Progress

Dan

Sorry I have been offline for a few days, due to pressure of work/ awkward shift pattern,
Thanks to all, for your comments and advice, I have concentrated on one axis, and I am almost convinced that the ICs are causing the problem.

>>>Just as a precaution I changed the 555, and the 0.1 and 0.22 caps, still no change.

>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)

>>Have you measured the output using a digftial VOM to make sure that you have the full voltage swing for full + and full - rating of the power supply. If not stop and isolate that portion of the circuit and correct.

>>>The Digital Multimeter that I have does not react fast enough even at the slowest timer setting to register full voltage swing, it measures 16v+/- this decreases as the 555 is turned up, I have got 36v going into the Fets, so can I assume 36v out ?



>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

>>Are you sure the fet s are installed in the correct orientation with a 9z 34 two z34s then two 9z 34s and then two z34 and a 9z34?

>>>The 9Z34s and the Z34s are all installed correctly, and with their backsides facing away from the board, (if you will excuse the expression).

>Y axis

>Still nothing running at all, but the PBL 3776 gets warm after a while ?

>>With the power off use a digital VOM set at the lowest ohm scale. Check for shorts between the center lead and both sides. They should read open. If not replace.

>>>They are open circuit when checked with my multimeter (lowest setting 200 OHMS) Nothing heard when checked on the audible continuety setting.


>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.
>>The one that you get no reading is the bad one. Replace. it.


>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 ?

>>It sounds like you fried that portion of the circuit that is the reason that the fets are cold on that side.

>>>I have tried one new PBL3776 This gets hot the same as the old one, I can't locate a PBD3517 to try out, could this be causing the problem,

Paul is there any chance you could locate one of these, I have tried Maplin,Farnell and RS and local dealers, but no joy.

Ericsson
Y814
PDB 3517

>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