Denon DP-75 runaway

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bendoggie
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Denon DP-75 runaway

Post by bendoggie » 26 Feb 2018 06:49

I have a Denon DP-80 and a DP-75. I have not used the 75 for about a year and now that I have a new plinth for it the 75 has decided to malfunction. I turn it on and it speeds up to rediculous rpm and i have to shut it off. I also noticed that the wires connected to the read head are green with oxide. This might just be a coincidence and it might be an IC. any Help will be greatly appreciated as these are my absolute favorite turntables.

tckmet
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Re: Denon DP-75 runaway

Post by tckmet » 26 Feb 2018 07:27

Try cleaning the oxide first.

bendoggie
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Re: Denon DP-75 runaway

Post by bendoggie » 26 Feb 2018 14:23

I dont see how i can clean that without cutting off the wires and resoldering them. Will the heat damage the head ?

TudorTurtle
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Re: Denon DP-75 runaway

Post by TudorTurtle » 26 Feb 2018 14:31

Try cleaning with deoxit first. Work on the messy solder connection and the speed control switches. Cleaning the speed controls did the trick on my vintage DD that was spinning out of control.

Coffee Phil
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Re: Denon DP-75 runaway

Post by Coffee Phil » 27 Feb 2018 06:30

If the connections are still intact clean the oxide with a solution of baking soda and water. Use a flux brush. After that, rinse the baking soda off with water. Don't get nuts with making it pretty we just want to stop the corrosion. Use the same brush several times rinsing it with water between steps. After the leads are dry cover the bare parts of the wire with clear RTV silicone sealer.

The above will not likely restore the operation but it is the right thing to do.

The service manual is here: https://www.vinylengine.com/library/denon/dp-75.shtml

With an oscilloscope observe the signals from the heads at each stage until you find the failure then investigate the cause. Note that there are two heads each with its amplifier to resolve the direction of rotation.

Phil
bendoggie wrote:I dont see how i can clean that without cutting off the wires and resoldering them. Will the heat damage the head ?

funkhawk
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Re: Denon DP-75 runaway

Post by funkhawk » 01 Mar 2018 20:42

Try to reposition the "reading head".
Normallly it is strongly recommended never touch the position of the reading head, but now you experience problems, it might solve your problem.
Only reposition the head a tiny little bit could be sufficient.

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