4-400s by 304tls

[kc2ifr]

I have an amp.......pair of 4-400's that will run in ab2 or class c by selecting the mode by switch.
I would like to modulate it with a pair of 304tl's but im not sure what mod tranny I can use. The rig has a HUGE power supply from a b'cast transmitter so power is no problem.
Any suggestions....

Thanks in advance,
Bill

[Opcom]

Probably any iron rated over 500W minimum, but according to the tubes capacities and your HUGE power supply, more like something rated 800-900W for the best performance.

Here are some P.W. Dahl specs that might get close..

COLLINS 820D-1 MOD XFMR
OIL FILLED P/N 667-0497-00 (PP 4-400A'S)
CORE) A-518   C-CORE         STYLE #) 09 HIPERSIL C-CORE
PR) 2511 VCT (9000 OHMS P-P, PP 4-400A'S)
S1) 2262 VAC @ 0.310 (7300 OHMS @ 3200 VDC)
DM) HT = 10.375 WT = 10.500 DT = 8.125 MD = 7.625 MW = 7.500
WEIGHT) 68 LBS

COLLINS 820D-2 MOD XFMR
OIL FILLED P/N 667-0497-020(PP 5-500A'S)
CORE) A-0525/ C-CORE         STYLE #) 09 HIPERSIL C-CORE
PR) 2764 VCT (11600 OHMS P-P, PP 5-500A'S)
S1) 2192 VAC @ 0.301A(7300 OHMS @ 3100 VDC)
DM) HT = 12.187 WT = 7.469 DT = 6.063 MD = 5.000 MW = 5.750
WEIGHT) 49 LBS

GATES BC-1 MOD TRANSFORMER
P/N 478-0410-000
CORE) A-0525/ C-CORE         STYLE #) 09 HIPERSIL C-CORE
PR) 2450 VCT PP 833A'S
S1) 1800 VAC @ 750 VA
S2) 80/110/155 VAC @ 8 VA
DM) HT = 10.625 WT = 7.375 DT = 6.750 MD = 4.750 MW = 5.750
WEIGHT) 49 LBS

Hope these specs help with a general idea. The ratios of the pri:sec, and the VA ratings, and then multiplying the secondary RMS voltage by 2.828 to get the peak to peak modulation voltage (assume it to be twice the DC power supply volts, right?) tell the tale.


Your tube lineup sounds alot like the Tucker TX's original configuration, except with two 4-400's instead of a 4-1000 in the PA. The Tucker runs 3000V or so. The mod iron is from an RCA 1K near as I can figure and it looks like it is worth 800-1000 watts of audio. The 1K's supply ran at 2650V. the operating conditions are shown here:
http://www.bunkerofdoom.com/lit/rca1k/e.gif
The iron has not been identified for certain. I asked about some pictures of similar iron someone posted but they did not reply, or I missed it. The recent picture was of several power and mod irons apparently on little furniture dollies in a garage.

Anyway I was hoping others would suggest some transformers from their actual rigs, since mine is not identified, but sine no one jumped in, I thought these specs from PW Dahl's list and a suggestion from a similarly-tubed rig also with a big power supply might be helpful.

[W2PFY]

Hi Bill, I think that one you use to mod the 4X1 that you got from Gary originally used 4-400 to mod a pair. You'll need a mod reactor as you know.

Best of By Golly's to you.

[kc2ifr]

Terry,
Thats the mod iron Im using on the 4x1......

Bill

[Gito]

Bill
two 4-400 class C transmitter with 3000VDC on plate loaded to 550 ma has an impedance of 3000:550 ma= 5500 Ohm

Modulator using 304 using 3000VDC has a 9100 Ohm impedance
The turn ratio is the root of 9100 : 5500 = 1.285

Gates BC-1 mod transformer has
Pr:  2450 VCT Plate to plate
Sec 1800 VAC
The turns ratio is 2450 : 1800 = 1.36 .
You can use it as your modulation transformer since the turn ratio is close to the modulation transformer that you need.
Yes You need a modulation reactor.

Regards

Gito