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?

Re: Schaub Lorenz 5001 help needed
 

First verify with it in the case but without the signal leads connected.

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.

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.

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

Re: Schaub Lorenz 5001 help needed
 

Thanks Ricard. As far as I can see, the solenoid that is oscillating only has one coil.

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.

Re: Schaub Lorenz 5001 help needed
 

Thanks Dave. I've had a poke around and everything seems sound around the switches. 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.

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.

Re: Schaub Lorenz 5001 help needed
 

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