Having Trouble With the Math!!

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Hi guys. I have an old Magnavox branded pt that came out of an old radio. I would like to use for a SLO nakid 40 build, but I’m having trouble figuring out if it will work amperage wise. It ran a bunch of tubes, 6l6 gt pair, and a lot of smaller nine pin tubes. Assuming it can run the four 12ax7’s and two 6l6gc’s in the build seem like it would be a bad idea. Everything I see online is very confusing to me. Is there anyone who can explain, or link me to what exactly I need to measure and how to use the measurements to calculate the current it’s capable of putting out? Any help is appreciated!! Thx all!!!!!

[thetragichero]

do you have a schematic for (or at least the model name of) the radio it came out of?

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Yes. It’s a magnavox CR223E radio.

[thetragichero]

well i've found this as one of the first google search results: https://www.tubesandmore.com/schematics/magnavox-co/cr-223
i may be missing some tubes i've never heard of (62? 63? 64? results unclear, ask again later)
6u5g (300ma) 6sn7 (600ma) 6ba6 (300ma) 6be6 (300ma) 6sg7 (300ma) 6sr7 (300ma) 6sg7 (300ma) 6h6 (300ma) 6sh7 (300ma)
so 10 x 300ma not including the two power tubes

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It sure seems to me that even without doing any calculations on the secondaries it’s more than powerful enough for the slo nakid 40 build!!! 6l6gc’s draw what, .9ma per, and the 12ax7’s draw .3ma per. I know I’ll have to mod the dropping resisters due to the measured 380-0-380 I got off the high voltage taps. Feeling pretty good about it. I only wish the ot from that radio was a 40 watter!!! Thanks for your help boss!!!

[thetragichero]

or run the 5u4gb rectifier? should drop a few volts. you've got the 5v filament tap

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That’s a great idea sir!! I’ve even got that tube direct from the radio salvage!!!! An slo with rectifier sag, very interesting…

[PRR]

...6l6gc’s draw what, .9ma per, and the 12ax7’s draw .3ma per.

Check your units.

Also: Not 6L6GC. (Same heater, but very different typical application.)

That PT is unlikely to support a 40 Watt amp. The Magnavox was 25 Watts on a good day. Losing the vacuum rectifier and the (unclear to me) field coil may leave a bit more power, but not 40W IMHO. Losing the tuner tubes frees some heater power but does very little for B+ power. RadioMuseum lists it as 1950, and it was a VERY deluxe model (fifteen inch TV! fifteen inch speaker!), so may have a lot of hours on it.

> tubes i've never heard of (62? 63? 64?

Those are probably chassis reference numbers, not tube numbers. Funny that the tube line-up is a lot of post-war but the field coil speaker would be a pre-war design. Perhaps they had a crate un-sold in 1942 and needed a way to unload them-- hey, deluxe TV! Everybody wants to hear Dagmar's bass!

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Copy that. Thank you for the input sir!!!!