Greetings to all,
There is some misinformation being passed out here about these
tubes. There are two common 4CX1,500 tube types, the "A", and the "B". The
"A" tube has a 25 watt grid dissipation rating but will not work in the
30S-1 without changing the tube socket. The "B" tube has a 1 (one) watt
grid dissipation and will directly replace a 4CX1,000 in a 30S-1 amp. As I
said in an earlier post, this is a X 10 increase in grid dissipation over a
It is important to know, and understand, that the band switch in the
30S-1 was never intended to see more than about 600 watts of RF. This amp
was designed at a point in time when US Amateurs were only allowed to run
1,000 watts AVERAGE INPUT power, not OUTPUT. This band switch is made on a
thin sheet of G10 fiberglass with contact points riveted on. My point is,
be careful how you handle this switch, both power applied and switching. I
had to pay $500 for the last one I changed out for an RTTY operator. In my
opinion, the 30S-1 should never be operated on any continuous mode. High
speed CW is also very hard on it.
Despite the other numerous faults with this amp, it is still around
and quite a topic of conversation. Ask yourself why has it not increased in
value comparable to other similar amps. If you ever had to maintain a
"fleet" of these amps, as with the MARS program, you will understand why.
I have a 30S-1 with grid drop-out mod, fused step-start, and
4CX-1,500 with increased screen voltage. With these mods, it runs reliably
in SSB but I still cringe every time I turn it on -- so many more bad
things, than good things, can happen every time it is turned on.
73 de Lon, K5JV
1110 Golden Bear Ln.
Kingwood, TX 77339
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