I have acquired a D&A PDX-400 10 tube amplifier using (9) 6lq6's ranging from 92%-100% and (1) 6jr6 tube @ 100%. I am hitting it with 1 watt swinging approx 20 watts. Using a bird watt meter I can only get a maximum wattage output of only 535 on SSB and 375 or so on AM. I have read that these boxes are capable of doing better than this. Is there something that I should be looking at. The 3 transformers check good as well as th 8 electrolytic caps with no hum whatsoever. Any help would be greatly appreciated. Thanks, "313"
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Here is a 10 tube amp question
- Thread starter 313inthegarden
- Start date
Does the Bird have a peak reading kit?
How many tubes in parallel in the final stage?
Hi Kamikaze, The Bird meter is strictly RMS with (6) 6LQ6 tubes in the final circuit (3) 6LQ6 in the driver circuit and (1) 6JR6 as a regulator? tube before the driver tubes. So, I would tend to think (1) hitting (3) hitting (6) if that makes sense. And I am seeing 535 on SSB and 375 or so on AM. Thanks, "313"
The Bird you have is not going to read peaks. The peak power can be much higher than the average power. I'm not so sure RMS is the proper term. Your meter might only show 30% of peak depending on waveforms.
6 big sweep tubes making anything over about 700 watts P.E.P. is either on borrowed time or moderately distorted.
If it were me I'd check it under carrier conditions very briefly. Only a few seconds at max power. Tune it up on low power to get in the ballpark. Tweek it with the drive turned up a little. See if it will make a brief 700 watt carrier. Reduce the drive for use.
You could also borrow a peak reading meter from somebody.
Tube testers do not usually tell the whole story with larger tubes. The best tube tester is the circuit it's designed to work in if the design isn't defective.
6 big sweep tubes making anything over about 700 watts P.E.P. is either on borrowed time or moderately distorted.
If it were me I'd check it under carrier conditions very briefly. Only a few seconds at max power. Tune it up on low power to get in the ballpark. Tweek it with the drive turned up a little. See if it will make a brief 700 watt carrier. Reduce the drive for use.
You could also borrow a peak reading meter from somebody.
Tube testers do not usually tell the whole story with larger tubes. The best tube tester is the circuit it's designed to work in if the design isn't defective.
Kamikaze, I agree with you about the tube testers because even though a few of the tubes do show in the 90%+ range upon key up of the transmitter the tubes will show some blue in them. Also, I am hitting it with a (1) watt dead key. Do you think that is to low of a carrier. What would be the maximum dead key for the tubes because I don't want to blow them out either for I can't really find any user info on this amp. Thanks for your help,
"313"
"313"
Blue isn't always bad. It depends on where the blue is.
I'm basing my figure on the number of tubes in the final amp. Not really sure of the drive needed but most of those older amps were built when everything was 4.1 watts carrier and 16 P.E.P. on a good day.
Thanks a lot Kamikaze. Any other members input would be greatly appreciated as well. Thanks, "313"
RatsoW8
Supporting Member, W9WDX ARC Member - WD8T
To replace that many 6lq6 tubes you're better off spending the $700 and buying a new bullet proof AL-811.
That tube was not made to do what those old CBamps want it to do, but in 1970 when you could buy a 6lq6 for $4 who cared? You could fry them all day long.
That tube was not made to do what those old CBamps want it to do, but in 1970 when you could buy a 6lq6 for $4 who cared? You could fry them all day long.
tube amps were designed for 4 watts carrier input (most of them ).you could try the higher carrier ,then retune and see what it does.
for instance see below
this is a maverick....4 driving 4 final tubes and they say in excess of 250 watts for 4 finals .so it doesnt sound like your doing bad .if you wanna see higher numbers ,get the peak kit.
Shot at 2011-03-10
for instance see below
this is a maverick....4 driving 4 final tubes and they say in excess of 250 watts for 4 finals .so it doesnt sound like your doing bad .if you wanna see higher numbers ,get the peak kit.
Shot at 2011-03-10
Agree. The ham linears are all "high drive", so to speak, but they are very linear. An AL-811H will do 750W output (average), easily, with 40W drive. So 1W will produce about 20 more or less; that 20W swing will do about 370W or more. You could drive the 811 amp with a small amp. The AL-811 will accept up to 100W input. 811A's are cheap, about $25.00 each but last almost forever.
Or even cheaper!! Back then, they were about $2.00 a piece! Try and find one today for under $40.00 each! :headbang
Depends on what you mean? If your talking AM modulation, yes, except the 811 will never do 750W on AM. The most it can do on AM is 175W (average). Any more and your overdriving the bejeezus out of it!!!That's over 2kw peak
My rule of thumb is that what ever the amp does flat out with maximum drive is what the amp will do PEP. Fer example: If on SSB, I whistle the amp up to 1000W, then that's the maximum PEP I'll get out of it, (single tone). That 1000 W is the maximum the amp will do. Now voice is different and depends on voice characteristics, symmetry, etc.
I had a Hammond HL-500 years ago which ran 4 811A's, and it ran about 700W (+/-) output with a 100W dk. I also drove it with a Yaesu FT-7 which ran 20W PEP and it drive it to about 250W +/- output (average).
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how many drive tubes. and tubes are not like transistors raise the DK up to at least 4to 5 watts and if that increases your swing all the better