Tube amplifier - tube bias and time to warm up

Just speaking generally on push-pull tube amps: 0 mA is perfectly safe, unless the bias reading mechanism is severed (very unlikely) and it’s not actually sitting at 0 mA. In any case, you would see the KT88 plates start to glow orange (usually a large oval patch) and then cherry red as your final warning to quickly SHUT DOWN the amp.

The bias comes up slowly, and you should start to see some reading after a minute or 2. It will increase gradually from there before hitting stability (after ~ 10 minutes as per the manual). But looking for something at 15 - 20 seconds is way way too early.

I’d give it a few minutes, then start adjusting the screw to increase bias until you see a non-zero reading. If you go all the way to the spec’d mA bias early on, it will get too hot later on. So start low and gradually increase. Just keep checking and adjusting (iterate) so it doesn’t run away. You’re a human servo lol. If you’re in trouble you will see the plates glow as your warning. After 10 - 15 minutes do a final adjustment and enjoy.

If it’s using a trimpot you don’t want to overuse that mechanism, so don’t make biasing a daily or even weekly occurrence.

I scanned through the manual and it looks like there's just 1 bias adjustment / reading for all 4 KT88 tubes (cumulative). That probably means you need to stick to tightly matched quads. 

I agree with mulveing, Check your manual and you will probably find that it has  automatic muting on turn on to protect it tubes. With my amps I let them warm up for a couple of minutes, then set the bias, let them run for about 20 minutes and check/reset the bias as necessary. Then I check the bias the following day after running the amp an hour or so to make sure the tubes hold their bias. If they do I check the bias about every three months.

To use a multimeter in the current mode it must be in series.  voltage probes are in parallel.  very few people have ever used a multimeter in current mode.

Bias currents are very seldom set in the current mode.  Generally there is a 1 ohm resistor in the circuit so if you read millivolts across the resistor, that equates to milliamps.  very convenient.  

Sounds like this one wants you to put the meter in the circuit.  Is there a jumper you remove and put the meter in it's place?

Ok so with all of that discussion, my point is that most likely you don't have the meter set up correctly.

You imply that you get sound out of the amp.  You would get no sound if bias was really at zero.  

So if you're getting sound, then the bias is not zero and you have a meter problem.

Jerry