NAD 5420 CDP STA341M overheat

I have a NAD5420 cdp that IC506, STA341M gets very hot and cd stops playing.

Voltage supply to STA checked normal +/- 15V.
Cleaned spindle and sled motor, tested 5.9v current looks good, but no improvement.
New STA replaced, same thing.
Anyone can help here?
 
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The first thing I would check is the ac voltage readings on the dc voltage rails to the chip. Failing supply lytics could be dumping too much ac into it. The only other thought I had is that perhaps the platter motor has developed so much carbon buildup that it is drawring excessive current or its brushes may have worn through and are intermittently shorting.
Frankly, though, if this player has the MASH dac that it's listed as having, it's not worth putting much effort into. Those dacs are quite mediocre at best, no matter what you do with them.
 
According to the service manual Q506 is driving the sled motor and the pickup linear servos. You may have some machanical problem in the pickup itself, this may cause the IC to overheat. you can (VERY GENTLY!) lift the plastic cover of the pickup and look for anything that might limit the lens movement. If its not something very obvious, I would return the plastic cap and try to check capacitors C506 ; C503 (1000uF 16V) to see if there is any visible deformation (infalted or leaky). If you have a scope, check dc volatge on these caps as stephensank suggested. If you don't, I would offer to replace them. One important check is to see if the IC runs hot while NOT playing a cd.

If you need a service manual for this model you can get it at HIFI engine.

Let us know what you found.
 
According to the service manual Q506 is driving the sled motor and the pickup linear servos. You may have some machanical problem in the pickup itself, this may cause the IC to overheat. you can (VERY GENTLY!) lift the plastic cover of the pickup and look for anything that might limit the lens movement. If its not something very obvious, I would return the plastic cap and try to check capacitors C506 ; C503 (1000uF 16V) to see if there is any visible deformation (infalted or leaky). If you have a scope, check dc volatge on these caps as stephensank suggested. If you don't, I would offer to replace them. One important check is to see if the IC runs hot while NOT playing a cd.

If you need a service manual for this model you can get it at HIFI engine.

Let us know what you found.


IC is not hot while cdp is not playing.
Will check the lens later.
I have the service manual.
Thank you for help.
 
When cd is not playing, STA341 is not drawing much current from the power supply, so dying electrolytics(which I am fairly sure you have) may still have enough capacity to have low ac ripple. When cd runs, larger currents are drawn, so dying caps will cause excessive ac ripple to appear. Dying caps will not physically show signs of it most of the time. So, don't assume caps are good just because they look good. Measure ac ripple voltage with cd running.

And, btw, it was VERY rude the way you seemed to dismiss my previous advice out of hand. You don't know that I have 35 years of professional audio service/upgrade experience, but you could have at least been polite and acknowledged my post.