[Hammarlund] SP 600 date of manufacture

[Les Locklear]

Well, this got my curiosity going this am, so,  I pulled the bottom cover 
off of my JX-21, s/n 19655. This particular variant is another John R. Leary 
remanufactured SP-600 (No. 32). The three remaining bathtub capacitors are 
re-stuffed, and are all dated 2-57. As noted, the engineering change sheet 
date is 2-13-53. That isn't the manufacturing date, just a general timeframe 
when that model was being built. You failed to mention what suffix number 
your SP-600 was.

Several years ago, Alan S. Douglas discovered that the SP-600 serial numbers 
were consecutive, no matter the suffix (model) number. So, I have a general 
idea within about 90 days of when my particular SP-600 was manufactured. 
(manufacturing facilities would usually have approximately a 3 month 
inventory of components, so that 90 days is an estimate that may or may not 
be accurate)

Another caveat, John R. Leary may or may not have used the proper tuning 
capacitor cover for my JX-21 which has the suffix number and serial number 
stamped. The rivets are gone, and screws are holding the data plate on. So, 
this may or may not be a JX-21. However, this has the original factory 
wiring intact with the exception of the Leary modifications. And the ceramic 
disc caps all look to be factory soldered as do many other components. And, 
the bathtub could have been removed from another SP-600 John Leary was 
rebuilding. So, I cannot say with any degree of certainty that it was built 
within 90 days plus or minus of February, 1957.

What does this tell us? Well the JX-21 was built from the early 1950's until 
at least February, 1957. The majority of "all" SP-600 production was during 
the early 1950's to early 1961. The exception being the JX-21A which was 
produced in the 1972 - 1973 time frame.

If you could provide a suffix number and check the dates of the bathtub 
caps, filter electrolytic capacitor or crystal you can get a decent estimate 
of when it was manufactured.

The highest serial number I have personally seen was 20137 on a JX-17. Late 
production variants used a different numbering scheme, a foil label on the 
rear panel with the serial number lightly stamped on it. This was also used 
on late production HQ series receivers. I have never found any information 
that would explain how to decode it.

Les

-----Original Message----- 
From: James A. (Andy) Moorer
Sent: Friday, November 07, 2014 9:30 PM
To: hammarlund at mailman.qth.net
Subject: Re: [Hammarlund] SP 600 date of manufacture

There is no way to find out for sure.
You can check Les Locklear's compilation of contracts and model numbers
here:
http://www.hammarlund.info/sp600.html

If yours still has the model number on it, then you can find out the
year the contract was made. That won't be the year the radios for that
contract were made - they might have dribbled out over a number of years
after that. The radios were numbered sequentially as they came off the
line and the lists of which serial number was made when and what model
it was are long gone. Having said that, a number that high would have
been towards the end of the tenure. I would guess 1955-1957 or so.

Note that many of the bathtub capacitors have date stamps on them. Look
for a "55" or "56" stamped into the case. That gets you within a year or
two.

Enjoy!
-A


On 11/7/2014 9:57 PM, Howard Krimko via Hammarlund wrote:
> I am trying to find out when SP600 #19534 was manufactured.
>
> Howard. WF2Q
>
> Sent from my iPad
>

-- 
James A. (Andy) Moorer
www.jamminpower.com

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