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Help with diagnosing problem with pcb from charge controller
- Thread starter sandtaz
- Start date
Perhaps not. They're the most obvious and easily replaced part.
Can you describe the behaviour of this unit now, and if it has any behaviour (well, any good behaviour) how that differs from the normal behaviour.
Also, can you tell us exactly what is written on the 28 pin package.
Is your turbine a three phase design? Do you have three wires coming from the alternator that will cause it to rotate "roughly" if any two are shorted together?
The problem I have is that I can't see any connection to the third (from bottom) lug. It is also unusual to see two diodes(?) across the bottom two lugs.
With nothing connected to the controller, can you measure the resistance between the bottom 2 lugs (do it both ways and tell me if there is any difference) Then repeat the measurements from the top lug to each of the bottom 2 lugs. (this should be 6 measurements) Use your lowest ohms range.
Can you describe the behaviour of this unit now, and if it has any behaviour (well, any good behaviour) how that differs from the normal behaviour.
Also, can you tell us exactly what is written on the 28 pin package.
Is your turbine a three phase design? Do you have three wires coming from the alternator that will cause it to rotate "roughly" if any two are shorted together?
The problem I have is that I can't see any connection to the third (from bottom) lug. It is also unusual to see two diodes(?) across the bottom two lugs.
With nothing connected to the controller, can you measure the resistance between the bottom 2 lugs (do it both ways and tell me if there is any difference) Then repeat the measurements from the top lug to each of the bottom 2 lugs. (this should be 6 measurements) Use your lowest ohms range.
After the incident, the controller did not come on. Neither of the two lights (one to show charging and one for diversion) came on. Pressed and held the reset button with negative results. According to manual, when the controller is connected to the batteries, the unit should power up and initialize. It does not. The 28 pin package has "pic16f876-20/so and under that 083GS3." This is a three phase ac generator with three wires running thru three bridge rectifiers with dc output. Holding the board up to a light does not show any connection to the top lug. When installed in the enclosure, the top lug is one of the two connecting points for the diversion load wires. The other wire goes to the lug on the upper portion of the board. Measurements on the two bottom lugs were 479 and nothing (meter on 2000 scale). No reading from top to either of the bottom two (four reading). Midnight here. Thanks for your help.
Looking forward to the next step. Thanks. Tom.
Sorry for taking so long to get back to you.
You need to set your multimeter to a voltage range (20 v is fine) and place one probe on the vss pin and the other on the vdd pin.
This page will show you which ones they are
http://www.futurlec.com/Microchip/PIC16F876.shtml
be VERY careful not to short the pins out. If traces lead away from the chip to other components, it may be easier to measure them from there.
Needless to say, this measurement must be done with the power on.
Tell us what probe was connected to what pin and the reading you obtain
You need to set your multimeter to a voltage range (20 v is fine) and place one probe on the vss pin and the other on the vdd pin.
This page will show you which ones they are
http://www.futurlec.com/Microchip/PIC16F876.shtml
be VERY careful not to short the pins out. If traces lead away from the chip to other components, it may be easier to measure them from there.
Needless to say, this measurement must be done with the power on.
Tell us what probe was connected to what pin and the reading you obtain
Could I leave the board on my workbench and hook up any power source, like a six volt battery? If I put it all back together in the case hanging on the wall in the pump house, not much room to get in there and get probes on pins. Thanks. Tom.
Thanks. Will put two 12 volt batteries tomorrow and do the test inside. Should be about 100F tomorrow in the pump house. A bit cooler here in the house. I can't tell you how much I appreciate all the help I am getting. Have a great day. Tom.
With meter set on 200V --- neg lead on vss pos lead vdd reading of 2.5. Switched leads and received same reading 2.5.
Input voltage was 25.2.
You are correct. One was -2.5.
Sorry again about the delay. Yes, you did have an overview. 
I also presume this is where you placed your probes to get +2.5V?
What I'd like you to do is to trace back those connections. They connect to the other side of the board here, the black one possibly going to a large expanse of copper, the red one perhaps to lots of places...
If you can identify the pins on all the other devices with 3 to 8 pins that are connected directly to either one of these pins (you can use your multimeter rather than tracing them out if you wish.
I have looked at the board, but it appears many of the chips are either unreadable or have codes on them :-(
I'm hoping that you will find the regulator this way.
I'll try to identify what I think are the most important ones to trace to...
I also presume this is where you placed your probes to get +2.5V?
What I'd like you to do is to trace back those connections. They connect to the other side of the board here, the black one possibly going to a large expanse of copper, the red one perhaps to lots of places...
If you can identify the pins on all the other devices with 3 to 8 pins that are connected directly to either one of these pins (you can use your multimeter rather than tracing them out if you wish.
I have looked at the board, but it appears many of the chips are either unreadable or have codes on them :-(
I'm hoping that you will find the regulator this way.
I'll try to identify what I think are the most important ones to trace to...
Checked the wrong pins. Sorry. With pos probe on vdd 4.81v, neg probe -4.81v. Will continue with trace the connections.Sorry again about the delay. Yes, you did have an overview.
I also presume this is where you placed your probes to get +2.5V?
View attachment 13518
What I'd like you to do is to trace back those connections. They connect to the other side of the board here, the black one possibly going to a large expanse of copper, the red one perhaps to lots of places...
If you can identify the pins on all the other devices with 3 to 8 pins that are connected directly to either one of these pins (you can use your multimeter rather than tracing them out if you wish.
I have looked at the board, but it appears many of the chips are either unreadable or have codes on them :-(
I'm hoping that you will find the regulator this way.
I'll try to identify what I think are the most important ones to trace to...
View attachment 13519
A regulator is at the top right of the picture beside the round silver and black component ( 100 25s 8l6). The number on the regulator is CLAB LM78L 05ACM. The numbers on the other components of interest are from the nine o'clock position clockwise - 86AD N01A; CFAB 2597H M-12; and 23021 81M A90N. These components are identified on the board with a "U" and a number. There are a total of nine of these U components. Hope this helps.Sorry again about the delay. Yes, you did have an overview.
I also presume this is where you placed your probes to get +2.5V?
View attachment 13518
What I'd like you to do is to trace back those connections. They connect to the other side of the board here, the black one possibly going to a large expanse of copper, the red one perhaps to lots of places...
If you can identify the pins on all the other devices with 3 to 8 pins that are connected directly to either one of these pins (you can use your multimeter rather than tracing them out if you wish.
I have looked at the board, but it appears many of the chips are either unreadable or have codes on them :-(
I'm hoping that you will find the regulator this way.
I'll try to identify what I think are the most important ones to trace to...
View attachment 13519
OK, so what we have so far:
If you measure between pin 4 and pin 6 on this chip, you should see 12V (the red probe connects to pin 4).
On the 78L05, if you place the black probe on pin 3, and the red on pin 1, I hope you get 4.81 volts (or thereabouts)
If you now place the red probe on pin 8, you will probably see 12V.
Please confirm these.
7805 pinout is in here: http://www.ti.com/lit/ds/symlink/lm78l05.pdf
LM2597 pinout is here: http://pdf.datasheetcatalog.com/datasheet/nationalsemiconductor/DS012440.PDF
(They're actually both the same, but the datasheets may come in handy later).
Can you put your finger on these chips and tell me if either feel hot enough that you can't keep your finger pressed against them? (try the same for all other ICs as well).
- No obvious damage
- Mosfets not internally shorted
- Power getting to microcontroller (within a 5% of the correct voltage)
If you measure between pin 4 and pin 6 on this chip, you should see 12V (the red probe connects to pin 4).
On the 78L05, if you place the black probe on pin 3, and the red on pin 1, I hope you get 4.81 volts (or thereabouts)
If you now place the red probe on pin 8, you will probably see 12V.
Please confirm these.
7805 pinout is in here: http://www.ti.com/lit/ds/symlink/lm78l05.pdf
LM2597 pinout is here: http://pdf.datasheetcatalog.com/datasheet/nationalsemiconductor/DS012440.PDF
(They're actually both the same, but the datasheets may come in handy later).
Can you put your finger on these chips and tell me if either feel hot enough that you can't keep your finger pressed against them? (try the same for all other ICs as well).
Test done. 2597 12v. 78L05 5.07v and 12.12v. Could not feel any heat. Input voltage was 25.1. Data sheet for 2597 pinout did not look correct. Used pinout for 7805 for both test.
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