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-   -   Marantz 2275 vol. pot problems (http://www.diyaudio.com/forums/solid-state/220432-marantz-2275-vol-pot-problems.html)

djb 26th September 2012 12:54 PM

Marantz 2275 vol. pot problems
 
I need help with the vol. pot in my 2275 Marantz. It workd ok fo awhile them the right channel goes staticy and out. If I move the knob to a hight vol. it starts to work, but when I move it back to lower vol. it returns to the no vol. I have cleaned the pot with electrical contact cleaner and it worked for awhile then went right back to the same symptoms. Is it shot or did I do smoething to damaged it with the cleaner.

Ian Finch 26th September 2012 01:35 PM

I dare not guess just how old your receiver is but it's easily old enough to need a complete refurbishment or replacement of all moving parts and electrolytic capacitors, lamps, etc.

Variable pots, as used in the volume control have a limited life of so many thousands of rotations before the carbon film which the rotor contact arm wipes as you turn the knob, simply wears away and you lose continuity and the signal. Nursing it with lubricants can obscure the problem for a while but the end is near and now you must replace it.

This is not easy for old Japanese style amplifiers which usually have loudness controls incorporated. You can see this if there is an extra terminal, placed about midway around the pot body. You will have extreme difficulty sourcing one of these as this system of tapped volume controls was dropped 30 years ago. You will have to lose this feature in order to fit a standard part that matches the resistance value and the dual logarithic taper potentiometer required. Apart from any difficulties arising with the loudness circuit, this should be a simple operation if the replacement is big enough to either hard wire or fit in the pcb. Check fits, shaft size and type (spline or plain shaft) etc. before ordering.

djb 26th September 2012 05:03 PM

Thanks Ian. I will explore this avenue. I love the reciever and hate to part with it. I will start my search for a possible replacement. Wish me luck I will need it I am sure.

RJM1 26th September 2012 06:17 PM

The service manual with schematic is available at HIFIengine you just have to create a free account to download. They crammed too much into one page for me to find the volume control on the schematic with my 15" laptop at the bar.
Marantz 2275 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine

Ian Finch 27th September 2012 05:24 AM

Thanks RJM1. Yes it appears pot R005 is tapped and works in concert with switch ST01-3 and its RC low pass boost/filter. It wouldn't hurt to lose this and use the bass control if necessary, anyway. Getting original pots is still a huge headache. Perhaps the 2275 web fan club members have some assistance to offer?

djb 27th September 2012 11:30 AM

Thanks Guys. Loosing the low/pass boost filter means nothing to me as I use the amp in the tone off setting. Finding a pot that will just keep the amp working would be satisfactory to me. I will look into the 2275 web club for assistance.


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