Tracker model 1005b repair help?

Started by Gregatron, August 02, 2010, 03:47:44 PM

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Gregatron

Hello, I recently pulled out an old "Dead" Tracker of mine to repair.
It only had a dot in the middle of the screen. I repaired the oscillator by removing it and reflowing the protruding pins.
It now has a trace but it's still not as it should be. It seems to have an issue with the horizontal part of the trace.
I can adjust it with the pots to look like a circle and other various vertical lines but it will not adjust to a horizontal line (in hi and med ranges) and it will also not adjust to a diagional line in lo range. It seems to actually be always vertical as if there were a short applied to the output terminals but there is not. I have replaced IC1 and IC2 also Q1 and Q2 and verified all three range switches to be good. could this be a signal transformer issue? I have verified correct voltages on the individual transformer taps and the waveforms also look OK. any help would be greatly appreciated.
Thanks

Gregatron

#1
Well, I looked at this thing again just after I posted this and found the problem.
It looks as if a previous tech reflowed the header for the CRT connector and in doing so bridged
the pin of B12 (vertical plate) to the trace for the pin at B10 (horizontal plate). which caused the weird display issues.
The problem was the bridge looked like it was supposed to be there. Double checking the schematics and a magnifying lens did the trick.

admin

Welcome Gregatron.

Good job getting that old Tracker working. You were lucky to revive the oscillator as in many cases once it is dead that is it. There is not a replacement for it.

Thanks.

TS
The most important troubleshooting tool is your eyes.

rohmell

There might not be a replacement for the oscillator per se, but its components such as the 1458 opamp, transistors, etc., are still very easily obtained.