How to bias a tube amp with a Multimeter

The amp is fully operational. It works just fine. However I’ve not been able to get the MM to function. Yes, it appears to be operating fine in the above ^ example. But it’s not registering any readings when placed at the bias points.

Tubes are already in and warmed up. That was a photo taken without tubes. Thx 

@larryi yes, and the bias points are so close I can barely get the tips of the MM onto them! I don’t know what to make of the screws,

I tried searching for a manual for the amp with no success.

yes, speakers are connected, and the amp is fully operational. No there is no incremental mV adjustment on the MM

@freediver yes I’ve tried turning each pot, and still no reading on the MM. I’m afraid I have to take it to a technician, which means a 45 minute drive each way. Oh well!

Yes, probes are properly connected. 
 

I was just quoted $130 to bias the amplifier. But I’d have to wait 4 weeks to have it done because of other jobs ahead of me! Argh. 

@freediver excellent points all around. I requested a later tech I contacted that I’d need to be instructed how to bias the amp from the bias points. He accepted that. 
 

Since I don’t have a manual, and haven’t found a pdf on the internet I’m kind of at the mercy of someone who has knowledge. I’ve been running the amplifier for several hours without any runaway tubes, but don’t won’t to run the risk of having that happen, and simply operating the amp without knowing the status of the current bias seems a bit foolish. 

@larryi @freediver thanks for your suggestions. I will try adjusting the MM, and the screws on the amplifier tomorrow to see if I can get a reading. Thanks for your assistance!

@larryi okay, so how do I set the multi meter to display Milliamps? No, I didn’t turn what appears to be the small screws. Are you suggesting to turn the screws while hoping the MM on them at the same time? If that’s the case, what of the larger outside screws?

That’s what I thought was the way to raise or lower the voltage.

I know from several owners of the S8Mk that it’s correct bias point should be between 35-40.

Sorry, an electronics technician I am not. In fact, I’ve never attempted to bias any tube amp that didn’t possess a meter and a clearly defined bias switch to determine which tube I was trying to adjust. With no manual I’m flying in the dark with this amp.

@freediver thx for following up. I’ve a new MM arriving today. I’ll report back