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T 130 L-C - calibration issue - sealed pots R99/100 on low range adjustment

Richard Kelly All Messages By This Member #208116 Having does the necessary restoration on my T130L-C, I am now running through the calibrations. I have an issue with the 0-3 and 0-10pF calibrations. The controls, R100 and R99 respectively., have the 'range' but it's clear that the points at which they were set have become 'burnt in' for want of a better description. At those very points where it is almost correct the control loses its authority and idle goes full scale. A spot of cleaner I figured. But no... On inspection, they both seem, uniquely amongst the rest of the pots, to be wax-sealed or similar. I'm assuming in pursuit of stability, but sadly now working against that at 50+ years on! Anyone come across this issue, and therefore recommended resolution? Before I extricate then and attempt to clean.
Tom Smith All Messages By This Member #208119 Is it possible to drill a small hole in the case +- 1/8” and give it a small shot of Deoxid? If that works and you feel so inclined, you can put a small amount of wax or some other sealer to close the hole. Tom N5AMA
pac1085 All Messages By This Member #208122 I have an early 130 here (brown case) - those look to me like regular RV4 style 2w 10k pots which can be had on eBay for around $10 NOS. Such as RV4LAYSA103A. I do notice one of them says "S-taper" on them, but not sure how critical that is in this application? Good luck!
n4buq All Messages By This Member #208124 Would it work to place a parallel resistor to effectively move the defective part? Thanks Barry - N4BUQ toggle quoted message Show quoted text Having does the necessary restoration on my T130L-C, I am now running through the calibrations. I have an issue with the 0-3 and 0-10pF calibrations. The controls, R100 and R99 respectively., have the 'range' but it's clear that the points at which they were set have become 'burnt in' for want of a better description. At those very points where it is almost correct the control loses its authority and idle goes full scale. A spot of cleaner I figured. But no... On inspection, they both seem, uniquely amongst the rest of the pots, to be wax-sealed or similar. I'm assuming in pursuit of stability, but sadly now working against that at 50+ years on! Anyone come across this issue, and therefore recommended resolution? Before I extricate then and attempt to clean.
SCMenasian All Messages By This Member #208126 I have 2 potential solutions. The first is to simply swap the 2 pots since they are both 10k. It is unlikely that the bad spots are the same in the 2 pots. The second is for me to send you 2 pots from my unit which I've converted to all solid state operation. The 2 pots are probably still there (I'll have to open the unit to check) or they are in my junk box. Let me know if you want to pursue this and we can work out an arrangement (as long as shipping is to the US). The eBay prices are way above my range.
Richard Kelly All Messages By This Member #208128 Firstly, thanks for all the helpful, and generous, responses. I decided to dribble Deoxit ‘down’ the spindle entry and it appears that it may well have got to the track and adjustment is very much improved. I hadn’t expected this to work. Too early to confirm success but I’ll give it (a) some more and (b) some more time and retry tomorrow.
Richard Knoppow All Messages By This Member #208129 It seems to me there was a pressure device for forcing cleaner around the shafts. It screwed onto the mounting and pushed cleaner in around the bearing. Have not seen one for years. If these are the Allen-Bradley/Ohmite type pots you can pry off the back coverings and use Deoxit faderLube on them. Takes some care. The little tabs on the covers can be bent back into place to hold them. These are very good pots but, because they can't be easily cleaned, often develop bad spots or get noisy. I have even heard of drilling holes in the caps but would worry about particles getting into the pot. toggle quoted message Show quoted text On 1/19/2025 12:38 AM, Richard Kelly via groups.io wrote: Firstly, thanks for all the helpful, and generous, responses. I decided to dribble Deoxit ‘down’ the spindle entry and it appears that it may well have got to the track and adjustment is very much improved. I hadn’t expected this to work. Too early to confirm success but I’ll give it (a) some more and (b) some more time and retry tomorrow. -- Richard Knoppow Los Angeles WB6KBL SKCC 19998

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