Hi All
I am building a Fender 6G15 from scratch I can buy clone power transformer but would prefer to have separate heater supply to switch on first before B+ as it a silicon rectifier . The circuit diagram doesn't give voltage of power tranny secondary only 300 volts after the half wave rectifier and I am at a loss as how to find the RMS voltage of the of the secondary if someone could help with the math as I would prefer to get one wound . The second question I don't understand why did fender used 3 diodes in series as half wave rectification .
Thanks Nigel
I am building a Fender 6G15 from scratch I can buy clone power transformer but would prefer to have separate heater supply to switch on first before B+ as it a silicon rectifier . The circuit diagram doesn't give voltage of power tranny secondary only 300 volts after the half wave rectifier and I am at a loss as how to find the RMS voltage of the of the secondary if someone could help with the math as I would prefer to get one wound . The second question I don't understand why did fender used 3 diodes in series as half wave rectification .
Thanks Nigel
If I recall correctly, you divide the unrectified voltage by the square root of 2. this gives you your RMS voltage, but bear in mind this is a LOADED voltage, what you want will have to be slightly higher than that. So take 300V, subtract roughly 3 volts for the rectifier diodes, so you have 303V peak divided by 1.414 equals 214.3V RMS.
Now you can find the turns ratio if you need to.
Also, don't worry about that B+, it will work even if it's off by as much as 30%.
two more volts or three less volts is no problem. The only thing you have to worry about is exceeding any maximum voltages like the capacitor voltages or Plate voltages.
The reason why you see a chain of diodes of early circuits like this is because Germanium diodes didn't have a very high Vforward max. So, they put a few in series to increase the overall Vf rating of the whole rectifier.
With Si diodes, it's not a problem, at least not with 1N4006 or 4007 in your case.
Now you can find the turns ratio if you need to.
Also, don't worry about that B+, it will work even if it's off by as much as 30%.
two more volts or three less volts is no problem. The only thing you have to worry about is exceeding any maximum voltages like the capacitor voltages or Plate voltages.
The reason why you see a chain of diodes of early circuits like this is because Germanium diodes didn't have a very high Vforward max. So, they put a few in series to increase the overall Vf rating of the whole rectifier.
With Si diodes, it's not a problem, at least not with 1N4006 or 4007 in your case.
Instead of a separate heater supply, just add a switch to the B+ winding. A standby switch so to speak. Main power on starts the tube heaters, then flip teh B+ switch.
But that is really not necessary. The tubes are under no stress. After all, these things have been around 50 years without burning up tubes, so I doubt they would start now.
But that is really not necessary. The tubes are under no stress. After all, these things have been around 50 years without burning up tubes, so I doubt they would start now.
OK This thread is going in the right direction,. Gain-Wire is right about the B+ and the diodes, and Enzo is right about not needing a seperate filament transformer. Nigel, got any part's yet?
Bob
Bob
Hi
Thanks for your replies . I have made the chassis I got an accutronics tank the valves and caps and ordered the opt and choke . I was going to switch the power on via 2 switches the first turns on the heaters the second switch is wired to to the first switch so no matter which switch is flicked on first the heaters will always come on first I saw this idea in the tube amp forums I understand tubes are rugged little critters but they are all nos and getting expensive and ss diodes do come on with a bang unlike tube rectifiers but wanted to try keep it as original a possible . I am making this to go with my pro junior which I have rebuilt to make it harp friendly .
Thanks again Nigel
Thanks for your replies . I have made the chassis I got an accutronics tank the valves and caps and ordered the opt and choke . I was going to switch the power on via 2 switches the first turns on the heaters the second switch is wired to to the first switch so no matter which switch is flicked on first the heaters will always come on first I saw this idea in the tube amp forums I understand tubes are rugged little critters but they are all nos and getting expensive and ss diodes do come on with a bang unlike tube rectifiers but wanted to try keep it as original a possible . I am making this to go with my pro junior which I have rebuilt to make it harp friendly .
Thanks again Nigel
euh... I don't want to dissappoint you, but no, the heaters will not come on first in one of the possible situations. That is if you flick the Hi-Voltage switch first then the Main switch, the heaters will come on at the same time as the Hi-Voltage, which is what you were trying to avoid. Not that it's bad, but true, I'd rather have my eleven seconds thank you before someone drags me out of bed.
It will however prevent the user from turning on the Hi-Voltage alone.
Original in what way? do you mean looks or functionality?
No gainwire you won't disappoint me because if you think about it the mains and the heater transformer are wired to first switch . When the first switch is turned to the on position and the second switch is wired to the first switch and it is in the off position then there can be no current to the second switch and seeing the second switch provides current to power transformer there is no B+ voltage .
And to answer your second question original as in functionality as the 63 reverb is still regarded as the better design than the reissues .
Nigel
And to answer your second question original as in functionality as the 63 reverb is still regarded as the better design than the reissues .
Nigel
Who are you to question what I am doing I was just asking for some advice because I know my limitations , I didn't think for a moment that I had to fulfil some else's expectations .
Nigel
Nigel
Wow, hold on, I had no hostility in my post, I merely asked the question to determine what your overall intent was. I am quite sure you are not going to abandon your project because of anything I suggested. Speaking only for myself, I don;t know you nor your skill and experience level. I merely wanted a little clarification as to why you want it to not divert from stock and yet you also want to change it from stock.
Peace to you, I'll not bother you further.
Peace to you, I'll not bother you further.
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