Pultec Eq Power Supply Question

Status
Not open for further replies.
Jump to Latest
Y

yan6

Member
Joined 2008
#1
Hi there, I'm looking some options on a pultec eq with a tube make up stage that I'm building. It looks like I mis-spec'd the power transformer as it was supposed to have a 220v-250v and 9v secondaries. I chose a Edcor XPWR152-120 which has 235v and 6.3v secondaries. The issue is with the 6.3v; my circuit is looking for 6.3v dc as the heater voltage and is using an LM317 to regulate. My problem is that I obviously dont make enough voltage to regulate down to 6.3v.

Is there anyway to connect it to the heater directly from the B2 bridge rectifier to the heaters. Maybe through a voltage divider to drop some off?

The tubes are ECC88 btw

Power Supply.png
 
#2
yan6 said:
Is there anyway to connect it to the heater directly from the B2 bridge rectifier to the heaters.
Click to expand...

Yes, substitute a single series power resistor for the regulator.
Delete the other resistors and the smaller capacitor.
Keep the 4700uF capacitor.

The heater needs 365mA. Divide the voltage drop by 0.365A for
the resistor value.

Multiply the voltage drop by 0.365A for the needed power dissipation,
but multiply that by 2 or 3 for derating.

You may need to adjust the resistor's value a little to get the
filament voltage close enough.
 
Last edited:
#3
How much 6.3 VAC current is available? If lots of 6.3 VAC current is available, you can "full wave" voltage double it and then regulate to 12 VDC. Series wiring the ECC88 heaters allows 12 VDC to "save the day". Use Schottky diodes in the doubler, for their low forward drop. 1/4 of the 6.3 VAC RMS current is available as DC.
 
Status
Not open for further replies.
Top Bottom