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Old 4th August 2012, 09:34 PM   #721
woodturner-fran is offline woodturner-fran  Ireland
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If you think of it as 3 different supplies:

1 x 300V
1 x 6.3
1 x 6.3

The 300V gnd and the 6.3 gnd are connected together.

The elevated heater GND is not connected to the same GND as the other 2, but rather to a point on the HV supply so that it actually floats at ~1/3 the B+. This point is made by the 2 resistors on the bottom of the PSU sch (220K, 470K). So even without the heater connected, testing voltage at this point should give you 1/3 B+. The bypass cap in parallel with the 220K stops hum.

Post a pic maybe too?


Fran
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Old 4th August 2012, 09:56 PM   #722
Salas is offline Salas  Greece
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Valve Itch phono
1/2 B+ in the revision actually (same value resistors as in yours too).
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Old 4th August 2012, 10:33 PM   #723
woodturner-fran is offline woodturner-fran  Ireland
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Yes - forgot about that, thanks Salas.
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Old 5th August 2012, 11:19 AM   #724
merlin el mago is offline merlin el mago
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When I connect the 150V dc elevated heaters to gnd heaters the voltage drops to 0V
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Old 5th August 2012, 11:32 AM   #725
woodturner-fran is offline woodturner-fran  Ireland
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The 2 heater circuit gnds do not connect together....

"low" heater gnd connects to main circuit circuit gnd only
"high" heater gnd connects to 150v point on hv power supply only
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Old 5th August 2012, 11:43 AM   #726
merlin el mago is offline merlin el mago
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Quote:
Originally Posted by Salas View Post
For the top halve of each totem pole only.
Fran if I understood Salas 150V goes to gnd heaters of valves V3 & V4 right? not to +6.3 heaters?
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Old 5th August 2012, 12:07 PM   #727
woodturner-fran is offline woodturner-fran  Ireland
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Yes, connect the GND of the heaters for V3 and V4 to the 150V point on the HV supply. Those heaters do not connect to "normal" or circuit GND at all but that heater then "floats" above ground.

If this is done correctly, then using the DMM, measure:

Circuit GND to elevated heater GND = ~150V
Circuit GND to elevated heater POS = ~156.3V
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Old 5th August 2012, 03:31 PM   #728
merlin el mago is offline merlin el mago
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Fixed the issue was connected heater gnd to chassis gnd instead to leave floating, now I have the heaters elevated to 150V
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Old 5th August 2012, 04:32 PM   #729
woodturner-fran is offline woodturner-fran  Ireland
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Good work merlin!
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Old 5th August 2012, 08:12 PM   #730
merlin el mago is offline merlin el mago
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Thanks Fran.
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