More on test equioment.

[Tony Duell]

A couple of things I forgot to put in my other message.

Firslty, another instrument that you _need_ is a bench PSU. Adjustable 
voltage (at least up to 12V, preferably twice that), and at least 5A, 
with current limiting. You will find this invaluable for powering up 
logic boards outside the main machine, temporarily substuting for battery 
packs, testing motors, solenoids, etc. running motors when doing 
mechancial alignments, and so on. 

One somewhat unconventional use I put mine to recently was to 'lock' a 
stepper motor. By connecting one winding of the motor to the PSU and 
turning up the voltage until a moderate current flowed, I could lock the 
motor spindle and thus the pulley on said spindle. Running the steel 
cable that went onto that pulley and which operated the pen carriage in a 
ploter was a lot easier with the motor locked.

Secondly, 'good' does not mean 'lots of features'. Many such features are 
little more than gimmicks to be mentioned in the advertising. For 
example, many digital multimeters have a transistor Hfe range. Since I 
have no idea what collector current is used, this is somewhat useless. If 
I need to test a transistor, I will use my real transistor tester (a Tek 
575, OK...). You can do a quick go/no-go test on a transistor using the 
diode test range to make sure the junctions are still intact and not 
shorted, of course.

[OK, there is one use for the Hfe range. Once you've used the diode test 
range to (a) determine the polarity) anf (b) find the base lead, connect 
it to the meter (Hfe range) with the base going to the right socket and 
the other 2 leads going to the emitter and collector sockets. Try it with 
the latter both ways round. The connection that appears to give the 
higher Hfe is likely to be the correct one. No, it's not a substitue for 
looking the thing up in a data book, but if you have a house-coded part 
it can be useful...]

-tony