Hi, I‘m working on a Bogner Shiva 20th Anniv. and need Informations on the setting of the small orange trimpot on the separate heater pcb. There‘s no schematic of the Shiva‘s power supply available. Thanks for Informations, hints and help
Zouto
Bogner Shiva heater trimpot
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Stevem
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Re: Bogner Shiva heater trimpot
What makes you think it needs to be adjusted?
Are all the heaters, or maybe the preamp heaters powered by DC?
Are all the heaters, or maybe the preamp heaters powered by DC?
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Bogner Shiva heater trimpot
I run thewould start by measuring the heater voltage on the tubes.
There is a plethora of schemes for heater supplies. Some are:
> run them all on AC, grounding a heater winding center tap
> run them all on AC, but making a "center tap" by stringing resistors across the AC winding
> run them on AC but use a pot to adjust the "center tap" for lowest hum
> run the power tubes on AC, but make regulated DC for the input tube, or several front end tubes
> run some or all tubes on AC, but elevate the heater AC on top of a DC voltage for lower hum
With no other information, you could be looking at items 3, 4, or 5. If the input tubes' heaters run on DC or have a DC offset above ground, the pot probably adjusts the DC. If it's a small trimpot, it's unlikely that its item 3, the variable centertap.
Once you have more info on how the heater voltages work, adjusting the trimpot should be simple - either adjust for nominal heater voltage across the heater connection of any tube not run on strictly AC, or adjust the trimpot for minimum hum while watching the voltage across the heater pins that it adjusts.
There is a plethora of schemes for heater supplies. Some are:
> run them all on AC, grounding a heater winding center tap
> run them all on AC, but making a "center tap" by stringing resistors across the AC winding
> run them on AC but use a pot to adjust the "center tap" for lowest hum
> run the power tubes on AC, but make regulated DC for the input tube, or several front end tubes
> run some or all tubes on AC, but elevate the heater AC on top of a DC voltage for lower hum
With no other information, you could be looking at items 3, 4, or 5. If the input tubes' heaters run on DC or have a DC offset above ground, the pot probably adjusts the DC. If it's a small trimpot, it's unlikely that its item 3, the variable centertap.
Once you have more info on how the heater voltages work, adjusting the trimpot should be simple - either adjust for nominal heater voltage across the heater connection of any tube not run on strictly AC, or adjust the trimpot for minimum hum while watching the voltage across the heater pins that it adjusts.
"It's not what we don't know that gets us in trouble. It's what we know for sure that just ain't so"
Mark Twain
Mark Twain
Re: Bogner Shiva heater trimpot
Thanks for replies. It‘s a somehow complicated switching heater and relay supply for 12.6 Volts DC, no schematics or instructions available. It had some issues with the relay supply and a shorted flyback diode, but now I set the trimpot for 11.98 Volts DC and the Amp is working again.