Restoration and repair to a vintage AVO valve tester. dating from the 1970s But still the finest of its type.
AVO 163 Valve Tube characteristic meter V.C.M. Continued.
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The details of the op amp TL071 can be seen on this site. You can see the amplifier and the new meter being installed into the Avo unit . The mains supply to it is separately fused. Final adjustments to the full scale and zero, and switch on . The results are better than expected, with the measurements compared to the Standardized valve spot on. The old movement has been installed on the right hand side of the Avo for the G/M meter, the inaccuracy here won't matter as the meter is calibrated within the Avo set up. The original scale has been edited on the Macromedia Fireworks program to resemble the original G/M scale 0-20 and 0-6 with the calibration mark The small G/M good / bad scale on the original meter is far to difficult to make, so it has been left undone for now. The Fireworks program is a bit like Photoshop, but much easyer to use.
See the op amp with its power supply being installed in the unit.
Not finished yet, but the project has turned into a super, very accurate piece of test gear. A good search around over time and, I may find 2 matching meters.
Have now fished the remake of the missing G/m meter scale, again using the Macromedia Fireworks program. A pal on ebay kindly took a digital photo of his 163, which I have edited in the fireworks program, on a close inspection it is a bit rough around the edges, but it has not turned out too bad. See below the bits and pieces ready to be assembled.
Have found on ebay another Dymar meter, I've made another op amp and installed it. I have left out the GM scale as I never used it, the meter gives constant readout of GM. I think this one is finally finished now. I am really pleased with the dymar meters they are spot on calibration and excellently engineered.
Avo instrument dust covers, all models, made to measure. If you are interested drop us a line.
