Ham Radio Question

[SilverFox]

I picked this up today for $15.00. I thought if felt light for a tube product but figured I'd just use the chassis for an amp if nothing else. Anyway, the power transformer is external so I've got to either find one or junk it. Nice to know the tubes are selling for $78.00 each from Tube Depot. 6LF6. I may be able to get the tranny tomorrow it the flea market dealer I picked it up from has it at all.

Now, is there someone that could walk me through the operations theory of the schematic? It appears as though this is some sort of grounded grid application where the output amplification is based upon the higher B+ running on the anodes.

Another question I have relates to being unable to find any frequency range/limits of the tubes employed. Only thing I find relates to voltage and current characteristics.

Thanks,

silverfox.

[Structo]

If it has a decent chassis you could re purpose it for guitar.
But it is a radio linear power amp so it has inductors and tuning caps.

The 6LF6 12 pin Pentode is a 40w tube.

Not sure if it will work good for audio.

But hey, you can experiment to see how different configs sound.

[SilverFox]

The tube and any substitution for it comes up as a Horizontal Deflection Amp rated for something like 7kv. Lot of fun available with this tube. It would be nice to find some operational frequency data but I couldn't find a thing.

I realized I may have a power transformer that would work with it in the form of a Peavey Roadmaster power transformer. That powered, I think it was eight, 6L6 heater filaments and these 6LF6 pentodes consume, as I recall 2 amps each... Also put out 450 volts rectified DC so that would likely work in getting it back to spec.

Thanks for the input,

silverfox.

[Kagliostro]

At http://el34world.com/Forum there is a guy (PRR) that is very expert about Ham Radio Apparatus

You can try to ask on that forum about your unit reuse

Ciao

K

[Aurora]

I've had a ham license for well over 40 years, and have frequently used and repaired grounded grid linears, although most of them are ususally triode based. There have been and still are modern tubes designed mainly for GG linears. That amp is based on pentodes, which is actually the first one I've seen, but otherwise the design is trivial and common, working in AB2 ( I guess).
The first pair acts as drivers for the second quad, with tuned circuits in between to act as impedance converters and filters. There's a series filter on the input to adapt to the driven cathode, and a parallell tuned filter between the two stages, - then a pi filter on the output as load filter and impedance converter to the 50 ohms output. The amp has automatic RF based keying of the RX/TX relay,. There's also a smal transistor based RX preamp..... nothing fancy -schmancy about this one.... probably sold as a lower priced medium power linear back in the days, most other commen linears were based on quite more expensive triodes, giving something in the range of 1-2 kW......... I doubt that this tube setup has any value for plain audio or guitar - did a search and found mostly nothing of value, except for some OTL talk.. ( output - transformer-less, - for HiFI geeks )

[Kagliostro]

I don't know how far are the 6KD6 spec from 6KG6 spec

(here the spec of both tubes - I'm not a good datasheet reader)

http://www.mif.pg.gda.pl/homepages/fran ... 6/6KA8.pdf

but 6KG6 was used in guitar amp on a model of Traynor

the YBA-3A Custom Special

[img1913]http://i.imgur.com/BEGEY6a.jpg[/img]

K

[SilverFox]

Thanks for the responses. So far it may be the case the tubes in question are at least good to 40 Mhz.

silverfox.

[RB]

I have been a ham since 1959. Have drifted in an out of the hobby all my life.

What you have is what's was known as a sweep tube linear amp. This is a very cheep way of getting 250-500 watts PEP from a low drive device say <than 20 watts for cheap.

There were many brands of these device's around and the target market was the CB er who was limited to something like 12-15 watts PEP on SSB by FCC Regs. They were sold as Ham gear to get around FCC regs. Eventually the Ham fraternity suffered in the end by the FCC making manufacturer's of all linear amps have the 10 meter/28MHZ band removed from the production amps so that the CB guys couldn't use them on 11 meters/27MHZ.

From a spectral purity perspective most of this type amp was very dirty and created all kinds of RFI/EMI problems. They were built to a price point so the designs were bare minimums.

The Palomar line also included legitimate Ham gear and was built in Oceanside CA near were I have lived most of my life.

[13GB5]

Take a look at Pete Millett Engineer's Amplifier designed for sweep tubes. http://www.pmillett.com/DCPP.htm By disconnecting pin 11 [omitting R3,4,5,6] and adding the plate cap it should substitute for the 6JM6/6JN6. And it appears to be a much stronger tube than those two. I would use a B+ of 450v and an output primary of 3400 ohms neighborhood.

No... wait a minute, I would sell these tubes and use much cheaper sweeps that are just as powerful.

[boots]

I'm a ham also: WA7VHW since 1973. I keep thinking it would be cool to get some amp building hams together on the air. I know there are a few here on TAG. Speak up!

As previously mentioned, the Palomar amps were pretty cheaply made and (among others) were known for causing TV interference. You may be able to harvest some parts from it, but many of the parts values and layout are specific to RF, rather than audio, so it would probably become a matter of gutting most of it and starting over.