Digital Test
Hewlett-Packard 3430A

Manufacturer: Hewlett-Packard
Model: 3430A
Year: 1967
Schematic: RE
Functions: DCV
Display: NIXIE
Digits: 3
Logic: discrete transistor Si/Ge-PNP/NPN

A conventional design for the A/D converter using a staircase ramp. The staircase is generated by a D/A converter fed by the counter circuits and is compared with the input level to control the clocking of the counter.

- Unit Log -

Serial Number: 723-00193
Year of Manufacture: 1967 (Component date stamp 6752).
Other Identification: Canadian Armed Services
Navy CD 665110
Digital Voltmeter
Serial No. 00193
Date of Receipt: 1997
State upon Receipt: Non-functional. Unit had previously failed and various components were then removed from board A1. 8 transistors on board A2 appear to have been previously replaced. Otherwise good physical condition.

Date: 1997
Procedure: Components on board A1 which had been removed replaced with best guesses. Removed components were A1-Q7,8,16,17,20,23,27, A1-R38,45,54,81,90, A1-C3,15,17,19.

Date: 1997
Procedure: Transistor A5-Q1 in power supply (2N3053) faulty, replaced with 2N5681. Functional.

Date: 2003 Apr 05
Procedure: Numeral '3' of tens digit does not display properly. Gold film path on ceramic LDR matrix open. LDR matrix of tens digit swapped with that of units digit, so problem is in LSD digit.

Date: 2006 Apr 11
Procedure: HP parts list obtained. Previously replaced resistors and capacitors on board A1 replaced with proper values. Transistors were replaced with 2N3906 but should be 2N4122. 3906 spec has lower min gain but all seems OK.

Date: 2006 Apr 25
Procedure: Display intermittently sticks at 1000 in the range 600 to 1000 (after 599 display jumps to 1000 and stays there through to 1001). Third digit is rolling to 0 from 5 rather than to 6. Heat applied around A2Q5 and A2Q6 will force reversion to proper operation. Q6 replaced, still faulty. Q5 replaced, OK (replaced with 2N1192). (Q6 original placed back.)

Date: 2006 Apr 26
Procedure: Old-style power connector repaced with IEC standard. Some cabinet screws replaced with shorter ones obtained from scrapped HP equipment.

Date: 2006 Apr 27
Procedure: Variable resistor A2R6, which was missing when received, and then shorted as initial replacement, replaced with 10K, probably should be 3K. Full calibration performed in accordance with instructions in HP manual (obtained from Decode Systems).

  .. | Hewlett-Packard 3430A | ..
Early Digital Test Equipment