Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Vlada on October 06, 2023, 10:53:50 pm
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Hello there, I am in a proces of modding my friends Marshall (2204 - built with CT transformers)
Wanted to add 2 ecc83 tubes (one for aditional gain stages and one for fx loop)
Since that transformer is rated 150mA for HT, does it have enough current to supply 2 el34s and 5 ecc83 tubes?
I am refering to 50 watt Marshall PT (1202-164)
A lot of modded Marshalls use the same tranformer without any problems, but recently I bumped on this inhttps://www.valvewizard.co.uk/smoothing.html
What do you guys think?
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Tube Data Cheat sheet attached. Maybe this will help?
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... Wanted to add 2 ecc83 tubes ...
Since that transformer is rated 150mA for HT, does it have enough current to supply 2 el34s and 5 ecc83 tubes? ...
I think you're fine to add the extra preamp tubes.
The current rating of the high voltage winding is mostly chosen to support the power tubes' plate & screen currents at maximum output power.
After you figure out how much the power tubes will pull when the amp is at full-tilt, the current draw of the entire preamp is almost a "rounding error." In other words, it's a small % of the overall high voltage current rating, as the two extra tubes might only add 3-4mA of current draw at the most.
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The HT won't be stressed. How about the heater winding?
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Thank you all
Heater current is not a concern I think, since 6,3 volts secondary winding is rated 5 Amps
2x EL34 = 3A
5x ecc83 = 1,5A
Cant remember how much light bulb draws :dontknow:
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Cant remember how much light bulb draws :dontknow:
6.3VAC Type 47 lamps can draw 150mA, 300mA or 500mA- you need to check the actual rating stamped on the lamp bayonet.
A low-current alternative would be a Type 47 6.3V LED bulb