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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 13th Jan 2017, 11:26 pm   #1
Spectreman
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Default Tandberg 1241 reel to reel deck help

Hi all.
I now have a very nice Tandberg 1241 4 track reel to reel deck, in very good physical condition.
It is basically working ok, but the L channel audio is dead.
But what I want to ask about is the correct way to install the main belt, which I have replaced. There is no diagram in the service manual for this !
I think I have done it correctly, the Play & FF functions work fine.
But Rewind is very slow & sluggish.
Can someone please advise me about the main belt installation ?

Thanks ! Cheers, Chris
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Old 14th Jan 2017, 1:00 pm   #2
Michael Maurice
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Default Re: Tandberg 1241 reel to reel deck help

The reason why rew is possibly sluggish is because the clutch material has failed.
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Old 15th Jan 2017, 3:54 am   #3
Spectreman
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Default Re: Tandberg 1241 reel to reel deck help

Ok Michael, thanks, I will check this out.
By the way, the record works fine on the R channel.
Just have to sort out the L channel audio fault.
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Old 15th Jan 2017, 9:54 pm   #4
saxmaniac
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Default Re: Tandberg 1241 reel to reel deck help

Check dirty rec/play switch. You may need to strip it to clean properly. It's doable if fiddly
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Old 16th Jan 2017, 1:57 am   #5
ben
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Default Re: Tandberg 1241 reel to reel deck help

I have also found slow rewind caused by the backtension being out due to hardened grease on the slide plate(s) which I think also affects braking. Quick check, without a tape put a business or credit card in the tape end sensor, put it in rewind and see if the take up spool rotates counterclockwise. If it does, grasp it and see how much tension you can feel (should be very little, a light touch ought to stop it). That should give you a rough idea if this is the cause.

PS. Main belt should cross over itself just after the supply spool and sitting on the upper and lower parts of the motor pulley. pic
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Old 16th Jan 2017, 8:53 am   #6
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Default Re: Tandberg 1241 reel to reel deck help

Regarding the belt, if you look at the service manual in the link for the in this respect mechanically identical model 6X, there's a picture of the belt path on page 8 and a textual description in section 4.4.1 on page 17:

http://www.sportsbil.com/tandberg/tb-6x-sm.pdf

Is the L channel dead when listening via the external low level outputs too, or only via the speakers? If it's only via the speakers, a common cause is the driver transistors on the power amplifier boards which can suffer from the so-called tin whisker problem, causing the transistors to short internally. They can be replaced, although replacements may be hard to find, but it is often successful to attempt to short 'burn away' the internal tin whiskers which have formed by removing the transistor in question from the machine, tying the three transistor connections together, and connecting them to a charged 10µF/10V capacitor or similar for a second or so. Although the problem will eventually come back, it can take many years for it do so. Getting at the transistors is fairly awkward though (if I remember correctly not only do the power amplifier boards have to be removed, which is awkward in itself as the mounting screw is a bit fiddly to reach, but the heat sink for the output transistors needs to be removed to get at the back of the board, necessitating desoldering the power transistors too).

What is the serial number of the machine? Machines below 2209550 are problematic in that the rec/play switches quickly get scratchy even after cleaning, whereas higher ones seldom have problems to start with.

My experience with the clutches on these machines has been that since they are composed of a felt disk pressing against a mylar film, the never wear out, but the felt seems to get slightly slippery with age, causing loss of friction. I've corrected this by applying small amounts of so-called 'damping grease' (not ordinary grease, that just makes matters worse!), but it's hard to hold of.
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