In article , Dan Robinson
writes:

R388s, which do not have the mechanical filters
like the 51J4s, often go for high prices if they are
in excellent to "new" condition (the latter being quite rare).

How does the value of an R388 compare with the nearly-identical 51J3?
Is there any functional difference? Do Collins collectors prefer the "pure"
51J3 to the military R-388?

But as far as performance goes, 51J4s with the
filters are just great and provide greater flexibliity.

Yep, when playing with my R388 I often wish for the better selectivity control
of the J4. Xtal filters just don't hack AM or SSB all that well.

Though I don't suppose even the J4 has a product detector, right?
73, Mike K. AA1UK


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"Mike Knudsen" wrote in message
...
In article , Dan Robinson

writes:

R388s, which do not have the mechanical filters
like the 51J4s, often go for high prices if they are
in excellent to "new" condition (the latter being quite rare).

How does the value of an R388 compare with the nearly-identical 51J3?
Is there any functional difference? Do Collins collectors prefer the
"pure"
51J3 to the military R-388?

But as far as performance goes, 51J4s with the
filters are just great and provide greater flexibliity.

Yep, when playing with my R388 I often wish for the better selectivity
control
of the J4. Xtal filters just don't hack AM or SSB all that well.

Though I don't suppose even the J4 has a product detector, right?
73, Mike K. AA1UK

No, it did not have a product detector. I did do one author's mod to these
receivers over the years, where you convert the cathode follower for the
I.F. output to a product detector. It was great, because the mode switch on
the front panel has an extra set of contacts that you can use for routing
the audio.

Pete

In article , "Pete
KE9OA" writes:

No, it did not have a product detector. I did do one author's mod to these
receivers over the years, where you convert the cathode follower for the
I.F. output to a product detector. It was great, because the mode switch on
the front panel has an extra set of contacts that you can use for routing
the audio.

Would that mod also apply to the J3/R388? The need for extra audio switching
is a big problem in most PD mods, leading to use of relays in R390A for
example, with all kinds of problems. Don't recall seeing extra switch contacts
on my 388, maybe just on the J4.

Since the BFO switch is broken on my SP-600, I just might replace it with a
3PST switch (good luck) and put a PD tube in place of the BFO driveer. --Mike
K.

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Mike Knudsen ) writes:
In article , "Pete
KE9OA" writes:

No, it did not have a product detector. I did do one author's mod to these
receivers over the years, where you convert the cathode follower for the
I.F. output to a product detector. It was great, because the mode switch on
the front panel has an extra set of contacts that you can use for routing
the audio.

Would that mod also apply to the J3/R388? The need for extra audio switching
is a big problem in most PD mods, leading to use of relays in R390A for
example, with all kinds of problems. Don't recall seeing extra switch contacts
on my 388, maybe just on the J4.

Since the BFO switch is broken on my SP-600, I just might replace it with a
3PST switch (good luck) and put a PD tube in place of the BFO driveer. --Mike
K.

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Wasn't an old trick to put a relay in the line to the BFO? So when
you turn on the BFO with the existing switch, the current through
the relay causes it to switch, and then the relay contacts can
route the audio properly.

Michael

In article ,
(Michael Black) writes:

Wasn't an old trick to put a relay in the line to the BFO? So when
you turn on the BFO with the existing switch, the current through
the relay causes it to switch, and then the relay contacts can
route the audio properly.

Yes, that's how the previous owner of my R390A tried to do it, and I bought
another relay to try to improve on the job, since his was sticking ON. The two
problems a finding a relay sensitive enough to trigger on the BFO plate
current, and with enough contacts to do the switching, and cramming the relay
into the underside of the BFO sub chassis (no mouse droppings in there -- mice
can't fit inside!). Without messing up the AVC voltage into the ANL.

The R390A job is complicated by the natural desire not to run any extra wires
to the IF module and spoil the neat connectorization. 73, Mike K.

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Hi Mike,
That mod should apply to all of the 51J series receivers. I know
for sure that it is on the J3 and J4, and on the R-388 version of the J3.

Pete

"Mike Knudsen" wrote in message
...
In article ,
"Pete
KE9OA" writes:

No, it did not have a product detector. I did do one author's mod to
these
receivers over the years, where you convert the cathode follower for the
I.F. output to a product detector. It was great, because the mode switch
on
the front panel has an extra set of contacts that you can use for routing
the audio.

Would that mod also apply to the J3/R388? The need for extra audio
switching
is a big problem in most PD mods, leading to use of relays in R390A for
example, with all kinds of problems. Don't recall seeing extra switch
contacts
on my 388, maybe just on the J4.

Since the BFO switch is broken on my SP-600, I just might replace it with
a
3PST switch (good luck) and put a PD tube in place of the BFO
riveer. --Mike
K.

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In article , "Pete
KE9OA" writes:

That mod should apply to all of the 51J series receivers. I know
for sure that it is on the J3 and J4, and on the R-388 version of the J3.

Thanks Pete, I'll look for the mod -- any pointers?
73, Mike K.

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I lost the documentation years ago. The next best thing is the SSB detector
for boatanchors that I have up on my website. It is based on an NE602.

Pete

"Mike Knudsen" wrote in message
...
In article ,
"Pete
KE9OA" writes:

That mod should apply to all of the 51J series receivers. I
know
for sure that it is on the J3 and J4, and on the R-388 version of the J3.

Thanks Pete, I'll look for the mod -- any pointers?
73, Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

I only caught the end of this thread. Is someone looking for the Paul
Lee product detector mod? I know for certain I've seen it online
before, and may or may not still have the orig QST article somewhere.
There was also a sort of general summary of the similar mod for 4 or 5
different rcvrs published around the same time, which I might find if
I have a year to lookg. My 388 had this mod when I got it, seems
pretty good or so-so depending on what your present standards are. I
have to dub carefully with the BFO knob to dial in SSB but once set, I
can copy across the band, or even leave it at the same setting for
months. Tuning is a little touchy. But the rcvr also hasn't had a
maintenance-oriented finger in it for at least 20 years, either, not
even aligned, and is only connected to the ether with 10 ft of
dangling wire.

"Pete KE9OA" wrote in message ...
I lost the documentation years ago. The next best thing is the SSB detector
for boatanchors that I have up on my website. It is based on an NE602.

Pete

"Mike Knudsen" wrote in message
...
In article ,
"Pete
KE9OA" writes:

That mod should apply to all of the 51J series receivers. I
know
for sure that it is on the J3 and J4, and on the R-388 version of the J3.

Thanks Pete, I'll look for the mod -- any pointers?
73, Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.