I was wondering if anyone has had a tube tester upgraded and/or calibrated. I've got a Hickok 6000A tester and it still has the old mercury vapor diode tube. I've seen solid-state replacement plug-ins, but I've been warned that these can throw off the calibration of the tester. Has anyone had their tester modded and if so, did it need recalibration? Who would you recommend for this work? I can replace the capacitors and such, but recalibrating is a different story...

Thanks!

You can replace the capacitors, keep the values very close to the same as what came out of the machine. It is important to replace the capacitors, old capacitors in some cases can short out the transformer, destroying the tester, beyond repair.
Tube testers are not 100 percent accurate anyways, and does not tell you how good the tube will actually work once back in the amp or TV it goes into.
So, I would not be to worried about calibration at this time, best recap first and keep the mecury vapour diode tube in place for now.

By all means, don't solid state a hickok.