HP41 MLDL2000 ready for production


For those interested, the MLDL2000 for the HP41 is ready for production. More info can be found at the MLDL2000 website. I have also written an FAQ for the MLDL2000.

The critical issue is now to get enough interest to justify a production that is large enough to make it economical to achieve the target price of EUR 260. Due to the cost of the PCB production and assembly is is unlikely that there will be a second production run, but I will make some spare unassembled PCB's anyway.

I hope to be able to start actual production within 4 weeks from now and start deliveries end August/begin September.



Dear Meindert,

Gratulation :-))

It seems to be that the last problems are solved now. Now I am interested (like you) how much HP41 enthusiasts will order your great MLDL2000 system....

With best wishes - Christoph Klug



Did you get my email with "please put me on the list". I know you must be terribly busy just wanted to make sure you got my interest.





Please send me an email with your real address so I can check.



> Due to the cost of the PCB production...

What method are you using? Are the boards multilayer? I've gotten many PC boards made from one layer for just a few components, to 12 layers and 500 components. While just the NRE (non-recurring engineering cost) of the latter was over $2000US at the board manufacturer and each piece after that was $40-50 (qty 100, bare but tested), I've also gotten simple double-sided boards with plated-thru holes for 36 components made for $10 each for 10 pieces at www.pcbexpress.com , with no tooling charge. You just FTP them the Gerber and Excellon files and credit card and shipping info, and a couple of days later your boards will be shipped. There's no point in sending a fab drawing because no one will look at it. You don't need to talk to anyone. Their computers will put your job on the same panels with other people's, so small orders are fine. It's common for the entire order to be under $100US. You're not limited to two layers with no soldermask, ledgend, gold, and so on, but that's the really inexpensive option.

I guess I'll need to see if I can get a dead card reader and module for my MLDL2000. The card reader is one thing I never did buy (I got the tape drive instead), and I definitely am not about to sacrifice one of my modules.


The cost is not really in the PCB. These are simple two-layer PCB's If you take a look at the pictures you will see that is is all smd components, I that is hard to handsolder reliably, especially the PCB with the CPLD, FLASH and SRAM. I have this professionaly assembled on a pick-and-place machine, soldering is on a vapour phase machine.
The main cost of the MLDL2000 is in the CPLD, which is almost 25% of the total cost.



Hi Meindert,

Please ,could you please add me on your list for the pre ordering of the MLDL 2000.
I sent you a mail but I am not sure of your EMail.

Kind regards



enough interest to justify a production that is large enough to achieve the target price of EUR 260

I realize that calculating costs for varying quantities is quite a lot of work, but it would be useful to know:

a) What would be the price if you made enough to fill the current order list?

b) How many more orders are required to achieve the target price?

I'm thinking that if, for example, the answer to (a) is "EUR 400", and the answer to (b) is "twice as many", then I would be happy to double my order to achieve the target price, and if that wasn't true of enough people, I would be willing to pay more than EUR 260.

If the answer to (b) is "ten times as many", then I would suggest the target price should be adjusted.


We are getting close to the target price. Based on the current interest, we are already below EUR 300, but I have not yet had response from all that expressed their interest in the MLDL2000. Also do not forget that this is the cost of only the MLDL itself, without shipping and possible cost for PayPal or bank transfer.



I now have enough 'orders' to be able to confirm the price of EUR 260. This may get somewhat lower if there are more orders. I plan to order production in two weeks from now.



Hello Meindert,

I sent you a mail, but it bounced.

However, here's my mail text:

Hello Meindert,

yes, I 'm still interested.

There are still some questions of which I didn't find an answer so far.

The supported 'general bank-switching', does it allow for the HEPAX

or the bank-switched version of the W&W RAMBox OS to be used?

Is the MLDL2000 auto-off aware, which means that it also goes

to a low power state when the HP-41 automatically turns off?

How will future hardware and/or software upgrades be handled?

As an example:

You wrote on your page that bank-switching is not fully tested yet.

What if it doesn't work, maybe due to a logic error?





Please try to send me an email again at meindert@kuipers.to to make you reservation final.

To answer the questions:

HEPAX does not work yet because of the special instructions that HEPAX uses for write protection and moving banks. The normal instructions to switch banks seems to work, but only the Advantage ROM is tested so far. If the W&W RAMBox only use the bankswitch instructions ENBANKx ($100, $180, $140 en $1C0) then it should work, but it is not yet tested. Every single page supports all 4 banks, but even and odd pages (for exampe Page $8 and $9) share the same bankswitching registers.

The MLDL2000 goes in low power state whenever the HP41 is not running, so it has very low power consumption in STANDBY and OFF. For possible future use there is an option to keep it powered in STANDBY and/or OFF mode. The local SRAM is powered by the HP41 whenever it is connected, but the additional current to keep SRAM contents is too small to be measured. The MLDL2000 takes between 5 to 10 mA when running, depending on battery condition and HP41 speed. When using a high value capacitor (recommended) there may be some extra current when the capacitor is charging. This capacitor of 0.1F can keep SRAM contents for several weeks

Future upgrades are fairly easy. The CPLD can be reprogrammed with new logic. Currently this has to be done with a special programming cable, but the hardware is available to do this with the USB interface, I just have not written the software for that yet. So any bugfixes or upgrades will be fairly easy. Planned is support for HEPAX, User Registers (to create extended memory inside the MLDL2000) and communication on program level between the HP41 and the PC. And of course bugfixes .....
The upgrades will be offered as a file on my website, along with the software for the user interface that will be constantly improving. All for free of course.



I've just placed my order :-))

I guess, the hunt for defective card readers is open now. Any Idea where to find them without sacrificing my own (presumably working) one?

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