Re: SP600 variants

[Les Locklear]

I haven't seen a real good chronological list of SP600 models versus likely year of production.
Was there a bunch of overlap or something?  It's a lot more difficult to establish the date of a given receiver compared to using the contract numbers of the R-390A, for example.

So I had a JX-17, and thought I'd simply get something newer.


Here is a JX-21 I picked up at Gaithersburg. So far, no visible date codes to tell me when.

Where to look? How to know ?

Paul,

Actually, the model suffix numbers were not built in numerical sequence. You could have a JX-26 with a lower serial number than say a JX-14. The serial numbers were sequential. Not the military serial numbers which were on the military order/contract number tag, but the serial number on the tag on top of the tuning capacitor cover. Alan S. Douglas and I collaborated on a serial number survey several years ago and Alan put that together, if you look at the date codes on the bathtub capacitors against the inside of the rear panel you can get an idea of the approximate build date. Usually with 90 days of the date of the caps. Approximately 25,000 SP-600's were built. Serial numbers higher than 17500 (approximate) came from the factory with ceramic discs in place of the infamous black tubulars, (some were gray). The dates on the Hammarlund Historian website are taken from engineering revision sheets, so they are only approximate build dates. Most were built in the early to mid 50's, with the JX-21A's being the last ones off the assembly line sometime in 1972-73. Those serial numbers on the very late models, had a foil sticker tag on the rear panel and an entirely difference sequence of numbers. That was also the case with the last of the HQ-180A's built.

Les Locklear

[WA3VJB]

Les,
Nice to hear from you, and thank you.

The website you offered is the most definitive among those I had found.

We are saying the same thing when I noticed that some of the production dates are open-ended, that is, no clear "replacement" model is listed, such that more than one variant is perhaps in production at any given time.

For the JX-21, showing  Feb. 1953 at the earliest, but it is not clear ot me whether its production ended with the first similar model, the JX-36 (Oct. 1957),  The JX-37 (Mar. 1961), or maybe the "JX-21A" said to have appeared starting in 1969.

Thanks for your follow up regarding the serial number sequence, and I shall take a look at the date codes on the bathtub caps when I get home.

[Les Locklear]

Les,
Nice to hear from you, and thank you.

The website you offered is the most definitive among those I had found.

We are saying the same thing when I noticed that some of the production dates are open-ended, that is, no clear "replacement" model is listed, such that more than one variant is perhaps in production at any given time.

For the JX-21, showing  Feb. 1953 at the earliest, but it is not clear ot me whether its production ended with the first similar model, the JX-36 (Oct. 1957),  The JX-37 (Mar. 1961), or maybe the "JX-21A" said to have appeared starting in 1969.

Thanks for your follow up regarding the serial number sequence, and I shall take a look at the date codes on the bathtub caps when I get home.

Paul,

Many times those bathtub caps have failed and have been replaced, look at the date on the filter electrolytic and there are one or two other bathtub caps along the side rail and the bottomside of the chassis. I have also seen many stamped "dates" on the inside of the front panel. One other item worth looking at if the others don't produce a date is the crystal filter inside the topside can (sorry, don't have a manual handy just now).

Looks like you got a high serial number and should be good to go!!!

Be suspect of the filter electrolytic though, most have high leakage!

[WA3VJB]

Bathtub caps show a stamped 3-56, multiple examples.
One 2-56 bathtub.

Is the "filter electrolytic" that triple 20 strapped to the chassis in there? 
The underparts look like they've never been touched -- clean, no foreign solder, no fires.

I may changeout that triple 20 on your advice, don't want to risk the transformer to a short.

Many thanks, Les.

[Les Locklear]

Bathtub caps show a stamped 3-56, multiple examples.
One 2-56 bathtub.

Is the "filter electrolytic" that triple 20 strapped to the chassis in there? 
The underparts look like they've never been touched -- clean, no foreign solder, no fires.

I may changeout that triple 20 on your advice, don't want to risk the transformer to a short.

Many thanks, Les.

That's the one. You can buy new manufacture ones from Antique Electronics Supply in Tempe, Az. The ones they stock are about half the size in length of the original. Re-stuff the can yourself. Or, simply replace with 3 20 mf caps 450-475 volts will work fine.



Looks like yours was built sometime between 2-56 and 5-56.

[KD2NX]

Hi Les,

It's funny you should be talking about the SP-600 variants. I have a query for you, maybe you can help me.

I have a friend of mine that has an SP-600-J, standard frequency range, with a steel front panel, without the tuning lock mechanism and without the fixed frequency oscillator (hence the J model). When you take a good look at where the tuning lock engraving should be, it is very weak, lightly scribed, and the hole for the tuning lock knob looks filled in. Also, the receiver came with factory ceramic capacitors under the chassis, but the chassis itself was drilled with the holes for the bathtubs. What can you make of this version?

[SM5JAB]

Hi all! These serial number questions are intriguing since my SP-600-JX-21 has quite a different number. It is "0014-QI" and appears not like any other number I've seen on the web. I bought the radio here in Sweden, must have been at least ten years ago. Do you have any idea what this odd serial number can be? It contradicts that the serial numbers were only incremental as I have read somewhere...

Could anyone shed light on this?

/Micke
PS It works like a charm.

[Les Locklear]

Hi all! These serial number questions are intriguing since my SP-600-JX-21 has quite a different number. It is "0014-QI" and appears not like any other number I've seen on the web. I bought the radio here in Sweden, must have been at least ten years ago. Do you have any idea what this odd serial number can be? It contradicts that the serial numbers were only incremental as I have read somewhere...

Could anyone shed light on this?

/Micke
PS It works like a charm.

Michael,

I had some mail correspondence many years ago with a fellow countryman of yours in Malmo, Bengt Wilander SM7BKH. He also had a couple of JX-21's. The serial numbers he had were in the same range and group of numbers as yours. The only thing I have to offer is they were built for the Swedish Government. The records I have regarding the SP-600's are from Engineering revision sheets and only contain U. S. Military and commercial versions built.

[Les Locklear]

Hi Les,

It's funny you should be talking about the SP-600 variants. I have a query for you, maybe you can help me.

I have a friend of mine that has an SP-600-J, standard frequency range, with a steel front panel, without the tuning lock mechanism and without the fixed frequency oscillator (hence the J model). When you take a good look at where the tuning lock engraving should be, it is very weak, lightly scribed, and the hole for the tuning lock knob looks filled in. Also, the receiver came with factory ceramic capacitors under the chassis, but the chassis itself was drilled with the holes for the bathtubs. What can you make of this version?

Why would that be funny? I have researched the Hammarlund SP-600 series for many, many years and have been an unofficial historian on the Hammarlund website for some time now.

To your question: I have had several with the steel front panel, and no hole at all for the tuning lock. I can't explain as to why that would be. I had a presentation model years ago, with a brass nameplate that was presented to an Air Force Colonel, the front panel was chrome plated and had no tuning lock. The tuning bezels were chromed and blasted on the front to cut down on the reflection I guess.

If it had the ceramic discs installed by Hammarlund, it was probably a chassis that was serial numbered higher than 17500 (approximate). Many had the panels, tuning condenser identification tag and other components changed either at depots or by previous owners. It isn't uncommon to see a standard JX variant with a JX-17 tag or vice versa. With the passing of years, who knows? If it was indeed an umolested J series, it could be a J-3, J-4, J-5J-11, J-13, J-19,J-20,J-22 or J-25. Even though several series of the plain J series were shown as being built, they are somewhat uncommon. There is a JX variant on E-Pay right now, item number 170038722573    without a Xtal Frequency Control and had one round filter choke and one hexagonal one. Obviously altered, modified and tinkered with.