Where 2 start????

[groovejet]

Hi there im a relative newbe and tend to take on projects that are more complex than i should be doing!! But i cant help that, i love fixing stuff cos of the satisfaction of it all!!
Anyway!
Ive troubleshooted on a photocopier m/c and have come 2 the conclusion that the Main pcb is the cause of the fault.

Photocopier- Minolta/Dialta Di 181 125v 3a

The fault code appearing is- co510.........Abnormal low fusing temp
I've tested thefusing thermoswitch and its ok
Also done fault finding chart & all pointing to Main pcb

SOOooooo!!!!!!!!!!! the qestion is Where the hell do i start, on the board?
Theres about 1000 smd's on board
30 IC's+, and about 10 very daunting Square jobby IC's, with about 100 connections on them
Ive got all the kit inc. logic probe, m.meter etc etc. But no Oscillascope or the like!
I know its alot to askof a mear mortal but PLEASE HELP
I can hook it up to power, as ive got bench supply. Just need afew pointers of where to start?
Testing smd's on board, i know u can come into problems regarding false readings ? Is there anyway i can test all these components without leading myself up the garden path?

Most grateful
Paul

 

[(*steve*)]

Have you checked that the fuser element is intact?

 

[groovejet]

Fuser element

Yea , its in good condition & i have tested continuity, A OK!!

 

[groovejet]

Here's a few pics, sorry there poor quality.

 

[(*steve*)]

Have you confirmed that any voltage appears across the fuser element?

Does it get hot? Does it get too hot? Or is it really under temperature?

(The above prepared before you posted the images)

You don't mark the result of testing the thermistor (which would have been an early guess of mine...) and also you have circled "replace power supply". Please tell us why you have skipped to the next step?

 

[groovejet]

Explanation of dodgy circled answers!!!

1st of all "YES" the fuser element does not get to temp (abnormaly low fusing temp)
Obviously i tested the copier in situe, and nothing but code co510 appears.

The question about the skipped results- Dont take any notice!!! I had the Fusing unit stripped on the desk, so i'd already discounted the thermister/fusing bulb/thermoswitch and associated wiring of the unit being the problem, I just 4got to tell u!!!!

The cicled step3, thats the conclusion i got from testing continuity accross CN5-1 and 2, on fusing unit side with disconnecting the plug.
- But i checked the power supply 2 and found it to be working because i got a nice wake up call fom it !!!!!!!!

ZAP AAaaaaarrrrghh!!!!!!

Thankyou 4 everyones input

 

[(*steve*)]

I would then look for the part of the main board that switches power to the fuser assembly (it may switch it directly, or it may send a signal to the power supply).

Look carefully for any damage first, then see if the signal to switch it on and off probably turned hard on if it's under temp.

 

[groovejet]

Power switching?

Thanx Steve, when its explained like u did, it sounds like common sense.
I never even though of narrowing down my search and looking at part of board that controls the fuser! Well i did, but not specifically the main pcb?
Totally makes sense, i was looking at the bigger picture, which would of took me a eternaty.
Thankyou

ps- still a lot of work 2 do though!!