Another tidbit, the 1000A is NOT a better tube than the 1500B for the
simple reason of the grid structure. the grid of the 1000A is very fragile
and will not withstand any Grid dissapation while the 1500b is much
hardier.
Larry L. Ravlin AKA (Laurence the Magnificent)
"Collins Equipt forever"
Ham Radio Operator AA7LR ex KØAEY
Walterville, Or.
sheepdip@continet.com
"this is not a rice storage facility"
----------
> From: Chris Tran GM3WOJ <gm3woj@talk21.com>
> To: amps@contesting.com
> Subject: [AMPS] 30S-1 power output
To: <amps@contesting.com>
> Date: Tuesday, September 05, 2000 7:32 AM
>
>
> Hi Jim et all
>
> > I have a weak memory that people used to put another
> > tube instead of the 4CX1000 in the 30-S1, can someone
> > refresh my memory.
>
> 4CX1500B...has same screen dissipation (12W) but LESS
> (nominally zero W) grid dissipation. In many ways the 1000A
> is a better tube than the 1500B - you get just as much RF out
> with the 1000A
>
> > How much power can then a 30S-1 put out, original and/or
> > modified.
>
> I don't have a 30S-1, but spent time repairing one belonging to
> GM4AFF. The un-modified 30S-1 is good for about 1000 W
> O/P but gets very hot at this power level in e.g. contest use.
>
> There are several problems about getting 1500W output from
> a 30S-1 :-
> 1. Poor cooling - the blower has too low a flow rate, and the power
> supply has no forced-air cooling. I fitted an extra fan blowing cold air
> in at the base of the PSU. It looks very difficult to replace the
> existing blower with one with a larger flow rate - one (drastic)
> solution would be to mount a large blower on the side of the RF
> deck and pressurise the whole plate compartment.
> 2. The plate voltage is too low - however a higher voltage xfmr
> cannot be installed without changing the (paper) HV smoothing
> caps. 4CX1000A/1500Bs need about 3200 V on the plate.
> 3. The plate blocking capacitor looks very small - maybe marginal
> at 1500W ?
> 4. Screen supply mods. as discussed, to give +325V DC regulated
> at + and - screen current.
>
> Despite all these comments, the 30S-1 is a great amp - it's got real
> 'presence' in any shack !
>
> 73
> Chris GM3WOJ
> www.qsl.net/gm3woj/
>
>
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