Re: Westamp - PWM Servo Amp

Hi,

What does it say on the TO-3 can? Why do you think the transistors
are bad? You can check them by measuring the resistance across the
collector (can) to emmiter. Silicon invariably fails shorted unless
there is enough power supply current to vaporize it. A good part will
read open or close to it (10K or more) a bad one will be 100 ohms or
less. Use a digital ohmmeter. It applies only 100mV, not enough to
forward bias a junction and give a false reading.

You sometimes can find a replacement based on what it says on the
can, or knowing what the amp requires, come up with a substitution.

Mariss

--- In CAD_CAM_EDM_DRO@y..., bdoherty01@e... wrote:
> Hi,
> I have a Westamp PWM servo amp model no. 30060-3 ,(1981),with a
> faulty output stage.Details:
> Supply voltage: 100vdc
> Signal :+/- 10v
> Bias :15-0-15vdc
> Max output:20amp
> Cont output:10amp
> Motor HP : 1.1
> The output bridge uses four T03 packaged NPN silicon transistors
> which appear to have an internal 100r resistor across base-emitter
> and an internal diode across emitter-collector ,part
> no:29782w /c38123102.I am unable to locate replacements and both
> UK/US agents refuse to supply drawings or spares and quote $850.00
> and 30 working days for repairs!
> Can anyone suggest a replacement component, possibly with the
> resistor and diode mounted externally ? All help is greatly
> appreciated,
> Jim.
> Hi,
> I have a Westamp PWM servo amp model no. 30060-3 ,(1981),with a
> faulty output stage.Details:
> Supply voltage: 100vdc
> Signal :+/- 10v
> Bias :15-0-15vdc
> Max output:20amp
> Cont output:10amp
> Motor HP : 1.1
> The output bridge uses four T03 packaged NPN silicon transistors
> which appear to have an internal 100r resistor across base-emitter
> and an internal diode across emitter-collector ,part
> no:29782w /c38123102.I am unable to locate replacements and both
> UK/US agents refuse to supply drawings or spares and quote $850.00
> and 30 working days for repairs!
> Can anyone suggest a replacement component, possibly with the
> resistor and diode mounted externally ? All help is greatly
> appreciated,
> Jim.