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Some time ago I had similar thoughts on accessing the connections to the pass transistors, as well as accessing the 25 VAC connections. I had a problem on one of my TM50X mainframes with one of these

Yep, the mainframe tester tests for short/leakage and beta, along with the DC and AC voltages, and phasing of the two floating AC windings.

Hi Larry, I might well be interested in a board set, so long as the cost and shipping to London, UK aren't too crazy. I have been intending to build one of these testers for a while and have a few of

Yes, These will cause a cascade of failures with certain modules. I always try to at least diode check those pass transistors before inserting any module or powering up. So your Mainframe tester

The trick is a bad pass transistor can quickly kill a module, which can then go on to kill another slot in the mainframe, etc etc. Using a module (that isn't the purpose built tester) to test the

I just used a prototype board and brought the pins out. I am sure that the traces on a dead plug in could be isolated and used as well. I find that many of the transistors read lower gain than

Ok, Thanks Chuck.

Hi all Quite a lot of years ago there was a topic posted here that went on for some time but never reached any conclusion as to the cause of the problem...unfortunately the exact problem I think I'm

It is a cute little scope, but very low bandwidth, something like 10MHz. Its HV transformer suffers from the epoxy disease that affects 547 scopes. They are quiet, not having a fan, and the plugins

Dennis the 26 cm Spectral tubes are the most popular, used in physics labs These use 5 kV open ckt current limited transformers and run at 5 - 20 mA. The optical spectrum is dependent on gas mix, and

The mesh is an electrostatic lens that magnifies the limited vertical and horizontal deflection to fill the viewing screen area. This is done to allow a lower deflection plate voltage on a fairly

Hi all, and Happy New Year 2021, Is a 564B a good grab, is it desirable at all? It’s not considered a 500 series, right? 56x family I suppose... Thanks ?

Hello perhaps you are confusing Helipot a multiturn precison 3,5,10,15 turn potentiometer with internal 1 turn pcb mounted trimpots or single turn controls? If you can précis your questions with

I'm sorry I arrive pretty late in the conversation. There are online tools to identify fonts, with easy yes/no questions. I used one once to find which font was used on Philips instruments (for a

Dear Dennis: We worked on arc and gas lamp ballasts since 1970s. Then designed and manufactured 12 kV HV modules, in 1980s..1990s. The encapsulant is a very high solids epoxy, specially cured. We used

HI Please,Larry,add me to the list.I am located at Spain. Regards.

I would also be interested in a set of the boards, please add my name to the list. I am in Dublin, Ireland so I am aware that shipping will be somewhat more than the nominal amount suggested. I am

Thank you to everybody! I have enough information to attempt a transplant. I'll post here the outcome Giovanni

Hi Dennis, I believe it's not worth the effort, I'd personally build a new one using instructions from Sam's Laser FAQ: https://www.repairfaq.org/sam/laserhps.htm#hpstoc You'll find wealth of

Supposedly a 50/50 mix of formic and acetic acids will do the trick but I've never tried it. DaveB, NZ