Byron -
Assuming your meter is a "standard" 10M input impedance meter, take a 1
Megohm, 1/4 (or 1/2) W resistor. Wrap one lead around your meter probe
tip, and touch the other lead to Pin 1. Effectively 1M in series with
the DC probe.
Per the Voltage chart, the measurements were made with a VTVM, which,
unless it has been "modified" (per a widely circulated "mod") by someone
who thought the resistor could be put INSIDE the cabinet and work just
as well. Of course they knew more than Heath's (or HP's, or... )
engineers! :-) This arrangement was standard on all meters intended
to be used on tube based equipment.
Your probe lead is loading down the oscillator, and the 1M resistor at
the TIP of the probe isolates the lead from the circuit.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs
<www.k4oah.com>
Byron Tatum wrote:
Hello-
I hit a snag in checking out a Drake R-4A, one of the 13 tube
versions. It works but is not quite right in my opinion. After doing
resistance checks, and not seeing anything way off, I thought I would
check voltages next. For V-3, the 12BE6 converter, in the manual
for pin #1 it shows -11.5 VDC as the normal voltage reading. I show a
little less than -0.05 VDC. Pin #1 of this tube has the 5645 Khz.
crystal and capacitive divider connected to it. The converter tube is
working, would the lack of negative bias being developed be a function
of the crystal activity? I tried several good 12BE6 tubes with same
results. The rest of the volttages on this tube check reasonably close
to what the manual says.
I thought I would ask if this is something I should pursue
further, or not worry about it since the converter is working, however
the receiver is low on gain.
Thanks, Byron WA5THJ
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