Varmint linear

[Timothy Scott Nichol]

What a mess

If the minimum SWR is reached with the screw all the way loose (clockwise), you may have the version that was sold wired wrong. Not too many folks checked input SWR in 1978, and a lot of them went out the door with this input circuit just wired wrong. Only fix is to add a small coil, around a half microhenry, in place of a wire jumper.

Don't have any pictures, or diagrams about how to fix that problem. Been doing it from memory for 25-plus years. Pretty sure most published diagrams won't match the way your input-match control is wired.

73

 

[Timothy Scott Nichol]

Two different amps, two separate messes.

 

[Nowurtalkin222]

Hi 555,
That adjustment is to minimize the SWR between the radio and the amplifier, NOT on the antenna side.

When the amplifier is keyed, the radio isn't feeding the antenna any more, it's feeding the two driver tubes. The input adjustment is to fool the radio into thinking it's driving a 50-ohm antenna with a low SWR, when the Varmint is keyed.

Requires you put a SWR meter between the radio and the amplifier. Keeping the jumpers short, like 3 feet or less tends to help. The internal SWR meter on a base radio may be accurate, or it may not.

With the amplifier keyed and tuned up for max modulated power, the input match is adjusted for minimum reflected power on the radio-side meter. You'll probably notice that turning it ALSO affects the max modulated power coming out of the Varmint when you turn that knob, as well.

In a perfect world, the spot where it shows minimum input-side SWR is is the same knob setting that shows max wattage coming out of the Varmint. In the real world, max drive may be at one spot on the knob, and least SWR may be at another spot. This calls for setting that knob for a "compromise" between the two knob settings. Generally, you should be able to get the input-side SWR under 1.5 without sacrificing more than 5% or 10% of the power coming out. If the amplifier's input SWR is much over 2 to 1, the radio's final transistor may get worked too hard.

You'll also fid that the Varmint's input SWR will change when switching from "Supermod" to "High". The tubes in the Varmint tend to run cooler on the Supermod side.

73

Hello. Can you see me, hear me, feel me...not meaning to post where I shouldn't but having a hard time making contact with wwdx. I logged in at the site and Left a msg for help. Haven't heard back from anyone yet. I have a question about amp. Got linked to this old discussion from a search and it seems to be letting me post. ?
Please excuse me. Long time not here. New cheapo phone. Sorry

 

[Enterprise312ok]

I have some scary looking varmint 1000 pics I could add to this thread. Beyond my skill level at the present time.

 

[Nowurtalkin222]

Hello. Can you see me, hear me, feel me...not meaning to post where I shouldn't but having a hard time making contact with wwdx. I logged in at the site and Left a msg for help. Haven't heard back from anyone yet. I have a question about amp. Got linked to this old discussion from a search and it seems to be letting me post. ?
Please excuse me. Long time not here. New cheapo phone. Sorry

Nomad radio is this you here? I've been trying to get in and get thru to you or anyone since yesterday but nothing looks right or is making sense. It looks like maybe someone did reply back to up above but he's talking about pics which is not why I'm here. I think this new cheapo phone is part of the problem. Also hadn't been here or logged in for a long time plus the heat hear is killing everything. Regardless, plz respond as I have a couple questions for you.

Thx

 

[Nowurtalkin222]

I have some scary looking varmint 1000 pics I could add to this thread. Beyond my skill level at the present time.

I bet you don't have a pic of the one I'm trying to find out some info on..m

 

[Nowurtalkin222]

Why can't I get anyone to reply back to me?

 

[AudioShockwav]

Why can't I get anyone to reply back to me?

If you are talking about Nomad Radio he is usually here in the evenings after he has worked during the day.
Not everyone is just monitoring the forum all the time, have a little patience

73
Jeff

 

[Nowurtalkin222]

If you are talking about Nomad Radio he is usually here in the evenings after he has worked during the day.
Not everyone is just monitoring the forum all the time, have a little patience

73
Jeff

If you are talking about Nomad Radio he is usually here in the evenings after he has worked during the day.
Not everyone is just monitoring the forum all the time, have a little patience

73
Jeff

Thanks loads for the reply. At least I know I'm getting thru now. I may as well ask you the 2 questions I have in case you might know anything regards my queries. The reason I asked about Nomad radio is I think it was him, some yrs ago, who posted an important piece about the need for a buffer or a remote keyline for when using amps. I think the focus was on base amps, likely older tube amps. I very much would like to locate that post or string of posts from at least a couple yrs ago or more. He might have even been replying to me about a project I was looking into. The other question is about a particular varmint amp I'm trying to help someone with. It appears to be very very unusual because it's the only one I can find out if all the varmint base amps that is a TX model rather than the usual XL model which is the only prefix I can find info on anywhere and I have searched extensively. It also is identified a bit differently on the front that all the others, besides the TX prefix, in that it's called a Quad power, same as all the 600s I've seen, but also says C.W. Transmitter on the front and none of the other Brewer Labs varmint 600s do. The others all just say Base or base amplifier. And I've seen (have pics) 2 different looking versions of the 600 base that are different than the one in question that I'm trying to find info on. All are 2x4 sweep tubes amps. The one in question seems to be a 1 of a kind. I've come to the conclusion that perhaps it's a well made counterfeit, which I know that kind of thing certainly happens esp with well made popular units. A very strange thing I noticed is that in the the black ink print looks genuine but the model number and the serial number are chicken scratched in, what were blank spaces. So this amp is on the front, a:
Varmint quad power base
c.w. transmitter
tx 600.
Here I'll try to post the pic
Ok it looks like the pic will attach ok. I have the back side pics as well. I cannot find any mention of image of this anywhere. So I noticed some varmint discussion here from 2006 and recently. I figure this is the best place to come to find anything about this apparent one off amp. It works well too. I hope someone knows something. I also came across a British discussion group where some dude said he was the 1st guy to import varmints into UK in the 70s and he mentioned the name of Abe Brewer as the creator of the company. Hoping someone knows something, anything and thanks to anyone who does. This is a real mystery as far as I can tell and I've searched high and low.

Tia
Jeff

 

[Enterprise312ok]

Abe had to start calling them cw transmitters after he got busted by the fcc, he had tried to get his amplifiers type accepted but the fcc would not go for it.

 

[Nowurtalkin222]

Please don't call that number. I failed to remove it, inadvertently

Abe had to start calling them cw transmitters after he got busted by the fcc, he had tried to get his amplifiers type accepted but the fcc would not go for it.

Thanks for the reply. I suggested the same idea to the owner. I alluded it to what happened with Texas star after they got busted in Vegas back in the later 90s and then after a year or 2 they made that deal with the fcc to put them out as cw keyers. It makes total sense except for the fact that other than your explanation, I could find absolutely no mention or acknowledgement of this model version anywhere on the web with tons of searches of all kinds and keywords. And no pics either. How can this be explained? Also, I can show you pics if need be but why would the serial number and model number be chicken scratched in on otherwise pretty well ink printed back side. I'm assuming all the other units, ie, the xl600s are stamped rather than chicken scratched with the serial and model #s but so far I couldn't find any good pics of the backsides of those units. Lastly, do you know your explanation to be definite facts and if so, where did the info come from. I want to let the owner know. I'm helping him with a small problem with the box. There are many pics out there of the xl600 but none of the one I showed you.

Thanks so much

 

[nomadradio]

That's a rare one. Good chance a schematic never escaped into the wild.

Don't remember seeing one of these in the flesh. Could be I did and just don't remember.

This particular "fig leaf over the private parts" was used by D&A, when their paint scheme changed from gray to brown. Wired them up with a band selector, a crystal socket and morse-key socket on the front panel. Maco never adopted this trick, and just took their sales underground.

Leads me to suspect Abe just lost patience with the harassment and exited making linears. But this amplifier suggests he considered using the "CW transmitter" ruse at least for a while.

Cool specimen!

73

 

[Nowurtalkin222]

That's a rare one. Good chance a schematic never escaped into the wild.

Don't remember seeing one of these in the flesh. Could be I did and just don't remember.

This particular "fig leaf over the private parts" was used by D&A, when their paint scheme changed from gray to brown. Wired them up with a band selector, a crystal socket and morse-key socket on the front panel. Maco never adopted this trick, and just took their sales underground.

Leads me to suspect Abe just lost patience with the harassment and exited making linears. But this amplifier suggests he considered using the "CW transmitter" ruse at least for a while.

Cool specimen!

73

No doubt on the rare...could be the only one. Not mentioned or pictured anywhere else. I still think it's possible to be a counterfeit by someone trying to hijack the popularity. Just another theory. Or could be the way see it as well. Besides this one I have pics of 2 XL600 tube base bilinears which are different. Similar but different with exact same model name. May or may not both be from Mr Brewer... Let me know if you'd like to see those pics.

Did you see my question about that old post where you (I think it was you) explained the whole importance and warning about how a remote keyer needs to be used with these old tube amps? Actually I don't even remember the part about it only being necessary with old (high current relay?) tube amps (been reading that currently) but I do remember how important you said it was due, I think, to transients and that it could be dangerous for both radio and amp? You might even have been replying to me about a project I had in front of me, or not. If you know what I'm referring to it would be great if you knew how to bring that post you made on the subject. If there's only 1 nomad here, it had to be you. I am trying hard to convince the owner of that tx600 "cw transmitter" to NOT continue to hit it directly with his president Lincoln II+ he bought from me, new. And all because of what you told me in that old post. Must've been 2-5 yrs ago?

Thanks for the info you share here
Jeff

 

[Beetle]

Nothing wrong with "cw transmitters" as long as they're operated using CW on bands where such emission is legal.

Lots of nice DX to be had there.

 

[Nowurtalkin222]

Than

Nothing wrong with "cw transmitters" as long as they're operated using CW on bands where such emission is legal.

Lots of nice DX to be had there.

Thanks. It's an AM/SSB amp. I don't know if the CW aspect is even for real but might be since this amp was apparently Mr Brewer's last ditch attempt to get them type accepted.