hp35


HP-35 Version 1- Red Dot
hp35




The HP-35 was HP's first pocket calculator. It was introduced in the year 1972, at that time 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. The desing of the HP-35 was slightly modified during the production time, therefore this calculator was subsequently developed to four versions. The first HP-35 - version 1 -was the earliest and only production version that had a red dot to the right of the power switch that showed when it is turned on. There are a few more HP 35 Red Dot signs, the main is the serial number label placed between the lower pads and the serial number should be typed in a narrow silver region. All but two HP 35 Red Dots  in this table have this feature. The two 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 HP 35 Red Dot version is very rare.  Most of them are in the hands of calculator collectors already.
HP-35 Red Dot calculators have serial numbers 1143A XXXXX, with a few exceptions. No Red Dot was found from 04281 up. From the collected data in this table follows that the total number of HP 35 Red Dots was approximately 4200-4500. The last Red Dots vere 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 some 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.
Among still existing Red Dots presented in this table many have not the 2.02 ln e^x bug.. They were returned to the service for a guarantee repair after the BUG discovery,

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 00007
eBay





1143A 00051
Nicolas Recalde Nicolas Recalde

Yes
OK

1143A 00357



Yes
OK

1143A 00429
Wlodek Mier-Jedrzejowicz Wlodek Mier-Jedrzejowicz



1143A 00463
Tom Drewski


Yes
OK

1143A 00516
Jon Bremner
Jon Bremner


Yes
OK

1143A 00754
Albert Threlfall



Yes
OK

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 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
eBay


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 01669
db
db



Version 2
1143A 01743
eBay




NO

1143A 01873
Tom Drewski

Yes
OK

1143A 02034
Ronald
Ronald

Yes
OK
Version 2
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

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
eBay

Yes
OK

1143A 02499
Alberto Fenini
Alberto Fenini


Yes
OK

1143A 02501
Reinhard Hawel
Reinhard Hawel

No
OK
1143A 02581
Scott Reynolds
Scott Reynolds


No
OK
1143A 02585
Paolo Reda
Paolo Reda

Yes
OK
1143A 02662
eBay



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
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 02986)
HP Journal 01




Image in the journal only
1143A 03007
eBay




No

1143A 03048
eBay



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 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 03779



No
OK
1143A 03770
Gianmaria Porrini
Gianmaria Porrini



1143A 04161 ?





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

?
?
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



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
eBay



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



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: 29. November 2013


Email: ecksteinm(at)volny.cz



 



2006-2013 (C)  Michael Eckstein
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