HP 29C CALCULATOR DIAGNOSIS and RESTORATION

Presented by: Jim JohnsonHP Handheld Conference 2013 – Fort Collins, CO

September 21-22, 2013

RESTORATION of an HP 29C CALCULATOR

Synopsis: The HP 29C is one of the last of the Woodstock series of calculators to be developed and introduced by HP in 1977 and was produced for the next 2 years until 1979. This was the top of the line Woodstock series calculator (code name “Bonnie”) along with its twin, the HP 19C which had a printer incorporated as part of the calculator. This presentation will follow my diagnosis of the electrical characteristics of the HP 29C and its functionality. We’ll take a look at the schematic, including the power supply section. Then we’ll dive into the output waveforms of the Arithmetic, Control and Timing (ACT) chip. Finally we’ll finish with the restoration of functionality of the HP 29C and the completed unit (S/N: 1811S20315).

RESTORATION of an HP 29C CALCULATOR

Agenda• Synopsis• Calculator acquisition – brief history• Disassembly, Photos, Identification of Integrated Circuits and Power Supply• Schematics• Troubleshooting and Diagnosis• Functioning HP 29C Calculator• Contrast and Compare Past with Present• Summary and Conclusions

RESTORATION of an HP 29C CALCULATOR

*Never* attach the charger of a Woodstock series unit to the calculator without a known good rechargeable battery in place. An AC charger connected to an HP 29C with a bad battery, bad contact or without a battery in place, has a high degree of certainty that the excess voltage will destroy or damage the unit.

A WORD OF

RESTORATION of an HP 29C CALCULATOR

What this presentation is:• A discussion of my passion and interest in vintage HP

calculators from a hardware perspective• Sharing information learned/not available on the web• Troubleshooting methodology for HP Woodstock Series• Bringing a vintage, rare HP 29C back to life!• A brief contrast and compare of HP 29C versus a modern HP

calculatorWhat this presentation is not:• Not an in-depth discussion of the operation of the HP 29C• Not a critical examination of the routines or ROM firmware

used in the HP 29C• Not an exhaustive study of the mathematical concepts used to

create “Bonnie”.

Setting Expectations

Personal Collection: HP01, HP10bII, HP12C, HP15CLE HP17bII+, HP21, HP25, HP29C, HP30b, HP32E, HP32SII, HP34C, HP35S, HP41CX, HP42S HP45, HP67, HP97, HP200LX, WP34S

RESTORATION of an HP 29C CALCULATORAcquisition of two HP-29C calculators

SN: 1811S20315May 7, 2012 - eBay

SN: 1904S21718June 28, 2012 - eBay

HP 29C’s sell on eBay for range from $81 - $372. Avg. sell price $202Listing prices range $0.99 - $495. Note: According to the Museum of HP Calculators, the HP 29C sold new in 1977 for $195.00 (USD).

RESTORATION of an HP 29C CALCULATORDisassembly, Photos, Identification of Integrated Circuits and Power Supply

To open remove the top 2Screws under the footpads

RESTORATION of an HP 29C CALCULATORDisassembly, Photos, Identification of Integrated Circuits and Power Supply

13

2

RESTORATION of an HP 29C CALCULATORDisassembly, Photos, Identification of Integrated Circuits and Power SupplyArithmetic Control and Timing (ACT) IC, RAM, ROM, POR/Battery Low Comparator

Arithmetic Control and Timing (ACT) IC ROM IC’s

CMOS Static RAM

I.C.’s

POR (Power on Reset),Battery Low Comparator IC

RAM/ROM IC

SN: 1811S203151

RESTORATION of an HP 29C CALCULATORDisassembly, Photos, Identification of Integrated Circuits and Power Supply

3.3uF, 10vNPN Transistor

NPN Transistor Tank oscillator circuit330pf cap. & 15uH coil

68Ω10KΩ 10uF, 16v

6.8uF, 10v

2.2uF, 6v

15uF, 10v

2.2KΩ

22uF, 10v

330pf

100pf

diodediode

diode

diode diode

HP 29C Power Supply PCB(Daughter Board)

2

RESTORATION of an HP 29C CALCULATORDisassembly, Photos, Identification of Integrated Circuits and Power Supply

3

Cathode Driver ICROM/Anode Driver IC

RESTORATION of an HP 29C CALCULATOR

1820-1596ACT

1820-1382Cathode Driver

&KeypadDriver

5061-0469RAM

HP 29C CalculatorHewlett-Packard

Page 1 of 1 Created: 2013 August 12

1990-055912-digit LED

Display

• Based on S/N: 1811S20315 • drawn by: JAJ – 2013 August 12

1820-0431Anode

Driver /ROM

1818-0379RAM/ROM

5061-0469RAM

1234

8765

1818-0377ROM

8765

Vgg

Φ 2

Φ 1

ISA

1234

Vss

Vgg

Φ 2

Φ 1

ISA

Vss

Φ 2

Vgg

Φ 1

Sync

ISA

Data

1818-0376ROM

1234

8765

Sync

Vss

Sync

12345678

16151413121110 9

12345678

16151413121110 9

Vram

NC

NC

Φ 1

Φ 2

NC

ISA

Sync

Vram

NC

NC

Φ 1

Φ 2

NC

ISA

Sync

Vss

NC

Data

POR

NC

Data

POR

+6.7 vdc

+6.0 vdc +6.0 vdc

+6.0 vdc

+6.7 vdc

1

2

3

4

5

6

7

8

9

10

11

22

21

20

19

18

17

16

15

14

13

12

Vss+6.0 vdc

Vgg-12.0 vdc

RCD

SYNC

Φ 1

Φ 2

NC

POR

NC

ISA

DATA

1820-1983Power-on Reset, low

battery

1234

8765

330pf

150uHOSC

OSC

+ 2.2uf

To pin 3 on POR

A3

A4

A5

A6

A2

A7

141516174567

20191813121110 9 8 3 2 1

+6.0 vdc

+2.4 vdc

NC

NC

Vbat

Vss

2KΩ

RCD

STR

+6.0 vdcVss

NC NC

NC

POR

+2.4 vdc Vbat

+ 47uf

33Ω

o oo o o o o oo o

o oo o o o o oo o

o oo o o o o oo o

o oo o o oo o

o oo o o oo o

o oo o o oo o

o oo o o oo o

Blue (g)shift

Gold (f)shiftGTOSST GSB

STOX Y R ↓ RCL ∑+

CHSE N T E R ↑ EEX CLX

8_ 7 9

5+ 4 6

2X 1 3

.÷ 0 R/S

To pin 3 on ACT

+6.0 vdc

123456789

Segment “a”

Segment “f”

Segment “b”

Segment “c”

Vdisp

Segment “d”

Segment “h”

Segment “e”

Segment “g”

A2 A3 A4 A5 A6

B1

B4

B3

B8

B6

B5

B7

K9

K10

K11

K12

K3 and B8

K2 and B7

K1 and B5

K6 and B3

K5 and B4

K4 and B6

K8

K7 and B1

181716151413121110

Sync

Φ 1

Φ 2

STR

Vss+6.0 vdc

NC

ISA

Vgg-12.0 vdc

ab

c

d

e

fg

h

HP 29C Schematic

RESTORATION of an HP 29C CALCULATOR

1. Acquired 1st HP29C. After examining the pc board for damage, put in charged battery pack and observed 12 zeroes lighting up on display. No keypad button presses would change the display.

2. Suspected one of the IC’s was bad. Measured current of 300-400mA. Much higher current than HP25 and measured HP29C supply voltages. The supply voltages measured lower than normal.

3. Unsoldered all RAM/ROM IC’s and applied power observing only one zero lit up in display (far RH digit in display). Suspect Anode/ROM IC.

4. Acquired 2nd HP29C (s/n: 1904S21718) which had no display when powered on. Power supply voltages measured good and the supply current measured good around 200mA.

5. I swapped the Cathode Driver and Anode/ROM Driver from s/n: 1811S20315 into s/n: 1904S21718 (2nd HP29C). No display in second HP29C.

6. Used good HP25 to measure signals on ACT: oscillator, data, Isa, sync, ɸ1 and ɸ2. I measured same signals from s/n: 1811S20315 and found ɸ2 amplitude was low at 9vpp. Suspected the ACT in 1st HP29C may be damaged.

7. Installed low profile IC sockets in HP29C s/n: 1811S20315. Removed ACT from 2nd HP29C and installed into 1st HP29C.

Troubleshooting and Diagnosis

RESTORATION of an HP 29C CALCULATOR

Tank oscillator circuit

Vss = +6.0vdc

Troubleshooting and DiagnosisIs the Power Supply Functional?

Vdisp = +4.37vdc

Vram = +6.5vdc

Vgg = -12.0vdcVbatt-IN= +2.4vdc

(switched)

RESTORATION of an HP 29C CALCULATORTroubleshooting and Diagnosis

Is the ACT Functional?

Oscillator Pins 13 & 14

Ref. Pin# 1

ɸ1 and ɸ2Pins 16 & 17

Arithmetic Control & Timing IC (ACT)

RESTORATION of an HP 29C CALCULATORFunctioning HP-29C Calculator (SN: 1811S20315)

8. Installed original IC’s from s/n: 1811S20315 with ACT from 2nd HP29C and turned on power switch. Single zero lit up in LH location on display.

9. Plugged in RAM IC’s and turned on HP29C. Display showed “error”. CLX key cleared the display to “0.00” showing in LH location.

10. EUREKA! Calculator seemed to be functional!

11. Continued to test functions on HP29C and tested programmingexamples in HP29C ApplicationsBook. All functions worked perfectly!

RESTORATION of an HP 29C CALCULATOR

• 98 program steps (with fully merged keycodes) • 30 storage registers. (16 were directly or indirectly addressable and the rest were only indirectly addressable.) • 3 levels of subroutines and 10 labels• 4 level stack (X, Y, Z, T)• Indirect storage, recall, branching and subroutine calls• Execution speed ~ 3,000 instructions/sec.• Continuous memory• Rechargeable batteries

HP 29C WP 34S• 928 program steps in RAM• 107 global general purpose registers• 112 global user flags• 6014 program steps in flash memory• 30 byte alpha register • 16 local flags and 144 local registers• 6 (min) levels of subroutines• 8 level stack• 34 digit decimal accuracy• Continuous memory• CR2032 (2x) disposable batteries

Math+,-,x, ÷, 1/x, √x, x2

LOG x, 10x, LN x, ex, yx, pi%, INT, ABSTrig (SIN, COS, TAN)Modes (degrees, radians, grads)

StatisticalMean, std. deviation (2 variables)Summation of n, x, x2

Summation of n, x, x2, ySummation of n, x, x2, y, xySummation of n, x, x2, y, y2, xy

Polar/rectangular conversionDec. hrs./hrs.min.sec. conversion

Math+,-,x, ÷, 1/x, √x, x2

LOG x, 10x, LN x, ex, yx, pi%, INT, ABSTrig (SIN, COS, TAN)Hyberbolic Trig. (SINH, COSH, TANH)Modes (degrees, radians, grads, fractional)

Conversions and Constants88 conversions available50 fundamental constants

Pre-programmed FunctionsHP-42S function set (solver, integration, matrix operations, curve fitting, etc.)HP-16C function set (Logical operators, floating pt. decimal math)HP-21S probability function set (Distributions, linear regression, Chi-squared, etc.)

+Euler’s Beta and Riemann’s Zeta functions, Bernoulli and Fibonacci numbers, +Lambert’s W, the error function, and the Chebyshev, Hermite, Laguerre, and Legendre orthogonal polynomials+ many statistical distributions and their inverses: Poisson, Binomial, Geometric, Cauchy-Lorentz, Exponential, Logistic, Weibull, Lognormal, and Gaussian, + programmable sums and products, first and second derivatives, solving quadratic equations for real and complex roots, + testing for primality, + integer computing in fifteen bases from binary to hexadecimal, + extended date and time operations and a stopwatch3 based on a real-time clock, + financial operations such as mean rate of return and margin calculations

Contrast and Compare Past with Present

RESTORATION of an HP 29C CALCULATOR

Summary and Conclusions• The goal of this paper was to share HP29C information with the HHC 2013 audience as well as other HP calculator enthusiasts.• Diagnosis of the HP29C begins with examination of the overall condition of the calculator, disassembling, cleaning and using a known good power source.• Measure the four power supply voltages in the power supply section.• Once the power supply voltages are verified good, then you can move on to check the oscillator, ɸ1 and ɸ2 signals.• If integrated circuits are damaged, either from battery corrosion or from excess applied voltage, the only alternative is to find a “donor calculator”. • If ACT IC is damaged; same applies in that you’ll need to find another ACT. • Finally, the restoration of these fine pieces of history is satisfying and rewarding and keeps part of Hewlett-Packard history alive for future generations.

RESTORATION of an HP 29C CALCULATOR

Acknowledgements

1. Tony Duell (UK) – Information on MoHPC site and email exchange in 2012.2. Jacques Laporte – HP Calculator Forum (www.jacques-laporte.org/forum)

email exchange and the very excellent paper “The ‘Woodstock’ generation”.

3. Museum of HP Calculators – (http://hpmuseum.org)4. Geoff Quickfall (Canada) – Email exchange regarding HP calculators,

particularly the HP19C.5. Dave Colver (UK) – Email exchange regarding HP29C schematics.6. Randy Sloyer – (www.fixthatcalc.com) email exchange in 2012.7. Eric Smith – Email and posts on MoHPC.8. Katie Wasserman – email exchange regarding HP29C.

RESTORATION of an HP 29C CALCULATOR

Thank you!

© All rights reserved regarding the information contained in this presentation . If you have any questions you may contact Jim Johnson. Email: jjohnson873@yahoo.com

RESTORATION of an HP 29C CALCULATOR

APPENDIX

RESTORATION of an HP 29C CALCULATOR

Single level HP 29C Power Supply Integrated into Main PC BoardSN: 1904S21718

Additional photos

RESTORATION of an HP 29C CALCULATORSocketed HP 29C PC Board

RESTORATION of an HP 29C CALCULATORAdditional Waveforms

ɸ2Pin# 16

DataPin# 11

IsaPin# 10

ɸ1Pin# 17

HP 25 Calculator Waveforms

ɸ1 & ɸ2

Data & ɸ1

Data & ɸ2

Isa &ɸ1

Sync & ɸ2

Display