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Author Topic: collins 30L-1 tuning question  (Read 3347 times)
WB2WIK
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Posts: 20567




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« Reply #15 on: June 18, 2011, 01:19:34 PM »

when I tune to zero as instructed in the manual.
on 20m my power out appears to be about 200w less than when I peak it with power out.


I'm not surprised about that.  However there is an alignment procedure in the manual (I think -- haven't looked at one lately) to actually "adjust" the "TUNE" (0 scale) meter so that it will agree with an output power peak.  If you do that, they should both occur at the same point.

Would have been better if they just grounded the grids, fed positive bias to the cathodes, and elminated that silly feedback circuit they used.  I guess whatever they did was to make it "easier for untrained operators in the field" as Phil says (sounds plausible), but the result was a silly design. 

Collins also used excessive plate voltage for 811As, above their rating; I understand that was done with an agreement from RCA, who supplied all the tubes.  Problem is, RCA stopped making 811As about 40 years ago and the Chinese tubes aren't as good.
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N4CR
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Posts: 1662




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« Reply #16 on: June 19, 2011, 05:28:38 AM »

I'm not surprised about that.  However there is an alignment procedure in the manual (I think -- haven't looked at one lately) to actually "adjust" the "TUNE" (0 scale) meter so that it will agree with an output power peak.  If you do that, they should both occur at the same point.

Section 4.7 in
http://bama.edebris.com/download/collins/30l1/30L1.pdf

Quote
Collins also used excessive plate voltage for 811As, above their rating; I understand that was done with an agreement from RCA, who supplied all the tubes.  Problem is, RCA stopped making 811As about 40 years ago and the Chinese tubes aren't as good.

I'm running Cetron tubes. My idle HV is 2kv and it dips down to about 1800 under full load. This is after I replaced all the diodes and caps on the HV board.
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73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
WB2WIK
Member

Posts: 20567




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« Reply #17 on: June 19, 2011, 02:52:00 PM »

The 30L-1 is certainly unique.  I've owned a couple over the years, but not in a long time.

I liked the 30S-1 better for home station use, and just sold my last one in 2007.  That's a powerhouse, but it sure generates a lot of heat!

I didn't even know Cetron made 811As.  I remember their 572Bs, which were quite good.  My 30L-1s all had RCA JAN-811As in them, which typically lasted a very long time.

My old homebrew 4-250A plate modulated AM rig (built in 1966!) which I still use sometimes to check into the AMI nets on 75 meters, has RCA 811As in the modulator, purchased new 45 years ago for $9 each, and they're still perfect. Smiley
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