The Hammarlund SP-10: A true Historical Relic has arrived

[WD8BIL]

Great looking SP-100 you gots there Todd!!

[Todd, KA1KAQ]

Thanks Buddly! Clearly you and the original owner took good care of her. I restored the headphone connection to the original rear apron and removed the jack added to the front panel, just need to fill the hole and touch it up.

Sadly, the old girl is in storage as I type this. One of the first sets to go over since it developed a problem and I didn't have time to troubleshoot it. Needs some new caps at some point.

Sure sounds sweet driving a big EV or Jensen speaker!

[Scott SWL]

Did you finish the SP-10?
I just received a chrome plated chassis SP-10, and was wondering how well it works

[W7TFO]

I just got in 4 Super-Pros, and a SP-10 is in there.

Sadly, it is beyond restoration but should yield some bits of unobtanium if needed.

73DG

[Scott SWL]

I'm going to need pics and pieces to finish mine, but I'm not sure if I should start a new thread, or add to this one, as there are many others in this thread with SP-10s.
 I also have a chrome BC-779 that Henry WA7YBS (www.radioblvd.com) believes may have been done by the signal corps, the tube numbers were stamped in the chassis in a very professional looking (factory looking) way

[W7TFO]

I still have my unmolested SP-10, and will be happy to E-mail you pix.

Easiest ID of all for the 10:  It has a tone control, the others don't.

Also in my collection is the SP-100 with the eye tube modification shown on Henry's site.

73DG

[Scott SWL]

Mine has a tone control, and the knurled nuts on the IF cans, the crystal filter and plate are missing, and the Audio was changed to 6F6, or that was the tube in the socket, just the audio(4 tube sockets) was converted to octal.It looks to have been rebuilt in the 50-60's by the type of coupling caps installed.
I would like pics of the crystal filter, and the connections of the tuner, mine arrived with the tuner just sitting on the chassis, wires everywhere.
I may be in over my head, I have been repairing and building tube amps for years, but this is a little more complex. Henry WA7YBS said I may be able to use the BC-779 as a partial guide to generally figure out where things connect.

[Scott SWL]

a couple more pics.
I am unable to find the serial number on this unit

[Scott SWL]

The caps, and some resistors appear to have been replaced in the 50-60's
I really haven't found a decent schematic for the SP-10 yet.
Where is the serial number usually located on the SP-10?
on the BC-779 it was over the speaker connections.

[Scott SWL]

The more I look at it, the more I realize that this was a never finished rebuild done in the early 60's-ish, it may have been chromed then, there are many never soldered connections on tube sockets and terminal strips.

[W3SLK]

I had the BC-779 and traded it to a Hammarlund collector for a BC-774(?) It had a chromed front panel. When I asked him why he told me that this was made specifically for the Admiral's quarters onboard ship. I do have the separate power supply that I use for the BC-774. It is a good AM receiver but its BFO is a little on the weak side.

[Scott SWL]

I will start a new thread about the Chromed BC-779, as I wanted to keep the op's thread about the SP-10 on topic, Do you have pics?

[Opcom]

In the tube socket picture, what is the red stuff? Apparently it is put on tube sockets and other terminals on very old gear, and it's soldered right through so it remains. Only seen it on really classic stuff.

The terminal boards, like 'pcb' but with upright pins - are these original to this radio or a product of the earlier resotation? I'm curious as to when they came into use.

Anyway that chassis looks pretty clean, will be very nice when completed.

[Scott SWL]

Guessing, I think the person rebuilding the unit marked the terminals with magic marker, or nail polish to verify they were soldered, or tested? I have never seen old equipment with these markings, but have seen it on other, more modern equipment, especially something that was worked on, and many kits when someone marks an assembly manual to keep track what was done.
I don't have a good picture of an unmolested SP-10 in this area, but I think those terminal strips look more modern than 1936, they look the same age as the capacitors to me.The small nylock nuts are certainly not original.
The turret boards look like some version of fiberglass possibly, and I believe they are not original as well.Turret boards are quite old as a construction technique,
but phenolic was the likely material used when this was built.

[KA3EKH]

Don’t think I posted a picture of this for a while; it’s my 1939 National HRO military RAS receiver. On the side of the rack is a autotransformer and voltmeter so it runs on 105 volts. I use to use it a lot on both 7290 and for a long time when I was on 1885 as the AM receiver. I replaced all the old wax capacitors about twenty five years ago and have not touched it from that point in terms of any other work and noticed its sensitivity is down a little so think it will have to come apart to resolve the loss of sensitivity but still very useable and has a great feel to it when running AM on non crowded bands. The IF filtering leaves something to be desired and the military version of the HRO has a 175 KHz IF so images can be an issue on strong signals but for doing easy AM QSO its hard to beat. It dose have the military noise limiter kit that helps a lot with static crashes on 160.
Its almost like there was a short period of time in the late thirties when National, Hallicafters and RCA were producing high end receivers where they have not learned about value engineering yet and tried to produce quality products that were capable of running forever. I have an old 1936 RCA commercial marine receiver that was never placed in service and think that may have to be the next project for the New Year.
Another interesting question, on the old HRO in the rack mounted power supplies there are four 8 Uf electrolytic capacitors that are now like seventy five years old and still are solid working electrolytic capacitors, how is this possible?

[Opcom]

old-time Made in U. S. A. and not abused much..

[Scott SWL]

That is in beautiful condition, museum quality! I like it!

[Scott SWL]

I'm putting this aside until I get some more parts, and info to start putting it together.

[N8ETQ]

    Check this out if u havent already....


http://www.radioblvd.com/hammarlund_super_pro.htm

GL
/ dan

[W7TFO]

Finally, got all the old ones together

3 10's, 3 100's.

73DG

[Scott SWL]

    Check this out if u havent already....


http://www.radioblvd.com/hammarlund_super_pro.htm

GL
/ dan

I have been to that site, and have been conversing with Henry WA7YBS for a while now, that was the first site I visited.
Thanks for the suggestion.

[Opcom]

That's a beautiful stack there!

Are those called 'super pros? Have separate power supplies?
Do those have interstage transformers from one 6F6 to push pull 6F6 grids?

[Scott SWL]

Sp 10s have push pull 42s, they all have interstage transformers, and use separate supplies. The supplies are almost interchangeable(some modification depending on whether a field coil speaker is used with some supplies, and B+ needs to be lowered if using a later supply on a SP-10)

[Scott SWL]

Here is some info on the SP-10 and SP-100 beginning on page 213
https://radionerds.com/images/3/31/TM-11-310-SCHEM.PDF
The schematic is pretty clear compared to the one I already had.

[Scott SWL]

I had the BC-779 and traded it to a Hammarlund collector for a BC-774(?) It had a chromed front panel. When I asked him why he told me that this was made specifically for the Admiral's quarters onboard ship. I do have the separate power supply that I use for the BC-774. It is a good AM receiver but its BFO is a little on the weak side.

I was wondering if you could post a picture of the chrome panel.