How to key an older tube amp

[cjruger]

I'm looking at picking this amp up for a good price. I had another thread askimg for input about it. The issue i cant figure out is how to use my 2950dx with it and keying the amp. Would a simple manual switch into the RCA jack on the back work? I was thinking of making a custom ptt pedal that would 1at key the amp then key my mic. Would that work or is it more involved than that? Here are pics of the amp and the CL add: I'm supposed to go look at it tomorrow so any input much appreciated.

I have for sale a ham radio amplifier which I acquired some years ago from a old "elmer" that liked to build these in his leisure time. I have little to no knowledge about this or any other tube amps. I have given this to several knowledgeable hams for inspection and they all agree that everything appears to be as it should, and the manner of construction is outstanding. It does power up but has not been tested on the air. I haven't got the suitable setup to test it. Their inspections however were all consistent with its ability to function as it should in every respect. They believed it to be rated at 1000w. Please inspect the pictures closely and I'm sure you'll agree with its quality and attention to detail. I am pricing this less than I paid for it because I am no longer involving myself in ham radio for now.

 

[BJ radionut]

Here's one solution
All the Best
Gary

http://www.hamradio.com/detail.cfm?pid=H0-006038

 

[cjruger]

Here's one solution
All the Best
Gary

http://www.hamradio.com/detail.cfm?pid=H0-006038

Yes i have been googling like crazey for that, I guess it does exist.
So is all that is needed to key the amp is a simple switch to close the circuit? then hit it with the RF?

 

[Tallman]

There is another way. Build a transistorized keying circuit and install it in the amp. Not to complex to build and install..

 

[cjruger]

I would love to do that but I would need detailed step by step instructions,my electronics and rf knowledge are not there yet. it would be a great learning experience though.

 

[w9cll]

I have used these..
https://www.surplussales.com/Relays/rfcoaxialrelays/rfcoax_uhf.html

 

[Tallman]

I would love to do that but I would need detailed step by step instructions,my electronics and rf knowledge are not there yet. it would be a great learning experience though.

I can draw a circuit for you but getting this site to accept it may be difficult. All you have to do is duplicate a circuit from an exsisting unit and wire it in. I have an old Yaesu 1200 amp that uses a wire that goes back into my receiver that keys it up. I am going to convert it and do photos and a step by step write up for it. Also I would not reccomend tinkering around the inside of a tube amp with out a little training. There are lethal voltages inside tube amplifiers. But I think you could be talked through it.

 

[BJ radionut]

Here's another option:
http://www.ramseyelectronics.com/RF...archPage=1&searchRank=salesrank&searchSize=12

GL
All the Best
Gary

 

[cjruger]

I can draw a circuit for you but getting this site to accept it may be difficult. All you have to do is duplicate a circuit from an exsisting unit and wire it in. I have an old Yaesu 1200 amp that uses a wire that goes back into my receiver that keys it up. I am going to convert it and do photos and a step by step write up for it. Also I would not reccomend tinkering around the inside of a tube amp with out a little training. There are lethal voltages inside tube amplifiers. But I think you could be talked through it.

yes I have read about the lethal voltage and dont plan on doing anything inside there, hopefully that Heil f-2 foot switch will work for me, I thnik thats all I need

 

[Captain Kilowatt]

I have used these..
https://www.surplussales.com/Relays/rfcoaxialrelays/rfcoax_uhf.html

Those are just change over relays.The amp already has a change over relay in it. It is the open frame type just to the right of the tubes. the OP is asking how to activate that hard-wired relay with a radio that does not have a TX line out and he needs to have the amp triggered by RF.

 

[Tallman]

Here's another option:
http://www.ramseyelectronics.com/RF-Sensed-T-R-Relay-Kit/dp/B0002NRKVC?class=quickView&field_availability=-1&field_browse=8159359011&id=RF Sensed T-R Relay Kit&ie=UTF8&refinementHistory=brandtextbin,subjectbin,price&searchNodeID=8159359011&searchPage=1&searchRank=salesrank&searchSize=12
Gary

That's the perfect circuit for the RF key. You just use the relay contacts to trigger the amplifier transmit. Although a bit more complicated than what I was going to do. But I'm sure that kit would work just fine.

 

[cjruger]

That's the perfect circuit for the RF key. You just use the relay contacts to trigger the amplifier transmit. Although a bit more complicated than what I was going to do. But I'm sure that kit would work just fine.

Thanks for the input, but I chickened out after looking it over. There were some hand notes in how to use it and looked like its over my head. I'd probably end up burning it up or my self. Seems like the guy selling had the same issue, he never used it either.

 

[Tallman]

Thanks for the input, but I chickened out after looking it over. There were some hand notes in how to use it and looked like its over my head. I'd probably end up burning it up or my self. Seems like the guy selling had the same issue, he never used it either.

I know what you mean. It is too easy to destroy equipment both meters and the device under test.

 

[2RT307]

That homebrew amp looks pretty darned nice. I'm always amazed at how some guys are really good at putting things together. What model number are those tubes? I can't tell from the picture.

73,
Brett

 

[cjruger]

That homebrew amp looks pretty darned nice. I'm always amazed at how some guys are really good at putting things together. What model number are those tubes? I can't tell from the picture.

73,
Brett

813 tubes. the guy said he got it from a 85 year old ham that loved building them and built 1 a year for a long time, kinda wish i grabbed it but all the unknowns made me pass it up, to top it off i got a speeding ticket on the way back, so I didnt really save myself any money