I ran into roughly the same situation a few years back. I had a 2-C
that was a real dog. It turned out that the manual said 12BZ6, the tube
was a 12BZ6, but the chassis was lettered 6BZ6. So I measured the
heater voltage at the socket just to be sure - 6.3 VAC.
Changed out the tube to a 6-volt unit and what a difference that made, hi!
On a little different subject, I was thinking that someone told me that
Drake had some units that were designed to use an 8-volt tube with 6
volts to the heater, for some arcane reason. Am I imagining this?
Vy 73,
Tom
Walker wrote:
I have a TR-4, 1968 manufacture date, serial number 28124. It has worked
well for years, with the last few being dormant as my vertical took a
hit a few winters ago with icing. I've replaced the vertical, and I'm
trying to re-tube the unit. Here is where the confusion arises:
The chassis lettering and schematic for tubes V4, V5, V11 and both agree
and are respectively: 6EJ7, 6BA6, 6BZ6.
Note: the schematic has V5 and V11 with a hand lettered "6" in front of
6BA6 and 6BZ6 versus all other tubes which have stencil guided lettering.
The Manual's Voltage Reference chart and Tube List for V4, V5 and V11
are: 6EJ7, 12BA6, 12BZ6
The Manual's Block Diagram shows V4 as 6HS6
I'm not sure what's supposed to be right, though I have a tendency to
believe the chassis lettering and schematic. The manual is internally
inconsistent, and doesn't agree with the physical hardware or schematic.
I probably can take out V5 and V11 and measure the filament voltage
present to see if it really is set up for a 6 or 12 volt tube in those
sockets.
I found some correspondence between the original owner, whom I purchased
the unit from, and the factory regarding a technical problem. The
factory rep wasn't sure in solving a problem whether the former owner
needed a 6BZ6 or a 12BZ6 so he sent him one of each. Apparently the
factory didn't know either!
Was there some changeover for different serial number ranges, between
various tube types or what, and what is the best way to tell which tubes
really belong in the circuits?
Thanks for pointing me toward a resource, if you know one, to help get
some answers.
Phil WA2CLX
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