Harvey Wells TBS 50

[M1ECY]

While I am amassing the parts for the big TX build I came across this on eBay US.

Its so mean - you guys over there have limitless great stuff to play with....

So, I shelled out... Hopefully it will be here in a couple of weeks, in the meantime, anyone have any good or bad things to say about it?

It cost me far more in shipping than it did to purchase it, so I hope I will have some fun!

Cheers
Sean

Who really ought to be kept off eBay!

[KL7OF]

The TBS 50...144 mhz to 3.5 mhz....single 807 final...carbon mic...Did the one you bought come with a power supply?.....They must have made a lot of these...I have a set that I use for bookends in my shack......You should have a lot of fun......cheers...Steve

[WQ9E]

As Steve said, the rig is a lot of fun.  It came in 3 versions:  the TBS-50B junior is CW only/missing the modulation section, the TBS-50C senior has 6L6 modulator tubes driven by a carbon mic, and the TBS-50D Deluxe has a low level speech amp built in.  As I recall the chassis is pre-punched so that you can easily build the low level "deluxe" amp into a senior.  I have never run across a junior version and I doubt if they were very popular. 

It does require an external power supply but it is pretty versatile and is not too picky about the voltage level used.  In addition to AC supplies the manual (available for free download on edebris) also details how to use a popular WWII surplus dynamotor to supply power.  One caution with this versatility comes a slight safety issue, a terminal strip on the back allows jumpers and resistors to configure it for the voltage used so I would put some sort of cover over this-especially if you have small children and/or pets.

It is a solid little transmitter so I am not surprised at the high shipping cost.  But I think you will enjoy it and Harvey Wells made a wide range transmitter many decades before the popular all mode all band boxes from Japan became popular.  I never tried to use mine on 2 meters but it was designed to provide some intentional output there and the manual also has modification instructions for use on 160.

Like Steve, I have a pair of bookends   I picked up my first TBS-50D with matching AC supply several years ago and then I ran across another one mounted on its VFO base.  That one is pictured here coupled with a Breting 40 receiver which I have used mostly on CW; it works on AM and I need to put it on 3885 or 7290 sometime.

[M1ECY]

I bought the one that looked like it had been sitting in water...... the Cabinet is rusty down one side, and has no PSU.

Still, for $25 im not complaining!

I reckon it will end up being the carbon mic version - I hope the chassis is pre punched for the other tubes - this will be something I would like to change - I cant stand carbon mics!

I just spoke to me - and is much cheaper than any of the "bigger brands" - the 50 and 144mc coverage should be fairly humourous as well!

Thanks for the heads up on this little beastie - im looking forward to it arriving.

Sean

[WQ9E]

Sean,

I think your odds are pretty good that it will have the low level audio section since they seem to be very common.  Both of mine are the D version as were two others I have repaired for friends.

It is a pretty simple unit and it is easy to work on and it doesn't use any expensive or hard to find tubes.   

[WA1LGQ]

I had one many years ago, and it was a simple fun transmitter. Nice looking too.  Though it had very low output on VHF and I never got any serious use out of it there. I remember that the audio was very good, plenty of it and very good sounding. I have only good memories of the TBS-50D. Have fun!...Larry

[WD5JKO]

I recently got one too, a TBS50D. The schematics are on line, but I bought a manual. It covered all the options, power supply, and most of the service bulletins. There is one on Epay right now:

150705990148

The drawings are large foldout covering three versions. To me this was worth the extra bucks.

It is interesting that the speech amplifier on the TBS-50D uses a pair of 6AU6's in triode connection for the low level stages.

I bought a bunch of resistors and capacitors to restore it, but so far it is "on-deck" at the repair bench. I have 6L6GC's in the modulator, but those old metal versions might look more authentic.

Jim
WD5JKO

[N6YW]

I have the TBS 50-D that has evidently been dormant for decades. I would like to find the VFO pedestal,
and I can build the power supply easily. This sounds like a real fun project, especially if we use a higher level of audio input to the 6L6's. The schematic shows the microphone input is transformer coupled to the modulator tubes. This looks like a perfect project for modern modifications.
This is directed to WQ9E: What are your thoughts on making this puppy sing?
I have a want to use this with my Skybuddy on 75 meters. What a hoot that would be!

[N6YW]

Here's an interesting link: http://ab7yd.home.comcast.net/~ab7yd/TBS50D.htm

[M1ECY]

Just waiting for mine to be shipped over here - it's on the way, hopefully will see it in time for the festive break.....

Sean

[WQ9E]

William,

The VFO pedestal isn't rare but they don't show up too often.  I found mine at a hamfest but you can find them on ebay occasionally.  It seems to be a decent VFO with reasonable drift.  I doubt if you find one without the attached transmitter but you never know what will show up at hamfests.

If your transmitter is the D model then instead of having a driver transformer for the 6L6 tubes it has a two stage low level amplifier and a 12AU7 to drive the push pull modulators.  The audio isn't bad but you could probably adjust the value of the coupling and cathode bypass caps in the low level audio stages to provide the bandpass you desire.   But if you already have a good sounding external audio driver then just pick up a good audio driver transformer.  If you do decide to go with external audio you might consider pulling the three low level audio tubes to save a bit of heat and power.

[N6YW]

Roger
Thank you. I must have looked at the wrong schematic. Mine is indeed the D model and is in good shape.
I would hazard a guess that it hasn't been energized in a few decades. The estate of my friend where it came from did not include the supply or VFO. That's cool, a supply is easy to put together... I have dozens of transformers and associated parts. It appears that this is a direct frequency crystal transmitter, so all I have to do is find a crystal for 3870 and maybe something between 29.000 to 29.100.
This will be a fun side project as I dig further into the Vike.
I also have a Lettine 240 that has sat dormant for years complete with the cabinet and a 40M plug in coil. This thing looks like it will make a nifty modulator too. Funny how both the TBS 50D and the 240 are similar, a pair of 6L6's in PP modulating an single 807. Fun fun fun.
Thanks again.
Billy N6YW

[KB2WIG]

"    it's on the way, hopefully will see it in time for the festive break..... "

Thats great if it happens.... I didn't know youse guys celebrated Festivus.


klc

[iw5ci]

I love the TBS-50, i have paired it with the common Heathkit VF-1

reversing the heathkit front panel, and painting it black the result in not bad...
Now i have changed also the VF-1 knobs and replaced with other similar to the
TBS-50 knobs.

The vfo works great on all bands even on citizen band and is very stable and precise.

It takes the power supply from the rear connector of the TBS and it powers when i turn on the Harvey wells.

Now i am looking for a non intrusive mod to have a ptt signal for my power amplifier and i would like to put a coaxial relay for a receiver so i can have a full working AM station..

Anyway i managed to make a qso with the states on 10 meters band with just the 16W oh the tbs-50

With a carbon mike the modulation is extremely good and with my ameritron AL-811 PA i have 200W carrier and the same performance of a "big" johnson TX.

[M1ECY]

Well, it has cleared UK Customs, so, hurry up postie, I want my transmitter!

Looking forward to getting it on the bench - will post some pictures when it arrives

Sean

[M1ECY]

Off to the parcel depot later - seems my transmitter has arrived!

Now, will I get it on the air this evening......

[M1ECY]

Well, it is here.

I am amazed just how small it is! - I was expecting something about twice the size!

Appears to be complete, has had a couple of mods to the front panel sadly, and is finished in silver grey hammered finish. Internally it appears complete, and in good order, I am amazed at the build quality, and the layout seems quite clever.

Piccys when I get a chance.

I need to refinish the case - it seems the paint was never keyed correctly to the cabinet, I won't be able to repilcate the same finish, but will try something close.

Cheers
Sean

[M1ECY]

Hi All, back again!

I am amazed, it has been nearly two years since I first mentioned this little transmitter, it has taken this long to get any power on to it.

It has been hacked about quite badly internally, with components missing from the Crystal oscillator, as well as all of the modulator, from the 6L6 grids out to the mic socket.

It appears that someone in it's past robbed the input transformer, or possibly the driver modification that would have upgraded it to a "D".

Does anyone own a TBS 50 D that would be willing to send me some photographs of the internals? - I want to try to restore this to as near "original" as possible - the front panel has already been drilled for the VFO switch, and thes has been some bodgery around the crystal sockets that will need dealing with.

I have chucked in a few of the missing components to get the oscillator working, and have had RF out of it all the way to 144MHz, so it really wants to live. I think the output is quite well down, but until I go right through checking everything i will reserve judgement.

Any help gratefully received.

Cheers
Sean

[WQ9E]

Sean,

It will be a few days before I can take photos but if nobody else comes through please PM me your email and I will take some interior photos this weekend.

It sounds like the little TBS-50 found a good home! Not many would put in as much effort as you.

[M1ECY]

Many thanks to Rodger, who has provided me with some excellent piccys - I can now fabricate the missing modulator driver, and also put right a few of the other modifications that this poor little thing has suffered.

Will give me something to be getting on with over the Christmas/new year period.

[N3GTE]

Hi Sean,
If your output power is down check the 22k resistor on the grid of the 807. Have seen them go way high in resistance. There is also a couple of resistors in the screen circuit of the 807 that may have gone out of tolerance.
Don't forget on the lower bands 80/40mtrs it requires a bit of extra of loading capacity. Should load up to 100 to 125ma. With everything in tiptop shape should see about 25w on fone and 30 on cw with 425v on the plates.
GL
Terry N3GTE

[M1ECY]

Hi Terry,

Thanks for that, It is certainly low on output, so I will pay special attention to those areas - I am just raiding the junk box for the required parts to build the power unit - I want to try to get it as close to the original design as I can, given the limitations of using a UK based junk pile.

Will update as project progresses.

Cheers
Sean

[N3GTE]

Just as aside the APS-50 (the HW power supply) runs about 425 on the plates on HI and 300v on LOW. You can run a bit more like 475 or so but any more will cause some issues. It will cherry the plate on the 6L6G's, cause arcing between the screen/plate pins at the 6L6's and the plate tuning condenser will flash over.

Sounds like you got one of the early ones. The first of the TBS-50's where the gray hammer tone jobs also they weren't known as Bandmasters just TBS-50's. Back then (abt 1947) there were just the TBS-50 and the TBS-50A. The plain one use a carbon mike the A had the 3 tube speech amp.Later abt 1949 they dropped the plain and A did a little redesign and called them Bandmasters. Three different versions the B,C, and D models where born. The B is CW only no mod section built in it but can be upgraded to a C or D model. The C is similar to what you have it has the mod section but no preamp.Made the drive the grids of the 6L6's with a carbon mike. Finally the D it has the the CMA-50 (HW for crystal mike amp). The reason I mention all of the history is that the early and later models are a bit different. For instants the wiring on the rear terminal strips are different. On the old sets terminal 8 is the B+ connection on the later sets it's keying circuit. Now that can be exciting!!
Probably the hardest one to find is the B. I don't think that very many where made. I don't know if HW heard though the pipe line that a new class of license was on it's way the novice class which came along in 1951. Or most buyers didn't want to fool with adding extra parts to upgrade them. A gray one in nice shape is pretty hard to come by too.
Terry

[N3GTE]

Hey Rodger
You said you've never seen a TBS-50B? Here's some pics of one or two. http://www.flickr.com/photos/53710524@N06/8749417316/in/photostream/
Poke around you might see some old friends.

Seam, Unfortunately the Speech amp is built on a small separate chassis from the tx. You will have to fabricate a little something to make it like the original. Or I've had good luck with this. http://www.swedeart.com/harvey/articles/tbs50/cq1955-hw1-pic1.jpg
It's quite easy to build and can be finished up in a hour or so. I made up a little L bracket to mount the tube upside down onto one of the bolts from the mod transformer.
Will work great with an old T-17 or a cleaned up amplified D-104. That circuit has the audio tailored a bit so you may want to play with R/C values to make them to your liking.
Hope I'm not boring you guys with all H-W talk!!
Terry N3GTE

[M1ECY]

Hi Terry,

Thanks to Rodger's pictures, I will go the whole hog and build the speech amp from the D model, this will allow a wider choice of microphone, it is also handy because I am missing the driver transformer for the modulator, while I could cobble something in that would work, I much prefer the refinement of the higher spec model.

I am just collecting the required parts for the PSU from the various junk boxes (read barn!) I have, despite having lots of iron, I do not think I have anything suitable from stock for the HT supply, so might end up running with a bit more HT.

I certainly need more of this sort of kit to play with!

Cheers
Sean