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Kev's "Cobble Together a Good 3000 PL Preamp" thread...
- Thread starter jbeckva
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The zener diode is downstream from the capacitor, which means that the transistor won't turn on until the capacitor charges to the zener diode voltage + vbe (5.6V + 0.6V = 6.2V)
There is no diode on the emitter in my time delay circuit.
The zener diode must be downstream from the capacitor.
There is no diode on the emitter in my time delay circuit.
The zener diode must be downstream from the capacitor.
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Yes The zener diode is connected directly to the base effectively in series. A total of 6.2 volts that the capacitor must reach before the transistor will be forward biased.
EDIT 1: There is only one zener diode in my circuit.
EDIT 2: Maybe I should post a schematic?
EDIT 3: Schematic added to post 99.
EDIT 1: There is only one zener diode in my circuit.
EDIT 2: Maybe I should post a schematic?
EDIT 3: Schematic added to post 99.
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No need ... 
12 volt zener "in"... relay a clickin.... Drops the collector to a little shy of 1.8 volts now - enough to energize it.
12 volt zener "in"... relay a clickin.... Drops the collector to a little shy of 1.8 volts now - enough to energize it.
I will post the schematic in the appropriate thread later so that everyone can see it.
It's quite a useful circuit that allows a longer time delay for the same capacitor value.
The principle it works on is charging the capacitor to a higher voltage before the relay driver transistor will turn on. The zener diode used in my circuit is 5.6V or higher, but can't be lower than 5.1V because very low voltage zener diodes tend to have unpredictable characteristics at low current levels.
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Thanks for letting me know.
I will post the schematic in the appropriate thread later so that everyone can see it.
It's quite a useful circuit that allows a longer time delay for the same capacitor value.
The principle it works on is charging the capacitor to a higher voltage before the relay driver transistor will turn on. The zener diode used in my circuit is 5.6V or higher, but can't be lower than 5.1V because very low voltage zener diodes tend to have unpredictable characteristics at low current levels.
I will post the schematic in the appropriate thread later so that everyone can see it.
It's quite a useful circuit that allows a longer time delay for the same capacitor value.
The principle it works on is charging the capacitor to a higher voltage before the relay driver transistor will turn on. The zener diode used in my circuit is 5.6V or higher, but can't be lower than 5.1V because very low voltage zener diodes tend to have unpredictable characteristics at low current levels.
I'll probably get this guy halfway back together tonight. Man I am STILL debating on whether or not to bug up the 3 relays needed for the phono section (well.. 2 if you just use MM cartridges...).
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Not yet, Lee... keeping it simple...
...
Until I figure out WTF is up with this damn HUM!!!
I think I am looking at the power supply now.... Tell ya tho it was a testament to those LME49740's and their PSRR rating. Put the originals back in, and damn if that hum/buzz wasn't a hell of a lot worse.
M'fer.... I am going to get at least ONE good decent preamp for ya Kev!!
...
Until I figure out WTF is up with this damn HUM!!!
I think I am looking at the power supply now.... Tell ya tho it was a testament to those LME49740's and their PSRR rating. Put the originals back in, and damn if that hum/buzz wasn't a hell of a lot worse.
M'fer.... I am going to get at least ONE good decent preamp for ya Kev!!
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Yeah, time to regroup a little bit. Thing is ... (and reflecting on it now..) the ONE thing I left in the pre I am working on is the power supply, as I did not want to go back in on the other one I have and knock the volts down. Also recall a few posts back where I had the pre doing pretty good, but then at THAT time about a day later it too had this hum going on.
So I figure... let's grab at least the regulator board out of that other one (unproven.. but at least not THIS board...), modify the output voltage on it, and swap it in.
That'll be tomorrow tho... gotta lick me wounds til then, LOL. Damn Kev.. I am about ready to pull mine off the stack and send that to ya... heheh.
So I figure... let's grab at least the regulator board out of that other one (unproven.. but at least not THIS board...), modify the output voltage on it, and swap it in.
That'll be tomorrow tho... gotta lick me wounds til then, LOL. Damn Kev.. I am about ready to pull mine off the stack and send that to ya... heheh.