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City: Jackson
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Terry just couldn't stand the thought of me leaving without anything to repair so he made me take his Tektronix 465 scope to look at.
Once powered, it looked like the H-sweep amp malfunctions: I can see the flickering but cannot find the beam.
Sure'nuff, once I started to look at the H-output amp, I found a bad 2N2222A transistor. The Emitter junction is open. Q1274 namely, if someone wants to bother looking.
Another thing, the 110V power to the output seems to be 150V. Wonder why.
Anywhoo, Terry, if you have 2N2222A little buggers, get me some by mail.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 7,303
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Oh you mean the 2n2222a the most popular transistor on the planet??? For a guy who mostly services vt stuff I'm pretty sure I have some.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 05-15-2017, 11:46 PM by Radioroslyn.)
Posts: 16,533
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City: Jackson
State, Province, Country: NJ
I will see if we have anything close in junk at work. I do not have any at home - no need for them......
PS. Was able to solder gold-plated lead clippings I save (come handy!) to an SMT SOT-23 MMBT2222A transistor which is pretty much the same device. Will try tonight.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 16,533
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Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
OK. Came after 9pm home from grappling class, decided I had just enough energy left to attempt the repair.
The culprit. 2N2222A transistor.
The sub. MMBT2222A, SOT23 with leads soldered, inserted in the socket.
The channel lines, chopped.
The channels showing the test meander signal from the scope front panel itself.
Ideally, Terry, if you have a 2N2222A, you could put it in, though I think this one is just fine. SOT23 dissipates half of what TO-18 can, but then I do not think there is much dissipation here.
About 1.5hr for the whole thing. Not bad. I never fixed a scope before.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 7,303
Threads: 269
Joined: Dec 2009
City: Roslyn Pa
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
Posts: 16,533
Threads: 573
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
Yeah I saw that picture on some tech forum where a guy was trying to fix his 465 
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 3,160
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Joined: Apr 2011
City: Lexington, KY
Great job Mike!
Terry Layman just bought a batch of test equipment and I checked his three Tek scopes for him. The 465 powers on with no trace, the 485 seems dead, but the 475 seems to work OK. So if you want to hone your scope fixing skills I'll let him know 
John KK4ZLF
Lexington, KY
"illegitimis non carborundum"
Posts: 16,533
Threads: 573
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
I thought I never get to fix this one until late summer, as I am deep into 38-690 now.....but it is in waiting for the rebuilt electrolytics which I have yet to cut open and I had a little intermission, so I got to the scope.
It's fun to fix solid state, plus this is something I really know quite a bit better than vacuum technology.
But as everywhere, one's got to be methodical in diagnosing, poke, smell and listen
I have to give proper dues to my mom when it comes to good diagnosis: she was a medical doctor in her pre-American life, and was considered the best everywhere she worked, and for a good reason. She once kind of opened my eye to how to diagnose: pay attention to everything, undress the patient fully and do not be afraid to ask questions, even if people around think the questions are silly. Helps a lot.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
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