A humble question to the AMP Experts, I have a spare Heathkit sb-200 amp. The 572-b tubes are required for this amp. If you have not noticed, the 572-B tubes are becoming more scarce than rattlesnake hips and chicken lips. Good NOS Cetron, GE etc. are not so easy to find as they were. The China Taylor 572 tubes are so bad now that RF parts no longer sells them and claim a new China tube plant will soon produce a close to Cetron clone tube. This has been posted now for over 1 yr. They just change release date from in the spring. In the fall, in the summer. I see many, more than the norm, SB-200 amps being sold / unloaded on the market. I have a gut feeling this is because of the lack of reliable new 572-b tubes on the market. So...here we go with my question.
As most of us know you can replace an 811-A with a 572-b tube in an 811 or 811H Ameritron amp. This is because the 572-b tube has same characteristics as an 811 tube but the 572-B has higher voltage and plate dissipation rating. Thus when a 572 is used inplace of an 811 the tube should/does have more durability and expected life as the tube is not driven as hard. My question to the amp gurus is when this process is reversed and we use an 811 to replace the 572 tubes, AFTER A Home Brew DIVIDER is placed on the transformer, CUTTING THE VOLTAGE IN 1/2 (From 2400 volts to 1200 volts), The 811 tube now will work in the SB-200 with out any further mod? By my calculations the 1200 volts will match the 811specs per 60-65 watt dissipation and max voltage know this is a backwards mod that turns a 500 to 600 max watt amp into a 300-400 watt amp but with all the SB-200 amps dumped on the market for 200 bucks or less this mod should make for a keep it simple alteration to keep the amp on air for the next 30 years with the current supply of NOS and reliable new 811 tubes. Question # 2 is that there is a myth that the Ameritron AL-572 has a tap on the transformer that cuts the voltage in 1/2 for the use of the 811 tube if wanted to. Any owners of the AL-572 amp that can confirm this? 73 Bill WS5H
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