[Top] [All Lists]

Re: [Amps] AL1500 PSU design

Subject: Re: [Amps] AL1500 PSU design
Date: Mon, 23 Jul 2007 12:15:37 +0200
List-post: <>
Just as a conclusion of my previous posts:
- Replaced all diodes and capacitors on the rectifier board (used BY255, and new
2kV ceramic disk capacitors)
- Installed a new capacitor board made of 12x 330uF / 400V and 100k resistors.
- replaced the 10ohms original "starting" resistor, by 2 "sfernice" 4.7 ohms

No "bang" this time, everything is working fine:
- So, in case of similar unfortune (*), it might be advisable to replace all
components on the rectifier board, not just the burned diodes (like I did on the
first repair attempt).
- Of course the caps discharge time is a bit longer than on the initial design,
but still OK as it is practicaly impossible to remove all screws before the HV
has reached 0...

(*) As a reminder the amp was unused since 2002, and the PSU blew up at first
power on, probably due to a defective electrolytic capacitor.


Re: [Amps] AL1500 PSU design
from [f6irf] [Permanent Link][Original]

To:  Tom W8JI <>
Subject:  Re: [Amps] AL1500 PSU design
Date:  Thu, 14 Jun 2007 09:35:33 +0200
List-post:  <>

> Someone asked if you could be putting 240V on a 120 winding
> through a wiring error, and indeed you could be doing that.

The first thing I did after the first bang was to check the transformer. I found
that it was wired for 220V, I rewired it for 240V according to the manual
indications (I have around 235V +/-5V at home), and checked the transformer
alone using a HV-probe 1st (*), then a voltage divider made of 4x1Mohm
resistors. The AC voltage was found conform to the expectations (around 2320V
AC- if I remember correctly, with the primary wired for 240V - of course subject
to resistance tolerance)- that should make around 3280 DC without load - isn' t
it?  And of course I checked more than twice that the wiring was conform to the
manual indications...

(*) the HV probe is a 1/1000 commercial model; associated with a digital
multimeter, it measures correctly the mains value, but while connected to the
transformer secondary, it was giving highly fluctuating indications - I guess
due to the important magnetic field around the transformer. It is why I tried
with the voltage divider and an analog multimeter (40,000ohm/V - 1500V AC) my
digital multimeter being limited to 500V AC.

Quoting Tom W8JI <>:

> Patrick
> Someone asked if you could be putting 240V on a 120 winding
> through a wiring error, and indeed you could be doing that.
> That was a good suggestion!
> Be sure you do not have a wiring error that is applying too
> much voltage since the dual primary has two 120V windings,
> one with a 100V tap.
> 73 Tom

Amps mailing list

Amps mailing list

<Prev in Thread] Current Thread [Next in Thread>
  • Re: [Amps] AL1500 PSU design, f6irf <=