Heater problem in Marshall build
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stompjunkie
- Posts: 75
- Joined: Mon Jun 05, 2006 4:13 pm
Heater problem in Marshall build
I just "finished" building a 50w 1987 style amp with 6550s. The PT used is a P4550JT from Mercury Magnetics. I'm only getting 3.3v from it's 6.3v heater taps. I thought some of my wiring may be faulty, so I disconnected the heaters and measured the PT and again I have 3.3v. What will the side effects be of having this low of voltage? Thanks for the help.
Re: Heater problem in Marshall build
If you are really running your tubes at 3.3v, they will die a premature death, very premature. A little bit of time shouldn't hurt them.
What exactly are you measuring? One wire to ground would be ~3v. Across the pair should be over 6v. Maybe you've got one with a CT and you are using the CT as an outer leg by mistake? That would account for half of what you expect. Just guessing here.
Post a picture? Is this a schematic of the tranny? If so, which terminals are you using for the filament supply?
What exactly are you measuring? One wire to ground would be ~3v. Across the pair should be over 6v. Maybe you've got one with a CT and you are using the CT as an outer leg by mistake? That would account for half of what you expect. Just guessing here.
Post a picture? Is this a schematic of the tranny? If so, which terminals are you using for the filament supply?
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skyboltone
- Posts: 2287
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- Location: Sparks, NV, where nowhere looks like home.
Re: Heater problem in Marshall build
How are the other voltages? Have you got an "International" xformer with 120/20V primary?Phil_S wrote:If you are really running your tubes at 3.3v, they will die a premature death, very premature. A little bit of time shouldn't hurt them.
What exactly are you measuring? One wire to ground would be ~3v. Across the pair should be over 6v. Maybe you've got one with a CT and you are using the CT as an outer leg by mistake? That would account for half of what you expect. Just guessing here.
Post a picture? Is this a schematic of the tranny? If so, which terminals are you using for the filament supply?
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Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Re: Heater problem in Marshall build
Yes you have to measure across the two heater wires to get the 6.3 vac.
If you just measure one side to ground you will get the 3v .
If you just measure one side to ground you will get the 3v .
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: Heater problem in Marshall build
Dont feel bad. I was making the same mistakes too.
Rookie with Determination
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stompjunkie
- Posts: 75
- Joined: Mon Jun 05, 2006 4:13 pm
Re: Heater problem in Marshall build
Heh heh....I feel like a moron sometimes. Yeah, I was just measuring one side to ground. 
one of these years I'll figure out what I'm doing. Now I just need to figure out why my MV isn't working. .... I guess thats the next step, then I can start fine tuning it. Many thanks guys. I'll try not to be such a noob next time. 
one of these years I'll figure out what I'm doing. Now I just need to figure out why my MV isn't working. .... I guess thats the next step, then I can start fine tuning it. Many thanks guys. I'll try not to be such a noob next time. Re: Heater problem in Marshall build
You aren't the first to do this. Don't think about it. Move on. Glad you got the help you needed.