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Super topic.

I think the PS is not well designed. Specially too much voltage in AC area.

So I will try other approach. To reduce the heat, because the PS is always hot, and worse cooled than the PA that runs reasonably cool

A silly calculation tells me that 200V should be enought with primary at 234 (I guess that less that 190 will be the figure). So I am going to try.

Above all because the biggest risk ist failure of PS letting full voltage to PA, that wold be destroyed inmediately.

So after 40 years... I will try.

73 EA1FC

I tested with a 500VA Variac that drops about 3V when transmitting.

185V in receive, the FT-980 24V show voltage right in the middle of area, but fluctuates a bit inside range when transmitting FM full power.

190V in receive and the voltage meter does not move when transmitting FM full power. The Variac drops 3V. So I decided to leave it in 193V so it drops to 190V when transmitting FM full power (I guess this is not advisable)

Of course SSB gives full power.

I have not done detailed calculation, but I guess this halves the heat dissipated in the PS. Now I see that temperature in PS and PA are more equal.

When I consolidate tests, I will have two options, an autotrafo 230/190V that is the best solution or somerhing like a 15 Ohm 100W resistor in series with the mains, that would not resolve the overheating in receive, but help in transmission.

But the radio beast says that is a 530VA (that I doubt to produce 100W out) if so there is the real proof of the heat. 530VA IN >> 100W OUT not a very ecologic radio.

I have not tested with a local OM to see effects (if any) in the quality of transmission.

73 EA1FC

Tested with 200V wired for 234. I have small changes of voltage, I tried with 195V but sometimes mains voltage lowered and I was told that the signal worsened.

So I leave for 200VAC in reception. The variac is 500VA, so a small drop of 3V is normal.

Now PS and PA have similar temperatures in normal use, and cooling fan stops some 3 minutes after a long transmission. The PS temperature stabilises in 41?C (22?C in room) and the fan never comes in reception.

Having lower AC voltage in the PS has another advantage. The conducting cycle in the rectifier is longer, needed to smaller difference in voltage between input and output to capacitors. As the power is R x I2 (squared) if the rectifier conduct double the time at half the intensity for the same Culombs to charge capacitors, the power dissipated if rectifier halves. And at full power (12A) the difference may be 5/7W less in rectifier (1,2V loss)

Adding all it may come close to 70W less in transmission. A difference. Main advantage is for the PS.

73 EA1FC