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Found the problem(s). Had tested the tubes some years back on an old emissions tester I have, and they looked "good". Picked up a Philco 7052 Mutual Conductance tester about three years ago, and finally got around to replacing one paper capacitor, and one electrolytic, and checking/calibrating it. The 7052 is just a re-packaged Hickok 533A, so tube data and components/wiring are the same.
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Went back to the 130 this evening and checked all the tubes on the 7052 (except the rectifier and VR tubes as the voltages look fine). Lo and behold there were one 6U8 out of spec. (weak, one of the buffers), and V70 was severely out. Since V70 is the multivibrator, I suspect that was the major issue. V110, a 6BH6 is the Guard Voltage tube, and it also proved to be weak. I was fortunate enough to have a sleeve of NOS 6U8A tubes in stock, plus a very strong 6BH6 used tube. Replaced these tubes and the meter will zero with ease and no longer has the wild swings. After about 30 minutes warm-up, it stabilizes quite well. With a little luck, I will try to calibrate it Wednesday or Thursday. Thank you all for the guidance. On 3/22/22 08:55, Albert Otten wrote:
Jerome,The procedure for adjusting the variable osc. is:The Factory Calibration calls for 20 degrees. But remember that this is merely a preliminary setting before further tuning of T1 is done with the S-30. If the latter works (meter can be zeroed in the iterative process) then the initial setting (degrees) was simply OK. |
