[Hammarlund] SP 600 date of manufacture

[Richard Knoppow]

     FWIW, there is also a serial number stamped on the 
front of the tuning capacitor. I think this may be the same 
as the number on the TU cover.  The problem is that seeing 
it requires removing the capacitor, not a trivial job.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com
----- Original Message ----- 
From: "Les Locklear" <leslocklear at hotmail.com>
To: <hammarlund at mailman.qth.net>
Sent: Saturday, November 08, 2014 6:37 AM
Subject: Re: [Hammarlund] SP 600 date of manufacture


> 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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