The input diodes were actually BA482's, while the output diodes were
1N4148's. The former has about .7dB lower losses, but also has a breakdown
reverse voltage of only 35v as opposed to 75v for the latter, so I think
that is why they were the ones to fail. The BA482 seems to be made of
unobtanium, but the 1N4148's are readily available...I actually had 9 in my
junk box. Looking deeper at the next board, the 1st Mixer, I think several
of the BA type or PIN diodes there may be zapped, as well, but I found a
board from a parted out Paragon that I have on the way, and hopefully that
will save a lot of time on component repair.
I did test each band section on the Hi-pass board and the voltages are
switching correctly, although the actual voltage seems a little off to what
I would have expected. I identified the bad diodes using the forward/reverse
resistance check, but on my digital meter I had to use the 2Meg scale to get
readings.
=Vic=
WA4THR
__________________________________________________________
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Subject: Re: [TenTec] Paragon problem
From: "Bob McGraw - K4TAX" <RMcGraw@Blomand.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sun, 13 Jul 2014 22:36:34 -0500
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
Correct and one reason I keep my old Triplet 603 VOM, it has a + & - switch
on the front, thus I don't have to flip the test probes on the device. Of
course my FLUKE DVM has provision for a diode test as well. But with it I
have to flip the leads to measure forward and reverse resistance of the
diode.
I'd expect some of those diodes on the High Pass Filter board are leaky and
thus two or more filters may be engaged at once. I find it somewhat
interesting that 8 diodes were open and all on the input side of the
filters.
73
Bob, K4TAX
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|