[Premium-Rx] Collins HF2050 problem

[Don Moman VE6JY]

The +15v rail draws ~1.05 amps so presumably your substitute supply can
supply in excess of that.

In my experience in years past with the 2050's (30 something in quantity)
 I don't ever recall the power supply being drawn down by a faulty upstream
device, but rather it sometimes did a fine job of just failing on its own.
I'm certainly not saying it can't, just no idea where to look.  As Peter
suggested, uplugging the various boards would narrow it down a bit.  Maybe
an IR thermometer or a finger might help locate a suspect too..

Good luck, 73
Don
VE6JY





































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On Tue, Dec 29, 2015 at 8:28 PM, Richard Pederson <rpederson at eastlink.ca>
wrote:

> After finally getting some time off over the holidays I decided to listen
> to my Collins HF2050. It has been sitting on a basement shelf for about 6
> years, since I last used it and it was working great then.
>
> I turned it on and nothing. No screen, no lights, what a disappointment. I
> checked out all the power supplies and the 15VDC supply nearest the
> transformer fails under load (and the transformer buzzing increases too) .
> This 15V supply outputs a nice 15.1VDC when the interface cable to the main
> board is unattached, but is zero volts otherwise. The supply seems to be
> fine, both the BD240 and 2N3055 test fine.
>
> I should also mention that I have checked out that 15VDC PS board (not the
> tantalum caps) and replaced some of the other capacitors in particular the
> disc capacitor on the (LM273) regulator IC, pin 13.
>
> As a quick test to check if the problem is within the PS itself or
> upstream,  I substituted in my bench power supply to supply the 15VDC and
> that too was drawn down in voltage. So all indications are that the issue
> is not PS related but somewhere within the main system.
>
> But without a schematic or service manual to reference finding the issue
> somewhere on one of the multitude of boards and display is almost
> impossible.
>
> Any ideas or hints on where to look or test would be appreciated.
>
> Cheers,
> Richard
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