Potentiometer seems to be the same on both 1987 series and 1990 series.

I can read something on the side of the blue 1990 potentiometer :
91D1DW32D15
10K MEXICO
J9139X

I can't read much for the 1987 potentiometer, it's blocked by the 1/8 headphone jack.

Edit :
Adding a picture of an 1987 AdLib under a light, to see how many connections that potentiometer has, and the distance between pins.

So there are only 3 pins, that's a mono potentiometer. They are pretty close together too, between pin 1 and 3 there are 5 millimeters.
Also, the pins are in a row that is perpendicular with the knob itself.

Searching for a match or equivalent, will report findings.

Edit 2 :
Part number 91D1DW32D15 seems to indicate that this part is not produced anymore.

Closest equivalent seems to be this one, in regards to size, shape, position of pins, and distance between pins :
http://www.ebay.ca/itm/51AADB28B15-10K-BOURNS … S-/370606237078

That ebay one is not so great a match IMHO.
The original is audio taper. The eBay one is linear taper.

91D1DW32D15 is also written 91D1D-W32-D15
It's a Bourns model/series 91. https://www.bourns.com/pdfs/90SERS.pdf (updated)
These are 5/8" square.

51AADB28B15 is also written 51AA-DB28-B15
It's a Bourns model/series 51. https://www.bourns.com/pdfs/50.pdf
These are 1/2" square.

The PDFs have part number decoders a page or two down.

91D1DW32D15
91 - Single Turn, In-Line PCB Pins
D - 3/8"x3/8" bushing, unthreaded (updated)
1 - Single Deck
D - No Anti-rotation Lug
W - Plastic Shaft, Knurled, 1/4" Diameter
32 - 1" Shaft Length
D - Clockwise, Audio Taper
15 - 10k Ohm

51AADB28B15
51 - PCB Pins, 0.1" On Centers
A -3/8"x3/8" Bushing
A - Single Deck, No Detent
D - No Anti-rotation Lug
B - Slotted Shaft, 1/4" diameter
28 - 7/8" Shaft Length
B - Linear Taper
15 - 10k Ohm

Found a newer datasheet for the 91 series - updated.

PCBONEZ wrote:

7/8" Shaft Length

Pffftcchhh!

Worst case scenario, you can use resistors in place of the pot. You just won't be able to change the volume without changing the resistors.

PCBONEZ wrote:

The original is audio taper. The eBay one is linear taper.

Something I completely overlooked. Thanks for the correction.

I had tried searching on the Bourns website directly by part number, with "91D" but no results came up.

Beegle wrote:

PCBONEZ wrote:

The original is audio taper. The eBay one is linear taper.

Something I completely overlooked. Thanks for the correction.

I had tried searching on the Bourns website directly by part number, with "91D" but no results came up.

Yes their site is a PITA. Hard to find anything.
Their cross-reference doesn't even work for their own parts. That's why I listed all the specs.

Replacement parts should be available but maybe not that brand.
Mouser has an assortment but I saw that before I found the specs so haven't looked in detail.
.

Any with threaded bushings (threads to panel mount them) may have issues fitting through the hole in the card's back-plate.
Measure carefully.
.

http://www.mouser.com/search/ProductDetail.as … y91A1A-B28-D15L
http://www.digikey.com/product-search/en?mpar … D15L&vendor=118

Wow, thanks everyone for the overwhelming amount of replies, and especially PCBONEZ for finding the part. I'm going to order it, and get it installed, and then report back if the AdLib is back to life or not... Fingers crossed!

BTW, do you think it would be safe to install the card in this condition in a PC, just to see if it's still detected by software? Of course I would not connect anything to the output.

Chain-Q wrote:

BTW, do you think it would be safe to install the card in this condition in a PC, just to see if it's still detected by software? Of course I would not connect anything to the output.

I think it would be as safe now as later.
Anything wrong with the card that would blow something on the mobo will still be there after you replace the volume control so you might as well check now as later.
Such a problem would most likely be a power issue (not a signal issue) and the volume control should not make any difference to that.

I don't -think- the lack of a volume control would prevent the card from starting.
If it does then temporarily use a resister 1/3 to 2/3 of the pots range (10k - so between about 3k and 6k) to replace the pot for testing.
-
For the test resistor anything between 1k and 10k should work.
Trying to stay in the middle 1/3 of the range is an attempt to keep it form being so quiet you can't hear anything or so loud you can't stand it.
.

Ok, so... just to make an update since there was progress... It turned out I wasn't exactly in a hurry with this (...), but two weeks ago finally ordered the part. I got it in mail yesterday, and by today it's even soldered to the card. 😁

Pictures: https://twitter.com/chainq/status/1056245130255052800

To be seen if it still lives... But at least it's complete now!

Looks great! If you need a replacement OPL2 or DAC, I have some left from when Iassembled the Adlib replicas. But my guess is that it willbe fine.

It works! 😁 Also the volume control works as expected.

First I thought it was dead/buggy, because most software had glitches (but some, like Prince of Persia worked) but then it turned out for some reason I had to disable the clock doubler and/or caches on my Make-It-486 (TI 486sxlc/40) upgrade in the 386sx/20 where it lives. After this, all software I tried (PoP, LHX, Indy 500, Prehistorik, few others) sound as expected. I wonder there's a workaround for this, or indeed, this box is just too fast for the AdLib.

I'm so glad it works! Good job 😁

I made a short (and bad quality) video about testing the card in my Amiga 2000 with the CBM PC Bridge it sports:

https://www.youtube.com/watch?v=uWiOHXu--8M

I know it's been a while, but thanks once more to everyone for the help!