Thanks, Pete,
I'm thinking maybe the Astron was putting out too much voltage. I don't
trust Astron supplies and don't have any in my shack. In general, I
don't like running a radio on a power supply that has front panel
variable voltage and current. It's just too easy to make a mistake and
it appears that this Paragon failed on turn-on. I'm going to disconnect
the B+ wire that powers the final and see if the rest of the rig powers
up. The ohmmeter doesn't show a dead short, so maybe something is
breaking down with applied voltage.
I will also repair the Ten Tec power supply to take the Astron out of
the picture.
73,
Bob WB2VUF
On 1/29/2019 8:43 AM, Peter Bertini wrote:
If the PL issues are resolved, I'd fix the radio, or sell it for parts.
The Paragon rigs are aging beasts, and even buying another Paragon may mean
you end up with TWO parts radios in short order!
But, back to this unit. My only experience is with my Paragon II, which is
a more reliable radio.
The TenTen power supply should be repaired and used with the radio. It
provides high current limiting which protects the expensive finals from low
impedance loads. The Astron would be poor choice.
Regarding the MRF-458 transistors, it is my understanding that the MRF-454
devices have similar gain, but are rated for higher collector currents. You
may want to check around with someone with more knowledge to see if the
MRF-454 would be more reliable.
The short on the DC bus could be related to other work, a pinched wire,
etc. I'd want to prove that the PA was the cause of the short before
taking any drastic action, or needlessly replacing expensive PA
transistors.
Every Omni VI I've picked up over the past few years, all five of them,
have had issues... some subtle, some major. I will eventually just keep the
best two on the operating bench, and keep two for spares. The earlier VI
will get sold. I think almost any vintage TenTec should be approached with
the expectation that there will be a problem in the rig if you look hard
enough, or there will be one soon.
regards
Pete k1zjh
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