Knight Kg-600b Tube Tester, Fully Serviced, Calibrated, Manuals & Paperwork

US $360

Saint Paul, Minnesota, United States
Jun 20th

Open on mobile:
QR code

This Knight KG-600B tube tester is in very good physical condition (there are some small spots of rust along the edges; nothing to worry about; see photos). It has been fully serviced and calibrated and it is working as designed. Servicing included the following: All but one of the resistors were replaced with 1% modern parts. The one that was not replaced is a large power resistor that tests just fine and doesn't need replacing. All controls and sockets were cleaned. All sockets that can be retensioned were retensioned. All of the original knobs are included in this sale, but I have installed a higher quality knob for the A-Circuit selector switch with a metal insert and two set screws rather than the cheaper all plastic stock knob. The reason I did this is because the original knob is showing a hairline stress crack and it wasn't grabbing the shaft firmly enough. The new knob works perfectly. The tube socket complement on this tester covers an impressive range of tubes, including: 4 pin 5 pin 6 pin 7 pin 8 pin octal 8 pin loctal 9 and 10 pin like the various dual triodes and even the rare tubes with a 10th pin in the center 9 and 12 pin compactron This unit was purchased at the Pavek Museum of Broadcasting here in Minnesota. The Pavek probably got it from the estate of the original owner. I say this because all of the paperwork for this tester is present including the letters the tube chart updates came in! It's neat to see the old 6 cent and 8 cent stamps and the old literature and advertisements from the supplier. I buy and sell tubes for a living so most of the time I use a pair of Amplitrex AT1000 testers to screen tubes. Since the Amplitrex testers measure tubes against the manufacturer's specifications in the tube manuals, this gives me an easy way to evaluate vintage testers I work on. I can take a tube that measures as the manufacture intended and compare it to the results I get from the tester currently on my bench to see how it compares. I can also evaluate the tester with known marginal tubes and known bad tubes. Here are some notes based on this: 6L6 tubes that check at 100% of spec check within 5% of 100 (full scale reading) on this tester. A very weak 45 checks low in the reject section on this tester. A marginal 45 tests in the low range of the good portion of this tester. A new production GZ34/5AR4 tests at full scale on the meter 5Y3's seem to have a roll chart error. The chart shows 48 on the first section for the C-load and 31 for the second section. The other rectifiers, even other directly heated types like the 5U4 and 5R4 show the same setting for both sections. The 48 section gives what appears to be the more accurate reading. On the 48 settings, a new testing 5Y3 with balanced sections reads about 75 which is near the middle of the "good" zone. 12AX7's can be screened for shorts and failed filaments on this tester. But both strong and weak 12AX7's check about the same (close to 100% full scale), so you can't meaningfully check for matched sections or relative strength. Just a basic pass/fail. 12AX7's only pass about 1mA of current in normal operating conditions so a checker like this is probably not refined enough to see much difference between 0.5mA vs 1.5mA. Of course, with a 12AX7, that's the difference between a weak tube and a stronger than expected tube (1.2mA being spec on vintage tube data sheets).