Sunday, April 2, 2017

Building tube curve tracer, new meter for TV-3 tester and progress on Alto ethernet gateway


Today Ken is at Marc's house collecting more testing data for his ethernet gateway device. I had to meet a drywall service that is doing some work on my home, so I could not be there during the tests. They did discover the small issue that was blocking the Alto from accepting packets sent by Ken's unit. Now he will focus on building up the protocol stack - file serving, ftp and other functions.


I picked up a physically identical meter that will fit into the panel of the tube tester. It features a removable faceplate allowing me to install the original tube tester plate. This will make it appear identical to the original meter.

All that remains is to validate the shunt and series resistance values so that it yields full scale deflection at 200 uA and offers a total resistance of 2365 ohms. That will make it perform the same as the original meter.

I will need to work inside the meter to deal with the series and shunt resistances, which exposes it to the same risk that I will damage the meter during the manipulation. This was how I ruined the original meter during a 'repair'.


I picked up a kit that allows me to fully test vacuum tubes, producing the various characteristic curves and evaluation the gain at a wide sweep of voltages. It connects via RS232 to a PC and features a nice GUI control panel.

The kit is designed with many testing steps as it is constructed, helping to verify each stage of construction before proceeding to add more components. For example, digital power is validated, then the RS232 communications, before installing the microprocessor circuitry. All that must work before the various high voltage producing circuits are installed.

I am gradually accumulating tube sockets, ferrite RFI suppressors, fuses, rotary switches and other items needed to install the tracer into a cabinet and make it fully usable. I haven't settled on a cabinet to put everything into yet.

I have installed circuits and tested up through the negative power supply. After this, I will be working on grid bias, current amplifier and boost converter/high voltage sections. 

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