That's a bit on the high side for sure. I can certainly see why the already-hot Allied was unhappy.
My home is around 120VAC this time of year. It drops down to 110 or lower in the summer. George also has very poor waveform at his home after lightening took out the old school transformer outside of his house (if I remember the story). With all of the rectified power supplies that live on our power system these days, they put a nasty notch in the wave form where the diodes cut-off. This creates harmonics that can exacerbate the audible buzz from a power transformer.
My home is around 120VAC this time of year. It drops down to 110 or lower in the summer. George also has very poor waveform at his home after lightening took out the old school transformer outside of his house (if I remember the story). With all of the rectified power supplies that live on our power system these days, they put a nasty notch in the wave form where the diodes cut-off. This creates harmonics that can exacerbate the audible buzz from a power transformer.
Mine varies from 115-117 to 127 also! I saw somewhere on a form where a fellow made pre ps transformer filter out of IN4007 diodes and 3,300 uF caps . If I remember right they were only 16V.
I guess 16V is okay as your after DC which will be very low. He said it got rid the DC and so made the trans. run a lot cooler. I don't remember about noise being a problem in that case though.
Randy
I guess 16V is okay as your after DC which will be very low. He said it got rid the DC and so made the trans. run a lot cooler. I don't remember about noise being a problem in that case though.
Randy
Line voltage is 123 today. I did a quick checkout and came out with 440 B+ right on the nose. I measured right where the very last cap screws to the board. Plus side of cathode resistor to ground measured 41. I used two 6550's, one 5ar4, one 12at7. Solid state diodes are not in use. I used this very same board for two years with another transformer. It ran hot, but that transformer is notorious. The old one also made a hum, but it sounded like a normal hum that many things make when turned on. I could hold my hand on that one for 5-6 seconds after rocking out for a couple of hours. I ran the new one for two hours this morning and could only hold my hand on it for 3 seconds. I would've actually measured the temp if I thought of it.
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OK, so you are running ~73mA per tube. Total B+ load should be something like 160-165mA. Seems like you are well within spec on the B+ side of things.
Solid state diodes are not in use...but are they installed? They are present to the transformer even if the switch is not thrown to make them the source of rectification. What diodes are you using?
Aside from that...yeah it seems like there is something amiss with the transformer.
Solid state diodes are not in use...but are they installed? They are present to the transformer even if the switch is not thrown to make them the source of rectification. What diodes are you using?
Aside from that...yeah it seems like there is something amiss with the transformer.
Well I ran it for about two hours with el 34's and 5ar4. Same 12at7. It was cool for a while then just warm by the time I shut it off. What a bummer because I think it just can't handle what it is rated for. I bought it because it was 380-0-380 as opposed to the 375-0-375 of the Allied. Also the alleged current rating is 200ma versus Allied's 175ma. So disappointed because I wanted the extra oomph and current for solid state operation. Also this one was the cheapest one they offer that will work in the sse. I think it is cheaper because it is cheaper if you know what I mean. Also I think this one is partially, if not totally, outsourced. I say that because it is the exact same dimensions as the Allied and the exact same holes. It made it convenient, but I found it curious.
Maybe you can run the amp like mono blocks with one Trans./CH. Besides better separation, you may gain lots of headroom in the PS then too. You would have to maybe perfboard the second PS caps etc. I'd try it with the 2 different Trans. first.
Maybe a crazy thought!
If you run it with one output tube out is it quieter and run cooler?
Randy
Maybe a crazy thought!
If you run it with one output tube out is it quieter and run cooler?
Randy
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The triad that everyone else uses. I was using a Hammond that was too low on the dcr. It worked fine with the Allied transformer.
The biggest edcors. 5k 8ohm. Does not hum nearly as much with el34's. Sounds just about normal. By the way I have the ugliest, most poorly built, generic Chinese el34's that some guy gave me for next to nothing and they sound fantastic. Better than my winged c el34's, 6550's, and eh kt88's. Just a funny little side note.
You must be a mind reader. I just plugged them in. I'm about ten feet away and can hear a faint high pitched hum almost like a cooling fan is on. Much quieter than the 6550's. Don't forget I put felt feet on the transformer.
I've been running old vintage Eico HF-12 Mono EL84/6BQ5 PP amps, and have been running a fan on them as the PS trans get too hot to touch even using a variac to bring the voltage down to 115V to help tube life & it seems to bring the temp down a fair bit. One PS trans does hum a bit also, but it's a low hum. They too are also notorious for running hot.
I think I may buy replacement Eico HF-81 (Stereo Version) PS trans for each amp eventually , then I will have very cool running PS trans with a much lower DCR (resistance) to boot. Heyboer Transformers in Michigan sells them. The only thing is they are much bigger so I would have to make separate chassis for the PS.
I'd try the one PS trans per/CH with what you've got. It may work out pretty even if your worried about the B+.
Randy
I think I may buy replacement Eico HF-81 (Stereo Version) PS trans for each amp eventually , then I will have very cool running PS trans with a much lower DCR (resistance) to boot. Heyboer Transformers in Michigan sells them. The only thing is they are much bigger so I would have to make separate chassis for the PS.
I'd try the one PS trans per/CH with what you've got. It may work out pretty even if your worried about the B+.
Randy
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