Got my hands on a used Advantest R6145 voltage/current source. These things are pretty unique. Not really usefull as a general purpose supply but very high quality and precision. The machine is essentially either voltage source with programmable current limit , or a programmable current source with a voltage compliance control. The output is fully push-pull and bipolar so in essence this thing works in all four quadrants.
built by advantest in Japan these sources are typically found in big ATE racks to test semiconductors. At 100$ in ebay this one was to good to let pass by.
Advantest is right up there with Agilent and Keithley when it comes to this kind of 'whacko performance' kit. Plenty of semiconductor manufacturing plants use large advantest macines to production test very complex mixed signal devices.
A brand to keep an eye on on ebay !
The machine was crusty on the outside. almost like it has sat under someone's turky fryer. coatedin sticky smelly cooking grease. A good wipedown with a mixture of soapy water followed by a polishing with hand sanitizer gel ( which is essentially 80% IPA mixed with a gelling agent and some glycol) restored the case and front panel to a clean state.
The guts themselves were sparkling clean. Not a speck of dust in sight. so this thing most likely spent its operational life in a class 10 cleanroom.
The beastie powered right up and still is spot-on. It offers several ranges. At the lowest voltage range (-300 to 300mV) you can adjust the output in steps of 10 microvolts ! At the highest range ( -60 to 60 volts) you still get to play in steps of 1 millivolt. Very respectable precision.
Current mode offers three ranges as well with the lowest range (-3 to 3 milliampere) offering a resolution of 100 nanoAmpere ... the highes setting (300 to -300 mA) is adjustable in steps of 100 microampere with max compliance voltage in the 60 volt range.
the machine can create , besides constant levels, burst pulses with two programmable levels, staircase or staircase bursts with a programmble amount of steps and levels. this supply has external sense lines as well as a guard terminal for when you are playing with precision stuff. The control loop time constant is programmalbe to dampen oveshoot.
This thing has some killer spec's ..
Output 1 Max. power: 10 Watts
Output 1/Range: 1 Max. Current 300 mA (300 mV to 60 V)
Load Regulation, Voltage: 0.0000024 mV
Load Regulation, Current: 0.0000000012 mA
Line Regulation, Voltage: 0.0000018 mV
Line Regulation, Current: 0.00000003 mA
All in all a very nice machine. i will finally be able to drive an LED without needing a series resistor
Picture time :
the frontpanel
the output terminals
300 milliamp range
3 milliamp range
60 volt range
300mV trange
The guts.
on the left front a classic power transofrmaer that makes +80 and - 80 volts DC post rectification and smoothing.
above that sits an HC 6303 cpu based (hitachi core) with a timer counter, TMS9914 for the GPIB a 32K eprom and a 8K static ram with 3.6 volt battery cell. The ram holds the calibration constants. Battery measured good. i need to take a ram dump through GPIB as i have no means to calibrate this kind of machine myself. I verified this machine against a calibrated 3458 and it is pretty much spot on.
The CPU section crosses a bundle of optocoulers into the control logic section.
The top board holds some control logic , a 12 bit multiplying DAC and a bunch of LM339 comparators
below that board sits the analog guts . A burr brown 16 bit dac as well as a dual 8 bit dac are the driving engines for the cotrol parameters. most likely these set the outer ranges of the multiplying dac that then generates a fractional division of the settings, essentially building a weighted 20 it D/A converter. Note : speculation , i could not find schematics or manual for this machine
the analog section is peppered with marked parts. the LT1008 opamps have yellow paint dots on em. most likely these were hand-picked. planety of other components have matching colored dots as well. so there was a fair amount of hand-tuning this beastie.
the output section employs mechanical relays for range switching. there is no audible click when changing polarity of the output so the output stage is fully push-pull and 4 quadrant. the relays only click when changin operating range for voltage and current leading me to believe these relays change the gain of the end stage and the divider for the readback.
the output stage employs 4 beefy PNP and 4 NPN power transistors
all in all a very nice piece of test equipment that only needed a bit of spit and polish to make it presentable. works perfectly fine.
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