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In Reply to: RE: Hickock Plate Voltage Measures High posted by unclestu on August 06, 2014 at 12:06:22
Although not familiar with the 600 specifically, don't most if not all Hickoks have a line adjust control and a "line" position on the meter so that line voltage isn't an issue?
Follow Ups:
yeah but usually it seems to affect filament voltage more and it is used to compensate for heavier current draw with larger tubes.
The line adjust affects everything. It is in series with the AC line.
My 600A has around 190VDC plate voltage also. I believe that was a design change that was made when they went from the 600 to the 600A.
Hi Al - That explains it. I knew the line adjust affects all the voltages, the puzzle was why all of them were close to spec except the plate. Actually, at first, I thought the Grid Signal Voltage was off too - I was getting ~2.5vAC instead of ~5vAC - then I read that this was a change made in the later versions of the 600A. The later versions also have a function that reduces the Screen Voltage to 56v with the push of a button, which mine also has. Apparently, at some point, they also increased the Plate Voltage, bringing it closer to actual operating voltages.
The voltages in mine are still just a tad high with the line adjust set, but they are consistent with each other. I'll just need to either adjust the meter a bit or compensate when I test tubes. While I realize that all testers have their limitations, I'm looking forward to having a "better" tester. I will still use the Eico 666 too - one of its advantages is that it tests interelement leakage directly - but I've always been frustrated by the numerous errors and conflicting set up data contained on the Eico's various charts. Perhaps there are errors in the Hickock data too, but I think they were in wider use and most of them have probably been spotted. Mine came with a couple of extra roll charts - earlier ones I suspect. I was also able to find and download a compilation of setup data that includes "obsolete" and foreign tubes. Lots of good Hickock resources online.
Thanks again for the info about the Plate Voltage!
. . . Charlie
Al - Well, functionally you were right, there is no problem with the ~190v reading but it's not because they changed it in later versions of the 600A.
I failed to mention that I didn't follow the testing procedure exactly (DOH!) in that I used a DMM without adding a shunt resistor. The instructions suggest a 250k "in parallel with the input" when using the 250v scale. Does that mean it's connected between the red and black meter leads??
I found the info on the Antique Radios forum at the link below.
. . . Charlie
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