yep those breadboards aren't the right choice for this work but after all it does work fine, some oscillations on the treble channel at high volume though, but for testing i guess is ok
did you used a specific formula or just ohms law? i'm curious, my math has been rusty since quarantine began
Although, if the plate current is low so also the screens? the circuit at idle is 20mA, 70% bias.
At peak values, to measure how much the screen voltage drops on heavy loads i measured them with a sine wave input and an ac voltmeter with the + on one and the - on the other, it gave me 50-ish volts peak to peak, also measured the DC value and substracted it giving me a value close to 300v(360-50=310V ),
how i can measure the current i don't know, but ltspice is my friend, but i assume if those values are on the margin, and if all seems to match with the ltspice results, everything will be ok... althrough i could be wrong.
thanks for all the replies guys
did you used a specific formula or just ohms law? i'm curious, my math has been rusty since quarantine began
Although, if the plate current is low so also the screens? the circuit at idle is 20mA, 70% bias.
At peak values, to measure how much the screen voltage drops on heavy loads i measured them with a sine wave input and an ac voltmeter with the + on one and the - on the other, it gave me 50-ish volts peak to peak, also measured the DC value and substracted it giving me a value close to 300v(360-50=310V ),
how i can measure the current i don't know, but ltspice is my friend, but i assume if those values are on the margin, and if all seems to match with the ltspice results, everything will be ok... althrough i could be wrong.
thanks for all the replies guys
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Still glowing......and extracting 300 watts from a single pair of tubes! See post #25 here:
If UNSET and the RCA50W Had a Baby
I have spent much of my time outdoors while the weather is still nice. Computer time has been spent on laying out a board for that big amp....the goal is 500 WPC. I turned 68 years old recently. I need to build the big amp before I'm to old to move it!
I have not read all of this thread, but I built one of my SPP boards at least 10 years ago that made just over 30 WPC from a pair of "Baldwin" branded Sylvania 6BQ5 tubes on 430 volts of B+. No red plating or glowing grids were seen.
As the name suggests the tubes were sourced from the amplifier in an organ pulled out of a church, where it likely got used once or twice a week for 30+ years. That amp was still working with the same tubes in it when I left Florida. As stated B+ was 430 volts, The OPT was 6600 ohms, and the screen grid voltage was much lower, maybe 250 to 300 volts, I don't remember and I no longer have the amp.
When I built it I tried a lot of different 6BQ5 / EL84 type tubes. Many either red plated or had the glowing grid of death. Most old 6BQ5 tubes worked, as did some JJ EL84's. Other new production stuff didn't like it.
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If you are referring to the 250 watt test amp, the OPT is rated for 1250 ohms, but I had the 8 ohm load on the 4 ohm tap for 2500 ohms at the tubes. In the final 500 WPC design either 4 or 6 tubes will look into 1250 ohms.
Over 10 years ago I squeezed 525 watts out of similar OPT's with 4 X 35LR6 tubes on 650 volts of B+. That experiment is in post #438 of this thread:
Posted new P-P power amp design
Over 10 years ago I squeezed 525 watts out of similar OPT's with 4 X 35LR6 tubes on 650 volts of B+. That experiment is in post #438 of this thread:
Posted new P-P power amp design
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