I need a small, reliable PC to go into a public kiosk.
I'm trying to decide between an LGA 1151 system with a small form factor ATX compliant PSU or a "mobile computing solution" with a BGA CPU and a power brick.
I have worked in a computer repair shop, and failed BGA joints seem pretty common in my experience (thanks RoHS). I don't think I've ever seen a socket CPU fail without obvious abuse.
I know mobile computers use less power and generate less heat which would be good for a poorly ventilated kiosk environment, but I'm not sure that will translate...
Winston Chadwick
Member
Last Activity: 05-25-2023, 11:44 PM
Joined: 03-21-2016
Location: Lawrenceville, GA
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Reliability of BGA CPUs vs Socket
Last edited by Winston Chadwick; 03-02-2017, 06:34 PM. -
Re: Modifying a Blood Pressure Pump to Switch an LED
Supply for the dump valve is 6.27V from the voltage regulator -
Re: Modifying a Blood Pressure Pump to Switch an LED
Dump valve impedance is 40 ohms.
There is no resistor between the ATMega128A and Gate 2 of Q1. Gate 2 is 5V above ground potential when the dump valve is closed.
R4 is connected to pin 2 (trigger) of the 555 timer.Leave a comment:
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Re: Modifying a Blood Pressure Pump to Switch an LED
I've attached pictures that show my access to the area when fully assembled. The dump valve board is through hole soldered to 12 pins on the main PCB. The holes here are a bit undersized, so it's a pain to desolder even with good equipment. If possible, I would like to do the modifications without having to desolder all of those pins, and I think soldering wires to the existing pads without removing the dump valve board or wires would be tricky at best.
What do you think about desoldering the positive...Last edited by Winston Chadwick; 01-23-2017, 11:04 AM.Leave a comment:
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Re: Modifying a Blood Pressure Pump to Switch an LED
Thanks I'll correct it....Leave a comment:
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Re: Modifying a Blood Pressure Pump to Switch an LED
Thanks again for your help.
I made a schematic (see attached pic) to get a better idea of what's happening in this circuit.
I tested the LED at 10mA, and the brightness is acceptable.
My current plan is to desolder the control signal wire and add the positive wire to the same hole. There is a conveniently unused grounded through hole nearby that I will use for the negative lead.
To get any benefit from the the existing MOSFET I would have to solder the...Leave a comment:
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Re: Modifying a Blood Pressure Pump to Switch an LED
Sorry for the delayed response. Thank you all for the replies.
From the data sheet: “For long term performance the drive currents between 10mA and 30mA are recommended.”
I had some trouble metering across the dump valve, but it looks like it has about 6.2V between the two wires going to the dump solenoid when the valve is closed. I considered running the LED from the 5V control line. I’m new to this, and I was worried about drawing too much current from the...Leave a comment:
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Modifying a Blood Pressure Pump to Switch an LED
I would like to modify a blood pressure pump to light an LED while the blood pressure test is in progress.
The pump has a motor, two smaller solenoids acting as control valves, and a larger solenoid for the dump valve. When the test starts, the BP pump closes the valves and runs the inflation motor until the max pressure is achieved in the cuff. The control valves slowly release pressure as the user's pulse and pressure range are measured. At the end of the test, the dump valve is opened to fully deflate the cuff.
I would like to add an LED that will turn on when... -
Re: Need help finding a replacement resistor.
OK, thanks for the info. I sent this thread to my manager. He should be contacting you soon. Thanks again for the offer.Leave a comment:
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Re: Need help finding a replacement resistor.
I've seen those PSUs from the 9020. I haven't opened one yet, but they are also found in the Optiplex 7020 SFFs that we use.
I know how much trouble it is to get parts off of those boards. You aren't planning on desoldering components are you?
I appreciate the offer but, I don't want to ask you to go through too much trouble especially considering I'm not doing this as a personal project.
We might be interested in just buying the entire PSUs if they're still working. Of course, I don't know how...Last edited by Winston Chadwick; 08-24-2016, 03:52 PM.Leave a comment:
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Re: Need help finding a replacement resistor.
I noticed that when I tried to desolder them. Using hot air, it seemed like the circuit layer delaminated from the backboard as soon as the solder joints reflowed. There's still a bit of a bubble under both of the boards I worked on. The board I tested worked even after delamination, but I think I'll try Chip Quik next time I have to remove that IC.
The 3W that I linked above is much closer in dimension than the 1W I was looking at, so I'll go with the 3W.
Good idea. I hope...Leave a comment:
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Re: Need help finding a replacement resistor.
Eventually, I will probably need hundreds of CP012A ICs. The company I work for owns over 2,000 Optiplex 790 SFFs. I estimate that about a third of our 790s have an H240AS-00 installed. Many of those are Rev 04 boards where they used two 1kV snubber caps in parallel (I'm hoping these won't fail like the Rev 02 boards). That still leaves quite a number of rev 02 H240s.
However, I would like to get between 10-20 CP012A for my first purchase so that I can be sure that I can get the repair running smoothly before...Last edited by Winston Chadwick; 08-23-2016, 03:09 PM.Leave a comment:
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Re: Need help finding a replacement resistor.
I was hoping it would be a simple misunderstanding. Thanks for your help.
If I go through Digikey, it looks like my choices are 1W or 3W.
I guess I'll get 3W rated resistors [URL="http://www.digikey.com/product-detail/en/vishay-sfernice/RWM0410R270JR15E1/RWMA-.27CT-ND/1587885"]like this[/URL] unless it's overkill.Re: Need help finding a replacement resistor.
I was hoping it would be a simple misunderstanding. Thanks for your help.
If I go through Digikey, it looksLeave a comment:
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Need help finding a replacement resistor.
I've been working on some H240AS-00 PSUs from the Dell Optiplex 790.
Apparently, it's made by HIPRO.
PCB is labeled Rev. 02
I've been seeing a failure that was reported in [URL="https://www.badcaps.net/forum/showthread.php?t=40726"]this thread[/URL].
The 1kV rated ceramic snubber cap (C52) blows and takes Q51, R25, and IC301 with it.
According to stj, who posted in the above thread, this failure can also kill various diodes and resistors around the MOSFET. Thankfully, this hasn't been the case for me yet. I was able to repair... -
Re: Transistor replacement for L240AS-00
Thanks for the clarification R_J. It was mounted with insulation, but I'll get the non-isolated version to keep it factory spec.
It doesn't look like the manufacturer used any thermal material between the MOSFET and the heatsink.
I have some Arctic MX-4 thermal paste. Should I put tiny dot on the front and back of the insulator layer for better heat conductivity?
Edit: It looks like the heatsink screw is insulated on both sides of the heatsink....Last edited by Winston Chadwick; 08-17-2016, 10:09 AM.Leave a comment:
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Re: Transistor replacement for L240AS-00
Thanks. I didn't know that was the full ID for the part. Should I reuse the ferrite bead around the gate if I get the isolated case? This is filtering noise right?
Noted. Thanks for the correction....Leave a comment:
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Transistor replacement for L240AS-00
I've been repairing Dell Optiplex 790 PSUs, and I'm finding a lot of dead LS240AS-00 rev. B models. The main input cap dries out which blows Q100 and the fuse.
Q100 is an [URL="http://www.infineon.com/dgdl/Infineon-IPI60R199CP-DS-v02_02-en.pdf?fileId=db3a304412b407950112b42c77ea4707"]Infineon Technologies 6R199P[/URL].
It looks like Summit Electronics and SemiconductorPlus carries the 6R199R in the US. Has anybody ordered from these sites? Are they better than Aliexpress?
It looks like Lite-On put a ferrite bead around the base pin of Q100.... -
Re: Replacing Caps on an LED Driver Board
Sorry for the delay in posting the pics.
I couldn't find YXJs in the quantity I wanted. I went with a Panasonic FC 22/100 (8mm diameter). I think it fits well enough.
I used an FM for the 220/35.
Display brightness controls and backlight on/off work as I had hoped.
Pics.
1. Elo back panel with the original inverter for the CCFLs
2. LED driver installed
3. LED test
4. LCD removed
5. Burnt CCFL
6. LEDs in lighting rail
7. Perfect fit
...Last edited by Winston Chadwick; 06-13-2016, 09:55 PM.Leave a comment:
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Re: Replacing Caps on an LED Driver Board
Thanks stj. The YXJ looks like it will work nicely.Leave a comment:
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Re: Replacing Caps on an LED Driver Board
Thanks, I'll look into those.
Thanks for the info. I'd be happy to post pics when I'm finished....Last edited by Winston Chadwick; 05-11-2016, 03:32 PM.Leave a comment:
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