When these radio controls are no longer available (from Kenwood Parts),
such as your Kenwood TR-751 Volume; Squelch control w/ switch function (power),
You need to determine the following:
1. The Big 3 (Kenwood, Icom, Yaesu) -- traditionally use Japanese (or Eastern Asia) component mfg.
Determine mfg. and part numbers -- by reading ANY marking present.
2. It is not uncommon to find identical parts used on other radios (same mfg, different mfg.)
3. For a control pot, you need to determine IF these are AUDIO or LINEAR taper.
A Volume control is usually AUDIO taper, while the Squelch control is usually LINEAR taper.
4. IF you substitute a different mfg., such as CTS -- then measurements are KEY.
USA made parts will be English and Metric, while majority of Big 3 eastern Asia parts are all METRIC.
5. It is possible to repair some of these control pots, that do not use conductive plastic.
Again, parts from control pots by the same mfg. are invaluable in this DIY repair approach (don't need to be same value).
6. Scour the surplus outlets for Japanese / Eastern Asia parts. Many resellers in Hong Kong are doing this today,
and selling parts and assemblies via eBay.
We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths. -- Walt Disney