Help a Newbie with Tube Amp

[shadowlight]

Hello,
I have never owned a tube amp (recently picked one up) or a multimeter before and need some help guidance on how to use the multimeter to set the bias.  I picked up the following from Home Depot yesterday - MS8260A.

Here are the steps that I followed:

• Plugged the red cable into mA and black one into COM
• Set the dial to 200m under the V on the right side with underline and dots
• Plugged the pointy end of the black cable into common on the amp hole number 3 which is common and the red on into pin/hole 1
• slightly turn the bias dial clockwise until the correct value is shown

When I turn bias dial the value does not change on lcd, which leads me to believe that I am missing some step or have no business using multimeter  

[AcidJazz]

Deepak, if its the Jolida...you measure mV, not mA.
Move the red lead to the V.

[shadowlight]

Deepak, if its the Jolida...you measure mV, not mA.
Move the red lead to the V.

Figures 

Thanks Martin.  Will try that tonight.

[richidoo]

Deepak, congrats on your new amp! As you're learning, tube amps can be so much fun!

Since you were flying blind and may have left the bias set too high, connect the voltmeter before start up so you can watch it rise from zero and prevent it from exceeding the recommended value.

Tubes can tolerate a few seconds of too high bias, but if it overheats then it starts drawing more and more on it's own, aka runaway tube, which will not last long. This might occur after 30 seconds or a minute if the bias was double or more of the recommended value.

I like to turn the bias all the way down before changing power tubes. Use a meter to watch, or make sure you remember if down is counter clockwise.

Have fun!!

[shadowlight]

Thanks Rich.  I was watching the meter and only turned it slightly.  Was scarred to blow something or getting electrical shock (I am terrified of power tools and electricity)

[richidoo]

Wise man! Tubes need some extra respect, but with a little knowledge they are very safe. Even if it breaks, usually a new tube and a fuse is all you need to fix it yourself. It's a good idea to have an extra tube (or matched pair if required,) along with spare fuses so you can fix it immediately instead of waiting for parts to be delivered. But in a pinch you can get tubes at any guitar shop and the fuses at hardware or home center.

[Putz]

Which Jolida? I have the 502 BRC Integrated which has the built in bias (Turn the screw until the red light don't blink no more).

[shadowlight]

Which Jolida? I have the 502 BRC Integrated which has the built in bias (Turn the screw until the red light don't blink no more).

Response Audio 3205 which has pins bias slots marked 34087.

[shadowlight]

Deepak, if its the Jolida...you measure mV, not mA.
Move the red lead to the V.

Figures 

Thanks Martin.  Will try that tonight.

no luck.  someone want to stop by and show me how to bias and use the multimeter    maybe i should just pickup a cheapo one that is easy to use

[etcarroll]

Deepak with a multimeter and electricity - oh, the humanity!!!!

http://www.bing.com/videos/search?q=how+to+bias+tube+amp&qpvt=how+to+bias+tube+amp&FORM=VDRE

[shadowlight]

Deepak with a multimeter and electricity - oh, the humanity!!!!

http://www.bing.com/videos/search?q=how+to+bias+tube+amp&qpvt=how+to+bias+tube+amp&FORM=VDRE

I watched couple of those but the numbers on the lcd does not move away from .000  .  Maybe the probes are not making the right contact.

[shadowlight]

The amp is up and running.  Thanks everyone.  Martin pointed out I need to push the pointy end all the way in until it snaps in, which I was not doing before.  ce I did that the numbers started to move but it still took quiet a bit of turn to make it move.  All the tubes are glowing around the same brightness so I think I have is set correctly and the numbers were hovering around 34.9 and 35.2 for el34 tubes.

[AcidJazz]

 Hey Deepak, good to hear you got it to bias.
Which EL34s are you using? Stock?
Since the amp and tubes are new, keep an 'eye' on the bias levels for the first couple weeks. Sometimes they drift depending on the tube...however I found the stock EL34(Svetlana, as supplied by Bill) to be quite stable.

I have more suggestions in regard to this amp, but you should 'live' with it stock for a while before chasing the tube roll enhancements.

Enjoy the tube sounds. 

[shadowlight]

Yep, the EL34 are stock Svetlana.

[etcarroll]

The amp is up and running. 

Good news - enjoy!