Sencore TC114 Tube Tester reconditioning

[stratomaster]

I recently scored one of these on Craigslist for $100.  It was functional, but a bit dirty and had the distinct odor of a failing electrolytic cap.

There are a number of videos on YouTube of guys replacing a few caps and drifted resistors on the TC109 version, so I took some inspiration from them.  The attached schematic shows the capacitors I replaced in red. 

My main question: is the value of the electrolytic cap critical? 

I can't imagine it is.  I've put a 50μF in its place as that is all I have on hand with a suitable voltage rating.  If I had to note a difference, the needle movement seems to be a bit more snappy.

I also replaced the 0.1μF wax cap with a film.  Both the original and replacement were very near nominal, so I'm not worried about that.

Finally, the 2x 10M and 1x 4.7M resistors are called out as 5%.  I've replaced the 4.7M and am waiting on some 10Ms to come in.  The replaced 4.7M was measuring close to 5.2M.

I removed the picture tube dongles to make room for a more stout polarized power cable.

This is my first tube tester, so I'm still feeling my way through the setup and calibration.  As far as I can tell, I think once those 10Ms are in that I'll be good to go. Are there any other things I should know about this/similar models before putting it into service? 

[shooter]

the cap should be fine, the only thing that jumps out is the rotary switch, verify it makes good contact through each of it's "stops"


did it come with the switch/tube setup chart?  (don't recall what the official name is)

[stratomaster]

Switches are good. Came with the reference booklet, and I found the operators manual online. That's where I got the schematic on the original post.

[stratomaster]

Swapped out the 10Ms for 1% (they were both over 5% high) and the ceramic cap between them which was about 15% low.

Zero set is at 115v, so I calibrated it all with a variac. 

I think this thing is fully armed and operational.

I've seen some warnings about using contact cleaner and compromising the grid leakage function.  There's still a good bit of corrosion on the switches contacts that I was unable to fully clean with no residue contact cleaner and some cotton swabs. I think deoxit would be better at getting it clean--just apprehensive to deploy it.

[shooter]

if the contacts are the "knife blade" type an Emory board (used for fingernails) works pretty good soaked in alcohol.