[Hammarlund] HQ-170A mods?

[Chuck Ochs]

No- The OA2 and OB2 are different VR tubes, and are not interchangable.
Seems to me (that memory thing again) one drops 150 volts, and the other
drops 105 volts, but I don't remember which is which (somebody help). Sounds
to me as though someone was trying to meddle with the design. My firm advice
would be to get the schematic, and restore everything to original.
Chuck N1LNH
----- Original Message -----
From: "Craig Roberts" <crgrbrts@verizon.net>
To: <hammarlund@mailman.qth.net>
Sent: Friday, January 02, 2004 1:06 PM
Subject: [Hammarlund] HQ-170A mods?


> Hiya Gurus -- and Happy New Year!
>
> While re-tubing my "new" HQ-170 VHF I discovered that it has been equipped
with an OA2 VR tube rather than the OB2 called for in my schematic. The OA2
tube seems to work okay. So, for that matter, does an OB2 (while glowing a
very bright orange).  Underneath, I've noticed what appears to be a
modification to the power supply circuitry (perhaps to accomodate the OA2
?). Two additional diodes -- besides the stock pair -- have been added.  And
then there's this gray "thing" down there. It's not the 3K 10W power
resistor but it is near it and resembles a "cement" power resistor, too. It
is small in diameter, somewhat long and cylindrical in shape. This thing is
as mysterious to me as a 1920's grid leak (which looks like a fuse) was
years ago.
>
> What is this device?  A choke?  (I don't have the radio with me here at
work so I can't tell you exactly where this thing is in the circuit). The
device is a bit scorched and cracked, which is why I'm worried about it.  If
it need replacement, I have no idea what to replace it with (!).
>
> Oh -- and is the OA2 conversion a documented mod?
>
> Many thanks and 73,
>
> Craig
> W3CRR
>
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