At 08:33 AM 2/27/2007 -0500, you wrote:
I think I may
know why it was so cheap. The power supply died
right after dinner today. Powering it up results only in
"tick tick tick tick..."
If this is why it was cheap, the seller would have had to have
known that it was going to fail.... See if it "comes back" after
having been off for a while. Perhaps this is a known condition
of the unit.
I've tried it once a day since Sunday. No go.
Shouldn't be all that tough to fix... IIRC it uses
invertor to generate an internal 50v supply which all of the
lower voltage supplies feed from - Sounds like the regulation
of the invertor is not working and it is getting shut down.
I've seen other 7904s which exhibited "ticking" like this, so
it may be a common problem.
Some other folks have mentioned "tantalum time bombs" in the power supply
that die shorted after several decades. I'm trying to decide whether to go
after it on that basis or try to get something out of the seller.
I recall that the service manual has a pretty good
of the power supply - if you don't already have it, you can get
it in PDF form from:
I spent two days before the scope arrived downloading many manuals (low
serial numbers, high serial numbers, mil-spec, commercial, all the
plug-ins) from the primary bama site. The mirror worked great for few hours
but I went back to the primary when the mirror started to act squirrely.
I had my own positive experience with a dead Ebay scope
I bought a dead HP54201D (300Mhz DSO) in the hopes of getting
parts for mine which has been experiencing problems (and HP
doesn't provide service information) - It was in pretty rough
shape, power-switch broken, case banged up, screen-burn, no
probes or state pods, and listed as "immediately blows it's
line fuse" - but I took a chance on it and picked it up in the
hope that the analog board would be in better shape than mine.
Arrived a couple days ago - inside looked to be in pretty good
shape, and I immediately noticed one of the primary line side
filter capacitors was "humped up" at the top of the can - so I
removed it and found that it had exploded/leaked ... cleaned up
the board and investigated a bit more and found a shorted diode
in the primary line recitifier bridge - replaced both components,
and the scope works perfectly! (Much better than my other one).
It also has newer firmware than mine, so I simply swapped all
boards into the nicer looking chassis... Next step is to use the
good/working scope as a reference to track down the triggering
sounds like you had a more positive experience than me. Good for you!
Hackers make toys. Crackers break them. (Peter Seebach)
--... ...-- -.. . -. ----. --.- --.- -...
tpeters at nospam.mixcom.com
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