neazoi
Advanced Member level 6
Hi,
My Linear PSU failed (burns the mains fuse). I was sold this second hand to be a 40A 13.8V PSU. It has 4 transistors 2n3055 on a left heatsink, another 4 2n3055 on the right heatsink and one more 2n3055 at the back of the PSU. The design is not regulated by a chip, unless there is a 3-pin chip that looks like a transistor. Anyway that's the info.
I operated it for 6 months or more with a 200W HF transceiver on SSB, which required 41A (by the manual). Even on full power out of the transceiver, I did not notice any significant heating of the heatsinks (cool when I added a fan myself). The PSU is an old one made by RMS (made in Italy) model K1540, which might mean 15v max 40A, or maybe not. At the time it was burnt out, I had not previously operated it. I switched this on, I drawn the power and it failed. So I had not previously heated it.
Now here is the question.
1. Was that PSU ever capable of giving out 40A or was I pushed it? (I have to say that when it worked at peak powers I could hear a bit more hum out of the transformer, as peak current was drawn. But I believe this was normal.)
2. I would like to build another PSU out of the good parts of this old one, so I wonder if the transformer alone can give me 40-45A?
Some info I can give which might help:
The transformer measures 11 x 15 x 13 centimetres in size (including the plastic bobbin of the winding) and the secondary enamel wiring into it is 4.14mm in diameter. The iron core alone is 6 x 15 x 13cm.
The 220v mains fuse was rated for 4A.
I have no other way to measure the transformer current, so I wonder if it worth's making a 40A PSU out of it (maybe with a few 2n3771) or if the transformer is not capable of this power.
My Linear PSU failed (burns the mains fuse). I was sold this second hand to be a 40A 13.8V PSU. It has 4 transistors 2n3055 on a left heatsink, another 4 2n3055 on the right heatsink and one more 2n3055 at the back of the PSU. The design is not regulated by a chip, unless there is a 3-pin chip that looks like a transistor. Anyway that's the info.
I operated it for 6 months or more with a 200W HF transceiver on SSB, which required 41A (by the manual). Even on full power out of the transceiver, I did not notice any significant heating of the heatsinks (cool when I added a fan myself). The PSU is an old one made by RMS (made in Italy) model K1540, which might mean 15v max 40A, or maybe not. At the time it was burnt out, I had not previously operated it. I switched this on, I drawn the power and it failed. So I had not previously heated it.
Now here is the question.
1. Was that PSU ever capable of giving out 40A or was I pushed it? (I have to say that when it worked at peak powers I could hear a bit more hum out of the transformer, as peak current was drawn. But I believe this was normal.)
2. I would like to build another PSU out of the good parts of this old one, so I wonder if the transformer alone can give me 40-45A?
Some info I can give which might help:
The transformer measures 11 x 15 x 13 centimetres in size (including the plastic bobbin of the winding) and the secondary enamel wiring into it is 4.14mm in diameter. The iron core alone is 6 x 15 x 13cm.
The 220v mains fuse was rated for 4A.
I have no other way to measure the transformer current, so I wonder if it worth's making a 40A PSU out of it (maybe with a few 2n3771) or if the transformer is not capable of this power.
Last edited: