Electronics > Repair
HP 34401a DMM with leaking segments
qu1ck:
floobydust, thanks for reply. Display I'm using is this one, it has different pinout from one on your pic: https://www.buydisplay.com/download/manual/ER-OLEDM032-1_Series_Datasheet.pdf
It is powered the same way but I plan to rip out the boost converter from the display and feed 12v directly where boost output is to minimize switching noise. 3v3 from voltage reg will also go in on the standard pin to power ssd1322.
Re MISO resistor, what does it matter what the pullup is? All the pins on that 10k RN are configured as inputs. My board does not output any signals, only listens on what is going on the CPU->FP data lines. It's the front panel micro that will be fighting against the MISO pullup. (Or rather the comparator they use to shift voltage levels, but the point stands).
I calculated heat dissipation on voltage reg and assuming there is 0.5inch^2 of copper attached to it I can dissipate about 0.5 watt before it goes past ~60C. For 8-9 volt drop that's about 55-60mA. I am hoping that stm32 + ssd1322 - high voltage consumption of ssd1322 will fit into that. Some quick searching did not give any specific numbers for either of these chips, I guess it varies a lot depending on used peripherals and display update frequency.
As a backup I can always tap from regulated 5v of the DMM instead.
qu1ck:
Poor chinese bastards have no weekends :D I already got a tracking number yesterday.
While I'm still waiting for the boards I though I'll show Kicad bom generating script I wrote a year ago. Adapted it to Kicad 5 as a plugin now, here is result (it will be deleted after a day):
http://ibom-showcase.bitballoon.com/
It doesn't support arbitrary polygon shapes, rounded rectangle pads, other things, but it is still useful. I used it before on a much more complex board, highlighting similar components was very handy for hand soldering hundreds of smd components. Let me know what you think, if others like it too I might make an effort to support pcb format more fully and I'll open source it.
Zucca:
--- Quote from: qu1ck on July 14, 2018, 08:36:06 am ---It's going to the fab!
--- End quote ---
Sorry for asking, which one?
Kosmic:
--- Quote from: qu1ck on July 17, 2018, 01:41:12 pm ---While I'm still waiting for the boards I though I'll show Kicad bom generating script I wrote a year ago. Adapted it to Kicad 5 as a plugin now, here is result (it will be deleted after a day):
http://ibom-showcase.bitballoon.com/
--- End quote ---
Really cool, good job! :-+
qu1ck:
--- Quote from: zucca on July 17, 2018, 02:54:21 pm ---
--- Quote from: qu1ck on July 14, 2018, 08:36:06 am ---It's going to the fab!
--- End quote ---
Sorry for asking, which one?
--- End quote ---
Allpcb
Their quality is good from my experience, although silkscreen is not highest resolution print. But nothing beats $10 prototype boards with express fabrication and free dhl shipping.
Sent from my moto g(6) using Tapatalk
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