I tried "matching" the FETs using the component tester; however, what appeared to be a "best match" caused the EXT waveform at the junction of CR23/CR24 to be offset more than I originally had it with

I can probe the right side of the plugin with it installed in the 7704A. At the junction of Q22A's drain and Q22B's source, the sine wave that's entering the EXT input is modified to show slightly fla

BTW, with regards to matching the FETs in the 7B80's EXT TRIGGER circuit, when I test one of the 151-1042-00 FETs with my component tester, it gives me Id at a specific Vg. If this reliably repeatable

I think I've seen other cases where only pieces of the P/N were listed but I presumed that was primarily due to real estate. This is good to know. I found and ordered some NOS 151-0367-00 (hopefully t

Jeff, I have some of the same traits but, apparently, not enough so as to keep me from sometimes allowing my desire to do something quickly to cause me to make terrible mistakes. Today's not a total l

Jeff, Thanks for that. In my defense, because of the way the numbers are formatted (e.g. "151367" as opposed to "151-0367", etc.), I didn't immediately recognize the lettering on the transistors in th

Hi Jeff, Sadly, I now realize that. I just looked and the 1042s are, indeed, clearly marked as such and are definitely NOT the ones in the thermal links. I pulled two of the 1042s and they do check as

Hi Mark, Are you saying that the diode leakage is abnormal? I presume so. Also, these are marked as 151367 which presume are 151-0367. Is that correct? Thanks, Barry - N4BUQ

Apparently, Q310/Q311 and Q411/Q412 in the 7B53A are not JFETs - at least according to my component tester. Assuming they were the same part numbers, I tried them in the 7B80 before testing them which

Hi Dr. G., I'd like to confirm that I can substitute a pair from one of my 7B53As and get the EXT triggering to work in the 7B80 before I declare the JFETs the entire problem. If so, then I'd be inter

Jeff, While I suppose it isn't a definite thing, usually when a single package contains two or more transistors, the package is drawn with a solid arc and a dashed arc to indicate they're not discrete

Jeff, I see they're Q310/311 and Q410/411 in the 7B53A. I should have a few to test with. Thanks, Barry - N4BUQ

Jeff, I have a few 7B53As. I'll see if I can swap one into the 7B80 and see if that restores external triggering. Thanks for the pointer! Thanks, Barry - N4BUQ

The signal coming in from the EXT jack makes it to the gate of Q22A but the junction of CR23/CR24 only sees a slightly negative voltage (maybe a diode drop). I removed the pair and tested them with my

The ones in my 7B80 have a wrap-around heatsink but not the S shaped kind. The JFETs are face-to-face with the heatsink wrapped around the round parts of both. Thanks, Barry - N4BUQ

I have a 7B80 which doesn't work in external triggering mode and I discovered one of a matched pair of JFETs in it (Q22A/B) decided it liked being a diode instead of a transistor. As the subject indic

Yes - that's all I need. Thanks again, Barry - N4BUQ

If it came down to needing to replace the socket and plug, then that would probably be a good option. I'm trying to keep this original so will go with the sockets that Dave's sending me. Thanks, Barry

Sure thing (provided PayPal lets me do that and I presume it will). Thanks again, Barry - N4BUQ

Would you at least accept a PayPal for a few dollars? You went to trouble for me... Thanks, Barry - N4BUQ