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Measurements are taken at power on.

Ok I have checked the Voltage at Q1980 collector, with r1878 full CW (max grid bias) = 60V, with r1878 full CCW (min grid bias) = 120V, so there is the correct range but shifted of 13V more or less.

Also some plug-ins like the ubiquitous 7B53A used chiefly in 76xx mainframes have no built in illumination anyway so adding the lamp power modification to the mainframe makes no difference for them.

Thankyou Roger and Menahem for your recommendations ... my Scope has run trouble free for quite few hours now ... and I am discovering its functionality is more complex than my el cheapo scope .... :)

Using the TM500 PSU / back plane as a standalone card tester : I did the same as Edward some years ago before I made up my own (TM503 ) plug in metal frame extenders, (turned out to be a fiddly job)

The easy way for people to add to a database is right here in the group. Create a Database here.

I was going to say yesterday, they should have just sent you a new nozzle and tube. At least they finally wised up. And yup, I meant both ends of the tube, you got me! =) --Eric Sent from my Samsung

One thing that kinda threw me was no trigger light. Well just now looked inside my 7b53a and the previous owner had plugged in the pin header backwards. So the trigger light is now working. Jeesh

If you have no control range to speak of on the bias pot, then I'd guess Q1980 has gone bad. Looking at the schematic, what the service manual states makes sense. Discounting Q1980s base current, its

Details,details,details. Thanks for helping me not go crazy. I literally looked at that schematic for hours yesterday and today. Finally got to the "well i gotta ask" point. I told my wife I was too

Note also that some plugins, notably the programmable ones (definitely 7A16P and 7B90P, probably 7A29P as well) use the 5V 'lights' supply to run their internal logic. They don't work at all in

Tom, Thanks for the thumbs up and congrats that it's now doing it... One of the atten. blocks showing flaky seems now much more sensible... What wasn't making any sense before was that all

I recently got a 453A off ebay because it was shown working with a bright CRT, and all the BNC connectors were still clean and shiny. It turned out to be amazing in real life, everything worked, (one

Firstly, thank you for taking the time for a lengthy explanation. Secondly, I didn't take any offence in any way. I'm only too aware that I have a lot to learn, especially when I ask a question! I've

They are being proactive. --------------------------------------------------------------------------------- Hello Stan, I have forwarded your concern to production team. They have tried several tubes

Hello Eric, Yes, it is either the nozzle or the tube. Your other post asked if I tried both ends of the nozzle, you must have been as tired as I was. I think your meant both ends of the tube. I

On Q1980 collector with grid Bias at min I see 120 V and I have already replaced C1991 and R1994 even if they tested good out of circuit (R1994 was indeed a bit low: 1% out of tolerance on the low

While I intend to do this mod to my 7623A, it is worth bearing in mind a couple of things. If you check the app note/mod sheet (040-0686-01) you will see that some things should be down-rated

Both the grid bias pot and U1890A shunt current away from Q1980. By your description it sounds like extra current is sneaking into Q1980s base - maybe C1991 has gone leaky? Page 3-37 has this descript

HAHAH. Thank you. That is good stuff. You are exactly right. Im'm going to wait until I get a donor parts 7633 to do that mod. Make her look pretty. Time to button her up for now.