490v to 400v dual tap no sound!

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herbvis
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490v to 400v dual tap no sound!

Post by herbvis » Tue Apr 24, 2012 5:57 pm

I have a 2203 metro kit with the MM MP100-460 POWER TRANSFORMER with optional 400v taps. I hooked them (the 2 brown wires) to the appropriate tabs on the standby switch, but get no sound when powered on. I assume something needs to be changed in the bias circuit. I currently am running 6550 power tubes. Amp works fine on the normal 490v taps. Any help is appreciated

General Power tube voltage with 400v taps

pin 4 11
pin 5 -34
pin 6 11
pin 7 3.15

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herbvis
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Re: 490v to 400v dual tap no sound!

Post by herbvis » Wed Apr 25, 2012 1:12 pm

Anyone? :shrug:

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toner
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Re: 490v to 400v dual tap no sound!

Post by toner » Wed Apr 25, 2012 3:13 pm

I couldn't find info for a dual voltage version of that PT so this may not help...

However, you're obviously not getting high voltage from the secondary. Either the "2 brown wires" are not the correct taps or they are not wired correctly. Are you using a 3 position standby switch to allow for dual voltages? Have you measured AC voltage on those brown wires?

Bias voltage has nothing to do with it at this point.

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Re: 490v to 400v dual tap no sound!

Post by herbvis » Wed Apr 25, 2012 3:58 pm

Looking at the diagram, the brown wires are 9v accsessory wires. I assumed they were 400v taps like the metro trannys have. I believe that would be my issue. If thats the case, what would 9v accessory wires be used for?

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toner
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Re: 490v to 400v dual tap no sound!

Post by toner » Wed Apr 25, 2012 4:26 pm

herbvis wrote:...what would 9v accessory wires be used for?
built-in tube screamer? :P Sorry, I couldn't resist! I don't know. ???

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herbvis
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Re: 490v to 400v dual tap no sound!

Post by herbvis » Wed Apr 25, 2012 4:36 pm

toner wrote:
herbvis wrote:...what would 9v accessory wires be used for?
built-in tube screamer? :P Sorry, I couldn't resist! I don't know. ???

Haha! I was wondering about a built in isp noise decimator :D :lol: Looks like I will go the zener diode B+ dropping route

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