taps on the shaft with a rubber mallet, or similar, in case the bearings have been disturbed in the past.

Paula
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