The PHILCO Phorum

Can the volume control on a Philco 90 or 70 be cleaned using standard electronic sprays? I know that some of the older controls (potentiometers) were made by applying a resistive trace on a cardboard like backing. They could easily be damaged by any types of spray lubricants.

For the better part of thirty some years, I have been using WD-40 to lubricate and clean controls and switches with great success. But, I will not use any lubricants on the volume control of my Philco 90 until I find out more about this construction. It appears to me that it might be this earlier type of control. Can anyone provide some info on these?

Thanks,

Ed

Ed

If your 70 (without AVC) or 90 (using two Type 45 output tubes) use the dual type volume control (250 ohms and 5000 ohms), AFAIK, all of these are wirewound and may be safely cleaned with any good contact cleaner.

If your 90 is a "mid" production (1-47) or "late" production (2-47), then it uses a 500K pot that may, or may not, have the resistance on a cardboard-like backing. I honestly do not remember the exact construction of these at this time, although I seem to recall cleaning them with no ill effects.

My 70 is the non-avc type with the dual controls, so it would be OK to clean and lubricate. The 90 I have is the mid type with the single 47 tube and the 500K pot. I have noticed that the pot looks to have a removable cover on the back of it, which I thought may be indicative of the older style construction. The pot is not noisy so cleaning is not so much of an issue. But, it is very stiff and could use a good dose of lubrication.

Ed

I just went down to the basement and looked at a 90 chassis I have with 1-47 output. It has the 500K pot...and it is an original CTS unit with the Philco part number (5366) stamped on the back. It is also stamped "DO NOT REMOVE COVER"...and they aren't kidding! I could not get the cover to come off...so I cannot confirm or deny your concerns at this time.

OK Ron,

Thanks. I have to use one of my favorite expressions on this one. ' I'll have to take this under advisement'.



Ed