Damn it! WTF? Bias Problem

[just42dave]

You need to set the DMM to read the highest DC Volts setting, not millivolts. Ideally 500VDC or higher on the multimeter setting. The plate voltage is going to be a very high voltage, like 400VDC and higher. That's why its freaking out when you're trying to take the plate voltage reading with it set to Milivolts.

Also do yourself a favor and before you fire up again... double check that you haven't ended up with an arc any of the powertube sockets. Look on both sides of the sockets and also the base of the powertubes and make sure there's no black scorch marks anywhere. If there is scorch marks on any powertube, everytime you switch the standby off it's gonna blow the fuse because the carbon scorch mark is acting like a jumper wire and shorting the voltage out each time.

I don't think that will be an issue, but double check it before you use up your last fuse!

Hope this helps man!!

Well it's the Eurotubes bias probe. The instructions say to set the multimeter to 200 ma to read the plate voltage, so that's exactly what I did. I have a Sperry DM350-a digital multimeter

https://www.amazon.com/W-Sperry-DM350A-F ... B000ET5VYC

I set it to the bottom left dial set on 200 m

I grounded the black probe to the chassis and touched pin 3 with the red probe and that's when it blows out my fuse. So I'm a little confused here since the instructions say to set it to test for amps.

Those are teh junkiez!!!Mine did the same thing...Got a real one..
*** said oh it must be the user our bias probes and meters are top notch,,and tubes too congrats man!!!!

 

[MrDan666]

I did it! Holy shit my Marshall sounds great! It was the faulty multimeter the 2nd time. I got a new DMM and it worked like a charm. Hell the tech I've been using hasn't been biasing my amp correctly or something because I'm using the same JJ tubes I've always used an it sounds better than ever.

Shit, I should have learned how to bias my own amps a long time ago. Just to think of all the money I've wasted on techs.

Thanks for all the help everyone, and special thanks to MrDan666 for going out of your way to guide me through the process.

Time to move on to biasing my Shiva now

Fantastic!! Glad to hear it finally worked out for ya!

No problem man, glad to help where i can I'm still surprised the instructions were so vague, i'm betting there's a lot more people who had the same issues as you did!