[rocketeer]

I found a Harvey-Wells TBS-50C Bandmaster!

Larry

(thread moved from Wanted Ads and changed to a discussion topic at the request of Rocketeer)

[Radioroslyn]

Hi Larry,
Did you get your General tic?? If not it will do about 10watts on 6mtrs AM and .5watt on 2mtrs. You know the A is just an old version of the D.
http://www.flickr.com/photos/42774321@N0...otostream/

Terry TBS50A@Aol.Com

ps There was /is a couple TBS-50 on Epay. If you look under completed there is listed a TBS-50D. Didn't sell could make offer. Actually it's an early TBS-50 (grey hammertone paint). Has been modified, Xtal socket,vfo rca connector, and cover over off/on sw. It's not too bad for an early model. Currently there is a C listed for $5 It's modified too, extra xtal socket, wrong loading var cap, and lamp on fnt panel

pss Had to move that DX-100 the other day darn near killed me!!!! It's a backache in a steel cabinet!!

[rocketeer]

Ain't it though! That's why I'm looking at a Bandmaster, just 17lbs.

I'm hunting for the D model with the built-in pre-amp for a crystal mic. The C model requires a carbon mic. That $5 one on Ebay has so many extra holes it looks like swiss cheese. In addition to the load vari-cap, the plate vari-cap doesn't look original either. Those kinds of mods scare the bejeebers out of me.

That grey one isn't really a D model. The "D" has been added to the lettering. There are numerous extra holes in the faceplate and some existing holes have been enlarged to accomodate the replacement switches, making it just about impossible to restore to original.

Larry

[Radioroslyn]

Wasn't sure if you where looking for one to use or look at. If weight is an issue then go for the B it's about 10pounds. no modulator section.
http://www.flickr.com/photos/53710524@N0...otostream/
http://www.flickr.com/photos/53710524@N06/8748273725/
Downside is very hard to come by. You may have noticed that the front panels on the B and C models are a bit more deco looking, the D is a bit plainer.

It's not uncommon to run into a C with the CMA-50 upgrade. (pre amp). I've used this circuit on the C to increase audio level to the modulator tubes.
http://www.swedeart.com/harvey/articles/...1-pic1.jpg
http://www.swedeart.com/harvey/collector...s50dvr.jpg
It's from Oct '55 CQ magazine. I uses it in my old grey one with a WWII T-17 carbon mike works great!!! You can play with the R/C values to change the fq response.

If you are contemplating using it on HF w/the vfo you'll be chasing your contact up and down the band! The vfo is awful! Poor design lots of heat inside which causes it to drift badly. It's useable on 80 on A3 but not so good on A1. Forget 40 and up . A good substitute is the Heathkit VF-1. Use a separate p/s for it. Work well on all bands.

As I noted the replacement loading cap that was a common modification for these sets. If you read the manual the original loading cap requires a additional cap in parallel with it on 80 and 40mtrs. It may not be a bad idea to grab a spare set as it's not uncommon for the tank coils to be in bad shape or missing.

Have found these little transmitters to be very reliable over the years. They have excellent audio on AM. I've had a bunch of them and have repair a fair number too! Customers where always happy with the end product. Soon as I get you antenna back up I'll have one on the air.
Terry N3GTE

[rocketeer]

Thanks for the info, especially about the VFO. By the way, take note in the photos for the $5 one on Ebay there are clipped wires off what appears to be the Xmit/Standby switch.

I know what you mean about the coils. I looked at some photos of a chassis and there was so much green corrosion on one of the coils that it filled the spaces between.

After all the advice I've received from various folks I think I'll expand to include a "C" model. People tell me I am over rating the pre-amp in the D model and with a good WWII carbon emulator mic a C model will perform very well.

Larry

[rocketeer]

OK, a C model it is thanks to a gentleman in California. I don't imagine a power supply would be too easy to find so I guess I best start researching on building my own. I have the APS-50 schematic but lack the specs for the transformers.

Larry

[Radioroslyn]

The p/s isn't very critical. Just needs to make 6 0r 12vac and 300-475dc 200ma. At 300v will make about 10w of rf output at 475v 30w fone/35w cw. The plate transformer in the APS-50 has a tap on the primary which varies the output voltage. You don't need to worry with that.
GL
Terry

[rocketeer]

I see in the schematic there is reference to a PTT circuit addition. Have you had any experience with that?

Larry

[Radioroslyn]

Yep
The ptt wiring is on pin 8 of the connector on the back and is connected to the tip of the mic connector on the front panel. The ring is the audio input. On my sets I've rewired it the other way round so the audio is on the tip and the ring is the ptt line. On the APS-50 there is no connection to pin 8. The reason for that is the power cable is shielded with lot of AC wiring which may induce 60cy hum into ptt/mic wiring.
http://www.flickr.com/photos/42774321@N08/3938290891/
Here's a pic of one I did about 20yrs ago. The small trans is to power the relay coil thought the mic switch with a small dc voltage. The contacts on the relay are used to open primary of the plate transformer on the APS-50. If your power transformer also supply's the heater voltage too you will want to use it to open the CT of the HV winding to kill the HV. When you build the p/s keep your HV filter cap 20MFD or less. Larger ones will cause the transmitter on lag on a bit before it completely dies causing terrific feedback. Other relay contacts can be used to mute the rx and ant changeover. You'll also want to change the transmit/stby switch to close the ptt circuit.
So what are you going to use for the rx??
Terry N3GTE

[rocketeer]

My primary RX is a Farnsworth BC-342N, at least until I get around to recapping my Hallicrafters SX-28A. The backup RX right now is a Hallicrafters S-20R.

Larry

[Radioroslyn]

Better eat your Wheaties for the SX-28A. They are a pita! Everything is buried under a bunch of other stuff. Which weighs more the DX-100 or SX-28??
Terry
Ps I sent one of my R-390A down to Chuck Rippel for him to work his magic on it. That was in Feb. It's just about done he sez it's working very well . Hope to see it soon.
It weighs in at about 85 pounds. A little bit better than the Benton Harbour Kilowatt.
Terry N3GTE

[rocketeer]

The SX-28A weighs in at 75 pounds, 25 pounds less than the DX-100 plus it's already upstairs where I can slide the chassis out making it even lighter to move around. Not too bad.

Larry

[rocketeer]

Got it yesterday. It's in really nice condition. Now I have to find an 8 pin power plug/connector or cable and start building a power supply.

[Image: http://i863.photobucket.com/albums/ab191...g~original]

Larry

[Radioroslyn]

Hey Larry
Looks pretty good! The xtal/octal socket been replaced, common issue. What's the switch for? How's the innards? Did you luck out and get one that has been upgraded?
Terry N3GTE

[rocketeer]

The toggle next to the crystal sockets is to replace the slide switch I think but I'd have to trace out the circuit to be sure. The plate on the switch says "VFO" at the top and "XTL" at the bottom. It does not have the pre-amp so I'll need to find a good carbon mic. The inside is very clean.

[Image: http://i863.photobucket.com/albums/ab191...g~original]

Larry