Crack in base of output valve should I test in amp see if it works or is it too risky

kipple

I recently bought 2 output valves 6l6GC both work fine, The Seller said he would include 2 spares and stated condition unknown as he had no way of testing them. both were 6l6GC and both have a crack in the base. The valves seem physically stable the glass part is not loose or wobbly  in the base but I'm not sure about putting them in my amp to test them to see if they work as I don't want my amp going tits up.  Should I just leave them well alone or give it a shot. I can put them in a bias meter when the amp comes om see if they go ballistic but I'm wondering if they might blow something in the amp soon as I take it off standby
See one of them in the pic they are both Sylvania 6L6GC 
https://i.imgur.com/H61qvNs.jpg

ICBM

They'll be fine, the plastic is an entirely non-functional part of the valve other than just to hold things in place. They do go brittle with age eventually - or heat, but there's no sign of overheating on the plate, you would see a discoloured area if it was that.

kipple

ICBM said:

They'll be fine, the plastic is an entirely non-functional part of the valve other than just to hold things in place. They do go brittle with age eventually - or heat, but there's no sign of overheating on the plate, you would see a discoloured area if it was that.

Ok thanks that's good to know as I paid for 2 and had the other 2 for free. I tested the 2 without cracks and they sound really great.
Cheers Ian