[Boatanchors] National HRO-500 Intermittant

[Carl]

What series and have you replaced any caps?

Carl
KM1H


----- Original Message ----- 
From: "Jim Wright" <hatisland8 at yahoo.com>
To: <boatanchors at mailman.qth.net>
Sent: Sunday, June 14, 2009 10:07 PM
Subject: [Boatanchors] National HRO-500 Intermittant


> I've got a HRO-500 with a strange problem and hoping someone out there has 
> seen something like this before.
>
> If used every day it works fine.  But if it sits for a few days, then when 
> it's turned on it operates for only about 30 seconds.  For that 30 seconds 
> or so the SSB or AM stations come in normally, and then the signal 
> strength (and the S Meter) start to slowly decay until there is no signal 
> received and the S Meter gradually goes to 0.  During the final few 
> seconds the audio distorts - sort of like AM splatter  sounds like. 
> Problem occurs on all bands and filter positions, and both SSB and AM. The 
> radio PLL remains "synchronized" (no red light from synchonizer) and the 
> 12, 11, 10 volt power measures okay.  After the signal goes away there is 
> some audio hiss but that's all.
>
> Turning the set off and on again a single time repeats the same thing. 
> However, after turning the power off and on four or five times the radio 
> resumes normal operation and runs without problem.
>
> At first, I thought it must be a bad cap but it seems like if that was the 
> case it wouldn't ever operate normally after the series of turning it off 
> and on.  I wiggled transisters in their sockets without any changes but 
> haven't replaced any.  It acts like the problem is somewhere in the RF 
> path up to the audio amp.
>
> Anyone experienced like this with a HRO-500?
>
> Thanks.
>
>
>
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