Steve -
The resistor in question is a 150 ohm decoupling resistor, not a plate load resistor. It's not all
that unusual for the low value carbon comps to fail shorted. Enough current to melt the binder into
a lump of coal ('tis the Season) rather than enough to just vaporize it! Also an indication of
'some', not 'catastrophic' overload.
By the way, the reason for the wildly out of range Pin to chassis resistance is sometimes a matter
of ohmmeter polarity, need to check both ways. The other problem is that Drake was not consistent
in changing the Resistance and Voltage charts to reflect schematic changes.
--
73, Garey - K4OAH
St Charles, IL
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Steve Wedge wrote:
I think Garey had mentioned you can fry the plate resistor on V8 if you short
one of the trimmer caps while tuning it.
It's still odd to me to have a resistor fail shorted.
The 6HS6 will have the same switch settings as a 6AU6 but it has quite a bit
more gain and a different bias setting.
TV-10 D/U settings are:
tube fil v switches bias shunt scale button min reading
6HS6 6.3 JR3-5672 12 --- D P3 3000
6AU6 6.3 JR3-5672 10 --- D P3 2050
The 6HS6 has quite a bit more gain (these are minimum, and I remember seeing
4200 from typical new ones).
Good luck.
Steve, W1ES/4
-----Original Message-----
From: rhule...@comcast.net
Sent: Dec 22, 2011 1:33 PM
To: Steve Wedge<w1es1...@earthlink.net>
Cc: Drakelist@zerobeat.net, kc9...@aol.com, k4...@mindspring.com
Subject: Re: [Drakelist] AC-4R Surprise
All,
Well my "luck" or lack thereof continues... I pulled the 6HS6 and then referenced my Eico 625. Of course
the 6HS6 isn't mentioned anywhere in any of the charts I have. So, based on some results of a search, tested it as a
6AU6 and then a 6HR6. Former showed "good", latter showed "marginal", neither showed
"short".
So, I guess r61 failed sometime in the past but not the cause of the power supply going
south. At least I don't need to try finding another 6HS6, my usual source for tubes
shows 6HS6 "out of stock".
I'm certainly old enough to know better, but suppose will just keep checking
tubes as a start while I have the tester out of the cabinet and on the desk.
73, Curt KB5JO
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