Its been a while since i got around to this project, here is a progress reports of sorts.
The G1 regulator in the form of a shunt regulator has been tested and works as its supposed to. Given that i am planning to do a lot in the analog domain, i thought it better to forego the digital control for the time being. This allows me the space on the 160x100mm boards to do a completely through hole single layer layout so i can etch it myself (and anyone else for that matter)
Given that the unit essentially consists of four or five adjustable power supplies, that need a signal to set their output voltage, and have a return voltage reading and current. My idea was thus to keep the digital sorcery out of the power supply boards and instead use a number of differential pairs to send and receive the analog signals, one could then simply control the entire unit with one card instead of a digital add on circuit for each of the cards. this also allows me to delete the +5V bus. Freeing up two pins on the connector.
The modules themselves will have connections for a ten turn control pot, however including the panel meters on the same front panel is a no-go. because the current panels are 8TE(~40mm) wide. which doesn't allow enough space for a 4 digit 13mm 7 segment display. Using wider panels is out of the question because i cannot etch a backpanel PCB large enough to accept more than 20TE. And having a PCB beyond 100x160mm made is extremely expensive in small volumes.
The interface card that interfaces the supplies with the test fixtures will feature the relay matrix and current sense circuitry needed to run through the different insulation measurements.
Pin connections as it stands.
8 pins (3 through 12 are reserved for the supply outputs) Allowing multiple anode, G2 or G1 regulators in one system. The filament supply board will feature a different H15 connector from the 31 Pin Din connector.
8 pins will be differential pairs, that feature a 2.5V positive offset, this because it simplifies grounding issues a lot. Full scale voltage levels will be 5V. as will the reference voltage.
3 Pins for ground,
Two for +-15V two for +-100V
two pins for external control of relays. this leaves two for adding other options later.
Ive decided to get to work on some of the fixture PCB's required, these are all based on the standard template that i have created in my CAD program. They are wired for specific footprints, or even types. there is the option of building a complete RC coupled amplifier on the double triode boards for measuring Hum and amplification in a real world circuit. Designing a new board for a specific type takes me about 20 minutes. The boards for the dual triodes can accept the entire ECC series and equivalents including the 88 because the sockets are wired manually.
they are designed to accept two identical tubes because i intend to re-use the design in another project. Two pins of the board feature the sense lines for the low voltage heater supply to compensate the voltage drop over the cables.
I've also had some made in china at about 40p each excluding shipping. the silkscreen is a bit messed up because i intended to place all components on the bottom side.
I've also built a +-15V supply card using two 7815 in TO-3. The connector is a H15 connector. the same i intend to use for the heater supply card.
Last but not least, i had a go at making a standard Backpanel this one will be used for testing and checking mechanical dimensions, the final version will feature 6 slots, spaced at 4TE appart, about as large as i can etch with my setup.
