Hello Neil, Would this be an 8-77 tester, and not a 7-88 ? I take it that you have already been to the Pacifictv web site to get the pdf of the schematic. Shame there is no manual posted. Without any fellow members stepping up. You might want to ask Glendalemaunals on E-Bay.com if he has one available. Maybe the demand is so little, he does not post one as available. Looks like it is identical to a Hickok 6000
https://www.ebay.com/str/glendalemanuals?_trksid=p2047675.m3561.l2563
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313&_nkw=stark++tube+tester+manual&_sacat=0
https://www.usaudiomart.com/details/649029938-stark_877_mutual_conductance_tube_tester/images/507899/
http://www.pacifictv.ca/wanted.htm#testequip
Tony
