Not DEC related but still hoping for some help: Problems w/ LJ 4+ Printer

[Ali]

Grant, 

> I miss my 4M+ with duplexer and extra paper tray.  :-(

Yes, these guys were built like tanks. This one acts as a 4M now because I added the PS module to it and it has local talk support. No duplexer or extra paper tray though :(.

> I've found that the age of the paper isn't as important as any dust
> accumulated on the top sheet.

I will have to keep that in mind. This paper was old - not sure how old but it was in the tray when I found the printer on the side of the road. So better to recycle it then risk it I think.

> I thought that there was a temperature sensor to detect how hot the
> fuser is and error if it's not warm enough.

It may be "hot enough". They are certainly warm. And I don't detect them getting any hotter to touch as more printing goes on so this part could all be in my head.

 
> I can't sign in to look at the picture.  If I can, I'll look at it
> later.

I can post it elsewhere if needed. It basically shows the picture getting darker with subsequent printings.
 
> How dark is the image that's being transferred to the drum?
I am not sure how to quantify it but it looks solid on the drum. I will have to repeat the test with a "cool" printer and see if it still looks solid or not.

> If the normal image is being transferred and toner is being consumed, I
> would wonder where the toner is going.

Never thought about it but the extra toner (I assume not all the toner is being transferred to every page of print) must get swept up back in to the cartridge somewhere, no?

> 
> How clean / dirty is the fuser cleaning pad?

Not too bad. It is worth mentioning that the printer doesn't seem abused in its old life either. Only 65K of prints...

> The things that come to mind are shifting High Voltage (…) and
> temperature.

Both of which should produce an error usually...

> 
> The other thing that comes to mind is possibly toner caked up in the
> toner cartridge.

I thought about bad toner but that doesn't explain the improvement with time/prints. Or why it would go bad again after cooling down.

> 
> How long can you wait after getting a good printout before they start
> to
> fade again?  (Assuming the printer stays on.)

I would say 5 - 10 minutes. Once I get good quality prints the subsequent pages all look great...

> I'll share your email with a friend who was a certified HP LaserJet
> repairman.  (I just pretended to be one a couple of jobs ago).

...
> My friend replied with the following:
>"""
>  - Bad / dirty contacts to the hi voltage
>  - Bad high voltage
>  - Bad DC power supply. 
> 
> 
> --

Thanks that was quick! I am pulling out the HV portion now to take a look. If I understand correct the DC (LV) supplies everything else except the engine. Those all seem to be working fine. Cleaning contacts is easy (and cheap) so that will be my first fix unless I see something glaringly obvious with the caps on the HV.

Thank you.

-Ali