HP75C Restoration (zebra connector ??)



#2

Dear All,

I have received this HP75C today, I knew it had some

cosmetic problems (see the ding in pic1)






and some display problems. As it can be seen in pics 2 and 3

all the pixels are there, but can only be seen at 30 degree angle.






I had opened the unit, and I was wondering if the LCD problem could be due to a bad zebra connection on the lcd dispaly

since I had some similar problems with the HP41s.

I also wanted to remove the aluminium bezel, in order to restore it
but it looks like it is a single piece with the lettering

bezel of the keyboard.


what the lcd people say ? is it worth a try ?


Last (stupid) question, what is the correct battery pack to be

used with ?? I was thinking about a classic one, but there is a third
connector that wouldn't not be powered ...


Thanks for help, and have a nice weekend !!

Alberto


#3

Hello Alberto,

I'm afraid I know nothing about the zebra connector (haven't opened a 75 so far) but the batteries are indeed the same ones as for the classics! I have asked that same question here a couple of years ago, therefore I know :-)

Saluti,
max

#4

IIRC the LCD module comes out from the back, you don't have to remove the bezel or any heat stakes to get it out. There will be a zebra strip between the LCD glass and the driver PCB, it probably is worth cleaning the contacts.

I have the HP75C service manual, I can see what it says. Although I think the LCD is replaced as a complete module in this machine.

And yes, the battery pack is certainly the same as the one for classics. The extra contact was for a never-sold battery I think.


#5

ciao Tony,

thank you very much for your reply.


I know the display comes away from the back,

the reason I want to remove the bezel is only for restoring it

to the original aspect, I would like to remove the ding.

Is it glued or what ? Is it a single piece with the keyboard faceplate ?


As far as for the display, I have seen that all the components

are "slided" into a metallic shield (I will post pics in a couple of days)

how can I separate all the components in order to clean the zebra contacts ?


BTW, do you know where can I get a copy of the service manual ?

take care Alberto


#6

You can get the service manual from the Australian HP museum site. I am not sure I should post the URL here...

Alas it doesn't describe how to dismantle the LCD module. If you can't work it out, I'll take my own 75C apart and have a look.

Again the service manual doesn't describe how to remove the bezel (you are supposed to replace the complete top case/keyboard assembly). I am sure it is glued in place (HP bezels normally are), and it may well be one piece with the keyboard faceplate.


#7

Thank you very much, I have found it.

I have a working HP75D, I could take the display from there

and see if installed in the 75C is working properly.

Then it could be worth trying to clean the zebra contacts of the non working one

Are the two displays swappable ??

Thanks again and take care, Alberto


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