andrewb
Well-known member
As for upgrades, there aren't many parts that need to be upgraded to different values on Amp deflection boards. You do want to follow what is in the FAQ however, regarding replacing the 0-ohm jumpers with straight wires.
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You're measuring them all in-circuit, right? Just confirming.
Have you checked any of the other smaller TO-92 package transistors below them?
It's odd that all four that you listed would be bad together. I'm not saying they aren't necessarily, but the next step would be to pull them and confirm, as you may get different readings when you do. However the fact that all four are bad (if they are) suggests something else at play, than just a standard deflection failure.
Did all four have the proper silpads and insulating washers? (Check to make sure they aren't shorted to the heatsink, before removing them).
You'll also want to keep checking back, through the other transistors and other components, working your way back to the power supply section. I wonder if a PS issue could have been the root cause, as it's really unlikely for both axes' transistors to fully fry on their own. Was the board
Also, regarding parts, I'm surprised if Fry's doesn't have 1N00x diodes, as they're super basic. I don't know if there are other local electronics places up your way, but when I am on the peninsula, San Mateo Electronics is a little hole in the wall place I'll go for basic stuff in a pinch. They're right off of El Camino. The transistors and other parts you're going to need will be too specialized for them, so you'll need to go online. Digikey usually gets me my orders in 48 hours, most of the time.
Also, you're likely going to need to sub those four transistors. I use the ZTX653/753's for all vector deflection boards. Different package though. If you want something closer to original, you're going to have to find a different source. Bill's page is pretty useful.
www.biltronix.com/transistor_subs_01.html
Also, you mentioned that you had a horizontal line on the display, which suggests one axis might have been working, which doesn't jibe with what you're seeing with the transistors, so there's something else suspicious there. You may want to doublecheck.
What function on what meter are you using to measure the transistors? Do you have a known-good transistor you can just sanity check the meter with?
I partially checked all the other transistors. Meaning that I didn't go into the same detail but I did quick checks on a couple legs each and nothing seemed out of whack.
You are right about the horizontal line. But....I powered it up again before pulling the board and I was getting zero graphics at all. So whatever fried one axis at first may have fried the rest of it the next time I powered on.
All four had mica insulators and none were shorted to the heat sink. I checked that before removing the two that I already pulled.
And yes, I was checking them in-circuit. I can pull them and check that way. I feel like I would understand the readings better anyway. It's just a pain in the butt but no big deal.