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ALPS Motorized Volume Pot- Repair (VTL 5.5 Preamp)

Hi,
Need some help diagnosing a strange problem with my VTL Preamp’s Volume pot. It uses an Alps motorized pot, that is controlled via the remote. When I turn on the VTL, the remote controls the volume normally for the first couple of minutes and then stops working. 

Manually the the volume pot works perfectly, smooth, precise and with no crackling. I’m guessing that there is something happening when the preamp warms up that cuts off the remote control of the pot.. any theories?

im pretty handy and would feel comfortable trying to perform a repair myself, but could use some experienced advice.

Thanks!!
128x128arniespin
5 responses Add your response
arniespin's avatar
arniespin OP
24 posts
 
Hi Cedargrover-
the preamp is solid state regulated. Haven’t started measuring voltages yet but I’ll definitely have a look at the volume motor ( before and after it cuts out).

Kijanki-
I’ll have to time it to see if it always takes the same amount of time to cut out. No numeric display on this pre.


kijanki's avatar
kijanki
4,428 posts
 
Arniespin, Does it always happen after exactly 2 minutes?  Does volume on numeric display change?
cedargrover
302 posts
 
Strange!

In the failure mode, have you put a meter to the motor driving the volume to see if it is getting voltage when you hit the remote button?  

If it isn't seeing a voltage maybe something power-supply related after warm up.  Does this unit use tubes in the power supply (like, is it tube regulated or solid state regulated), or just in the audio stages?  If so, have you tried replacing them?

Where's @almarg?  :)

arniespin's avatar
arniespin OP
24 posts
 
Thank you Kijanki!
I will try the shake method but I’m doubtful that it will work because the volume control is the only thing that cuts off- the mute and phase-shift buttons on the remote always work normally. 
kijanki's avatar
kijanki
4,428 posts
 
I had the same problem with Benchmark DAC3 HGC.  After half an hour of playing whole remote would stop working.  I found that infrared receiving diode was poorly soldered barely making contact.  I re-soldered it and it works fine.  Try, when it stops working, to shake chassis (or pound it lightly with the fist).
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