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There will be a replacement for the famous HP-01 chipset soon available.

I will offer it as a repair kit in July for international shipping.

All you have to do: remove the display from the defective circuit, attach it to the new circuit and insert the replacement into the case.

In most cases of a not functioning HP-01 wristwatch calculator leaked batteries damaged the subtle gold traces in inner layers, but keyboard and LED display are still working. The new chip takes over all signals on the board, communicates with all components and establishes a running display and keyboard matrix while emulating the arithmetic logic unit.

To avoid questions:
The chip is suitable for all models of HP-01 wristwatch calculator. It executes the original ROM Code. Accuracy will be +-2ppm, better than the original. Power consumption same or better than original.

If the LED display on your HP-01 is defective, the replacement will not making your HP-01 work again. In any other case, you will give your beloved HP-01 a new life and you will see its beautiful LEDs numbers 12:00:00 light again.

Price will be about 800,- Euro. (it is now actually 299,- for DIY)

Please mail to sales@panamatik.de if you are interested.
That's wonderful news for one of my HP-01 (the stainless one).


(03-06-2016 03:43 PM)PANAMATIK Wrote: [ -> ]Price will be about 800,- Euro.

...really?!?! o.O
While I don't have an HP-01, I am nevertheless thunderstruck at this announcement !!

Truly an amazing age in which we live !!
Hi Bernhard.

I need four!

Pm to send when I get home!


Oops, just read the cost. Let's think about four :-)
PM sent.
Hi Massimo and Geoff


The repair of an HP-01 is much more delicate than the ACT replacement. Therefore I offer a complete repair by sending the watch to me including insurance. If you really want to DIY then it will cost you much less.

Please consider also, that I had to buy and sacrifice working HP-01 to get into the details. Sad

Bernhard, wasn't questioning the cost. Especially if you are doing the work ;-).

Will pm you when I get home.

Cheers, Geoff
HP-01 Next step done!

I want to give you some news about the progress of the HP-01 repair kit.

When I created this thread I had only the concept in mind. From concept to finished product is a long way. Now I finished the schematic and layout and I will give it to the manufacturer for making some first prototype boards.

The new HP-01 replacement circuit contains both, the hybrid ceramic main board and the keyboard. The original keyboard could have been reused, but then you had to separate it from the main board, which is not easy. The new keyboard will have the same gold contacts as the old one and I made the layout identical to the original.

[Image: uc?export=view&id=0Bwx8KUfOUL_RYUZxellsZTdRb0E] [Image: uc?export=view&id=0Bwx8KUfOUL_RS1RDZWtoeldyX3M]

The board size is only 32x20 mm, red is top layer, blue is bottom layer.

So far! I hope the next step will be to show you an image of the first LED light of the new HP-01 Smile

Nice work Bernard,
I would be interested in one if / when available
(04-05-2016 11:07 PM)vk6ti Wrote: [ -> ]Nice work Bernard,
I would be interested in one if / when available

The original HP-01 circuit used five layers of gold traces on ceramic substrat with buried vias. This was really nice work.

I'm confident that the right phrase is "when available" Smile
First Light!

The first new HP-01 prototype board is running!

As far as I can see the design concept will be still OK. The board does not yet fit inside the HP-01 case, because the prototype board is too thick, but the next prototype will have reduced PCB thickness of only 1 mm and need some other modifications too, but I will come nearer to the aim of the project. The solder resist will become white in the final version.

What I can show, and you can see in the images below, is the prototype board with processor chip and real time clock and the original HP-01 LED display mounted on top. The LED display multiplexer is running already.

[Image: uc?export=view&id=0Bwx8KUfOUL_RdTV2ZVpJTG5nb2M] [Image: uc?export=view&id=0Bwx8KUfOUL_RT21kOWNnNFBtNjQ] [Image: uc?export=view&id=0Bwx8KUfOUL_RalNIRTFlek9oMWM]

As astronomers say to their new telescope, it gets first light, I can say now, it emits first light.

[Image: uc?export=view&id=0Bwx8KUfOUL_RSVRWSDJnVTJyTXM]

The emulation of the original microcode will follow next week. It is already running on a woodstock calculator Smile

Amazing !!!
Well done Bernhard!
Nice work Bernhard,
Thanks for sharing update

Thank you for complimenting the work.

Some thoughts about the 9 digit display.

If you have a look at the single 820 Ohm resistor of the display in the images. It has the function of limiting the forward current of the LED segments, giving them the right brightness. It controls a constant current source indirectly. In the new HP-01 it is not used, instead I needed 9 resistors of 220 Ohm (now 0 Ohm brightness is controlled by timing), which control the current passively. Theoretically the original method is the better, but I couldn't find a modern equivalent chip for it. And with help of software it behaves identical.

The original display driver hardware contained a constant current source to achieve identical brightness of the LED segments regardless of which segments are shown. They used a single resistor to regulate the LED current shown at the top of the display in the images. I couldnt find a suitable constant current source, and of course i couldn't develop a custom chip, so I decided to have a single resistor per digit, and software drives the digits in that way, that only one segment per digit will be light at the same time. After 9 multiplex cycles, because the digits have 9 segments including the colon dot, the cycles will be repeated. This leads to a constant current too and each segment has the same brightness.

If the battery voltage decreases at the end of its lifetime the display will gets darker, but when using SR44 cells, they have a constant voltage up to the very end of their lifetime, therefore I do not expect to see this effect. And if it becomes visible it is time to change the batteries.


How about a view of the keyboard side.

Email sent.

(04-30-2016 04:00 PM)Geoff Quickfall Wrote: [ -> ]UNBELIEVABLE!

How about a view of the keyboard side.


Thank you for writing in capital letters. Smile

Here is an image of the original and the new keyboard. I made the contact areas identical and manufactured it with chemical gold coating. There is no necessity to use the original keyboard PCB. This would be rather difficult anyway, because the separation of the ceramic layers is not easy.

[Image: uc?export=view&id=0Bwx8KUfOUL_RbkE4Mm1PTXZWOG8]

Following images show different views of the prototype board before assembly.

[Image: uc?export=view&id=0Bwx8KUfOUL_RaEFJbzBsNFlONzg] [Image: uc?export=view&id=0Bwx8KUfOUL_ROUJxdGFEVG16ams] [Image: uc?export=view&id=0Bwx8KUfOUL_Rd1o5TlhsdDdsMjg]

I'm very glad to have a prototype now to get all functions running. One of the challenges is the running stopwatch during sleep mode and the perfect power management.


I am sitting in Beijing in the hotel, being up for 28 hours straight. Must say, I don't think you understand the magnitude of the workload you have done for the hp community!

It deserves the capital letters. Enough said, 19:00 hours here and I have to go to sleep. I think I will order three.

Cheers, Geoff
Power consumption measured!

One important aspect for me of the "new HP-01" replacement is to give appropiate respect to the original watch and trying to keep their high claims entirely. A couple of highly skilled engineers were developing this masterpiece at a time, where they gave ultimately the best of what electronics could perform. They used much more dedicated hardware than today, they thought in single Flip Flops and gates, instead of modules to patch together. This gave the chips enormous power and performance even with low clock frequencies of only 800Hz ! in case of the HP-01. Today we can use multi purpose chips which lots of resources and MHz clocks to our service. Nevertheless it is still not easy to compete with the specifications of the original HP-01 and a challenge to choose the right components.

Now I'm glad that I got one goal confirmed. I measured the power consumption when display is off and processor is in deep sleep mode.

[Image: uc?export=view&id=0Bwx8KUfOUL_RMjZ6dmRGVmtob1k]

At 3.0 Volt it consumes less than 2 uA, as you can see in the image. Two SR44 cells in series will have nominal 3.0 Volt and claim to have capacities of up to 175mAh. I think you can get real 150mAh from them. This implies, that with two cells the new HP-01 will run about 79000 hours, this is more than 9 years. Of course you want to have a look at the time and the display lights up, this shortens the battery life. But it should give a good feeling, that the batteries will not be drawn empty when the watch is just waiting for its next mission somewhere at a party or meeting?

The original HP-01 used two cells for driving the display only, and one cell for the processor, in order to change the latter less often to keep the time running. My concept had to be different. I use two cells for both, display and processor, but in case you have to change the batteries, I provided a procedure to keep the time running during the replacement. Smile So you never loose time and date, unless you wait too long for the replacement and the cells were completely empty.

Sleep mode is performing well and any buttons wake up the processor for some seconds and are processed immediately.

Next report will be about accuracy of date and time.

HP-01 original microcode extracted!

For the first time ever the original HP-01 microcode was extracted.

Today I completed the last step of my preparations and could read the microcode of both ROM dies directly from the HP-01 hybrid module. Believe it or not, it was an odyssey.

Since last year I planned to read the original ROM of one of my two HP-01s for making an exact replica as part of my repair kit at all costs. But I did not even know how to open the sealed ceramic case. For a long time it just lay in my drawer waiting for what to come. Then, in february this year, I took some courage and heated up the case and could melt the glue, that connected the upper and lower ceramic parts and for the first time I could separate them and see the hybrid module and its 6 silicon dies inside. All the years before, there existed only a black and white photo, which was reproduced in the December 1977 HP Journal.

[Image: uc?export=view&id=0Bwx8KUfOUL_RREdSOS1ud0pacmc] The HP-01 Hybrid module in color.

Again after hesitating many weeks before going on, I finally connected 1.5 Volt power to the module and tried to measure some signals with the oscilloscope. This was very difficult, because I could damage easily one of the tiny bond wires while applying the probes. And after 10 Minutes of measuring exactly this happened. I was totally upset, because I never could reconnect any bond wire, and I saw my last chance gone to get to the ROM code. My idea just to listen to the instructions and call every possible function step by step to collect the ROM code was not longer possible, because the watch wasn't running any more. As I recognized later the carry bit of the Arithmetic and Register Circuit was ripped off and the program flow was wrong, it not even came out of the initialization and was caught in an endless loop. But I was very lucky that it was not another more important signal.

[Image: uc?export=view&id=0Bwx8KUfOUL_ROEFVUFVIeU4xeEk] The HP-01 ROMs

[Image: uc?export=view&id=0Bwx8KUfOUL_RQUhRVkxBNTl2YkU] Close up

The bond wires near the ROMs were still intact. And possibly they could be read by applying addresses externally and reading the opcodes. But how could I apply probes without fear to damage the circuit even more. I got the idea to buy expensive spring loaded pogo pins and to use the old toy microscope of my son as an elevator to establish the contacts. This was indeed very practical. Then I was thinking about how to injects the signals. It turned out, that this time I had to deliberately rip off a bond wire to inject my signals. This decision was very hard for me. Before I tried to cut one of the gold paths by a scalpel, with no avail, then I tried to cut the trace with a 0.6mm drill and a small drilling machine, with no success. The traces behaved like steel instead of gold. The only remaining chance was to remove the bond wire. Fortunately this went well. First I thought that I needed four connections to apply system clock and sync signals and so on. Then I could reduce the no of pins necessary from four to only two for connecting a PIC microprocessor to apply the addresses asynchronously. It needed also a passive bidirectional level converter to interface from 3.3V to 1.5 Volt. Always knowing, if I made another mistake it would be over. Buying another HP-01 just for damaging it as well, was beyond my imagination.

[Image: uc?export=view&id=0Bwx8KUfOUL_Rd3dJeExWdXFJUFU] Bond wires

After two days, the program was working and preparations were done, the interface was working. And with all my courage I connected the HP-01 with the PIC processor (I used an new ACT for this purpose) via the interface and got miraculously a signal from the ROM. It answered the opcode of address 0000. Immediately I saw that it was a jump instruction. This was what I expected. Then I could increment the addresses via terminal and could write down the next opcodes. And they also made sense. They were similar to the beginning of the prototype microcode, that was published in the US patent 4158285. Only a few hours later I was able to read and verify the complete 2k ROM code automatically.

[Image: uc?export=view&id=0Bwx8KUfOUL_RZmdRSjhvb3RrSzQ] Microscopic surgery

[Image: uc?export=view&id=0Bwx8KUfOUL_RZmlRZzBSdzRXT0k] Pogo pins

[Image: uc?export=view&id=0Bwx8KUfOUL_RUUVpcWRqQ0REem8] The first signal on the scope

I read three times the whole 2k ROM with different timings and all readings were identical.

But it would have been too easy, it is not running completely yet. I discovered eight new opcodes, which are not used in the documented prototype code and therefore unknown to me. After some time, I deduced, that they must be direct jump instructions between ROM pages and changed the emulator to what I thought it should be right. For the first time, I got the emulation running until it showed "0." in the display and entered sleep mode waiting for keys. By pressing keys I could see, that also time and stopwatch are running. But number entry doesn't work yet. But I'm sure the reason can be found soon.

("5-12-16.": Finally the microcode is running completely. It used program counter increments over page boundaries, which the emulator can handle now.)

If all goes well, the first HP-01 repair kit will be available in july as promised, running the original microcode. Smile

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