buckaroo50,
Don't know that amplifier so take this with some 'salt'.
If the adjustment is labeled for 'matching', then I would have to guess that it's for matching the amplifier's output impedance to the feed line/antenna. Either method, watt meter or SWR meter could get you to the same place. I think I'd use one, then check it with the other maybe. And since there can be quite a difference in the adjustment range, I think I'd do it at the lowest power output that I could. That makes sense to me anyway.

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Just for 'grins'.

That '400' and '500' thingy with the tube names is the plate dissipation capability of the tube. A 3-400 can dissipate 400 watts and live with it. The 3-500 can dissipate 500 watts on the plate an live with it. Any more dissipation than those means that the life of the tube is being shortened by some amount. A lot more than those numbers means that you get to buy a new tube. That deals with measured plate current and voltage, not output power. There's also a sort of 'fudge factor' built into those ratings, but don't expect much of one. That means a single 3-400 will produce something on the average of maybe 200 watts output power -reasonably-. (Modulation Power + carrier power...measured on the meters, not the output RF power meter). Difficult to do with voice modes, so not done that way very often. Much easier using CW, and it still means the same thing. Them old HeathKits were nice amplifiers in their day! They didn't do miracles though, and lots of misunderstood 'numbers' are associated with them. When compared to what's available today, they ain't so nice, sort of. Still, nothing wrong with them if operated correctly.
- 'Doc

(Do I want another one? No, thank you, three was all I can stand. And there are some very worthwhile mods for them!)

I don't think so Doc. Matching the amp impedance to the antenna/feedline is the job of the tune and load controls. I believe the match control on the back is for tuning the INPUT of the amp to provide a low SWR to the exciter. Must have missed your morning coffee did you?

Well, maybe not enough coffee. Although, I did say I wasn't familiar with that amplifier, didn't know what 'other' controls/knobs it may have. I figured that being on the back, it either had to be for the input or output matching. Guess I should have figured a little harder, huh?
Oh well. Got to make the occasional mistake (being perfect isn't that easy to put up with you know). Also doing well in my other occupation, fertilizer salesman!
- 'Doc

I did the match dial on the back as suggested, first with a watt meter then the swr...

I guess I made out pretty well, I had checked some forums and feedbacks on the MaCo 200 and all said that with 100% tubes that the amp should be close to 200-250 PEP range... Not sure what kind of watts were used for the feed but I loaded mine to 140 dead key and then backed the load dial off to a 70 watt dead key (feeding it with 1.5 watts in) - it will swing to over 300 watts (checking with my Dosy Pm-2001-TS and also the meter on my antenna tuner MFJ-949B).. So I would assume that the tubes are fine... My radio swings from 1.5 to 20 watts with tons of audio... Doing some radio checks, the reports were that the amp was very clean and the audio very very loud... makes me smile thinking that I swapped a Uniden 510 CB worth about $10 for the amp... after doing some cleaning and painting the cover it now looks very presentable and I am happy with the performance and audio... I made a trip to radio shack and bought an AC fan and replace the origional noisy one - now it is a lot more quiet and the mic doesn't pick the fan noise up as I have it on a shelf under the desk where the radio sits.

Again thanks for the advise and help.

Nice job! I can remember when 510 Unidens were tossed in piles under the bench 'cause there wasn't any room inside for toy(s) ie; copy-cats, connex boards, etc., & a Maco 200 should have 4 ea. 8950 tubes @ $80 a piece!

BTW, w/the cost of fuel (& a LACK OF FUNDS!), whenever I need to replace a fan in a amp, I go to my "stockpile" of parts cannibilized from old microwave ovens that I've picked up on the side of the road. The fan shape is designed to move max cfm. for tube cooling w/minimal noise. Just remember to use soft rubber washers between the fan brackets & chassie mounting screws for sound isolation. Believe it or not, there's quite a bunch of good, "usable" stuff in an old microwave... fans, grounded three-prong plugs, sheetmetal screws, fuse holders, micro-switches, caps, diodes, etc... It saves time parts-running, & $$$! Just as long as you've got the room to store it all.


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