Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Byron -
The NBK board was required to use the wired-in 34-NB in the TR-3 and
early TR-4 _ONLY_, the ones with the original "soupcan" filter. These
filters required an output termination of 2200 ohms while the NB is 500
ohms. The 34-NB wired-in and the PNB-34 plug-in circuits are
electrically identical.
The terminating resistors on T6 and T13 were also changed from 2.2k in
soupcan filter units to 470 ohm, 5% in dual filter units. The dual
filters were adopted around s/n 23000, but the schematic was not changed
to reflect the R16 and R77 value changes until Version 3 in January 1967.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com>
Byron Tatum wrote:
Hello-
Maybe someone here may be able to answer this question:
Why did the 34-NB noise blanker require the NBK matching
board (had torroid matching into crystal filters, torroid matching
into 6EA8 mixer) ? I have studied the 9-NB board ( PC board for 34-NB
noise blanker) and compared it to the 34-PNB PC board. I really cannot
see any electrical difference with a casual glance between these two
noise blanker boards. On radios that had the socket for 34-PNB there
were no matching torroids installed. Perhaps I need to study closely
the torroids on boards for differences, I would assume the 34-PNB
board did not need external matching torroids because it performed
matching on board?
Who might have in-depth technical info on these boards beyond the
used manuals, brochures, etc?
Thanks, Byron WA5THJ.
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