hp35


HP-35 Version 1- Red Dot
hp35




The HP-35 was HP's first pocket calculator. It was introduced in 1972 when most calculators (including expensive desktop models) had only the four basic functions.The HP-35 was the first pocket calculator with transcendental functions and the first with RPN, Reverse Polish notation. During the production process, the revolutionary HP-35 was slightly modified developing to four distinct versions. The first HP-35 (version 1) was the earliest and only production version that reveals a red dot to the right of the power switch when turned on. Another Red Dot characteristic is the serial number label placed between the 2 lower pads on the back of the calculator. The serial number should be typed into a narrow silver region. All but three HP 35 Red Dots in this table have this feature. Two of the different ones (S/N 1143A 03288 and 1230A 89591) have several other features from higher versions, therefore there were either substantially repaired or rebuilt from spare parts. The third one 1143A 01097 was twice returned to HP for service.
The HP 35 Red Dot version is very rare. Most of them are in the hands of calculator collectors already.
Now that you know where the serial number is, check the number. With few exceptions, the number will read 1143A XXXXX. The highest recorded serial number on an authentic Red Dot is 1143A 04280. From the collected data in this table, it follows that the total number of HP-35 Red Dots is in the range of 4200-4500. The last Red Dots were produced concurrently with very early versions 2. Therefore, the exact count is not possible to determine. There exist a few HP-35's, which have Red Dot S/N, but in fact are versions 2 or higher.Those calculators changed from Red Dot to version 2 during an HP service repair. Some very early versions 2 with Red Dot serial number could be produced as versions 2, such as 1143A 04196 in this table. Some of the Red Dots represented on this table may not have the 2.02 ln e^x ROM BUG. They were recalled by Hewlett Packard who guaranteed repair after the BUG discovery
Recently, another extremely rare BIG bug has been discovered in some very early Red Dots!

In this database are listed most of known and still existing HP 35 Red Dots.



Serial Number
Reference
Owner
Images
Click to
resize
the BUG
Functionality
Comment
1143A 00051
Nicolas Recalde Nicolas Recalde

Yes
OK
This Red Dot has the BIG bug
1143A 00100
Michael Eckstein
Michael Eckstein

Yes
OK
This Red Dot has the BIG bug
Back side with labels is from a newer version. S/N label was replaced by a substitute and placed in the battery compartment during some repair in a HP service. There exist an another HP 35 without any bug and not Red Dot, but has the original back side of this RD and has the correct S/N label 1143A00100.
1143A 00159
John R. Galie

No
OK
Version 4!
1143A 00357



Yes
OK
This Red Dot has the BIG bug
1143A 00403
Tom Drewski


No
OK

1143A 00429
Wlodek Mier-Jedrzejowicz Wlodek Mier-Jedrzejowicz



1143A 00516
Jon Bremner
Jon Bremner


Yes
OK

1143A 00754
Albert Threlfall



Yes
OK
This Red Dot has the BIG bug. No Red Dot with the Big Bug was found after this S/N
1143A 00840
Scott Reynolds



Yes
OK

1143A 00944
Tom Drewski Tom Drewski
Yes
OK
Version 2
1143A 00957
Tom Drewski
David J

Yes
OK

1143A 01003
Scott Reynolds



No
OK
The Red Dot switch has no red on it. The back label is from the newer version. This HP 35 has other parts from a newer version possibly replaced during The BUG repair.
1143A 01045
John R. Galie



Yes
OK

1143A 01062
Rudolf Maximilian Foerste Rudolf Maximilian Foerste

Yes
OK
ARC key not functioning
1143A 01097
Chris Bennett
Chris Bennett


No
OK
The back instruction label is from the newer version. Original back S/N label was also removed and replaced by a newer one during one of two repairs of the calculator in a service.
1143A 01173



No
OK

1143A 01233
Scott Reynolds


No
OK
The Red Dot switch has no red on it. The front and the back labels are from the newer version. Labels were probably replaced during a repair of the switch or ROM replacement in a service.
1143A 01257




No
OK
The Red Dot switch has no red on it. The back label is from the newer version. The label was probably replaced during a repair of the switch or ROM replacement in a service.
1143A 01279
Tom Drewski
Luis S

Yes
OK

1143A 01563
John R. Galie
John R. Galie


Yes
OK

1143A 01640



Yes
OK

1143A 01660
Katherine Wasserman
Katherine Wasserman


No
OK

1143A 01723
Michael Eckstein
Michael Eckstein


Yes
OK
The back instruction label is from a newer version.
1143A 01743





NO

1143A 01873
Tom Drewski

Yes
OK

1143A 02069
Mike Morrow
Mike Morrow


No
OK
This Red Dot was traded for a new TI 58 in 1977
1143A 02141
Paulo Roberto Alves
Paulo Roberto Alves


Yes
OK

1143A 02198

Michael Eckstein




Yes
OK
1143A 02282
Ed Sternby Ed Sternby

Yes
OK
1143A 02338
Scott Reynolds



No
OK

1143A 02369
Tom Drewski
Tom Drewski

Yes
OK

1143A 02373
Tom Drewski Tom Drewski

No
OK
Version 3
1143A 02461


Yes
OK

1143A 02499
Alberto Fenini
Alberto Fenini


Yes
OK

1143A 02501
Reinhard Hawel
Reinhard Hawel

No
OK
1143A 02581
Scott Reynolds



No
OK
1143A 02585
Paolo Reda
Paolo Reda

Yes
OK
1143A 02662




No
OK This unit has a name plate personalized with a name of a member of the HP 35 design team.
1143A 02736
Scott Reynolds



Yes
OK
1143A 02741
Paul A. Grace


Yes
OK Version 2, no sign of any service repair!
1143A 02852
Tom Drewski
Tom Drewski

Yes
OK

1143A 02874
Ignazio Cara
Ignazio Cara

No
OK
1143A 03007





No

1143A 03048




Yes
OK
The Red Dot switch has no red on it. The back label is from the newer version. The label was probably replaced during a repair of the switch in a service.
1143A 03102
Tom Drewski Mark H

No
NO
Version2
1143A 03153
David Ramsey
David Ramsey


No
OK

1143A 03179
Michael Eckstein


Yes
OK

1143A 03212
Borislav Agapiev
Borislav Agapiev


Yes
OK

1143A 03216
Derek Rowe
Derek Rowe


Yes
OK
1143A 0324X
Massimo Gnerucci
Massimo Gnerucci

Yes
OK ARC key not functioning
1143A 03288
Wlodek Mier-Jedrzejowicz Wlodek Mier-Jedrzejowicz


This HP 35 RD  has been repaired. The label at the front says HEWLETT PACKARD 35. The label with the number has bigger numeric digits, and the silver area of the label  is higher from  top to bottom than on all the others.
1143A 03541



No
OK
1143A 03711
Scott Reynolds
Scott Reynolds

Yes
OK

1143A 03770
Gianmaria Porrini
Gianmaria Porrini



1143A 03779
Michael Dietz
Michael Dietz

No
OK
1143A 04161 ?





OK
Serial number was guessed from the image.
1143A 04196
Adam Jones
Adam Jones

Yes
OK
This is the version 2 with the  Red Dot  serial number label. This calculator is in an original state, contrary to the other Versions 2 with lower S/N. One known Red Dot with a higher serial number is known. From that follows that some of Red Dots were made concurrently with very early HP 35 versions 2
1143A 04253
Marcel Soklaski
Marcel Soklaski

Yes
OK
This is the version 2 with the  Red Dot  serial number label. This calculator is in an original state.
1143A 04281
Michael de Estrada
Michael de Estrada


Yes
OK
This is an original Red Dot with
the highest S/N known sofar.
1143A 04452
Scott Reynolds




Version 2
The back instruction label is from the newer version, so this is either a  repaired  Red Dot, or one of the first original versions 2.
1143A 04793
Adam Jones


Yes
OK
Version 2
This is the version 2 with the  Red Dot  serial number label. This calculator is in an original state.
1143A 04799
Ignazio Cara
Ignazio Cara


No
OK
Version 2
This is a version 2 with the  Red Dot  serial number label. The back instruction label is from the newer version, so this is either a  repaired  Red Dot, or one of the first original versions 2.
1143A 05295




NO
Version 2
This calculator is in an original state, The label with the number has bigger numeric digits, and the silver area of the label  is higher.
1230A  89591
Claus Possberg
Claus Possberg


Yes
OK
The serial number is not the Red Dot one. The istruction label is from the newer version. The serial number label is from the newer version. The lower back label is missing. The back power connector is from a newer version.



The BUG

The first HP-35s had a famous BUG in the ROM IC. But not only the HP 35 Version 1 had that buggy ROM, there were produced more than 20000 such units, most of them were version 1 and version 2. Hewlett Packard company offered a free replacement of those ROMs and many owners used that possibility.

For example 2.02 ln ex display a result of 2. There was also a bug in the trigonometric functions for certain inputs. Below are presented some of the bugs.


Function          Buggy          Correct
ARC SIN 0.0002

5.729577893 x 10E-3


0.01145916
ARC COS 0.0002
89.99427042
89.98854
ARC TAN 0.0002
5.729577893 x 10E-3
0.01145916
ARC TAN 1.00020002
45
45.00573


There exists an another extremely rare BIG bug, which was not known until recently. This bug was fixed very early, so even most Red Dots don't have this bug in their ROMs. In fact, less than five such HP 35s are known today. There could exist a possibility, that this buggy ROM was accidentaly inserted to a HP 35, so your HP 35 might have this bug, too.
You could test for the bug by the sequence
1 eex chs 10 ln
and if the bug was present, then you'd receive an erroneous answer differing from the correct result by hunderts of percents. Therefore "BIG bug" :-)


Acknowledgements:
Robert Benson
Ignazio Cara
Tom Drewski
Rudolf Maximilian Foerste
John R. Galie
Massimo Gnerucci
Wlodek Mier-Jedrzejowicz
Adam Jones
Claus Possberg
David Ramsey
Paolo Reda
Scott Reynolds
Ed Sternby
Katherine Wasserman


Last update: 26. September 2014


Email: ecksteinm(at)volny.cz



 





















2006-2014 (C)  Michael Eckstein
HP is a trademark of the Hewlett-Packard Company.