voltage reg. Question

[David Halliday (Volt Computer)]

Sounds like an Arp Odyssey that I fixed a couple years ago.

There was a shorted tantalum cap on the main board and it caused the power
supply to show the same symptoms you are seeing.

Try disconnecting the supply and see what happens then.  Use a multi-meter
to check the DC resistance across the various circuit boards - you are
looking for a dead short.  A couple ohms is fine but dead short is a dead
give-away.


My technique for isolating the bad cap was quick and dirty but effective - I
used an Xacto knife to cut the power traces until there was no short across
the power in.  Once I had the section of the circuit isolated, I started
unsoldering one leg of each capacitor I found, checking and resoldering it
until I found the bad one.

I then used a short length of solid wire to bridge the cut power traces.

This technique is not recommended because you are cutting the pc board and
destroying any "vintaj" value. The unit in question was pretty well trashed
cosmetically and belonged to a friend who needed it fixed for a show that
day.

Good luck!

-----Original Message-----
From: Reverend bluE [mailto:djblue at asu.edu]
Sent: Monday, January 04, 1999 2:11 PM
To: DIY
Subject: voltage reg. Question



what signs does a blown voltage regulator exhibit?  (besides no output
voltage).

I have one that gets really really hot really fast, and there is no output
voltage...  

and what causes this?  I installed it and tested it, I got the desired
voltage, then after I hooked up my LED's the one didn't come on, and now
that
voltage reg is the one that gets really hot, while the other side (the
negative side) is. I'm using the big regulators that have a hole in the mfor
attaching a heat sink. (can't remember the part numbers)

again, much thanks.

VCO1 is done (mounted on a piece of cardboard for now) power supply is done
(except for the blown voltage reg), and I have my power cabling set-up and
made one cable (for the VCO).  gonna test it as soon as I put in the new
regulator (but I have to go buy one first)
-ben in Phoenix