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Mark, You are correct about the parts and board number. Also R2326 and R2336. On the A21 and A22 boards, the 9100 ohm 1/4W and 20k pot are known to go bad due to being run beyond the rating of the

Mark, Thanks for the tip, but I am unsure where the d-c restorer diodes are, but I think you mean CR2352-55 and CR2342-45 and R2356 and R2346, all on the HV board A24? ?? Mark

Mark, A correction. There are (4) 22meg resistors in each scope, not 8. Mark

Mark The d-c restorer diodes are bad, replace all of them with 1N4937. Also replace the 22meg 1/4W carbons with Vishay VR37 series, 594-5053DM22M00F. Get 10 of these to replace the 8 in the supply or

I have been working on a 7844 dual beam scope that has a beam intensity problem. The scope was working, then the power supply quit with a rapid tick. Ok I had another 7844 that has a different problem

Hi, TR502 is rather expensive even as an used instrument. There is one TR503 on eBay. (I know it is not the same thing). Too expensive for my

I tried to contact the seller about this but eBay won't allow URLs to be included in the message. Barry - N4BUQ

I thought TekWiki's images were those that were uploaded intentionally by someone who owns/owned the items. Maybe not. Barry - N4BUQ

Actually, I have not bought from that seller (had them mixed up with a different seller). In any case, the feedback and number of transactions certainly doesn't seem to point to a scam. Barry -

Barry, TekWiki often gets its images from eBay and this one appears to be from there as well, the width of 1,600 px is the telltale sign. Most likely this eBay seller took the original photo and the

That's more-or-less what I thought. I think I've bought from that seller with no problems. I might contact the seller to see what's up with those pictures. Thanks, Barry - N4BUQ

I assume tekwiki copied those photos. The seller uses the same background for other listings, and I've bought a few items from them over the last year (a 7B70 service manual back in March, and an HP

But then I see many many listing photos of that seller with the carpet and blue wall behind... and a 99.7% rating. So maybe they are the original source of the tekwiki photo...

Yep, selling something they do not have... scammer.

Does this look odd to anyone else? https://www.ebay.com/itm/375606603143 https://w140.com/tekwiki/wiki/T7510 Thanks, Barry - N4BUQ

Solid BeO is not dangerous. The only dangerous form is BeO powder (dust); as long as you don't grind BeO, you're safe. Ages ago, BeO microspheres were developed as a safe form of BeO for incorporation

Miguel, Sorry, it can't be fixed. Don't open it either, hybrids like this sometimes contain BeO, which may or may not be indicated on the cover.

Is there hv on the tube? Do you see the heater glowing? Measure the DC supplies with a scope, should be flat (-ish), no noticeable ripple.

Haven't seen these for a while now. I recall... even used...they were pricey... everyone "needed'' a TG. And you need an external counter... to 1.8 GHz... which isn't cheap either. AFAIK... nothing

Check the three transistors and IC associated with the 50V supply. One or more could be open/leaky/shorted. The series pass would be the first to check. Check to see if you have the 9V across VR1416