[TenTec] Paragon Finals and other woes

[Bwana Bob]

Hi, all,

I'm trying to fix a Paragon for one of the OTs here.  I just can't keep 
it running for more than a couple of weeks at a time. I fixed multiple 
PLL problems and got it running nicely.  Then, the Ten Tec power supply 
blew (looks like both pass transistors went), so an Astron power supply 
was substituted.  The Paragon kept shutting down until the owner cranked 
up the voltage all the way.  I determined that there was too much 
voltage drop (about 2 volts, key down) in the power cable, which was 
relatively long, with multiple splices. I suggested shortening it.  This 
was done and now the rig won't power on at all.  I went back and did 
some more troubleshooting. I found that the power switch ground return 
on the power control board was open.  I fixed that, but found a short on 
the 13.8 V bus.  I haven't dug into it yet, but fear that the Astron 
supply zapped the finals.

R.F. Parts still carries the Motorola MRF458 at a reasonable price, but 
would I need a matched pair?

I also have a couple of questions on the power control board:  The 
manual states that the fuse is an AGC-25, which is fast-acting, but the 
schematic shows an MDL-25 fuse, which is time-delayed. Which is correct, 
or is it non-critical?  I also notice, comparing schematics, that the 
Omni V has an additional circuit on the power control board that delays 
closure of the power relay.  I don't know what purpose this serves or if 
it is worth adding to the Paragon.

Finally, there is the question that at what point does it not pay to fix 
a Paragon.  I've fixed my own Paragon a few times and it works fine, but 
this other one is a nightmare!  It might be better to look for a parts 
unit or a used one in better shape, and keep this one as a parts rig!

73,

Bob WB2VUF


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