MP 780 will not power up

[jflan]

I have an MP 780 that one morning decided not to power up.
I've tried two Canon power cords from a known-good power source.

I have taken off the left side cover and do not see anything abnormal.
The fuse on the PCB appears intact and has continuity.
I don't have a service manual (ordered), but I believe that this PCB is the power supply.

After having thought about this, I think that I need to verify the power supply output and then go to the control panel (on/off) for more testing.

If anyone can illuminate something that I've overlooked, it would be greatly appreciated.

Regards,
Joe

 

[Trigger 37]

jflan,... I just checked the MP780 parts catalog and the power supply is a PC board which is located on the left side of the Sheet Feeder Assembly. The part number is; HY7-2916-000. The Service Manual shows a very good picture of the power supply board. There is no fuse visible in the picture but it could still be there. I suspect that you have had some kind of power surge that blew out a component. You would have to be a rather good technician, and have a detailed schematic and decent tools to trouble shoot such a circuit card. It appears to be made out of descrete components, transistors, resistors, Capacitors, transformers, etc,.. standard power supply stuff. I don't see any sophisticated IC's, so that may be a good sign for you.

Hopefully you can find a replacement part on eBay.

 

[jflan]

Thanks for the heads-up, Trigger 37.
Hopefully, the manual (when it arrives), will help me plan the attack.

 

[jflan]

It's looking like I need that power supply.
Unfortunately, the cost for this part from Canon is prohibitive.

Does anyone know of a used Canon parts source that may have this ?

The Canon part number is HY7 - 3313 - 000
I need this revised power supply with the internal regulator.

 

[Trigger 37]

jflan

Yes, the place I buy some of my parts is, http://www.beckscrs.com/. Tell him I sent you and maybe he will give you a discount. You will have to contact him and send him the part number as he does not have it listed on his site.

Do you have a volt meter or anyway of checking the components on the power supply board? Like I said earlier, if it is a discrete component board you may be able to trace the circuit yourself and then check each component one at a time. 95% of the time it will be one of the rectifying diodes. Didn't you learn this in Basic Electronics 101 when you got your degree in Electrical Engineering?

 

[jflan]

jflan

Yes, the place I buy some of my parts is, http://www.beckscrs.com/. Tell him I sent you and maybe he will give you a discount. You will have to contact him and send him the part number as he does not have it listed on his site.

Thanks for the link, Trigger 37

Do you have a volt meter or anyway of checking the components on the power supply board?

Yes, but I have no idea as to what values to test for on each component.

Like I said earlier, if it is a discrete component board you may be able to trace the circuit yourself and then check each component one at a time. 95% of the time it will be one of the rectifying diodes. Didn't you learn this in Basic Electronics 101 when you got your degree in Electrical Engineering?

LOL !
Too busy chasing girls to have paid attention to minutia like that

 

[Trigger 37]

jflan,....Gosh,.. there were girls in your school,.... was that what those people were that were walking around were dresses and long hair. I was too busy running to the next class to notice much. Oh well, maybe in the next lifetime,...LOL.

 

[jflan]

Checked with Beck's and their price is higher yet.
Either way, the cost of the power supply ruins a $100 bill.

I'll need to try to figure out a way to test that PS.

 

[Trigger 37]

jflan,.. I don't have a MP780,.. I only have the MP730's and the power supply number is very different. However I assume that they are very similar in design. I just looked at the MP730 wiring diagram and all it shows is a block diagram of the power supply with the AC on one side and a 7 pin connector and cable on the other side. I'm sorry but I am not due to work on the other MP730 I have for another week or so. If I get to it and take it apart down to the power supply level I will try do so some testing for you,.. but really, it is not even the same power supply.

I suggest you keep searching for that part on the internet Otherwise you can sell the printer for parts to help pay for a new one. Sometimes the parts are worth more than the printer, but you have to know how to get everything apart. When I get to fixing my next MP 730 I might be able to buy some of the parts from you if it uses a compatible part. Another way is for you to find another MP780 that someone is selling for parts. Not a lot of choices. If I had time I could probably fix your power supply but would cost you shipping it here and back plus some of my labor,.. and there is no guarantee I can fix it. If one of the key components is blown out, and has to be replaced, it would be very difficult to find another part like it. Canon and internet parts shops don't carry discrete components. If it was something simple like a diode, then radio shack would have a compatible part. It could also be something as simple as the main power switch.

Here is another bad thought. How do you know it is the power supply at all? If the primary logic board is dead, I don't think anything would light up either. If you have a volt meter, set it on DC volts of about 50 volts. Then with the covers off and everything still plugged in, locate the 7 pin connector coming off the power supply board. There are grounding screws all over my printer so find one of them and connect the black or ground side of the voltmeter leads to that point. With the AC cord plugged in, measure the voltages on each pin of the connector. You may have to do this from some angle where you can get at the pins that are soldered into the connector on the PC board. Typically there are three kinds of voltages for these machines,.. +3 volts for lower level logic, +5 volts for control logic, and +24 volts or higher for DC motor controls and Printheads. You should have all three of these and several of the pins will also be ground pins.

If you get all the voltages, then you need to start checking the power on switch on the main control panel and where it goes to the logic board. This is what really turns the printer on. The power is typically there all the time. Hope this helps some.

 

[jflan]

Thanks much for the input, Trigger 37

You're right, I need to verify the output from the board.
I was going on the Canon troubleshooter in the service manual, but it could very well be further downstream as you point out.

There is a seven pin and a two pin header on the board.
The left side panel is off and I may be able to get to it without further disassembly, but it will be tight.

Going out of town for about a week so it will have to wait.

over-n-out