[help needed] 1973 Chevy c20 5.7L SBC TBI conversion

[kb1gtt]

For now I would say do not change the jumpers. I would wager a guess that your soldering capabilities would add a layer of complexity that we can avoid by simply having you use a different pinout.

I agree with russian, you should remove the STM32 board, and LCD if you have it. Then you should verify if you have 12V getting to the board. If you don't have 12V to the proper spot, you won't get the 5V which is needed to power the STM32 board. Is your 12V connected with a 3.5A fuse? It's probably ok to use a 5A fuse, but it would really want to be 3.5A if you have it or can get it. In your application you will probably need something between .5A and 3.5A as your board will likely be using less than the full capability on that 5V supply. So I would suggest a fuse between .5A and 3.5A.

Lets start by verifying your GND. I'm not 100% sure what russian has populated for you. It looks like 12V is jumper-ed to some pins noted as GND on frankenso schematic. If you have connected GND as noted in the schematic, it may mean you have a dead short from 12V to GND. Can you verify via ohm meter or continuity beep test if you have GND on the board to your battery - terminal? See GND pad noted below, either that or JP07 on the other side of the board.

gnd_pad.PNG (12.47 KiB) Viewed 17347 times

I see you board should have 12V comming in on the below noted picture, but if you wired it per the schematic's noted pinout which was changed via jumper wires, you may have a dead short from 12V to GND. Can you check that you have 12V on this pin.

W39.PNG (21.06 KiB) Viewed 17347 times

Tracing the signal as it shows up on the board. 12V should come in on this pin noted in the below picture.

12V_1.PNG (9.01 KiB) Viewed 17347 times

Using a multi meter and when connecting a fused 12V to the frankenso board, can you measure the DC voltage between any point noted in the picture below, and GND? You can grab GND from that JP07 over on the left side of the picture.

12V.PNG (72.3 KiB) Viewed 17347 times

If you get 12V anywhere on that trace, that's a good start. Do NOT measure it, but this should mean you have 12V as noted here

12V_2.PNG (8.64 KiB) Viewed 17347 times

Which then means you should have 12V as noted here, can you measure 12V on P902 referenced to JP07 GND?

12V_3.PNG (11.51 KiB) Viewed 17347 times

If that goes well, can you measure 5V from the 5V pad noted here?

5V.PNG (9.67 KiB) Viewed 17347 times

It appears russian expect you to have R0.4, can you confirm? Do you see this note on your board?

R0.4.PNG (12.63 KiB) Viewed 17347 times

[3gAccord]

kb1gtt:
For the jumpering, would just a small solid wire (like a trimmed wire off a component for example) be suitable or should I track down some proper sized 0R resistors? I've got a coworker willing to sort that part out for a pretty fair price. For the power supply, I'll verify the points Russian showed and make some testing. After that we'll at least know if I hurt anything Thanks for the help guys! I'll let you all know more this evening. Wish me luck

[AndreyB]

you should remove ... LCD if you have it.

LCD is soldered, only way to remove is cut wires

[3gAccord]

Just to verify, basically pulling all the jumper wires at the 64 pin and jumpering across the pads that have 0 ohms in some. Right? Coworker said 20$ and a couple days. I figure in the interest of simplifying things it'd be best to go 1:1 with how these ship. A few people have asked me to help build similar setups

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[AndreyB]

Just to verify, basically pulling all the jumper wires at the 64 pin and jumpering across the pads that have 0 ohms in some.

Yes. Note that one red wire has a diode under the heatsink - that one has to stay, it's not a jumper wire it's the diode for IAC.

I do not remember why I have soldered that green wire in this weird way:

[3gAccord]

Also this. Is it normal? thank you so much for all the help with this. I hope I can make it up in some nice code for the project (:

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[AndreyB]

yes, the hanging piece is normal - that's moving 3rd connector position into the 2nd hole to make Honda pinout. This part we would not touch, we would wire trigger wires as honda.

[3gAccord]

Got ya. I'll do testing tonight then get my coworker to change the configuration so going forward im on the same page as stock. Seems like its less likely to make problems. Have safe travels, sir!

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[kb1gtt]

Little bits of wire is fine for the 0R's, but keep in mind that if it's to small, it can break and you may need to repalce it.

[3gAccord]

Removed everything but the red wire w diode and the black wire from bat sw to the resistor at p901 - 12v present on the connector side of p901 but not the inside... Sighs. I'm at a point im lost. Did a decent enough job jumpering it. No solder bridges etc but did manage to lift a trace on the connector side so I had to fix that with a small wire. On inp11 pin. Ideas for figuring out why no power? Grounds look OK. Pic to follow

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[3gAccord]

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[3gAccord]

beside the cut jumper at that resistor is the last place I see 12v. Cut the jumper to test since prior to doing so same results.

[AndreyB]

p901 is not a resistor - p901 is just a test point. hard to see what's going on on these pictures

here is how the PCB looks like with X-ray. p901 point should have +12v, same as both sides of F1001

[AndreyB]

I guess what you are saying is that white silkscreen is a bit confusing here since the W1 and W2 test is under the resistors, It might be more visible on the back side.

[3gAccord]

No 12v past the resistor. Connector side is live, other side is not. Bad resistor maybe?

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[AndreyB]

No 12v past the resistor. Connector side is live, other side is not. Bad resistor maybe?

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can you take a picture pointing at the resistor you are talking about? is it f1001?

it could be that we have burned 0R resistor at f1001 or weak soldering joints. could be that touching it with a soldering iron would fix the joints.

[3gAccord]

Unfortunately not til am. See the black wire beside the cut red one? That resistor. The one that's connected to bat sw by the black jumper .

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[3gAccord]

I'll try heating the solder tomorrow, be really awesome if it reflows and fixes it

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[AndreyB]

Something is wrong here. I would assume that my black wires are GND and poser would be red wires.

[3gAccord]

That's what I thought but that pin its connected to on the 22 pin is definitely the one labeled bat sw on board, +12V on pinout diagram :/ I wish I understood more than basic electrical.. I'd be a lot more help....

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[AndreyB]

I believe this is part of Honda wiring. How is Honda using this connector position? The top sides of W* positions are connector side and low sides of these W areas are the PCB side. If top side is not with bottom side of the same W* that means you have some kind of a re-route.

What I think this is is GND was routed to W1 somehow, 0R resistor on W1 connects connector side with PCB side. The small black wire routes GND to connector side of W2 making it GND as well, so that both these wires are GND on the Honda harness.

I suspect that you need to remove the tiny black wire and jump W2 same way as you've jumped other stuff. This would connect +12 from the connector as on default pinout to the PCB side of same W2 which would put +12v where it should put it and it would also put it into P901 test point.

I could be wrong, no warranties I am tired and a bit depressed here, my trip did not go well.

[3gAccord]

Sorry to hear that. I hope that things are better for you soon!

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[kb1gtt]

I see what you mean about P901. It's very close to W1, however technically that P901 is that single via and those 0R's are W1 or W2. As well I believe the little black wire you talk about is high lighted in the attached picture. That wire doesn't need to be there, I'm not sure if you have something connected to the harness pin that's connected to or not, but if there is something connected to harness 1A, then you should remove the little back jumper wire. If nothing is connected to that pin, then meh, you could leave it.

Lets look at F1001, which for some reason on your board appears the F is missing, so it just notes 1001. Do you get 12V on both side of F1001?

[3gAccord]

That's the one. 12v only on harness side

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[3gAccord]

Does the pad at w62 yellow wire need to go anywhere? It's the one w the diode wire for iac. What about the little black wire? The other side of that pad is bat sw (12V in). W2 is the pad.

Maybe that's the issue?

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[AndreyB]

I think you are applying 12v to the top side of W2. There is no jumper jumping W2 so 12v is not getting from top of W2 to the bottom of W2, insteat in goes (via the small black wire) to W1.

I believe that the small black wire connecting one side of W2 to W1 should be removed and W2 should be jumped instead. This would get 12v from the harness wire to F1001

[3gAccord]

That's what I was thinking but if I jumper w2, where does the iac red wire with diode go?

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[AndreyB]

That's what I was thinking but if I jumper w2, where does the iac red wire with diode go?

good point. You can either move red wire to P901 test point or jump from top of W2 (currently black) into P901 around the red wire which needs to stay if you idle valve is a solenoid.

[3gAccord]

I'll change the jumpering and leave the IAC wire free for the moment, then after confirming power at P901, i'll go ahead and move the IAC wire there. Lets hope tonight we see some signs of life. That'd make for a really happy week. Again, thanks for the help and patience!

[kb1gtt]

I agree, remove black wire from W1 and connect to W2 such that W2 has a jumper installed. Once W2 is installed, you'll probably get 12V to the 5V regulator. If you see 5V, then turn off power, connect STM board and turn back on the power.

Red IAC wire with diode can be insulated for now. I'm not sure it you'll need it or not. I scratch my head as I believe you can do the same as that jumper wire by adding a diode to the PCB. I'm not quite following the jumper wire arrangement. But that's mostly removed now, so I don't think I need to understand the jumper arrangement.