[Kenwood] Re ASTRON PSU RM50

[Tim Billingsley]

On Nov 12, 2016 20:43, "Jim Miller" <JimMiller at stl-online.net> wrote:
>
> Hi again Tim, I worked on mainframes when they filled rooms.  When you too
> many "pieces" involved and you are having trouble isolating it from the
top,
> go to the bottom.  Find something that does work and add to it.
>
> As in, disconnect the transformer from the rectifier, verify probably
> correct unloaded voltage, then put a load on it and check that you still
> have voltage near what you had previously and not zero as in bad
transformer
> of poor connection into (or inside) the transformer.  Verify while it is
> still "on" and the voltage at zero that the input AT the transformer is
> still as expected.  Poor connection in wiring to the transformer or bad
> switch or fuse holder or breaker or connections.   I have heard of  "bad
> transformer" but not sure they really knew.
>
> Add in the ridge rectifier or diodes (2 or 4) with their output
> disconnected.  Meter them when disconnected.  Do you have a scope?  Power
an
> and see what you get. Add a load to the rectifier output.  Still have
power
> out?  Add on the electrolytic capacitors with their load disconnected.
> Still ok?  Add you load resistor across the cap.  Power?  That is the
power
> supply, now you have the regulator section remaining.  Disconnect the
> crowbar circuit.  It will be an SCR or a big transistor across the power
> supply output and triggered from the regulator circuit.  The power supply
> will run without it BUT YOU WILL NOT BE PROTECTED FROM OVERVOLTAGE.  OK to
> test though using resistors for loads .  You are down to the 723 chip and
> its surrounding components.  You can order the board but call Astron first
> and talk to a technician.  Tell him your problem and what you have done
and
> he added a couple of resisters after he asked me what the value was and
> asked if I had components.  He stayed on the phone while I found some that
> would work and soldered them in!!!!  It fixed it.  Can't ask for better
> support than that.
>
> Let us know,
> Good luck and 73, Jim KG0KP
>
>

Jim,

Thanks for the step by step. Hopefully I can walk thru this and some of the
other objectives tomorrow.

Thank to all for the assistance.

Tim KD5CKP
likespecies.com