08-02-2018, 06:29 PM
During all the testing and making sure it is worth putting the panels back on I found a dead spot on the balance pot.
It is a 3-gang and as such it would be made of unobtanium and if that were not bad enough it is situated behind the mains transformer.
The problem was on all balance ranges so I figured that it would be RV5 as it is in circuit on all ranges of the balance selector.
Isolating the end of RV5 was easy enough but then I had to change the low ohms battery on my AVO as that had been bought and put by to be fitted. RV5 is 51 ohms so there was no choice with that.
RV5 came back no fault found so there was a bit on an anticlimax to be had.
RV3 was next and it had a dead spot on it and then RV4 with two dead spots on it.
I got my fat free cleaner out as it is even compatible with Tektronix switches and is safest.
It worked on RV3 and RV5 but RV4 was a problem. It has a plastic cover with a bearing cap over it and there is no space where the wiper conductor goes in like with the other two.
The bearing plate would not come off without getting the whole assembly out so I tried the fixing screws for the tags.
The things have got nuts on the other side so great care was needed to avoid them dropping inside. I got some cleaner in and the two dead spots on RV4 resolved.
With forceps and a screwdriver I got the nut to catch enough to tighten the screw again.
I am going to do a full round of testing again and see about getting the covers back on again.
You bet that my everything tester is going to get through a few charges during testing.
It is accurate enough to be a calibration standard for all the measuring devices we get from China.
The date code looks like 1977.
It is a 3-gang and as such it would be made of unobtanium and if that were not bad enough it is situated behind the mains transformer.
The problem was on all balance ranges so I figured that it would be RV5 as it is in circuit on all ranges of the balance selector.
Isolating the end of RV5 was easy enough but then I had to change the low ohms battery on my AVO as that had been bought and put by to be fitted. RV5 is 51 ohms so there was no choice with that.
RV5 came back no fault found so there was a bit on an anticlimax to be had.
RV3 was next and it had a dead spot on it and then RV4 with two dead spots on it.
I got my fat free cleaner out as it is even compatible with Tektronix switches and is safest.
It worked on RV3 and RV5 but RV4 was a problem. It has a plastic cover with a bearing cap over it and there is no space where the wiper conductor goes in like with the other two.
The bearing plate would not come off without getting the whole assembly out so I tried the fixing screws for the tags.
The things have got nuts on the other side so great care was needed to avoid them dropping inside. I got some cleaner in and the two dead spots on RV4 resolved.
With forceps and a screwdriver I got the nut to catch enough to tighten the screw again.
I am going to do a full round of testing again and see about getting the covers back on again.
You bet that my everything tester is going to get through a few charges during testing.
It is accurate enough to be a calibration standard for all the measuring devices we get from China.
The date code looks like 1977.
