board testing
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Re: board testing
i tested all the pins and based on the sheet it said might be some shift....for example a pin reading 0.595 is just about the 0.600v that the sheet says is good for pin being connected to load....but here are the pins i found anomalies on based on the spread sheet
u13 pin 5—.652
u19 pin 14–.430
u20 pin 14–.430
u21 pin 2—.434
u22 pin 2–.434 pin 10 —.900
u23 pin 2– .434 pin 10 .917
u24 pin 2—.434
i hope this sheds light on something im missing but a more educated man would see thanks
u13 pin 5—.652
u19 pin 14–.430
u20 pin 14–.430
u21 pin 2—.434
u22 pin 2–.434 pin 10 —.900
u23 pin 2– .434 pin 10 .917
u24 pin 2—.434
i hope this sheds light on something im missing but a more educated man would see thanks
Re: board testing
That's good news. U13 pin 5 must be firmly connected to ground. Same for U22/U23 pin 10. High values are typical for an unconnected input pin.
I wouldn't worry about the others. Those pins are also connected to the data bus.
Re: board testing
so a back cleaning might be all i need?
Re: board testing
The purpose of the procedure is to find disconnected pins. I would re-solder those.
Re: board testing
can i flow solder in from the top? or do i need to rensolder from the bottom?
and based on what i sent....i know its probably me being confused but can you list the ones that need to be addresssed i see the pin 5 of u13
and the pins of u22 and 23 but which others as well. thanks
basically if i read you right i should just have
u13 pin 5
u22 pin 10
u23 pin 10 to resolder? im sorry for all the annoyance i prob generate...i guess im a solder noob lol
and based on what i sent....i know its probably me being confused but can you list the ones that need to be addresssed i see the pin 5 of u13
and the pins of u22 and 23 but which others as well. thanks
basically if i read you right i should just have
u13 pin 5
u22 pin 10
u23 pin 10 to resolder? im sorry for all the annoyance i prob generate...i guess im a solder noob lol
Re: board testing
getting there....u13 pin 5, u22/23 pin 10 now read 0.....i plug the board in leds 5-8 come on for a second then go out.....now what or am i missing a resolder joint thanks
Re: board testing
The LEDs go off, therefore some code is running and part of the CPU is working as intended. This is what normally happens:
All our tips and tricks are on the troubleshooting webpage. I don't feel it's necessary to keep repeating what is written there. However the most important piece of advice from there is this:
- At power on, the LEDs are in an arbitrary state. This might be 4 lights on, or 4 lights off, or some on and some off.
- The MCP will reset the program counter and freeze it for about a third of a second.
- The "Power OK" LED is off during this time, and the other LEDs can't change.
- After that duration, "Power OK" lights up and the software is allowed to run. It will go through the following sequence:
- Switch all 4 LEDs off
- Do quick RAM check
- Perform 10 ms delay loop
- Switch left-most LED on
- Full memory scan
- Switch second LED on
- Test for cold or hot boot condition
- Setup vReset routine
- Setup serial input
- Switch third LED on
- Setup the sound tables
- Switch last and right-most LED on
- Start video signal and continuous back-and-forth scanning LED pattern
- Load and execute Reset.gcl (this clears the screen and writes the top two lines of text)
- Load and execute Main.gcl (this makes the startup sound and shows the menu)
- Wait for user input while flashing the arrow
All our tips and tricks are on the troubleshooting webpage. I don't feel it's necessary to keep repeating what is written there. However the most important piece of advice from there is this:
If you can’t find the bad soldering joint or short, assume you’ve missed it and look for it again!
Re: board testing
thank you...ill keep checking with my loup and meter if it doesnt work at this point its something i did wrong and i wont find it....i appreciate all your help....i will have to check the second board as well....if the same issues are there then im not sure what it could be as making the same mistakes 2x is usually rare.
Re: board testing
Early on you have removed and replaced some the resistor arrays. Personally, I would carefully check (with a multimeter in continuity mode) that each of their pins are really connected. When removing a component, it's easy to accidentally damage the copper connection in the PCB. I would focus on the pins of R4 and R5, because those are critical for operation of the system. Use the schematic to find test points elsewhere on the board for each of their pins.
I once had a board where pin 1 of R4 wasn't connecting properly, and it didn't work... this was indeed after R4 replacement and the cause was a damaged trace: it didn't connect to nearby C16 anymore. You can sometimes fix such issue with some extra solder and bridge the gap that way. Otherwise you have to run a patch wire to restore the connection.
I once had a board where pin 1 of R4 wasn't connecting properly, and it didn't work... this was indeed after R4 replacement and the cause was a damaged trace: it didn't connect to nearby C16 anymore. You can sometimes fix such issue with some extra solder and bridge the gap that way. Otherwise you have to run a patch wire to restore the connection.
Re: board testing
thank you i will check those points...still need to test board two as i know those resistor packs are in properly