Bill -
TP3 is on the calibrator board, which they direct you to Figure 13 to
find the _board_ . TP-3 is actually on the foil side OF the
calibrator board and is "sorta" identified on page 24 of the manual.
VERY tiny print! The object is to pick off the 50 kHz signal (between
the two flip-flops) to use as an accurate source for alignment of the
IF, BFO and Passband Tuner. If you have an accurate generator and/or
counter you can use that as a source.
The Passband Tuner alignment is not difficult, but most likely your cap
replacement, (especially if you replaced C163, 166 and/or 168,) has
moved the BFO off frequency. This also accounts for why T-8 was "off
frequency". Adjust with T11 to your "accurate" 50 kHz source.
As for the loss of -1.35V, you may have zapped a transistor, or possibly
just a dirty switch contact. This circuit is VERY high impedance, and
it doesn't take much leakage in a switch wafer to upset it. Hopefully
you didn't SPRAY contact cleaner on the wafer switches!
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs
<www.k4oah.com>
Bill & Becky Marvin wrote:
*Hi Group My name is Bill KB9IV. I'm having a heck of a time with my
now refurbish R4B .*
**
*After I replace most major caps and electrolytic I found the T8 Notch
assembly had a shorted cable to 145 VDC! I bought*
*a used T8 with cables........great success.*
**
*The R4B had now superb receive although T8 notch had to be
re-centered. Also I adjusted the S-meter per the manual...all*
*went well. section (6.4.9 page 35).*
**
*The real trouble began when I needed to adjust the PB tuning to
re-center the function, after the Cap change it now has shifted*
*to the left of center (straight up).*
**
*With a attempt to adjust 50Khz Oscillator (step 6.4.2) page 30. I
could not find TP3 as indicated?? What TP3?? on Calibrator*
*Brd?? I Only find TP1, TP2 who wrote these lame instructions? What
other error typo's are there?*
**
*Must be a easier way? I do have the cap & resistor load.*
**
*Now I've lost the -1.35 DCV AVC..........only a narrow AVC voltage 0
to -1.0 Max, the S-Meter has little movement was OK*
*before adjusting T11 a bit and returning it to original
position.........it does nothing. The Bias will adjust with AVC Off but*
*little with AVC on...........did "Murphy's Law" strike? All Tube
Voltages and Resistive readings look normal, perhaps*
*a Diode or Transistor went bad in the AVC loop. The Tubes
were retested also.*
**
*Any suggestions or comments are welcome.*
**
*Desperate in Minnesota*
**
*Bill KB9IV*
**
**
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