It's time to restore the 11/45 - progress!

[Jacob Ritorto]

On Thu, Feb 5, 2015 at 4:54 PM, tony duell <ard at p850ug1.demon.co.uk> wrote:

>
> You are giving them the +15V DC input as well as the AC from the
> transformer?
>
> If so, sounds like the crowbar is firing. One thing that will cause this
> is a dried-up
> output capacitor (you get nasty spikes on the out thast trips the crowbar).
>
> I am not sure what you are asking with the 'How does one repair [a DEC
> regulator
> brick]'. The obvious answer is just like any other bit of electronics, but
> presumably
> there is some specific problem that you have in mind.
>
> -tony
>


  OK, please forgive my ignorance, here.  To give you some idea of my
electronics expertise level, I'd like you to know that I just googled
crowbar :D

  Now, I'm handy with a soldering iron and understand these sorts of things
OK once I have a run through, but I just have no idea where to begin.  So
again, forgive me, but I'm going to ask some very green questions.  I'm
sure you guys are going to want to strangle me or laugh me out of the room,
but, hey, I'm trying, darn it, so please don't plonk me!

  From the wikipedia article I read, I guess this crowbar thing tripping,
is just its way of trying to protect the rest of the system from
overcurrent, right?

  And the dried up cap is one thing what could make it think there was an
overcurrent situation, correct?

 I'v had a little luck in the past with such things, but I don't know that
I'm going to understand how to read the schematic.  I'm going to try and
find one now.  Also going to try to find a manual that describes the power
supply.  But how do I know which one is the output cap?  What is a valid
test once I find it?  I guess I could charge it up on a car battery and see
how long it holds or something like that.

  I don't have much electronics gear here.  Borrowed a Craftsman digital
VOM from my electrician friend (although it's telling me I have 140v AC on
the mains!) and I have a soldering iron, heated desoldering bulb thing and
some desoldering braid, flux and lead solder.

BTW, according to this VOM, there's 24.5 AC and 14.2 volts DC being input
into the H745 regulator.  Is this too low?  Maybe this has something to do
with the H742 adjustment that I didn't find?  Or maybe this VOM is
miscalibrated.

thx
jake