How to repair/upgrade Tenma 72-1095 bench Variac to separate Simpson analog meters

These are great Variac's (when they work), however they are reported to have a high failure rate of the V/A meter + driver board. Unfortunately, these are made overseas. There is no documentation available. Parts are not easily located. So, when they fail, it leaves you in a lurch. I have one here which has the open meter. Instead of searching and installing another poor quality meter, I decided to modify the Variac with dual Simpson 1257 series meters! The project turned out great. I love the smooth operation and not needing to use the cheap switches to monitor voltage & current. If you decide to do this mod, buy the meters on ebay. They range around $20ea. If you buy them new, they are $130ea! I will be posting more updates to this unit in the near future. Enjoy!

[@rejeanmichaud662]

Hello, I watch all your videos because you explain them very well and you don't speak too quickly because my English is not very good. THANKS

[@jeremiahlyleseditor437]

Excellent Job.
It's something that most guitar techs would need, or should need.

[@robmoffatt4997]

I prefer the Sencore PR570 Variable Isolation Transformer and Safety Analyzer. It's a very nice piece of test equipment and gets a prominent spot on the test bench! Keep up the good work T!!

[@srtamplification]

I have one of those Tenma Variacs. I love the fact that it also has an isolation transformer as well. One thing to be aware of one those however, the ground on the output receptacle and ground on the power supply, are connected internally through the chassis. So in order to have ground isolation you have to remove the ground jumper on the output receptacle from the chassis.

[@bobblum5973]

I'd prefer to have the dual metering myself, easier to get a better idea of what's happening with the device under test. Plus, analog meters give you a better "feel" than digital ones, glad you went with those.

[@sipet214]

Thanks Terry I have the same issue with my Tenma Isolation Variac I will follow your recommendations to fix it.

[@pearsedunne9938]

Brilliant job, Terry…..👍🇮🇪

[@atmylab]

Nice work, the meters look great; I can see toggle switches replacing those push-buttons when you perform your mod to replace the “board”.

[@mackfisher4487]

Nice Modification, the mfg should have been made like that in the first place.

[@brentnearhood8874]

Thanks! Terry

[@Tom-W7TMD]

Great Mod! I ended up Getting a BK 1655 AC supply/ Variac. I'm sure at some point I will have the same problem.

[@OIE82]

I have wished you would do that for awhile now.
I wondered when you would get aggravated flipping the switch. 😊

[@kenwhelan3003]

Terry...too many cool tools you've collected thru out your career..the hole punch came in handy!!

[@danrussell9357]

Fixed and Improved - Great Video!

[@JobyP]

Cool project man!

[@spyder8986]

Good job,nice work.

[@p-47m16]

I saw a video you made seven years ago about making a Princeton into a “Kingston” and I am looking into doing a similar project.
My fender custom deluxe reverb is 22w and my reasoning for wanting to do this conversion is that it breaks up early. I want to swap the 6v6 tubes along with whatever other components for a 6l6 tube setup. Or even some other setup but I want to make my 22w amp a lot more than 22w and I just need power because my amp breaks up at too low of a volume.
Do you have any information or advice for me, any would be appreciated.
-Thanks.

[@robertclark8351]

Nice.

[@jerryking2418]

nice mod. Where did you source the Simpson meters?

[@d-labelectronics]

Found these on ebay

[@mikemoran5439]

Awesome!