EBAY BUYING TIPS for Hickoks.
1) Buy a good working tester from a seller who is into tubes and electronics, and claims specifically that the tester works well in the here-and-now. Look at the seller's points rating on Ebay. A really good omen is when the seller says they have more than one Hickok, and the one being sold is in reasonable agreement with the others.
2) Don't buy a tester that is recommended by hearsay-like "it worked when my uncle had it 10 years ago" or "Ray the radio guy said it's fine, but I don't know how to run it". Fixer-Uppers will cost more to fix than buying a good one. Instead of buying a fixer upper, drive a 16 penny nail through your big toe. It is less painful.
3) Ask about how well the chart rolls. A good rolling chart makes the tester fun to use--- and good replacement charts are hard to get.
4) If you do buy a tester from a non electronic savvy seller-like an antique or estate seller-try to see in the photo if the front panel screws are there. If most of the screws are gone it means that somebody knowledgeable looked inside and decided the tester was SHOT and there was no point in bothering to put all the screws back in. Avoid like monkey plague.
5) Testers with crumbling line cords can be worth a gamble. If a non-electronic seller says they are afraid to plug it in because the cord is coming apart, it may be a tester that has just honestly sat for 25 years.
6) Get a guarantee of basic serviceability from your seller.