HP9100B: transistor specs needed

[jebem]

(04-18-2016 10:37 AM)isanchez Wrote:  Is it necessary to remove the transistor to determine the type PNP or NPN, with a multimeter? Even to determine if it is blown?

Hi, Ignacio,

Well, I usually check it in circuit using a regular ohmmeter set to diode testing just for an initial check.

Depending on the results and other information available, if I still suspect it may be defective, I remove it to check off circuit. Usually in circuit testing is not reliable because if there are other components in parallel it will change the readings resulting in misleading information.

For instance, we may read a short circuit between two of the three legs but we can not conclude that the transistor is faulty because if there is a low resistance component in parallel we are in fact reading this later component.

But because that calculator has a number of identical circuits we can compare the transistor readings (voltages and resistances) in circuit for a initial checking.
But sooner or later we will need to remove the suspect component to test it of circuit.

Also, an oscilloscope, even a modest one able to display just up to 10MHz Y-channel and 1uS time base X-channel, will be of great help because we can check the dynamic behavior of those transistors as well.
However it must cope with high voltages (at least 200Volt on the Y-channel amplifier input attenuator) specially when dealing with vacuum fluorescent displays.
I would recommend a classic legacy one from the 70's as they are usually robust. They can be bought for low prices in eBay. High calibrated precision is not a must for this kind of application.