Re: Got the V2000 HV blues...

I wanted to post once more to conclude this - although I still don't
have a truly satisfactory explanation...

Once more, I rigged F102 in an external fuse holder and through a DMM to
monitor the current. This time, I used a 1A fuse. Like with the 1.5A
fuse test, current started at 0.56A, and stabilized at 0.61A after about
15 minutes. I let this test run for about 80 minutes with the monitor
out of the cabinet, and the fuse did not blow.

New pc-mount fuse clips arrived, so I replaced the clips for F102. I
put in a brand new 1A slo-blo fuse from a fresh supply, popped the
monitor in the cabinet, and powered it up. Within an hour, the monitor
went dark, F102 blown. So, it's probably safe to say that neither the
fuse clips nor the fuse were to blame. So much for that idea. #grumble#

Some other parts had also arrived, so I replaced the BU409 at Q900 with
a new BU407. I didn't have a new 2SD525 for Q903, so I swapped in a
good used one. I also decided to put a 1.5A slo-blo in F102 (per the
schematic note for early versions of this monitor).

The monitor worked fine out of the cab for 90 minutes. I then put it in
the cab, and it worked fine for six hours. The next day, I turned it on
again and let it run for 10 hours. All seems good now.

I don't like the "solution" of over-fusing it, but I'm sick of working
on this thing! What I should really do is rig up some more test leads
so that I can monitor the current through F102 when the monitor is
enclosed in the cabinet.

I also decided to mount an 80mm 12vdc fan behind the monitor to help
keep it a little cooler.

Alan

Bill wrote:
> Although it looks like you identified the problem, verifying the root
> cause for this one will satisfy many folks curiosity including mine. I
> have been burned by misbehaving slo-blo fuses before as well but not on
> a monitor. It just seems like I put too much faith in the fuse being ok
> and exhausting all other causes first. If everything looks ok and the
> fuse is blowing, metering the fuse current before tearing everything
> apart is a great idea that I will file away.

-- 
Total Impulse - Just Having Fun!
Alan Estenson, totalimpulse@comcast.net
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