[sdiy] juno 60 death

[R. D. Davis]

Quothe gregory zifcak, from writings of Thu, May 06, 2004 at 04:00:16PM -0700:
> a friend's juno 60 suddenly stopped showing any signs of life. the fuse 

Hi, that's not good news.  After just obtaining a Kenton Pro-DCB for my
Juno-60, I don't want to think about Juno-60 failures. :-)

> appears to be intact. i measured some points with my meter, and it looks 

Did you check all three fuses at the power transformer secondary
windings?

> like the transformer is putting OUT 120v. this is not normal right? it 

That doesn't sound quite right.  Just a second... time to dig up the
Juno-60 schematics... they're burried around here somewhere.

> looks to me like the transformer has two outputs: 26vac and 18vdc. is this 
> correct? what appears to be the two outputs both read 120vac. can anyone 

No, a transformer wouldn't have an 18VDC, or any DC output, for that
matter.

Ok, found the schematics.  The transformer's secondary has two
windings; one of which is center tapped.  The first is 8.5 Vac where
it connects to fuse F1 and bridge rectifier D1; these should be orange
wires coming from the transformer.  The other winding: the center tap
goes to chassis ground (black wire).  You should measure 18Vac between
each of the red wires (going to fuses F2 and F3) and ground, or 36Vac
between the two red wires.  Are you certain that you're measuring the
output?  Does anthing look or smell burnt?

> corroborate my hunches? i suppose i'll need to find a replacement. any 
> leads? 

First, let's verify that this is indeed the problem before thinking about
specific replacement parts.  If that did indeed happen, and the fuses
didn't blow, you will probably need to replace more than a transformer
or even a few PSU parts, one would think, but let's not think that just
yet.  

> also, wouldn't 120vac damage the voltage regulators and caps? they 
> don't look burned at all.

One would think that some fuses would have opened if this was the
case.

-- 
Copyright (C) 2004 R. D. Davis The difference between humans & other animals: 
All Rights Reserved | My VAX | an unnatural belief that we're above Nature & 
www.rddavis.org | runs VMS & | her other creatures, using dogma to justify such
410-744-4900 | doesn't crash!| beliefs and to justify much human cruelty.