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-   -   MESA STRATEGY BIAS MOD (http://www.diyaudio.com/forums/instruments-amps/223614-mesa-strategy-bias-mod.html)

blackarab 15th November 2012 07:13 AM

MESA STRATEGY BIAS MOD
 
LOOKING FOR SOME HELP WITH ADDING TRIMPOTS AND RESISTOR TO THIS AMP ,NEED TO KNOW IF I NEED 1 OR TWO TRIMPOTS ,VALUES ETC MANY THANKS.

Enzo 15th November 2012 07:22 AM

How about post or link a schematic for this model?

blackarab 15th November 2012 09:31 AM

mesa strategy
 
Hi Enzo thanks for your reply enclose a copy of the schemetic for you ,many thanks.http://www.freeinfosociety.com/elect...trategy400.gif

Simon B 15th November 2012 12:51 PM

1 Attachment(s)
The url given for the schematic is correct, but it won't play nicely unless you've opened the page that references it:

The Free Information Society - Mesa Boogie Strategy 400 Electronic Circuit Schematic

My sprawling collection of schematics inclues the one below.

blackarab 15th November 2012 01:10 PM

MESA STRATEGY 400 SCHMETATIChttp://www.tubefreak.com/fschema.htm

snaggletooth 15th November 2012 08:55 PM

I assume you want to add an adjustable bias circuit. The two resistors in the schematic are not labeled; one between the two caps, and another to ground- form a voltage divider. The bias voltage is determined by the ratio of these two resistors. Look at the resistor going to ground. Replace it with a pot and a resistor, the resistor on the ground side to prevent the bias from being adjusted too low. You will have to figure out the value of the pot and resistor based on the current value of what's in there now.

blackarab 16th November 2012 06:31 AM

Thanks for your reply Snaggletooth ,the resistor to ground might possibly be 22 k does that sound about right would be the one to change ,looking at the schematic to 100k resistors the ground one to be changed is this what you are saying?

snaggletooth 19th November 2012 06:37 PM

Yes, replace that with maybe 10k to ground connected to maybe 50k pot with wiper connected to one side. You may also have to reduce the value of the resistor in the pi filter.


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