Sweep tube amps (so-called because they use a tube originally designed for the horizontal flyback or 'sweep' in early color TV sets) were very popular back when you could still buy them for 2 or 3$ each in any drugstore - and who could forget Radio Shacks 'Lifetime Tube Warranty'?
Most of the sweepie amps used 6LF6 or 6LQ6 tubes. The Varmint used 8950s which was actually designed as a power tube but still falls into the sweep tube catagory. 8950s and their military version, the M2057 are rare as hens teeth now and priced accordingly. If you can find one that's NOS expect to pay upwards of $75 for one tube. The Varmint uses how many? Gets pricey quick.
The Nitro should be using 6LQ6 tubes. 5 of them IIRC. Not a bad amp for it's time but of the two I would use the Varmint with the Tram.
In the shady world of sweep tube CB amplifiers circa the 1970s, most of them were derivative of a design culled from some amateur radio article years before. IMO this is why they all pretty much ran the same tubes, typically a 1x3 or 1x4 combination using 6LQ6s. Since most of them were built by hand most likely in a garage somewhere, build quality varies widely.
Some were better than others though. The Nitro was made by Transel which was a real company and not some guy working out of a shed. As these types of amps go, they aren't bad compared to some of the crap that made it into the marketplace.
The Varmints, however were a bit different. Mr. Brewer (I forget his first name) was a bit of an eccentric. AFAIK he personally built each and every amp, or directly supervised it's construction. So protective of his circuit design was he that he never published any type of service manual or even a schematic, although many have been reversed-engineered through the years. He didn't want anyone but himself poking around inside his amps. If one of his amps needed service he would insist on it being returned to him. Whether this policy was to protect his brilliant design or not let anyone see the crap he was producing is a subject for much debate that I will not enter into here. Suffice to say the man was picky.
As with most sweep tube CB amplifiers, Varmints didn't bother with little niceties such as harmonic filtering or RF shielding. They were built for one thing only and that's output. When they worked, they were the loudest damn thing on the air. Of course you would tear up every TV and radio on the block and probably bleed onto 10m but that was par for the course.
On my D201A I run a 10-tube Phantom, arguably the only other amp that could come near the Varmints for sheer brute strength. If I didn't have the Phantom I would probably get-and restore- an XL-600 or XL-1000. Find one that is still in good condition and they aren't bad amps to look at - I always liked the blue tops some of them had.
Whichever amp you choose, I would seriously consider having it rebuilt to use a more common, less expensive tube. For the Nitro, or any amp that uses 6LQ6s, consider having it converted to a 24LQ6 or a 31LQ6. They were made in similar quantities to the 6LQ6s but weren't used nearly as often in CB amp applications, making them much more available and less expensive today. My Phantom uses 24LQ6s and I buy them NOS for around 6-7$ each. Way better than the 40$ each for a NOS 6LQ6- if you can find them.
For the Varmint, convert to the 6LB6. Again, this tube is much more available and less expensive than the 8950.
Conversion isn't difficult if you know your way around high-voltage stuff and have a good source for parts but if you don't, GET IT DONE PROFESSIONALLY. Remember: This stuff can and will kill you if you aren't careful.
If you go the conversion route, I heartily recommend Alan at
www.tubesplus.com. The man is a genius when it comes to this kind of stuff. He did my Phantom and it's better than new.
A great tube radio such as a Tram deserves nothing less than a vintage tube amp. Putting a solid-state device behind that great plate modulated audio would be sacrilegious, IMO.
Good luck.
