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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 23rd Jul 2019, 5:15 pm   #1
Tandy01
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Default Schaub Lorenz 5001 help needed

Afternoon all,

I have a really strange fault with the rewind on my machine: With the chassis removed from the case it works perfectly on pressing the stop button, or when it gets to the end of the tape. I have the power leads connected, but the signal leads are too short to connect with it out of the case.

With it in the case, (and the signal leads connected) the solenoid engaging rewind randomly oscillates, making an awful racket.

I thought this might be the LDR tape end sensor somehow getting illuminated by reflections from the box, so I connected a switch to disconnect the LDR. The problem remains, so I can only think the problem must be to do with the signal leads in some way.

Any thoughts?
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Old 24th Jul 2019, 2:45 am   #2
Maarten
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Default Re: Schaub Lorenz 5001 help needed

First verify with it in the case but without the signal leads connected.
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Old 24th Jul 2019, 1:49 pm   #3
Tandy01
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Default Re: Schaub Lorenz 5001 help needed

Thanks Maarten.

Okay, I just tried it. Now it even oscillates with just the power leads connected when it is inside the box.
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Old 31st Jul 2019, 12:17 pm   #4
ricard
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Default Re: Schaub Lorenz 5001 help needed

It's not one of those solenoids where there is a low-impedence pull-in coil and a high-impedence hold coil, with some form of switching between them? I.e. so the pull-in coil is energized until the plunger is home, and then the hold coil is energized, with less current drawn and power dissipated, as it is still strong enough to hold the plunger in place but not to pull it in.
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Old 31st Jul 2019, 12:30 pm   #5
Radio_Dave
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Default Re: Schaub Lorenz 5001 help needed

I would check the pcb for the push buttons for for broken tracks. It's a poorly designed, flimsy part and could be flexing when you return the chassis to the cabinet.

Regards
David
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Old 31st Jul 2019, 10:28 pm   #6
Tandy01
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Default Re: Schaub Lorenz 5001 help needed

Quote:
Originally Posted by ricard View Post
It's not one of those solenoids where there is a low-impedence pull-in coil and a high-impedence hold coil, with some form of switching between them? I.e. so the pull-in coil is energized until the plunger is home, and then the hold coil is energized, with less current drawn and power dissipated, as it is still strong enough to hold the plunger in place but not to pull it in.
Thanks Ricard. As far as I can see, the solenoid that is oscillating only has one coil.
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Old 1st Aug 2019, 8:54 am   #7
ricard
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Default Re: Schaub Lorenz 5001 help needed

Sometimes there is a series resistor and associated switch which achieves essentially the same function. I've had the pinch roller solenoid in a Grundig TK819 end up in an oscillating state when activated due to failure of the resistor - essentially, the whole mechanism turns into a (low frequency) buzzer.
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Old 2nd Aug 2019, 7:08 pm   #8
Tandy01
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Default Re: Schaub Lorenz 5001 help needed

Quote:
Originally Posted by Radio_Dave View Post
I would check the pcb for the push buttons for for broken tracks. It's a poorly designed, flimsy part and could be flexing when you return the chassis to the cabinet
Thanks Dave. I've had a poke around and everything seems sound around the switches.
Quote:
Originally Posted by ricard View Post
Sometimes there is a series resistor and associated switch which achieves essentially the same function. I've had the pinch roller solenoid in a Grundig TK819 end up in an oscillating state when activated due to failure of the resistor - essentially, the whole mechanism turns into a (low frequency) buzzer.
Thanks. I think you might have put your finger on it. If I'm looking at the right bit of the circuit diagram, there seem to be voltage dependent resistors in series & parallel with the solenoid coil. I will investigate further.
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Old 2nd Aug 2019, 9:04 pm   #9
ms660
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Default Re: Schaub Lorenz 5001 help needed

So far as I can make out the brake solenoid is actuated using the full 30 volts, and when home, bm contacts 1&2 and 3&4 break, that then in effect connects the rewind solenoid in series with the brake solenoid so the rewind solenoid is in effect acting as the dropper for the brake solenoids holding voltage, around that part of the circuit the VDR's look like snubbers.

Then again I might be wrong.

If someone can convert this PDF to English text it might shed light on some of the circuit operations:

http://www.ilove-schaub-lorenz-music...el%201998).pdf

Lawrence.

Last edited by ms660; 2nd Aug 2019 at 9:13 pm.
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Old 9th Aug 2019, 7:21 pm   #10
Tandy01
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Default Re: Schaub Lorenz 5001 help needed

Quote:
Originally Posted by ms660 View Post
So far as I can make out the brake solenoid is actuated using the full 30 volts, and when home, bm contacts 1&2 and 3&4 break, that then in effect connects the rewind solenoid in series with the brake solenoid so the rewind solenoid is in effect acting as the dropper for the brake solenoids holding voltage, around that part of the circuit the VDR's look like snubbers.

Then again I might be wrong.

If someone can convert this PDF to English text it might shed light on some of the circuit operations:

http://www.ilove-schaub-lorenz-music...el%201998).pdf

Lawrence.
Thanks Lawrence. I think I'll have to type sections of that into Google translate and see what it comes up with.
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