Musicians Roadhouse

hello i want to bias my tube amp marhall haze 15 watts.....can u tell me the factory settings pls...........for biasing that amp......and is it the marshal ahze 15 watts have a 1ohm trim pot or variable resistor???

According to our Service Dept; -

Haze 40 = 39mVDC

Haze 15 = 29mVDC

When taking measurements across a 1 Ohm resistor, millivolt readings on a multimeter equate to milliamps, so, if you measure 29mV at the bias test point, that means there are 29mA flowing through the 1 Ohm resistor that voltage is measured across.

Just picked up a used Haze 15 full stack, all original tubes, those black 6V6 with the marshall badge, surprised to see all 3 preamp tubes with the red lettering and coding to all be JJ's. I used my Weber Bias Rite. The bias was 13+ for V4 and 18+ for V5, the plate voltage was reading around 368. I took the 29 and halfed it as 14.5 per tube and set it there the plate dropped to 354. I used a calc I've seen on the net, watt/plateVolt * .80 = bias. So 6V6 = 14 watt tube / 380 * .70 = .028. Now the haze is not a 28 watt amp so 1/2 of 15 is 7.5 per tube so I set the bias at 14 on each tube.

Will try some other tubes.

Question - With a bias adjustment pot for each tube is it true that a balanced PI in not needed and a match set of tubes is not needed?

If the above is true could I then use different brands of 6V6's say a JJ and a TungSol?

If I have a balanced PI and a matched set would I be better off with those ?

Btw the Haze 15 is a nice little beast great classic rock tone

Yes, you could use miss matched 6V6s because of the separate bias controls.

Jamesm
=0^0=

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