Portable fax machine thermal printer printing blocks of black with no text visible

[waigy]

Re: Portable fax machine thermal printer printing blocks of black with no text visibl

I have found the data sheet for the chip on the right side which is upside down.
It is an A3967

I can't find datasheets for the other chips.

The two large chips say :
13CG3FK G4
AHC16373

And the smallest one can be made out easily in the attached image, I think it says :
16AF5KK G1
AHC00

[stj]

Re: Portable fax machine thermal printer printing blocks of black with no text visibl

for AHC ad 74 at the begining.
74AHC00 is a quad 2input gate
the 74AHC16373 is probably a 16 element latch

[waigy]

Re: Portable fax machine thermal printer printing blocks of black with no text visibl

Ok downloaded those datasheets thanks.
What easy measurements can I take with a multimeter.
I could see that voltage was getting to the load supply pin 5 on the A3967.

[waigy]

Re: Portable fax machine thermal printer printing blocks of black with no text visibl

I still suspect the printer head might be either broken or just past it's normal operating life.
These machines are old now and I've seen thermal print heads stated as lasting around 10 years.
They are only supposed to work for so many metres of paper.
I took the print head out from its connecters and I don't know if it should have any continuity from one end to the other, but none of the pins at one end connect to any pin at the other end.
I was able to touch the heatsink on the print head while it was printing and only one end gets warm.
I realise that could still be a faulty chip only feeding a signal to one side of the print head.

[stj]

Re: Portable fax machine thermal printer printing blocks of black with no text visibl

if you can get the pinout of the head you can compare the resistance of all the heating elements

[waigy]

Re: Portable fax machine thermal printer printing blocks of black with no text visibl

I can't find out any info on the print head anywhere.
See attached for numbers

[waigy]

Re: Portable fax machine thermal printer printing blocks of black with no text visibl

Is there a good tutorial video for checking these kind of chips against the datasheets with a multimeter?

[stj]

Re: Portable fax machine thermal printer printing blocks of black with no text visibl

no idea.
but you can learn a lot from this guy:
https://www.youtube.com/c/TheCod3r/videos
https://www.twitch.tv/thecod3r2015/videos

[waigy]

Re: Portable fax machine thermal printer printing blocks of black with no text visibl

Can you tell me how to check the resistance against the datasheet?

[stj]

Re: Portable fax machine thermal printer printing blocks of black with no text visibl

i searched that head number, found a rohm datasheet but it didnt have the pinout.
it did make me pretty sure the head is the problem though - it has over 1000 elements with onboard switching.

[waigy]

Re: Portable fax machine thermal printer printing blocks of black with no text visibl

Do you have a link for the datasheet?
I can't find a replacement head anywhere but I have asked a few places if there is a similar one that will work with no replies yet.

[stj]

Re: Portable fax machine thermal printer printing blocks of black with no text visibl

https://yandex.com/search/?text=rohm+ka2008-af51b

[waigy]

Re: Portable fax machine thermal printer printing blocks of black with no text visibl

Yes I already have the ka2008-A10 datasheet but it shows as having 7 pins on each end and the KA2008-af51b has 9 pins.

[waigy]

Re: Portable fax machine thermal printer printing blocks of black with no text visibl

I was wrong about the pins on the KA2008-AF10A it does have 9 pins so might work but I can't find one of these to buy anywhere in the world.

[stj]

Re: Portable fax machine thermal printer printing blocks of black with no text visibl

it probably needs different current to run too.
i noticed on a smaller one the last part of the number can mean the heater resistance