5G9 Tremolux PTP Build
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martin manning
- Posts: 14308
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
Re: 5G9 Tremolux PTP Build
I was trying to work my way through the HT VAC to DC story. To predict that accurately you need to consider a several factors beyond the VAC and rectifier voltage drop. But 40 mA at 345V is 13.8W- too high for a 6V6. 70% of it's 12W max would be 8.4W, which would mean 24 mA at the same 345V. Lowering the current draw by 30+ mA will bring the voltage up a bit for sure.
Re: 5G9 Tremolux PTP Build
Thanks Martin. Yes, I was on that; I knew they were too hot. The tubes seem to bias about 5mA apart even at colder settings. I've got them at ~20mA and ~25mA; making ~7W and ~9W.
As expected, voltages all around came up near the schematic values, except, of course, V1 where I departed from the schematic. Plates = 374, screens = 373. B+ values are 378, 375, 318. Even the PI straightened out.
I must have munged the Lo input jack, as it didn't work. That pair of jacks was recycled. I opted for a pair of fresh jacks, thinking maybe they were somehow a source of the hum, but there was no change except now the Lo jack is functional. The hum, livable, dies when I pull V1, so I guess there it is and not related to the input jacks. I'm not sure how much effort I'm going to put into it. I don't see a spare 12AY7 (maybe that's the cause?) in my tube box. Maybe I'll be able to steal one from another amp.
As expected, voltages all around came up near the schematic values, except, of course, V1 where I departed from the schematic. Plates = 374, screens = 373. B+ values are 378, 375, 318. Even the PI straightened out.
I must have munged the Lo input jack, as it didn't work. That pair of jacks was recycled. I opted for a pair of fresh jacks, thinking maybe they were somehow a source of the hum, but there was no change except now the Lo jack is functional. The hum, livable, dies when I pull V1, so I guess there it is and not related to the input jacks. I'm not sure how much effort I'm going to put into it. I don't see a spare 12AY7 (maybe that's the cause?) in my tube box. Maybe I'll be able to steal one from another amp.