Re: Progress

Peter,
I do not know anything about your circuit or problem except that something bad happened and you are now trouble shooting it.

You might try as an intermediate step, to just fire up the board without any load (stepper) connected to it. Nothing should get too hot.

If it does, disconnect the drive signal to the stage that gets hot and see if that helps.

My guess is that you either has a shorted output transistor or the drive circuit tries to turn on both outputs at the same time.

An other crude intermediate step might be to thereafter connect light bulbs instead of stepper windings as loads. You can see which ones are turned on and that they alternately blink as you send a slow move command. Watch out
to get suitable voltage ratings on the bulbs. Applying lower voltage than rated is fine as long as you can see it glow.

I would use a scope but I do not know if it is available.

Resistors typically fail open and I would not expect that you have a problem with them

Bertho Boman
=================================

> "Peter Smith" <peter@...> wrote:
>
> Dan
> I have resoldered all the sockets, replaced all the 4700 caps, and some of the mossfets, ( I was given IRFZ 34N as a direct replacement for the IRFZ34 I assume these to be OK, or not ? ).
> I am running all axis at 1amp (no heatsinks fitted) with a 2 1/2volt 4 1/2 amp test motor, I have changed the ICs from axis to axis with no difference in performance, so assume all of these to be OK, or all U/S
>
> Z axis
> On the B b side of the axis, the 2 9Z34s get hot very quickly, while the 2 Z34s remain cold, (running at 1amp), the 9Z34s and Z34s on the A a side of the axis remain cold, (see later comment on 13FR100 Resistors)
>
> If you hold the bases of the 2 9Z34s on B b side when running the motor slowly you can feel the current, you cannot feel this on the 9Z34s of side A a .
> and the motor is erratic and sounds rough.
>
> X axis
>
> All 9Z34s get hot very quickly, and you can feel the current off them as in the above. Motor erratic and rough
>
> Y axis
>
> Still nothing running at all, but the PBL 3776 gets warm after a while ?
>
> I have tested all the OHMITE resistors, I have 5 which read 0.5 ohm on the 200 ohm scale, which is the same as joining the two probes together ie. no resistance, on the other one I cannot get a reading.
>
> Refering back to the Z axis
> The Ohmite resistor on which I cannot get a reading is on side A a the cold side of the axis, could it be that I have 5 reistors u/s ?
>
> I have tried to get these or equivilant resistors here but no luck yet.
>
> IF ANYONE IN ENGLAND KNOWS OF A SUPPLIER, THE RESISTORS ARE 3 WATT NON INDUCTIVE AND MARKED AS FOLLOWS
>
> OHMITE
> 13FR100
> 0.10 OHM 1%
>
> Best Wishes
> Peter Smith
>