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Marantz 7 Volume Pot?

J

jpk000

New Member
I had my Marantz Model 7 restored last year after many years in storage. Since then the volume pot has been getting more and more scratchy in the right channel until around 11 o’clock. The volume pot was not touched during restoration as it sounded fine at the time. I brought it back in to the shop and they cleaned it up. Sounded ok for a few months but now scratchier than ever. Anyone know of a good replacement volume pot?

I have seen the ones posted on eBay saying they are direct replacements for a number of different amps Including the model 7, but I know the resistance on those pots are not the same so I doubt this is a good replacement. Thanks
 
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I have been waived off of those $90 Volume pots on eBay by several AK members when considering for replacement in an old Sansui.
 
The correct vintage replacement is like $500+. The modern replacements are junk. You would be best off either having yours rebuilt or investigating whether it’s being affected by DC voltage leakage and that’s what’s causing it.
 
I would second the DC on the pot causing it to repeatedly get noisy theory. One of the coupling capacitors that block DC from the pot may have gone leaky (infant failure), or may have been put in backward.
 
jpk000 said:
I had my Marantz Model 7 restored last year after many years in storage. Since then the volume pot has been getting more and more scratchy in the right channel until around 11 o’clock. The volume pot was not touched during restoration as it sounded fine at the time. I brought it back in to the shop and they cleaned it up. Sounded ok for a few months but now scratchier than ever. Anyone know of a good replacement volume pot?

I have seen the ones posted on eBay saying they are direct replacements for a number of different amps Including the model 7, but I know the resistance on those pots are not the same so I doubt this is a good replacement. Thanks
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Look at the current thread on this current page 1 forum for replacement pots, do not buy from this guy at all. Buyer beware!!!
 
I know its not what youre looking for but AK member Crooner has had good success installing a Khozmo stepped attenuator in these. They also have a remote option.

Out of curiosity, anyone ever attempt to clean a carbon track volume pot in an ultrasonic bath?
 
Thank you all for your input. I’ll bring it back to the shop and see if he can check for DC leakage or rebuild the pot. Dave at HiFi Sound in Minneapolis did the restoration and he has a good rep here on AK. I would be surprised if he missed DC leakage but stranger things have happened.
 
This is a ganged pot and I was able to remove the cap from the outer pot and thoroughly clean it with deoxit. I also sprayed deoxit through the tiny split where the cap is held onto the inner pot and just turned the shaft back and forth a million times. Started it up and the pot is dead silent. Amazing.

Before doing this I tracked down a source for a replacement pot in case I broke a metal clip or screwed something up poking around. Also I am expecting the degradation to return at some point. Mark Oppat at Old Radio Supply (https://www.oldradioparts.net/) builds potentiometers for, you guessed it, old radios and equipment. I reached out and he said he could build a 500k ganged pot for a very reasonable price. I sent him the specs of the shaft and Marantz part no. I am hopeful that Mark will be able to pull through. Sharing this source for others looking for an old unobtainium potentiometer and for good audio karma.
 
If the noise comes back fairly soon, I would still check for DC on the pot before replacing it.
 
jpk000 said:
Thank you all for your input. I’ll bring it back to the shop and see if he can check for DC leakage or rebuild the pot. Dave at HiFi Sound in Minneapolis did the restoration and he has a good rep here on AK. I would be surprised if he missed DC leakage but stranger things have happened.
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Check....I've seen some units with the HiFi Sound sticker that verge on hack jobs.
 
jpk000 said:
Uh oh, I thought I had put these in good hands. Do you know of a better repair shop in town?
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Tyler at TC Tubes knows his stuff. Or Savage Audio, I do all the solid state stuff that comes in there. However, both places are backed up and spendy.

I've heard good and bad about HiFi. One of my friends that works at Midwest Speaker says great things, but I have seen at least 6 units with their sticker on it. And if I'm seeing it, it's not working currently.
 
Well you all were correct and the scratchiness has come back quickly and in full force. Thinking it is definitely DC leakage and will have to check.

Also, the volume pot I ordered arrived. Despite providing exact measurements for the shaft protruding from the faceplate and thickness of the chassis and faceplate the cut shaft is much too short. The pots are also flimsy with too many plastic components, not a smooth turn, and the open back is protected only by a sticker, which fell off. :whip:
 
Hi, I have the dreaded Marantz 7 noisy volume pot problem and found this thread.

I acquired this Model 7 several years ago and it worked beautifully for a few months and then the volume pot (I assume) started to go to hell - as in barely move the control and major noise. Eventually could not even switch to an unused input, move the volume around a bit and then switch back to the live input, i.e. noise is just there permanently. (My reason for suspecting the pot is that the previous owner said it was taken apart and cleaned so I assumed it was already a problem component. Yes, we're talking the original pot here.)

So I see in this thread that DC leakage could be the problem. How does one diagnose that? Do I lift capacitors and measure something?

Anyway, I have this gorgeous unusable amp and it is fix or sell decision time. (Note: I have always powered it up for a few hours every month or two even though I can't listen to it, so it has not been in a storage locker letting the electrolytics deteriorate or anything like that.)

I can solder, replace components, use a multimeter and pay attention to details and good at things like restore Dynakit amps, but I lack advanced diagnostic skills.

Any advice or thoughts here is appreciated.
 
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