From: K9SQG{at}aol.com
Subject: Re: [drakelist] L-4PS - Difference in Schematic Diagram 


K9SQG{at}aol.com made an utterence to the drakelist gang
----------------------------------------------------------------------
To my knowledge, the same transformer and thus the same voltage was used on
all L4B and L7 power supplies.  Some diodes had equalizing resistors and/or
capacitors across them.  With later versions of the supplies, better
quality control of the diodes, etc, some of these components were dropped.

It is generally a good idea to replace all the diodes with higher ratings,
e.g. 1 KV at 3A.  In addition, replacing that 5K 7 watt resistor on the
underside of the supply is a good idea as well.  When that resistor opens
up, it puts high voltage across the ALC pot and takes it out.  That pot
hasn't been made in over 20 years and is unavailable.  Hence, that resistor
should be replaced with one of 20-30 watts to help guard against such a
failure.  

It's a good idea to check the bleeder resistors as well.  In the 8-10
supplies I've rebuilt, failure rate seems to be around 75%.

To reduce heat related problems, I use two 220v muffin fans, that will
start on 110v, by placing them on top of the power supply cage with a
small, stick-on rubber foot (thin) under each corner.  The fans are very
quiet and reduce the internal temperature of the supply dramatically.

73s,

Evan
----------------------------------------------------------------------
On Behalf of K9SQG{at}aol.com
Submissions:        drakelist{at}www.zerobeat.net
Unsubscribe:        majordomo{at}www.zerobeat.net - unsubscribe drakelist in body
Hopelessly Lost:    majordomo{at}www.zerobeat.net - help in body of message
Zerobeat Web Page:  http://www.zerobeat.net
Brought to you courtesy of TLCHost.net  http://www.tlchost.net/
----------------------------------------------------------------------

---