813 Transmitter What is it...

[W1JHJ]

Hi everyone,
This is my first post here.
I've had this transmitter sitting in my cellar for a few years.  I finally pulled it out a few days ago to see exactly what it is.  It looks like a Handbook special from the 50s but darned if I know what year.
Single 813, 80-10, VFO.  It doesn't look to be in the best of shape, some components are unsoldered on the underside.  Nothing burned.
Anyone have any ideas which version this may be?
I was thinking of going through it and restoring it but it may be over my head.

Thanks,
Jon

[K5UJ]

Hi, Welcome--there is something about the way you uploaded the photos so that they can't be clicked on to enlarge in a separate window, therefore I can't really see well enough to say anything with certainty.  I did't see anything that looked like push pull modulator tubes but I might have missed something.  If you can figure out how to upload the photos so they enlarge that would be a big help.  Maybe someone here knows how to do it.  I suppose the problem could be with my setup here though 

73

rob

[KA8WTK]

If you are using Firefox, right click on the picture and the "View Image" for a larger view.

[K5UJ]

Okay thanks.  What do you know--I didn't know about that trick with the right click on the photos, duh.  Back to the rig, hard for me to say exactly.  It looks like part of a homebrew single 813 rig, maybe two or three chassis in a rack originally.  The h.v. supply is separate -- I see the millen B+ jack on the back of the RF chassis you have.  I don't know if it is a cw rig or if there is a separate audio chassis.  I think I saw a 1/4 inch jack on the back, maybe for a cw key.  Is this the whole thing that you have or is there anything else?  Show everything.   The single 813 modulated by 811As was a popular homebrew combo and used in a few manufactured rigs.   I saw three UHF jacks on the back, probably one is for a driver for the 813, maybe 7 watts from a signal shifter right to the 813 grid.  Probably other guys here will be able to look at it and give you information overload   

73

Rob

[W4AAB]

I believe that there was an 813 transmitter in QST either in 1953 or 1954 by Vern Chambers.

[Pete, WA2CWA]

I believe that there was an 813 transmitter in QST either in 1953 or 1954 by Vern Chambers.

That one had a 6146 mounted on the underside of the chassis. All the info for the Vern Chambers design can be found in ARRL AM section of their web site http://www.arrl.org/am-phone-operating-and-activities Look under the title "Three Control Six-Band 813 Transmitter". There are four PDF articles.

[K1JJ]

Jon,

My guess is this is a class C, (not linear) neutralized, CW transmitter with a driver, built in the early to mid 1960's.   The loading cap and possibly the plate tuning cap look a little small to support AM plate modulated peak power - but it might at lower voltage/ power levels.

Or could those other tubes be part of a grid modulated scheme?  Hard to tell from the pics. Trace them out and see where they go. Maybe some power supply tube rectifiers too.

Looks like it might work after cleaning up some of those loose hanging power resistors below and replacing some of those old electrolytics.

Good luck with it and hope you post some pics once finished.

T

[W3GMS]

Hi Jon,
As others have said the 813 Chambers Rig was a very popular self contained transmitter.  That transmitter was typically modulated with an external pair of 811A's.  The other 813 self contained transmitter that ARRL published in the 50's was in the 1954 Handbook.  It was much simpler than the Chambers rig.  The 1954 used a 6AG7 VFO driving a 6AG7 which in turns drives the 813.  The output of that rig is link coupled to the antenna. From your photo, it appears you have a Pi Network on the output.  It was not unusual for a Ham to modify published circuits and borrow a bit from this one and that one. 

I would encourage you to develop a schematic for the rig and bring it back to life.  If the construction practices do not suite you, transfer the design over to a new chassis.  After all, it appears you have all the parts.  An 813 is a great tube and in my mind its worth pursuing. 

Bob, W2ICQ is the resident expert on the Chamber Transmitter.  He has built a beautiful one and has restored another one which I believe Dave, KA2J now has. 

Welcome to AMfone!

Regards,
Joe, W3GMS           

[cx2ua]

Hello greetings it shows that it is a homebrew rf stage was very common to mount the transmitters in 3 chassis, at the bottom and all the power transformers in the center chassis module and the top chassis rf stage.
would be nice to restore it because it would be a very good team despite being homebrew that gives more value to be unique.
I see a little weak at blocking capacitor plate 813 is not its features but I would reinforce a bit of that in addition to rebuild all greetings and good luck with the transmitter.

[W1JHJ]

Thanks for the welcome everyone.
A bit more info...
I didn't notice the socket for the 6146 but there it was.  The two tubes that are in the sockets on the top side are a 5V4GA & 6X5G.


There is a three position mode switch on the front panel labeled: CW/Set/AM

A high voltage supply did come with it.  I have no idea if the supply had been used with it.  The HV is 950 volts.  I suppose it could have been used with and would explain the reason for the smallish loading and plate tuning caps noted by K1JJ.
When I get some time, I'll have to trace it through and try and match it up to the available schematics.  Then I'll have an idea if it's something I'm capable of getting up and running again.
And then there is the matter getting it modulated too.

Thanks again for all the help and comments.
Jon

[KM1H]

I also have a Chambers 813 rig, its currently all original and unrestored. It may be the actual one he built and when I did the exchange at ARRL in Newington with the seller from LI, NY several of the staff came out to look at it and take photos and were to compare it to what was in their archives from original photos.

Condition is excellent and all it needs for cosmetics is a new dial cover and scale.

Carl

[Pete, WA2CWA]

I also have one along with the power supply; W2ZM was using one the last time we worked on the air; I bet there are several members that also have the same transmitter.