Ok, I removed the HOT, and the short / overload is still present. If the flyback is unplugged the extra load goes away. I found that with flyback pin 3, the red wire, unhooked the extra load goes away too. Unplugging the yolk makes no change. There aren't many things on that ground return from the flyback, I'll take them out one at a time till I find the shorted part. -J On Sun, Mar 12, 2017 at 1:15 PM, Matt Patoray via vcf-midatlantic < vcf-midatlantic@lists.vintagecomputerfederation.org> wrote:
Jason,
Pull the HOT and try to power it on, and see what the current draw is then.
Sent from my iPhone
On Mar 12, 2017, at 12:37 PM, Jason Perkins via vcf-midatlantic < vcf-midatlantic@lists.vintagecomputerfederation.org> wrote:
Looking for some advice on getting a Heath WH19 terminal going again.
First, some schematics:
http://www.rsp-italy.it/Electronics/Kits/_contents/ Heathkit/Kits/Heathkit%20H-19%20video%20terminal.pdf
My annotations on the x-ray view: https://goo.gl/photos/ PF8N7wRDPLc1czUU7
What I observed: When first powering the terminal it did nothing. The fast blow 1A fuse was open, the wire was broken. As it was handled it broke more, suggesting it could have simply failed from vibration? The manual said that a 2A slow blow fuse is appropriate for 120v operation.
I replaced the fuse with the smallest one I had on hand, a 4A slow blow, connected the terminal to a current meter, and powered it up. It beeped :) But was drawing 5A :( and then there was a little smoke :( :( I quickly powered it off.
R263, a 1.2 ohm 2W resistor had cracked. R263 supplies the +53v rail to the horizontal section.
C228 seems to be good (open resistance, correct mfd), D208 and D211 seem to be good (.5v one way, open the other), C229 isn't shorted but my meter can't measure its capacitance.
I replaced R263 with a 4w 1.2 ohm resistor I had on hand, and powered up again. Still too much current draw, and more smoke in the area of Q217.
Does this suggest Q217, the HOT, is bad? I pulled it out and did the diode test on it, it seemed to test OK? It's a BU500, and I see some NOS ones on ebay.
I'm unsure what my next step should be.
Thanks for your input!
-- Jason Perkins 313 355 0085
-- Jason Perkins 313 355 0085