HP 41C Display

[J J Mac]

The second digit on my HP 41C LCD display does not work properly. Can the display be repaired or replaced?

[Diego Diaz]

Hi,

HP-41C's are more likely of the "Coconut" type (squared display corners), so chances are that the display (LCD and driver PCB "sandwich") can be replaced.

A picture of the faulty display however would help to narrow the problem among several possible causes. Some of which do not require the replacement of the display.

In case it becomes necessary you'll need to find a suitable donor (coconut) 41 and someone skilled enough to do the job.

Details about the replacement procedure are described on the service manual, pages 3-4 to 3-5. Google for "HP41c service manual" (direct links to such info are not allowed in this forum).

Hope you find this information useful.

Best.

Diego.

[J J Mac]

Thanks. Here is a picture of the display. What do you think? Can it be fixed?

[Garth Wilson]

Yep, a coconut.

[Diego Diaz]

Hi,

As Garth has already pointed out it is a coconut, hence the display can be replaced following the directions in the service manual.

Note however that the display driver has suffered several changes along the life span of the coconut series (Ver. F to Ver. G) and some earlier *tall keys* 41 models (as yours judging by the picture) needs capacitor C2 to also be changed from 0.01uF to 470pF in the CPU board if the display is replaced with one of the newer version.

Details about this procedure are also included in the technical note 41C-13 of the service manual (page 156 of the PDF document).

Hope you manage to get your 41 back to full working order soon. ;-)

Best

Diego.

[Diego Diaz]

Hi again,

After a more detailed look at your picture, it maybe that the problem is in the interconnecting "zebra" strips between the LCD and the drivers PCB.


Please set your 41 into ALPHA mode and write a "K;" in the 2nd digit to confirm.

Report back the result for further checking.

Diego.

[J J Mac]

Thanks for your help. Just getting back to this. Here are pictures of my HP 41C display with the number 8 shown and the letter K shown.

[Diego Diaz]

Hi,

Yes, it's clear now. The 2nd digit, (3rd character) has missed two (maybe three) columns.

The problem is in the *zebra* strip. LCD and drivers PCB are ok but the interconnection between both has some missing lines.

It often happens due to corrosion, but you'll need to take your calculator apart to find out; and the display board also needs to be removed to check for possible repair options.

Keep posting as you dig into it.

Best.

Diego.

[J J Mac]

(02-14-2022 11:18 PM)Diego Diaz Wrote:  Hi,

Yes, it's clear now. The 2nd digit, (3rd character) has missed two (maybe three) columns.

The problem is in the *zebra* strip. LCD and drivers PCB are ok but the interconnection between both has some missing lines.

It often happens due to corrosion, but you'll need to take your calculator apart to find out; and the display board also needs to be removed to check for possible repair options.

Keep posting as you dig into it.

Best.

Diego.

Thank you very much Diego! Do you know of anyone that does good repairs that I could contact to see what the prognosis and cost might be?

[Diego Diaz]

Hi,

Well, the problem is that the cost of shipping both ways and the job/parts may sometimes exceed the value of the unit*.

In my estimation, the job itself will be about $50/$100 including diagnostics, repair and final double check. Also bear in mind that after opening the calculator some other problems may arise: broken/cracked screw post, severe internal corrosion and the like.

So, unless you find someone really near to your location or decide to do it yourself; purchasing a working unit and selling this one for parts is probably a more cost-effective solution.

However, placing a "Service Wanted" ad in this very site may help in finding someone near enough to give it a try.

Best of lucks.

Diego.

(*) This is why I'm not in the repair business. Living in the Canary Islands, thousands of km. away from everywhere, only very expensive/unique items justify such expenses.

[J J Mac]

Thanks Diego. Think I will just sell the unit on eBay for parts. I was preparing to sell my 41C, 41CV, 95LX, + modules and manuals for the 41s when I discovered the problem with the 41C.

[GreyUser]

Send me a PM if you still want it repaired.