I replaced the bridge rectifier in one of my 300b amps with some fast soft recovery controlled avalanche rectifier diodes I had on hand. The voltage has dropped to 3.35V from the normal 5.0V. It seems to work very nicely but with reduced gain. Any ideas as to fixing this? Does it hurt to run the 300b's at 3.5V or less?
During warm up, after a few mins. it did get a little louder, but not the way it used to be.
The tubes are TJ mesh plate golds.
Thanks in advance
Tom
During warm up, after a few mins. it did get a little louder, but not the way it used to be.
The tubes are TJ mesh plate golds.
Thanks in advance
Tom
Hi,
I'm not surprised, you're starving the 300B which actually linearises the bottom end of the curves.
If you have a DVM, set it to lowest resistance and measure the series resistance of the diodes before you do the other channel.
Maybe you received the wrong kind of diodes?
If anything, I'd expected a slight rise in voltage, not a drop.
Cheers,
Sounding very sweet though
I'm not surprised, you're starving the 300B which actually linearises the bottom end of the curves.
I'm tempted to do the other just to see what happens but if I get the same drop then what?
If you have a DVM, set it to lowest resistance and measure the series resistance of the diodes before you do the other channel.
Maybe you received the wrong kind of diodes?
If anything, I'd expected a slight rise in voltage, not a drop.
Cheers,
Hi,
Should be more than ample....strange, really strange.
Cheers,
The cap across the 5.0 volt (suposedly) wires is 10,000uf.
Should be more than ample....strange, really strange.
Cheers,
"If you have a DVM, set it to lowest resistance and measure the series resistance of the diodes before you do the other channel."
Could you clarify at which two points do I take the measurments?
Maybe as you say these diodes are not suitable for this application.
Is there any long term problem with using the 300b at 3.5V?
Could you clarify at which two points do I take the measurments?
Maybe as you say these diodes are not suitable for this application.
Is there any long term problem with using the 300b at 3.5V?
Hi,
But of course, I forgot about that entirely...in HV sullies this doesn't really matter but at 5V it sure would.
Good of you to remind us of that.
See D'Haen's reply...you're losing too much voltage.
Not a problem as such but it won't exactly be a 300B you're listening to...could be better, could be worse.
I'm not going to take side on this one....
Cheers,
The Fast-Soft Recovery Diodes that I have come across have high forward voltage drop.
But of course, I forgot about that entirely...in HV sullies this doesn't really matter but at 5V it sure would.
Good of you to remind us of that.
Maybe as you say these diodes are not suitable for this application.
See D'Haen's reply...you're losing too much voltage.
Is there any long term problem with using the 300b at 3.5V?
Not a problem as such but it won't exactly be a 300B you're listening to...could be better, could be worse.
I'm not going to take side on this one....
Cheers,
Hi,
Yeah...I expected that...
The Schottkys will bring it back to a more lively listen....let us know what you experience.
Cheers,
It's warm and thick like a quilt on a winter morning.
Yeah...I expected that...
The Schottkys will bring it back to a more lively listen....let us know what you experience.
Cheers,
I havn't shut this thing off since I did the mod. It keeps getting louder and louder and better and better. And it's in stages. Meaning during a song it will just get louder all at once.
Any ideas why?
I guess the diodes are braking in and passing more current.
I'm off to do the other one.
Any ideas why?
I guess the diodes are braking in and passing more current.
I'm off to do the other one.
Hi Tom,tom1356 said:Oh, it's still warm but not thick anymore.
Yes, that's typical of an underrun heater. Just a few degrees more, and a big change.
Frank is right about the linearity, but other parameters associated with the circuit will suffer when the current passed is lower than the design value.
Cheers,
Hi,
That's not considered as normal break-in observation.
Cheers,
Meaning during a song it will just get louder all at once
That's not considered as normal break-in observation.
Cheers,
Indeed not, it's the valves sputtering into life, as the internal temperature rises.fdegrove said:Hi,
That's not considered as normal break-in observation.
Cheers,
Really, they'll work best at the rated heater voltage. Give 'em a chance...
Hi,
No, don't think so.
No, not necessarilly either...have a Stella on me and a headache....stupid brewers...
Cheers,
Indeed not, it's the valves sputtering into life, as the internal temperature rises.
No, don't think so.
Really, they'll work best at the rated heater voltage. Give 'em a chance...
No, not necessarilly either...have a Stella on me and a headache....stupid brewers...
Cheers,
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