Ok - this isn't a stomp box per-se but it is an old analog effect.  Figure someone here might some ideas: 
I've come into possession of an old Yamaha E1005 delay that seems to have spent most of its life in a cloud of cigarette smoke. IMHO the pots are unsalvageable so I'm going to replace them first.

Because nothing is easy, most of the pots are common tapers and a few are not.  Would like the forum's thoughts on replacements:

Service manual and schematic are here: Yamaha E1005 Service Manual

Common pots:

• Inputs A & B : A25K # Easy!
• Delay Feedback: B10K # Easy!
• Mod Speed: C250K # Reverse Log pots are somewhat unusual but not too hard to find
• Mod Depth: B10K # Easy!

Weird Tapers

• Delay time: ZD5K # This one really has be stumped.  Internet sleuthing says "D" pots are log with a slightly different curve. But can't find anything about the "Z"
• Mixing: D/B 10K # This is a wet/dry control so I figure linear pot but with slight curve cause of the "D".  Maybe just a B10K?

Any advice is welcomed!

Thanks.

I could be wrong, but I know too much about tobacco: Carb Cleaner will probably flush the tar and dirt and even nicotine, and then 99.88% evaporate. I had to check, but you can still buy carb cleaner.

This stuff is TOXIC! Use outdoors in a breeze. Wear goggles!!! (My cataracts came a month after a face of carbcleaner, and they are expensive.) Also rots lungs and kidneys. Not fun to snort. But it will remove a lot of substances. (Yes, paint!) You will need to re-lube the pot after this.

Haha thanks PRR, that stuff looks pretty nasty!!!  I have to remove the pots to clean them anyway, so I'd rather just go ahead and replace them.

So the question remains.... what replacement to use for:
ZD 5K Potentiometer
D/B 10K Potentiometer

ok - so upon closer inspection of both the schematic and actual unit, I've solved half of the mystery.

"B / D 10K" Pot - is a dual gang affair with B and D tapers on separate wipers.

Still puzzling over the ZD 5K Pot - this post seems to indicate that a Z pot is just another term for a log pot, but seems odd that this device specifically calls for Z pots (vs A pots in other parts of the circuit): Potentiometer FAQ

That's an excellent service manual.

Unfortunately, I couldn't find much about that BA617 VCO chip. There's a little bit in the Yamaha IC guide, but it's slight. Specifically, it doesn't say anything about how the CV inputs respond (whether they're V/Oct or V/Hz or whatever). So it's hard to guess what the pot taper might need to be.

Oddly, when I built the bigger brother/sister, the E1010, I used the bog standard EH 4047 clock for delay only!

For those following along at home...

Further internet sleuthing seems to indicate there is no such thing as a dual-gang pot with linear and log tapers.  In fact, it would appear that for Wet/Dry controls the thing to use a "MN" tapered pot.

The MN taper means that at the center position both signals will be at 100%.

Likely the "B/D" pot in this device is actually an MN pot anyhow.

Google-fu has failed on the ZDF pot though, I will probably just order a linear and log 5K pot and try my luck.

Quote from: box_maker_1 on June 02, 2024, 11:26:40 PMGoogle-fu has failed on the ZDF pot though, I will probably just order a linear and log 5K pot and try my luck.

Yeah, good plan.