The low voltage is right out of the transformer secondary. It is about 1/2
of what it should be.
I used to be an astron distributor. I sold about a dozen of these supplies
to a customer and he sent this one back saying it had low output. Never did
get around to sending it back to the factory.
They do supply these power supplies with 220 volt transformers on request.
However this particular one was supposed to be 120 and it is marked as 120
volts but all the symptoms of the voltages indicate that there is something
other than a 120 volt transformer in it.
No markings on the transformer thus my request of what the primary
resistance should be on a 120 volt and a 240 volt transformer.
Just getting around to doing something with this thing after sitting around
for several years.
73
Gary K4FMX
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Will Matney
> Sent: Monday, May 08, 2006 1:10 AM
> To: amps@contesting.com
> Subject: Re: [Amps] Astron RS20A primary resistance
>
> Gary,
>
> 1/2 voltage can be caused by a rectifier, main filter cap, or the voltage
> regulator. I'd check the voltage regulator first off to see if I had high
> enough DC voltage from the rectifiers going into the collectors of the
> pass transistors. If it's low there, it's in the transformer, rectifiers,
> or filter. A 20 amp supply generally is only 110 Vac. The biggest thing to
> fail on these is the regulator transistors because they handle all the
> power. Next would be a bad bridge rectifier. If it's not that, the
> regulator IC could be bad, the driver transistors, or the voltage divider
> resistor network used to set the output voltage. If you have the proper DC
> voltage going into the pass transistors, then it will be in the regulator
> circuit itself.
>
> Best,
>
> Will
>
>
> *********** REPLY SEPARATOR ***********
>
> On 5/7/06 at 10:59 PM Gary Schafer wrote:
>
> >I need to know what the primary resistance is of the Astron RS20A
> >transformer. I would like to know the resistance of a 220 volt
> transformer
> >and a 120 volt transformer.
> >
> >Maybe someone has a 220 volt RS20A that could measure the resistance
> across
> >the power plug, that will do it.
> >
> >
> >
> >I have a power supply here that is supposed to be a 120 volt unit but it
> >looks like it has a 220 volt transformer as I only get around ½ the
> voltage
> >out on 120. This transformer measures around 6 ohms primary resistance.
> >
> >
> >
> >Thanks for any help.
> >
> >
> >
> >73
> >
> >Gary K4FMX
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