Question on Tube Swapping and Biasing

Thanks, super helpful response. I've unplugged the amp, and will wait until I have a multi-meter to check bias before I power it up again. From your advice it appears I can't really rely on a technician to do the bias check, as it really should be checked on a regular basis. 

Any multi-meter you would recommend? 

Apparently there is no Service Manual for the Luxman MQ-88se. I contacted Luxman USA and they sent me the following: 

Bias Procedure for MQ-88uSE

WARNING * SHOCK HAZARD * This procedure should be performed by a qualified technician only.

Main body, just in front of LR output transformer, there are 3 points where you can insert tester leads.

The center point is for the ground, left and right points are for Left + RightKT-88 test points.

Please insert tester lead in the center point and left point, then using an insulated Phillips head driver, adjust the left potentiometer as needed.

The value should be 0.48V (480mV) +/- 5%, please adjust if needed.

Repeat procedure for right points and right potentiometer.

It is good practice to check the bias on the other set of KT-88’s to be sure they are within 5% of the specification.

Great, thanks!

As is usual with Luxman this is all they have to say about it in the manual "When repairs and adjustments are needed, please consult 
with the dealer where you bought the unit." since they'd really rather have you not messing with it.

FYI, bias is a moving target. Knock your brains out trying to get it right on the money then blink. In theory a matched quad is all you all you need to do but the primary caution is not having a single tube or tubes drawing significantly more current than any of the others. Other than that, the bias is likely to be all over the place at anyone given instant and is nothing anyone with a tube amp should ever obsess over.

Your JJs are probably still just fine and unless you have any particular indication that things are not as they should be, you should leave them alone.

Thanks for your suggestions. Obviously there's a variety of opinions on how to approach this! 

From a dealer / manufacturer point of view, they obviously want to err on the side of caution and recommend that you use a professional audio repair shop to carefully check the bias on a regular basis. So I suppose that's one end of the spectrum. 

I was told by the Luxman guy that, since I stupidly removed the original JJ tubes without noting which one went where, if I out them back in I'd have to bias the JJ tubes all over again. The Gold Lion are indeed a matched set. So technically I need to bias the tubes. 

Then again, I've had the amp 5 years without worrying about bias at all. I'm sure it's changed over time. 

Have to say, I'm more confused than before!