HP6632B Teardown - Page 1
Forum section: electronics / general

author: free_electron
author_rank: Super Contributor
timestamp: July 08, 2012, 03:53:05 am
content: I know there's another one of these floating out there but it's just a collection of pictures...So here we go :The top view.bottom left the big fat hunk of iron we call the transformer ( no, not those plate-iron robots from out of space )Top left the brains of the outfit and to the right the analog and power board.The front holds no surprises. A rubber membrane keyboard, rotary encoder and a custom noritake VFD under control of a local 87C196 do the work. This one has OTP rom on board with the code.There seems to be a spot on the left for a second rotary encoder. Looks like this board is used in more than one supply ...The brains of the outfit are formed by a TI DSP (biiig chip in the center) accompanied by two static rams just below it. To the left of the static rams is an eprom holding the firmware (socketed with sticker). Above the eprom is the MP9914 GPIB controller with to the left of it the classical SN75160 bus transceivers.A little PLD holds some glue logic ( small plcc with sticker). And a 16c550 Uart completes the entire outguard system. The link between inguard and outguard is done over two optocouplers.The inguard logic consists of a Xilinx 3000 families FPGA , a small config rom for the FPGA ( labeled device in socket above Xilninx) and a bunch of opamps and A/D D/A chips.This time no multislope system like in the other supplies, then again this design is a generation older. The reason most likely is that multislope is too slow for what they do with these supplies , and such precision is not required.There is a variant of this supply that can react very fast to changing loads. (66320) The difference is probably only firmware.The inguard/outguard is done using two optocouplers. For some reason one is a SMD device and , to guarantee standoff voltage, they had to mill a slot in the board underneath both of them.A jtag connector is visible next to the DSP as well.The power section uses discrete diodes in TO220, each heatsinked, and twin bulky capacitors provide energy storage. A heatsink tunnel has a speed controlled fan mounted to it to cool the power stage.The power stage is built around 8 TO-273 body MJL21194 and MJL21193 transitors. Just like the 6632A version this system is a full push-pull stage that can both source and sink.Attempt to externally pull the output higher than what is programmed and this machine will growl and snarl at you and pull it right back to where it needs to be ( within its capabilities of course )Current sensing is done the right way using a kelvin resistor.

author: T4P
author_rank: Super Contributor
timestamp: July 08, 2012, 03:15:05 pm
content: Oops, i think you mean TO-3 transistor

author: Unknown
author_rank: Unknown
timestamp: July 08, 2012, 03:25:30 pm
content: Quote from: DaveXRT on July 08, 2012, 03:15:05 pmThey don't look like TO-273 to me either, but do you really think this is a better match:

author: free_electron
author_rank: Super Contributor
timestamp: July 08, 2012, 03:29:31 pm
content: there is a To3P P for Plastic. could be ...I looked it u . They are TO264 packages. The To3P is smaller than a To264.very uncommon packages.

author: T4P
author_rank: Super Contributor
timestamp: July 08, 2012, 06:35:36 pm
content: Quote from: free_electron on July 08, 2012, 03:29:31 pmIt's either TO-264 or TO-3P i meanIt's not uncommon, it's VERY common at least if you have been doing high power sutffsBut yeah i went to re-read it again, i see you mean the TO220 diodes ... sorry 'bout that