[Milsurplus] Collins 75A-4 Receiver Coverage

[John Kolb]

Collins made a series of different mechanical filter adapters
for different receivers, the 353-A, -B, -C and -D.
These were available in different bandwidths. One of the IF
amplifier tubes would be unplugged and the adapter plugged
into the rx in it's place.  The adapter replaced the single
tube with two tubes and a mechanical filter

An old Western Radio catalog lists the 353D-08
and 353D-60 for the HRO-50 and HRO-50T1. The last two digits
of the number are the bandwidth in 100's of cycles (Hz),
800 Hz and 6 kHz in this case. For the SP-400 and HRO-60,
there were the 353A-08, -31 and -60. For the SP-600JX their
were the 353B-08, -12, and -31, and for the 75A-1, their
were the 353C-14, -31, and -60. Not much pattern to which
bandwidths were offered for different receivers. There may
have been other bandwidths offered than the listings in this
particular catalog.

The differences between the different versions would have
been the wiring on the octal plug depending on what type
of tube it would be replacing, and also the indexing of
the octal socket keyway to the sides of the rectangular
case. Adapters for the 6K7 tube had a lead out the top
for connection to the lead which would have gone to the
tube grid cap.

There was also a 354 adapter for the 51J-3/R-388 or 51J-2
S/N 501 or higher which converted it to a 51J-4.  This consisted
of the actual 51J-4 parts that were different from the -3,
T103, V107 and a handful of R's and C's were removed and the
new module installed.  The installation included linkage
for a front panel selectivity switch.  The module does not
include mechanical filters, which were now plug-in as in
the 51J-4.

John



At 08:04 AM 2/16/2009, WA5CAB at cs.com wrote:

>Right.  If anyone has one of the R-388/51J-3 kits and wants to 
>install it, I have the instructions.  If anyone has one and wants to 
>sell it, I have the want.
>
>In a message dated 2/16/2009 9:56:22 AM Central Standard Time, 
>gzook at yahoo.com writes:
>>They also had a kit for the R388/51J series.  I had forgotten about 
>>the one for the 75A-1.  The filters were at 500 kHz in the 75A-1 
>>whereas at 455 kHz in the 75A-2, 75A-3, and 75A-4.
>>
>>Glen, K9STH
>
>
>Robert Downs - Houston
>wa5cab dot com (Web Store)
>MVPA 9480
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