[Premium-Rx] Collins 2050 help please

[VE6JY Don Moman]

Well, this seem like a PS issue to me (or a very dead micro - is the green
LED on the A2 board lit? ) The draw on the 5 volt line is a bit light - my
notes show I measured 3.05 amps.  It should be noted the voltage is listed
as 5.20 volts - and is somewhat critical.  You may try running it up a bit.
+15v at 1.05 amps and -15 at .45 amps - are the other draws.

The electrolytics on the +/- 15 v are often dried out from the heat, it's
likely a good plan to swap them out just because.... also C5, the 100uf
tantalum on the 5v regulator (actually Vcc for the 723 vr) is another common
culprit to fail. Poorly filtered Vcc to the 723 doesn't help the regulation
characteristics... You may be measuring 5 vdc "average" on the meter but a
scope on the line would tell the whole story.

Good luck!

73 Don
VE6JY

----- Original Message -----
From: "Paul Wende" <pwende at arrow.com>
To: <premium-rx at ml.skirrow.org>
Sent: Wednesday, April 09, 2003 15:08
Subject: [Premium-Rx] Collins 2050 help please


> Hello fine group,
>
> After a 15 month hiatus, to stop and have a baby, I am now getting back
into
> the radio scene and have acquired another 2050, which of course has a
> problem. I made the mistake of giving my wonderful manual from Walter away
> with the last radio so I need two things. Does anyone still have a depot
> level service manual they would like to sell, and number two, the problem
> with the radio.
>
> It's pretty basic, push the power button, the fault light comes on
> immediately, the power supply growls and there is absolutely no display or
> speaker noise. To me, this points to power supply, which I checked, and it
> looks like someone may have been in there as the trim pot on the 5V supply
> was set to 3VDC, I turned it to make it 5 and the power supply seems okay,
> with all voltages correct. I measured the 5V draw at 2.5 amps, which seems
> reasonable.
> Side note, the construction of this power supply is certainly second rate,
> compared to the build quality of the radio. Looks like someones high
school
> project. :-)
>
> Until I get schematics, I am flying blind, which I really don't wish to do
> with this rig as it is in mint condx. and I don't wish to go blindly
> desoldering things, looking for the trouble.
>
> Anyway, any help would certainly be appreciated. Has anyone scanned the
> schematics to a PDF file yet? Any other suggestions? I started checking
the
> tantalums as I know they can be problematic but every one I tested seemed
> okay.
>
> Kind regards,
>
> Paul Wende
> VE7KHz
>