Bias adjustment in Cary SLI-50 integrated amp


I purchased a Cary SLI-50 integrated amp in 1997 and recently replaced the output EL-34 tubes, which requires bias adjustment. The amp has two bias adjustment jacks but does not have adjustemnt screws, like the latest model - SLI-80. I don't know how to make bias adjustment. I can insert a multimeter but cannot make an adjustment, because there are two grey round-shape plugs each located near the respective bias adjustment jack instead of adjustemnt screws.
Can anybody advise me how to make an adjustment?

Best regards,
Alexander
kolegov2bba
You MUST call Kirk at Cary--, I did when I had questions about my Cary bias adjust. Go straight to him or their FAQ on their site.
You can contact caryaudio.com, and leave a message on their website. You can call 919-355-0010. It does not matter whether you bought your unit new, or whether it is still under warranty. Their customer service is the best. It will be the day before Christmas, so call early in the day.
The SLI50 is an auto-bias and requires no adjustment after replacing tubes.