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|22nd June 2008, 11:36 PM||#1|
Join Date: Sep 2004
I recently purchased a Hickok 533A as i am getting more and more into tube amplifier repair and building.
I am about to send my unit off to be calibrated and check out and have anything that needs to be repaired, repaired!
The case for my 533A is in rough shape. My father who is retired now enjoys woodworking is going to build a new case for it. But before i give him the final dimensions i am considering some additions and upgrades and wanted to start a thread to talk about several of them and maybe see what others have done.
One website shows a new panel mounted in the upper cord carry slot with a removable power cord and the addition of 3 digital meters. one for Line Set. one for Grid voltage and one for plate current. other testers show other options like test points for every pin, binding post's for insertion of a ammeter for plate current. etc.
I am thinking about doing the same sort of thing in the new case with an upper panel added with a digital line set meter. Probably a 3-1/2 digit meter, but if i can find a 4-1/2 digit i might go with that for the increased accuracy.
I am also thinking about matching digital meters for Grid-V and Plate current but thought of going one step father and adding a digital filament voltage meter as well to check for transformer sag. and two steps further to add test points for all pins, Line V, Grid V, Filament V, and post's with a removable jumper for Plate current. This should allow me to roughly match tubes as well.
I wonder if i could add dual Plate Current and Grid Voltage meters to check both sections of a triode at the same time with the 533A??? Internally it only test's one section at a time so i don't think i can without major modifications. But one section at a time should be good enough.
I am considering changing out the 83 and 5Y3 tubes for solid state rectifiers for increased accuracy and reliability. There is some debate over if this should be done as i have found from website to website. Issues with increased voltage etc are problematic if the Solid state replacements don't take this into account. One eBay seller's adds even clearly shows the differences in readings right on his ad! I don't think he understands WHY the readings are different.
I am interested in discussing the SSR option if others have done it and have experiences good or bad with them.
Does anyone know of a source for replacement roll charts? I wonder how much interest there would be if i could have new charts made?? I have access to a large format inkjet plotter at work and i could easily make new charts if there was demand.
Looking at the schematic of this unit i see that they use a 200 ohm 20 watt rheostat in series with the transformer primary to set line voltage. would there be any advantage to changing that to a small variac? I have seen some small 2-3 amp units that would fit in place.
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