Oh, yeah the 87v supply comes up to 86.7V I guess I should have been clearer in my prior message when I said that all the voltages came up to within 0.03V of their intended values - that was referring to the 87, 42, 15 and 5v lines that were all low (all 9v or under) initially. Lifting Q1223 brought all the voltages in line, so that prompted the look at U800. Lifting the diode for U800 brought all voltages up to spec with a "normal" boot up, minus any horizontal display movements. Since everything came into spec and it booted with the 87v diode for U800 listed I didn't bother looking at U950 since U800 seems the apparent issue.
Sorry, hope that clears it up.
Thanks!
Chris
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--- In TekScopes@..., DaveC <davec2468@...> wrote:
Chris,
Measure the 87v supply with those doides unsolsered. THAT will tell us something.
Dave
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On Feb 23, 2013, at 3:26 PM, "Chris" <ckleman@...> wrote:
As a quick side note - I powered the scope up with the diode lifted(far side of the diode from U800, easier to desolder and lift), and pin 7 (the 87v input) of U800 shows -3.98V to -4.00V when the scope is powered up with the far leg of the diode in the air. Not sure if that tells you guys anything helpful though.
Chris
--- In TekScopes@..., "Chris" <ckleman@> wrote:
I lifted the diode CR807 feeding the +87v to the U800 IC and when I powered it up it booted up just like with I lifted Q1223 from the regulator board - Looks like it's U800. With U800 the panel controls boot up as normal, the LED's flash on/off and then onto the set positions. The screen turns on to a normal intensity, all traces will show up as points and I can control their vertical positions, but no horizontal traces or horizontal positions.
With U800's 87v feed disconnected, all of the voltages come up to within 0.03V of their intended voltages.
So I'm not quite sure where this leaves me yet. Being I don't know what the internal structure of U800 is, I'm not sure what to look for outside of U800. I know U800 hasn't been manufactured for years and is only available as a used and removed component. I read about the re-bake program, but it would seem mine falls under a different failure method than the re-bake program can fix. There's some available on e-bay for ~$120.00 shipped from China. Is it worth trying to swap it out with a Chinese salvaged part? Or is there another supplier of the salvage parts I'm not aware of?
You guys know these scopes better than I, and your guidance is much appreciated! I owe a huge thank-you to all of you who have helped me get this far!
Chris
--- In TekScopes@..., "Tom Miller" <tmiller11147@> wrote:
There are two diodes off the +87, one to U800 and one to U950. Both devices are known to have issues. You might just lift one end of each diode and see if the 87 volts comes up. That will isolate which device is causing the problem.
For reference, see diagram 11, power distribution.
Tom
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