OT - anyone having experience fixing 'scopes (100Mhz Leader)

OT - anyone having experience fixing 'scopes (100Mhz Leader)

Post by Sylvai » Mon, 24 Sep 2001 11:52:13



Got it for cheap, extremely clean 'scope,

Lights up fine (fixed the dead PSU) But there's only a very bright dot in the center
of the tube. Focus, Brightness don't change a thing, still very bright dot.

If anyone with experience could give me an idea see if it's worth fixing or not.

Or is there a good place to either get a schematic or some help ?

Thanks, and sorry for the OT,
Syl

 
 
 

OT - anyone having experience fixing 'scopes (100Mhz Leader)

Post by Alan Dougl » Mon, 24 Sep 2001 19:49:10


Hi,
   Sylvain asked:

Quote:
>Lights up fine (fixed the dead PSU) But there's only a very bright dot in the center
>of the tube. Focus, Brightness don't change a thing, still very bright dot.

   Sounds like a low-voltage power supply failure, maybe even a fuse.

73, Alan

 
 
 

OT - anyone having experience fixing 'scopes (100Mhz Leader)

Post by Sylvai » Tue, 25 Sep 2001 04:56:19


Quote:

> Hi,
>    Sylvain asked:

> >Lights up fine (fixed the dead PSU) But there's only a very bright dot in the center
> >of the tube. Focus, Brightness don't change a thing, still very bright dot.

>    Sounds like a low-voltage power supply failure, maybe even a fuse.

> 73, Alan

Boy you're good. I went back to the bench this morning. I replaced a blown 7812 taht
I thought was good but still the same problem...then I dusted
my logic probe and took a few "readings", to find a burnt trace in the 55V circuit.

Works like new ! Hey, I got myself a 100Mhz Leader scope (3 traces) for 20$ !

Not an old radio...but I really needed a good 'scope.

Thanks to all responding privately to my request. Lou and Terry for directing me
to "sci.electronics.repair" (I couldn't find the right ng for that, thanks guys!)
and John Bartley for making available a pdf of a similar scope.

Sylvain
made in Quebec

 
 
 

OT - anyone having experience fixing 'scopes (100Mhz Leader)

Post by Alan Dougl » Tue, 25 Sep 2001 05:17:51


Hi,
   It's always a surprise when a logical approach to troubleshooting
actually works.

   Presumably the sequence of events was: bad HV supply, drawing too
much current, toasted the 7812 regulator, which shorted and blew the
"fuse" (pc trace).

Cheers, Alan