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Author Topic: Suggestions for Collins 75S1 and 32S1  (Read 2825 times)
KG4ABA
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Posts: 15




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« on: October 05, 2017, 11:01:16 AM »

Everybody has been so helpful here on eHam with my questions...here's another:  I have a line on purchasing a set of Collins 75S1 and 4
32S1 with matching 312B phone patch...any nuances or suggestions you'd offer about running these rigs?  Also, what's a good microphone for audio and driving properly the 32S1?

Thanks for your help, as always!  Lynn-KG4ABA
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KB7TT
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Posts: 17




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« Reply #1 on: October 05, 2017, 03:15:02 PM »

Read the tuning instructions in the 32S-1 manual.  They are very good.
I use a Shure 444 (high impedance) microphone which works well on the old collins gear. 

Gud luck,

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WB2WIK
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Posts: 21754




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« Reply #2 on: October 05, 2017, 03:53:37 PM »

Everybody has been so helpful here on eHam with my questions...here's another:  I have a line on purchasing a set of Collins 75S1 and
32S1 with matching 312B phone patch...

Suggestion:  Watch the seller put it on the air and use it to make contacts before exchanging any cash for hardware.

This is very old gear (1958-1963) and unless well maintained or recently serviced I'd stay away from it.   Remember this gear doesn't work on 160m or the WARC bands (or 60m) and tunes in 200 kHz segments, so you have to "switch bands" in the middle of each band to tune beyond that point.   Takes some getting used to.

But the mike isn't critical.   The mikes Collins sold for the rig (made by Turner and ElectroVoice, depending on model) were fine but a Shure 444 (ubiquitous -- they're everywhere!) works fine also.   
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W1UO
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« Reply #3 on: October 05, 2017, 07:25:54 PM »

If you are a CW operator, the 32S-1 is not a good CW transmitter.  You would need a 32S-3 instead.
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VK6HP
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Posts: 183




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« Reply #4 on: October 05, 2017, 10:18:42 PM »

Lynn

You might want to give some thought about how you wish to use the vintage gear.  In my case, I wanted excellent condition units that could be used for rag-chewing, at least.  I held out for a 32S-3 transmitter for the reason mentioned by W1UO, since I regarded the audio CW scheme of the earlier S-line transmitters as unsatisfactory in a modern band environment.  Similarly, I find the rejection tuning and variable BFO of my 75S-3B receiver to be very useful, giving good rejection of quite a bit of QRM and allowing a very convenient RIT (clarifier) equivalent when I use the TX/RX in linked mode (where the RX controls the TX frequency).

All that said, if the earlier series equipment you mention is in demonstrably good condition and the price is right, I'd give it consideration.  Is there a matching power supply (516F-2) for the transmitter?  You'll need one of those, or an equivalent, so factor that into your thinking.  The 312B is nice for the speaker, and the directional wattmeter is also quite useful.

Have a look at the Collins Collectors Association website (http://www.collinsradio.org/) to learn a bit more about the care and feeding of the equipment, including common faults and modifications.  The mechanical side of these old radios can be challenging so take a look at all the switch and control actions, just so you know what may need attention.

I get unsolicited good reports from my S-line station, and the associated 30L-1 linear amplifier.  For the audio, I often use my boom mounted Kenwood MC-90 dynamic mic fed via a W2IHY pre-amp and iPlus (high-impedance feed) to the 32S-3.  Other favorites are a Collins MM-1 high impedance, high output dynamic mobile mic, which is a heavy metal mic that looks great.  Occasionally I use a D104 crystal mic with a FET source follower (not the crummy Astatic amplifier) and that's also fun.  You do need extra audio drive relative to a modern radio, either direct from a high-ish output mic or via a pre-amp.  Running too much TX mic gain is inclined to give a bit of hum from the audio stage which, while not at all bad, is incompatible with what I want to hear from my Collins station.

Let us know what you decide!

73, Peter
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N8FVJ
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Posts: 373




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« Reply #5 on: October 06, 2017, 06:52:28 AM »

Replace electrolytic capacitors. These old caps fail.
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W5RKL
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Posts: 1032




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« Reply #6 on: October 23, 2017, 05:53:40 AM »

Everybody has been so helpful here on eHam with my questions...here's another:  I have a line on purchasing a set of Collins 75S1 and 4
32S1 with matching 312B phone patch...any nuances or suggestions you'd offer about running these rigs?  Also, what's a good microphone for audio and driving properly the 32S1?

Thanks for your help, as always!  Lynn-KG4ABA

There are issues with the Collins 32S1 transmitter when transmitting CW as Glen Zook, K9STH, explains in the following quote I cut and pasted from a qrz.com discussion pertaining to
the Collins transmitter and receiver.

QUOTE:
   

    The Collins 75S-1 / 75S-2 receivers are, to be blunt, pretty mediocre. They are generally better than most of the general coverage receivers used in the late 1950s into the 1960s. However, the receivers are fairly lacking except for SSB. There was a 500 Hz mechanical filter available and an optional BFO crystal which did help for CW operation. In addition, there is no way to "kill" the A.V.C. in the receiver and there was no rejection tuning available from the factory. Also, the audio output from those receivers tends to be less than with the 75S-3- series receivers.

    The 75S-3, 75S-3A, 75S-3B, and 75S-3C receivers are "light years" beyond the 75S-1 / 75S-2. Those receivers have a variable BFO as well as crystal controlled BFO frequencies, have slow, fast, and no A.V.C., have rejection tuning, and several other features. In addition, EVERY 75S-3 and 75S-3A came from the factory with a 200 Hz CW filter installed. Then, with the 75S-3B and 75S-3C, the CW filters were a high priced accessory.

    The 75S-2 and 75S-3A are the rarest of the S-Line receivers with about 500, of each model, being manufactured. Many Collins users consider the 75S-3A to be the best of the receivers followed by the 75S-3. The 75S-3B and 75S-3C were designed after the "bean counters" got involved and there was some cheapening of the construction. Not a whole lot, but there were some slight differences in performance.

    The Collins 32S-1 and 32S-2 transmitters are fine for SSB. However, one should NEVER use those transmitters for CW. Because of the side-tone CW generation process used, those transmitters will definitely put out 3-signals and, under some circumstances, 5-signals! The 32S-3 and 32S-3A transmitters use a true CW generation method and do not suffer from the multiple signal problem.

    I have 2-each 75S-1 receivers and a 75S-3A receiver. One of my 75S-1 receivers has the Water's rejection tuning modification and the other has a 500 Hz CW filter and optional BFO crystal. My 75S-3A receiver originally belonged to the Collins field technician who used to visit military bases to "fix" problems that the military technicians were not able to handle. When the 75S-3B / 75S-3C came out, every change made in those receivers was tried in this particular 75S-3A. However, every change, except for 1, was removed and the receiver returned to the original configuration. The one modification that was left in the receiver was the adding of a zener diode to regulate the voltage on one of the oscillator circuits. That modification really didn't have any obvious benefits. However, it is never a bad idea to regulate the voltage on an oscillator stage!

    There was one modification, which Collins came out with after the 75S-3B / 75S-3C were in production for a while, that moves one of the 455 kHz i.f. cans from the AM filter to the plate of the 2nd mixer stage that is definitely worth doing. I have done this to my 75S-3A and both 75S-1 receivers.

    Unless one is very familiar with the 75S-3 or 75S-3A, the subtle differences with the 75S-3B and 75S-3C receivers will not, generally, be noticed.

    The Heath SB-Line equipment is often compared to the Collins S-Line. When I obtained my 75S-3A, I ran it in parallel with my Heath SB-301 receiver for several weeks before deciding to go ahead and obtain the matching 32S-3 transmitter. I found that, in 9, out of 10, times, the Heath SB-301 could do anything that the 75S-3A could do. But, it was that 10th time that made me decide to go ahead and acquire a 32S-3 transmitter.

    I rate the Heath versus Collins equipment, from lowest to highest, as follow:

    Receivers: Heath SB-303, Collins 75S-1, Collins 75S-2, Heath SB-300, Heath SB-301, Collins 75S-3B, Collins 75S-3C, Collins 75S-3, Collins 75S-3A

    Transmitters: Collins 32S-1, Collins 32S-2, Heath SB-400, Heath SB-401, Collins 32S-3, Collins 32S-3A

    There were changes made to the transmitters that affect the performance.

    The original 32S-1 and 32S-2 transmitters used a 2-diode, full wave balanced modulator which was later changed to a full wave bridge (4-diode) balanced modulator. This change definitely improves the suppressed carrier.

    All of the 32S-1 and 32S-2 transmitters, as well as the earlier 32S-3 and 32S-3A transmitters, used a ceramic trimmer as the final neutralization capacitor. Unfortunately, when the 6146B/8298A or 6146W tubes are used, this capacitor is virtually assured of "burning up"! Collins had to change the neutralization circuit so that the later tube types could be used. This revised circuit uses an air variable capacitor.

    Glen, K9STH
     


UNQUOTE

73
Mike W5RKL
www.w5rkl.com
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KB7TT
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Posts: 17




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« Reply #7 on: October 23, 2017, 12:32:56 PM »

All Collins S-line radios and KWM2s ARE capable of WARC coverage with the proper crystals.  However they will not operate on 60M.  I have my KWMA crystaled for the WARC bands, works fine. 

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K1ZJH
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Posts: 3325




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« Reply #8 on: October 24, 2017, 06:58:30 PM »

All Collins S-line radios and KWM2s ARE capable of WARC coverage with the proper crystals.  However they will not operate on 60M.  I have my KWMA crystaled for the WARC bands, works fine. 



CP-1 crystal packs keep showing up for sale.
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