Help With Ross Phase R1

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retnev
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Post by retnev »

I need to replace the potentiometer on a Ross Phase R1 (Purple).
The potentiometer is utterly destroyed.
There is absolutely no resistance reading between the outer pins and the CTS potentiometer is not marked for value.

It seems someone put brakefluid in the potentiometer which in turn ate up the carbon track completely.

If someone has a purple Ross Phase R1, I would really appreciate it if you could
1) just measure the resistance between the outer potentiometer pins for the two cases of the potentiometer full open and fully closed.
and additionally if you have time,
2) set the potentiometer at 50% position and measure between wiper and outside pins respectively and send me the two readings

These 4 readings will pinpoint what it is as the original is not marked at all.

I would really appreciate it as I want to replace with identical potentiometer.

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george giblet
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Post by george giblet »

I don't have a unit to measure but the common CTS pots used on the Ross units are:
200-0003-00 500kC
200-0005-00 50kB

IIRC I saw one other number but it was very hard to read.

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retnev
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Post by retnev »

Thanks George
The purple ross has only one potentiometer.
Do you by chance know which of the two you listed are issued in the purple?
The 500k you listed seems to be a reverse audio taper.
Since there is no schematic available, the best is to ask users who have unmolested once to measure according to what I described in my original post. I can work out value and taper from those measurements.

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george giblet
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Post by george giblet »

Do you by chance know which of the two you listed are issued in the purple?
The 500k you listed seems to be a reverse audio taper.
I thought you might be able to read the back of the damaged pot.

I don't know the part used in the Purple unit.
There's a *very* high certainty it's a 500kC (reverse audio).
All the Ross pedals I've seen with a speed knob use the 500kC.

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retnev
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Post by retnev »

george giblet wrote: 08 Aug 2022, 02:49
I thought you might be able to read the back of the damaged pot.
.
No, as I stated in my original post
The potentiometer is utterly destroyed.
There is absolutely no resistance reading between the outer pins and the CTS potentiometer is not marked for value.
george giblet wrote: 08 Aug 2022, 02:49
I don't know the part used in the Purple unit.
There's a *very* high certainty it's a 500kC (reverse audio).
All the Ross pedals I've seen with a speed knob use the 500kC.
.
Thanks, it is a guess but a good guess. I will use that until someone can measure an original one.

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Post by george giblet »

Thanks, it is a guess but a good guess. I will use that until someone can measure an original one.
There's some back-up info in that those Ross units are MXR clones and the MXR also used the 500kC's.
But also a small amount of doubt as they could of up'd the pots to 1MC to increase the range or something like that.
(I don't have my detailed notes but the very early MXR's have some differences to the later ones. I know MXR change
the speed pot part number at some point but I can't remember if was a subtle change like 10% taper to 15% taper or
a value change.)

All annoying details when you are trying to do the right thing and use the right pot!

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retnev
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Post by retnev »

Exactly !
Thanks.

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george giblet
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Post by george giblet »

Still not entirely convincing but I found pics in a number of Ross pedals all with the pot I previously couldn't read.

In all similar pedals and all later Ross pedal the pot in this position is a 500kC pot.
There are no measurements to back this up.

The CTS/Ross part number is BY8534.

The Ross Phase R2 is the clearest pic.
If you download the images you can zoom in.


Ross Phase R1 script - speed
Ross Phase R1 script - CTS BY8534 speed pot pic1.png
Ross Phase R1 script - CTS BY8534 speed pot pic2.png
Ross Phase R2 block - speed (phase 45 board)
Ross Phase R2  (phaser 45 block) - CTS BY8534 pot.png
Ross Phase R2 (phaser 45 block) - CTS BY8534 pot.png (432.41 KiB) Viewed 1722 times
Ross Distortion script - Distort
Ross Distortion script - CTS BY8534 distort pot.jpg

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wildschwein
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Post by wildschwein »

I reckon that pot in the R1 closeup does say 13777... soemthing:
Attachments
Pic.JPG

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CheapPedalCollector
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Post by CheapPedalCollector »

Hah no wonder MXR got pissed at them. Total clones.

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Post by george giblet »

I reckon that pot in the R1 closeup does say 13777... soemthing:
The 137yyww number is the manufacturer and date:

137 = CTS (the manufacturer)
yy = tens and units of year of manufacture ; 77 = 1977
ww = week of manufacture

The other number is the part number. In the case of MXR pedals it's an MXR part number.
For the Ross pots it could be a part number designated by Ross or a number designated
by CTS for Ross.

The part number implies a pot value and a taper, maybe even a size.
You can't start with the part number and work backwards to the pot value and tape
unless you have a look-up table (which isn't published). If you have other pedals
with known values then you can cheat.

The later CTS pots have a different scheme. You can google the new and old formats.

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Post by Lithium_Grim »

With all due respect, but this is slowly changing to a cork sniffers thread. Solder a C500k in it and see if it works as you'd expect. Else try other values. If it sound as you like, just doesn't react to turning the pot as you like, try an A or B taper. Get on with it!
I only give negativ feedback and y'all love it!
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Post by george giblet »

It's clear the guy is trying to restore the pedal to the original state.

Given it's a speed pot there's no doubt it's a C taper.
The fact all the example pedals copy the MXR pedals backs that up.

The only hanging issue is if it is 500kC or 1MC.

Both will work but only one will match the original.

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Post by retnev »

20220812_203754.jpg
Same code, that was helpful.
I could barely make out, but it does seem to be BY8534.
It is badly pitted there.


Dont know what the prev owner threw into the potentiometer. Smells like transmission fluid, and as I mentioned no track left. Seemingly dissolved.
Automotive fluids will most likely dissolve carbon depositions.

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Post by george giblet »

Dont know what the prev owner threw into the potentiometer. Smells like transmission fluid, and as I mentioned no track left. Seemingly dissolved.
Automotive fluids will most likely dissolve carbon depositions.
That's a weird one. It has to be something done deliberately. At first I thought maybe a previous owner had the pedal in his car boot and something got spilled on it but it doesn't seem likely to make it all the way to the inside of the potentiometer.

The pitting on the back of the pot is usually due to corrosion caused by the foam. You can see some examples in the pics I posted above. You get the same problem on MXR pedals. It's not going to eat the inside of the pot away.

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