Next restoration project is a Hammarlund SP-200 that I recently bought. This set covers 5.4 KC through 20MC. I think that makes it an SP-200X. I got the receiver in it's original cabinet, and two correct Hammarlund power supplies. One has it's cover, and the other power supply does not. I did not get a speaker or the cable that runs to the set from the power supply. So that will have to be made.

The serial number is 10294. I think that makes this a 1942 production model. There are orange stamp marks on the chassis that say 'SC' then some other nomenclature. I think this was a set that was purchased by the Signal Corps for use during WW-2. There is no 'normal' plate attached anywhere with contract information that you normally see with military sets. I think this is a civilian set purchased by the government for use during the war.

I am going to restore the receiver first, then the power supply.

The receiver looks to have been in long term storage. Thankfully there is no mouse damage, nor any rust on the chassis. But the chassis had a dark buildup of grime on it. All the tubes were there, as were the covers over the tuner. Step one for me was to remove the front panel from the set and then give it a good cleaning to evaluate it. I removed it and then used some strong tire cleaner I have. You could see brown grime float off it. I washed it about three more times. I was able to see the white lettering where before, some of it was dark yellow, or appeared to be absent. I used 'Mothers Carnuba Wax' on it, and it looks nice. There is some aging of the black paint that you can see, but it looks correct for a receiver of this age. If I strip it and repaint it, I will loose that look of a well preserved original.

Next, I decided to separate the RF Deck from the main chassis. This requires unsoldering a few wires underneath the chassis and then removing some small screws that hold the unit to the main chassis. There are two screws that are hidden at the very back sides of the RF Deck. You access them by removing one small panel on each side of the very back of that RF Deck. Once you have unsoldered the wires and removed the screws, you can lift the RF Deck up.

I am going to rebuild the main chassis first, then rebuild the RF Deck after that. The main chassis looks like a few capacitors were replaced decades ago. There are some Solar brand capacitors; .05 mfd @ 500 volts that are encased in a red paper sleeve. There is also an electrolytic capacitor replacement too. I'd guess by the type of parts that these repairs were done in the 1950's. It does not look like any modifications were made. I'll be able to verify that as I go through the rebuilding process and compare things to a schematic. Pretty much otherwise looks undisturbed.

The chassis required a major cleanup effort. With the RF Deck out of the way, I was able to get into all of the tight places much more easily. I found that the best way to get this grime off was to use naval jelly on it, and lightly wipe that with 000 steel wool, then rinse it all off with water. It really worked very well, and quickly. I was able to get to the shiny steel and the difference was day and night. Looked like two entirely different radios once this was done. My next move is going to be to mask off the tube sockets and aluminum IF cans and spray lacquer on the chassis to help preserve it. I should get that done over the course of the week. Then I'll wax the aluminum IF cans to help preserve them as well. With the major cleanup on the main chassis done, then I will begin the electronic restoration. I plan on replacing all of the resistors and wax paper capacitors, and what ever else needs to be done. Then repeat the process with the RF Deck.

This is another big set for me to rebuild, and I am in no rush to get this done. The weather is changing for the better, and I will be doing other things, and this will sit for periods of time. So if this post goes quiet from time to time, its just because summer is coming, and there is less time available to work on this. But I will keep updating this as progress is made.

Anyone who has done one of these, please come in with any advise or stories of your rebuild. I think this might be a bigger project than the SX-28A was. But it was a competitor to it back in those times, and sure is fun to see the differences in how they were built. This set seems more like a military grade radio than any WW-2 era set I've worked on before. Sure will be a learning experience!

Frank, I've done several of these, and here are a few tips:

1. Look through the military manuals, and see if you can find one that matches your set. They are far superior to the civilian manuals.

2. Lots of pictures before disassembly.

3. Testor's model paints come in handy if you want to color-code any of the wires you disconnect.

4. There are caps hidden in some of the above-chassis transformer cans.

5. When you re-mount the RF deck, be careful of the plastic dial.

6. Remember there is B+ plus on the back of the chassis where the wiring harness attaches. Never forget this.

7. You'll probably find a fair number of resistors that have drifted high.

8. If you haven't already found this, it's a very informative and helpful article in three parts:

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

9. These are great receivers, and having the BCB is a big plus. You will not be disappointed.

Thanks Joe. I will need to remember those terminals on the back of the chassis because of the voltage. Someone removed the covers who knows when, so its wide open. I'll at least put some fish paper over all of that until I can locate the proper covers. Meanwhile, I am searching for info in the usual places, and print it out before I remove even one component!

Hi Frank,

The SP-200 Super Pro was my first "good" receiver, back in the 1950s.
I got the original power supply along with the receiver.

The original power cable had a fiber strip holding all the space lugs in position, so they didn't flop around randomly. Most importantly, it kept them in the proper order.

There was a metal cover bolted over those connections on the receiver rear apron to discourage curious fingers.

Excellent receiver.

- Leigh

I've had and repaired a number of the earlier SP series receivers over the
years. Nice receivers with a very unique way of switching RF coils.
If you need parts you'll find the SP-100 through SP-400 (and BC-779)
use the same key parts.

The only problems I've had is open antenna coils, probably caused
by lightning or abuse. I have a spare tuner section if you need any of
the coils. Just sent some to Henry Rogers to help with his SP-100LX
restoration.

Also have an extra power supply cover if you want to restore that
one too. Sold or given away all of my SP receivers except for the SP-600's.
The latest is next up for restoration.
Steve W6SSP

Hi Leigh, Steve,

Leigh, the seller included some new terminals that may be useful in making the cables, and sound like what you have described. I haven't
taken a close look yet to see if they are spaced properly. Still need to think through how I'm going to make the new cables.

Steve, I need the correct switch for the 'send - receive' function, and also, the short shaft for the crystal phasing control is broken off of the variable capacitor that it turns. If you have either one of those parts, please let me know. Probably find some other needs as I go through this rebuild.

Those split stator phasing caps are rather scarce. If the collar at the end of the rotor is in repairable condition you could probably remove the pin (if it's still there) and replace the broken phenolic shaft. Drill a new hole for the pin and maybe use a brass rod or small brass finish nail to retain the new shaft that could be made from a hardwood dowel. Best wishes Frank.

Michael,

I can see a pin on that collar. Its very small. I will try to extract it if I can. The shaft was broken right at the collar. I removed the remains of the phenolic from it. Not sure how I'll fix this at this point. Something will work out.

I might have a problem with the audio output transformer. This is a potted transformer made by Chicago Transformer, with number 4888 stamped on top.

The schematic shows two secondary windings. One is for the speaker, and the other is for headphones. When I took resistance readings, the speaker winding read 53 ohms. The headphone winding was open. The primary winding shows 553 ohms. I think the speaker should show 600 ohms per all the info I can find, and not sure about the value of the headphone winding, but it shouldn't be open.

Do I have a bad output transformer here?

That 600 ohms refers to the impedance of the speaker. You are measuring the DC resistance of the transformer winding that is feeding the speaker. Your resistance readings for the transformer look reasonable. I suspect your output transformer is OK.

Ed,

Why would the headset winding read open?

I am relieved to hear what you are saying, and am learning a little more from this.

Thank you.

If your headphone winding is open, it is defective and won't work. But, the speaker winding should work.

Received another SP-200 chassis. This one has the low frequency bands and no BC band (SP-200 LX). There is a plaque on the front panel that says 'Given to the PCDS Radio Club; Barry Goldwater K7UGA 1964; Brent Kennedy WN7CAJ 1965'. We all know who Barry Goldwater was, and that he was also an amateur radio operator, but what was the 'PCDS Radio Club' and who was Brent Kennedy? I did some internet searching, and came up with what might be the answer to this plaque. "PCDS' was 'Phoenix Country Day School', and they started a radio club in 1965. Brent Kennedy was one of the founding members of that club. The yearbook for that school comes up when you search for it, and you can page through and see all of this information.
In the yearbook, it showed Barry Goldwater speaking at the school at a general assembly. With this info, the plaque now makes sense.

Further searches produced nothing further for this Brent Kennedy, at least as far as I could determine. I wondered about it being the Viet Nam era, and possibly him having been sent there. Who knows.

The radio is serial numbe 5865 H. I almost hate to use the parts from it! I'll keep the plaque from it.

Are you sure about that?

The schematic in Rider XIII shows a single secondary and a front-panel switch selecting either speaker or headphones, thus:


- Leigh

Leigh,

There was a later version that had a different transformer that has two secondaries. I did see what you found, and had to verify which one my set had.
It has a Chicago Transformer number 4888.

Over the weekend, I was able to spend some time on this project. Recently, I received a parts set, and that is coming in very handy.

I replaced the audio output transformer, so now all of the windings are good. This part is a Chicago Transformer part number 4888. Here are the DC resistance values for it: Primary: 568 ohms (267/301 at centertap). Speaker: 53 ohms, and Headphone: 480 ohms.

I used the headphone jack from the parts unit as well. Slightly better condition.

I also replaced the 'Signal MOD/CW' switch with the one from the parts set. Someone had replaced the one on my set with a toggle switch. By replacing that switch, now all of the controls are correct and as they should be.

I still have to do something with that broken phasing control shaft, but I'll get to that later on.

With the chassis cleaned, lacqured, and all of the controls cleaned and lubricated, I can now move on to capacitor and resistor replacement. I know that some of the capacitors are hidden within transformer cans on top of the chassis. I will have to review the info on this and get that started.

The weather is getting nicer here, and I have a lot of stuff to do outside, so this will probably go very slowly. One thing I want to mention is how helpful it is to have another chassis to refer to as I go through this project. With the expected time frames to vary between work sessions, it will be great to be able to see how things are wired and not have to rely on notes and memory.

Lots of the WW2 vintage Super Pros had a mix of toggle and rotary switches, probably depending on what was available at the time. I've also installed rotary switches where appropriate. I've got some spare parts I'll probably never use, so post if you need parts (no, I don't have an extra power cord).

Ed W2EMN

Ed, I will post as I go along, so I'll let you know what I might need as I go through this set. Thank you.

The toggle switch was just a replacement that appeared to be put in just to get by. It didn't quite go through the front panel, and was short
although you could operate it. The correct replacement was a nice improvement. I don't think this set has been modified at all, and maybe just a
few capacitors were replaced as well as that switch. But time will tell (as RME would say.....).

Hi Frank-
I'm saying the radio was originally built with a toggle switch because of parts shortages during the war. I've seen several switches just as you described, one on a Howard-built BC779 that I carefully restored. Some of the guys on this list helped me with parts for that project, so I try and return the favor. Unfortunately, I already gave away the crystal filter with an intact phasing capacitor that was in my parts bin.
Best wishes with your restoration and keep us posted.

Ed W2EMN

This weekend was the local radio club meet and auction. I attended the auction Friday night, and the swap meet Saturday morning. It was a cool overcast day with on and off light rain. I decided to go home and do some more stuff on the SP-200. I worked around the 6F6 output tube area, and replaced the resistors that I think are for C bias, and the electrolytic capacitor for the 6F6 cathode. There is a ten watt 750 ohm resistor that was fine, so I left that in. Also another original high watt resistor that was ok, and was left in as well. As I do this, I am verifying that there are no modifications to this set. So far, so good. I want this in original form.

I'll continue through this chassis when I can, especially when we get weather like we had this weekend.