How to clean sealed volume pots? Marantz Model 7 sounds scratchy.
- Thread starter pete1729
- Start date
Register to hide this ad
Mr Creosote
Super Member
Drill a small hole. Put a little blob of grease where you drill the hole to catch the shavings.
pete1729
Super Member
I considered that. My subsequent view into the control suggests that if you do this, go through the back, not the side.
pete1729
Super Member
The volume pot on my Marantz 7 seems to be of a different external construction as I've been able to get Deoxit fader F5 into it. Unfortunately, it's always a temporary fix as the right channel eventually again makes a terrible sound if I rapidly turn the volume control up or down. Of course, I make it a point not to do that. I bought a replacement but have yet to install it. Maybe this summer. Take a look at the below comparison screenshot of your and my different looking pots. Sorry for the difference in the angle of my pic. PS-does yours have a resistor on one leg like mine? I think it attaches to the shield(?) edit -oops, I lollygagged too long before hitting "post", looks like yours has the resistor, too.
Last edited:
pete1729
Super Member
Yes, you can see it on the third and fourth photos, I think it's a 1K.
McCoy : My God, man! Drilling holes in the case isn't the answer!
Now put away your butcher knives and let me save this patient before it's too late!
pete1729
Super Member
I replaced the power supply, rectifiers, and a few coupling caps already. I'm trying to do a first class job, so I'm waiting to have sufficient squander money for some Cactus Caps.
I've replaced virtually all the coupling caps but none of the (lots and lots of) bumblebees on the tone controls. As a result, all bass and treble controls are in the center (off) position so hopefully no leakage from them. They would be an absolute bear to replace as confirmed by Kevin Hayes of VAC who should know! Is it possible they could be an issue?
should be able to just do a DC voltage reading at the volume pot. If its not zero volts, its coming from somewhere. Volume is upstream of the tone control stuff, so it looks like the only place its likely to get DC from is the output cap from the phono stage, whatever source(s) are on the line level inputs, or if somehow by wierd circumstance both V4A and V5A are gassy and have grid leakage problems.
Certainly not the hundreds of VDC seen in tube circuits. Also, most tube grids are not happy seeing a lots of VDC. I just check the VDC across the coupling caps. Especially, those with one side attached to the B+ taps. One side should read high VDC (hundred's), the other mVDC. Anything at or slightly above 1 VDC gets replaced. You can check your schematics, for the specific nominal voltages. Each sub-circuit within a unit has specific ratings, depending on their function.
DC Voltage tube's plate side.
DC Voltage tube's grid side.
So I'm fixing a Marantz 7 that needs a new volume control. Old one was completely noisy like if you barely touched the pot, major scratchiness and way beyond getting lucky with Deoxit and also not DC voltage leakage which I confirmed by breadboarding in a new pot and it works completely noise free. (By breadboarding, see picture for the rats nest of jumpers I used to test.)
Here is the pot I'm talking about. (No affiliation.)
Thoughts or other suggestions for a volume control for a Marantz 7? Certainly deserves the best. This project has been on my to-do list for a year and I'm done and no going back after I solder this thing in.
Here is the pot I'm talking about. (No affiliation.)
Thoughts or other suggestions for a volume control for a Marantz 7? Certainly deserves the best. This project has been on my to-do list for a year and I'm done and no going back after I solder this thing in.
Attachments
sometimes the carbon tracks just wear out and the only solution is a new part. At least that one doesn't look physically goofy so replacement shouldn't be horribly difficult. Is there a loudness tap? That makes it even easier. Also looks like a reasonable amount of space to work with.
maybe an Alps blue velvet if one will fit the space.
maybe an Alps blue velvet if one will fit the space.
Lavane
Lunatic Member
ALPS makes other more conventional looking pots as well.
If ordering an ALPS Blue Velvet, try and find a reputable vendor that sells the real deal. China sells a lot of fake ALPS pots. I'm pretty sure the 100K ALPS Blue Velvet dual pots without a loudness tap I've used in some of my builds are fakes. They track well and feel good, but I have read a few posts and a thread on them from another site that state these fakes dont last as long and aren't even the same inside. There's a way to tell by the lettering on the back, but I don't remember what it is. I do remember side by side pictures if real ALPS pots and fakes having subtle differences in the thickness of the lettering, etc. Maybe check out some Japanese vendors? ALPS pots most likely aren't real if coming from a Chinese seller.
If ordering an ALPS Blue Velvet, try and find a reputable vendor that sells the real deal. China sells a lot of fake ALPS pots. I'm pretty sure the 100K ALPS Blue Velvet dual pots without a loudness tap I've used in some of my builds are fakes. They track well and feel good, but I have read a few posts and a thread on them from another site that state these fakes dont last as long and aren't even the same inside. There's a way to tell by the lettering on the back, but I don't remember what it is. I do remember side by side pictures if real ALPS pots and fakes having subtle differences in the thickness of the lettering, etc. Maybe check out some Japanese vendors? ALPS pots most likely aren't real if coming from a Chinese seller.
