Capacitor lifetimes



#5

Hello,
Does anyone know if HP utilised discrete capacitors with known lifetime issues?

Thanks, David


#6

The one capacitor that almost always causes problems is the small blue dipped tantalum bypass capacitor in HP67 card readers (also some '65 readers). If your reader writes but won't read, this beastie is the problem. It will look and test good, but it develops a high internal ESR (equivalent series resistance) and stops doing its thing. When rebuilding a reader in these machines, I always replace this cap even if it seems OK. Eventually it won't be.

I have also seen bad tantalum power supply filter caps in Woodstock series machine power supplies (particularly HP29C units).

Very occasionally the main power cap in an HP41 will develop a leak and drain your batteries quickly.


#7

David Smith:

Regarding the HP-67:
Are you referring to the small capcitor which is attached
to the terminals on the motor itself? Thanks.

Larry


#8

No, the problem bugger is on the little reader circuit board. There are three tantalum caps there. Two are used in connection with the head windings and the other is the failing power cap. Also the HP97 reader can have the same problem (but not nearly as often as the '67)


Possibly Related Threads...
Thread Author Replies Views Last Post
  Hp-67 card reader: tantalum capacitor identification Ignacio Sánchez 8 2,243 06-02-2013, 07:26 PM
Last Post: aj04062
  Capacitor Value affirmation, 19C: ME needs EE Help! aj04062 24 3,816 09-26-2012, 06:30 PM
Last Post: Diego Diaz
  Original DM-15CC batch capacitor patch Neil Hamilton (Ottawa) 2 929 07-19-2012, 08:26 PM
Last Post: Gerson W. Barbosa
  WP-34s: Crystal and capacitor instructions? W. Bruce Maguire II 2 964 05-03-2012, 02:04 PM
Last Post: W. Bruce Maguire II
  OT (as in Out of Touch) -- 1.5 Farad (!) Capacitor??? Paul Brogger 24 3,686 08-19-2007, 06:11 AM
Last Post: Matthew W. Milligan
  Replacing AC + Battery with DC + Capacitor Howard Owen 0 479 11-29-2005, 03:45 PM
Last Post: Howard Owen
  HP-67 tantalum capacitor ALBERT 1 649 02-15-2005, 12:25 PM
Last Post: David Smith
  Woodstock capacitor values? John Garza 10 1,781 05-09-2004, 10:18 PM
Last Post: Tony Duell
  11c Power Supply Capacitor Lunn Sawyer 2 707 12-19-2003, 11:34 AM
Last Post: Nelson M. Sicuro (Brazil)
  HP-97 capacitor Michel Beaulieu 5 1,142 01-29-2003, 01:45 PM
Last Post: David Smith

Forum Jump: