Beogram 6000 arm doesn't move to the left

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FX Posted: Wed, Oct 25 2017 1:08 PM

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beogram6000_motor_diagram.jpg

Hi,

I am restoring a Beogram 6000 when a new problem showed up. The arm stopped moving to the left. Works perfect when moving right.

I tested the Motor drive Board and got the folloing results.

The technichal diagram (attached) provides the following values for the motor voltage:

Action     P5(2)     p5(4)

>>            1.4v      13.5v

<<         13.5v       1.4v

>            1.4v        5.5v

<            5.5v        1.4v

What I measure is

Action     P5(2)     p5(4)

>>         14.7v      14.7v

<<         12.5v       1.8v

>            6.3v        6.3v

<            4.4v        1.8v

It seems consistent as the Motor voltage (p5(2) - P5(4)) is 0v when there is a > or >> action.

Before I change all the possible transistors or  diodes, I wonder if anybody could lead me to the faulty component. I suspect TR19-26, but I'm not sure.

Thanks for your help.

FX

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ProGram replied on Fri, Oct 27 2017 5:22 AM

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Hi, I think the transistors 21 and/or 22 might be faulty, or the parts around there. Or bad solder joints. With a 4002 I think, i experienced a short to ground coming from a mounting point, that is in the near of one transistor contact.

Chris

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FX replied on Sun, Oct 29 2017 11:11 AM

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Thanks Chris for looking into this.

I'll start there and keep you posted to see if your predictions come true.

FX