HP 29C DIAGNOSIS and RESTORATION

Presented by: Jim Johnson HP 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 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

A WORD OF

*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. RESTORATION of an HP 29C CALCULATOR Setting Expectations

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 calculator What 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”.

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 CALCULATOR Acquisition of two HP‐29C calculators SN: 1811S20315 SN: 1904S21718 May 7, 2012 ‐ eBay June 28, 2012 ‐ eBay

HP 29C’s sell on eBay for range from $81 ‐ $372. Avg. sell price $202 Listing 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 CALCULATOR Disassembly, Photos, Identification of Integrated Circuits and Power Supply

To open remove the top 2 Screws under the footpads RESTORATION of an HP 29C CALCULATOR Disassembly, Photos, Identification of Integrated Circuits and Power Supply

3 1

2 RESTORATION of an HP 29C CALCULATOR Disassembly, Photos, Identification of Integrated Circuits and Power Supply Arithmetic 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

RAM/ ROM IC

1 SN: 1811S20315 POR (Power on Reset), Battery Low Comparator IC RESTORATION of an HP 29C CALCULATOR Disassembly, Photos, Identification of Integrated Circuits and Power Supply 22uF, 10v diode diode 100pf 6.8uF, 10v NPN Transistor 2.2KΩ 15uF, 3.3uF, 10v 10v

2 10uF, 16v 10KΩ 68Ω 2.2uF, 6v NPN Transistor Tank oscillator circuit diode 330pf cap. & 15uH coil 330pf diode diode HP 29C Power Supply PCB (Daughter Board) RESTORATION of an HP 29C CALCULATOR Disassembly, Photos, Identification of Integrated Circuits and Power Supply

ROM/Anode Driver IC Cathode Driver IC

3 RESTORATION of an HP 29C CALCULATOR HP 29C Schematic +2.4 vdc Vbat

33Ω +6.0 vdc Vss + 47uf 1 8 NC 1820‐1983 NC 2 Power‐on 7 +6.0 vdc To pin 3 on ACT NC Vgg 3 Reset, low 6 Sync 1 8 Vgg Sync 1 8 Vss 1 8 Sync POR 4 battery 5 2 7 Φ 2 2 7 Φ 2 Φ 2 2 7 ISA +6.0 vdc 1818‐0377 +6.0 vdc 1818‐0376 1818‐0379 Φ 1 Vss Φ 1 Vss 3 ROM 6 3 ROM 6 Vgg 3 RAM/ROM 6 4 5 ISA 4 5 ISA Φ 1 4 5 Data

+6.7 vdc Vram +6.0 vdc 1 16 Vss NC NC Gold (f) Blue (g) 1 22 2 15 SST GSB GTO shift shift ‐12.0 vdc NC Vgg RCD 3 14 o o o o o o o o o o 2 21 Φ 1 4 5061‐046913 To pin 3 on POR Φ 2 B5 SYNC X  Y R ↓ STO RCL ∑+ 3 20 5 RAM 12 NC 6 11 NC o o o o o o o o o o A7 POR 4 19 ISA 7 Data + 10 B7 ENTER↑ CHS EEX CLX Sync POR A2 2.2uf 8 9 5 18 o o o o o o o o o o 1820‐1596 A6 6 17 Φ 1 B8 _ 7 8 9 ACT K8 20 A5 Φ 2 +6.7 vdc o o o o o o o o 7 16 K7 and B1 Vram 19 NC K6 and B3 1 16 +6.0 vdc B6 A4 NC NC 14 18 4 5 Vss K5 and B4 + 6 8 15 2 15 +6.0 vdc NC Vss 15 13 1820‐1382 K4 and B6 o o o o o o o o A3 OSC 330pf 3 14 16 9 14 Φ 1 12 4 2KΩ NC Cathode K3 and B8 B4 150uH 5061‐046913 17 X 1 2 3 ISA Φ 2 Driver 11 10 13 OSC 5 STR K2 and B7 RAM 12 4 10 o o o o o o o o NC NC & 6 11 5 K1 and B5 DATA 11 12 ISA Data Keypad 9 7 RCD K12 B3 ÷ 0 . R/S 10 6 Driver Sync POR 8 8 9 +2.4 vdc K11 o o o o o o o o Vbat 7 3 2 K10 B1 1 K9 A2 A3 A4 A5 A6

Sync Segment “a” ‐12.0 vdc 18 1 Vgg Segment “f” 17 2 Φ 2 Segment “b” 16 3 Φ 1 Segment “c” 151820‐0431 4 NC Anode Vdisp 14 5 a ISA Driver / Segment “d” 13 6 f b ROM Segment “h” 12 7 g STR Segment “e” e c • Based on S/N: 1811S20315 +6.0 vdc 11 8 Vss Segment “g” d h • drawn by: JAJ – 2013 August 12 10 9 1990‐0559 12‐digit LED Display HP 29C Calculator Hewlett‐Packard Page 1 of 1 Created: 2013 August 12 RESTORATION of an HP 29C CALCULATOR Troubleshooting and Diagnosis 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. RESTORATION of an HP 29C CALCULATOR Troubleshooting and Diagnosis Is the Power Supply Functional?

Vss = +6.0vdc Vdisp = +4.37vdc

Vram = +6.5vdc

Tank oscillator circuit Vbatt‐IN= +2.4vdc (switched) Vgg = ‐12.0vdc RESTORATION of an HP 29C CALCULATOR Troubleshooting and Diagnosis Is the ACT Functional?

Arithmetic Control & Timing IC (ACT) Oscillator ɸ1 and ɸ2 Pins 13 & 14 Pins 16 & 17

Ref. Pin# 1 RESTORATION of an HP 29C CALCULATOR Functioning 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 programming examples in HP29C Applications Book. All functions worked perfectly! RESTORATION of an HP 29C CALCULATOR Contrast and Compare Past with Present HP 29C • 98 program steps (with fully merged keycodes) • 928 program steps in RAM WP 34S • 30 storage registers. (16 were directly or indirectly • 107 global general purpose registers addressable and the rest were only indirectly addressable.) • 112 global user flags • 3 levels of subroutines and 10 labels • 6014 program steps in flash memory • 4 level stack (X, Y, Z, T) • 30 byte alpha register • Indirect storage, recall, branching and subroutine calls • 16 local flags and 144 local registers • Execution speed ~ 3,000 instructions/sec. • 6 (min) levels of subroutines • Continuous memory • 8 level stack • Rechargeable batteries • 34 digit decimal accuracy • Continuous memory Math 2 • CR2032 (2x) disposable batteries +,‐,x, ÷, 1/x, √x, x Math x x x LOG x, 10 , LN x, e , y , pi +,‐,x, ÷, 1/x, √x, x2 %, INT, ABS LOG x, 10x, LN x, ex, yx, pi Trig (SIN, COS, TAN) %, INT, ABS Modes (degrees, radians, grads) Trig (SIN, COS, TAN) Statistical Hyberbolic Trig. (SINH, COSH, TANH) Mean, std. deviation (2 variables) Modes (degrees, radians, grads, fractional) Summation of n, x, x2 Conversions and Constants Summation of n, x, x2, y 88 conversions available Summation of n, x, x2, y, xy 50 fundamental constants Summation of n, x, x2, y, y2, xy Pre‐programmed Functions Polar/rectangular conversion HP‐42S function set (solver, integration, matrix operations, curve fitting, etc.) Dec. hrs./hrs.min.sec. conversion 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 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! RESTORATION of an HP 29C CALCULATOR

APPENDIX RESTORATION of an HP 29C CALCULATOR Additional photos

Single level HP 29C Power Supply Integrated into Main PC Board SN: 1904S21718 RESTORATION of an HP 29C CALCULATOR Socketed HP 29C PC Board RESTORATION of an HP 29C CALCULATOR Additional Waveforms ɸ2 Pin# 16

ɸ1 Pin# 17

Isa Pin# 10

Data Pin# 11 HP 25 Calculator Waveforms

ɸ1 & Isa & ɸ2 ɸ1

Sync & Data & ɸ2 ɸ1

Data & Display ɸ2