n2ihp
Plastic
- Joined
- Nov 5, 2002
- Location
- Winooski, Vt. 05404
I need some help with the variable speed on my Hardinge HC lathe. It will not change speed, up or down. It works
in speed range 1 and 2 but shows no change when shifting to speed range 3. This problem started as an intermittent
problem, coming and going for a few months. Now it seems to have failed completely. It did run for a number of years
with no problem. The power is from a rotary phase convertor but that has all been in place for 15 years and
nothing has been changed. Other machines are operating as normal so I don't think it is the power.
The machine is from some time in the 60's and has rounded corner sheet metal. Here is what has been done so far.
The numbered wires have been checked for continuity from the control panel to the main electrical box and on to
the speed change motor control under the headstock. The speed control pots have been cleaned and checked, they
show a variable resistance across the full range and look good. Same for the pot at the speed change motor which
seems to be used for a sense circuit? The transistors in the control box were "diode" checked and seem OK. They
were also put back in the opposite socket but no change was seen. All screws on the ring lugs on the wiring were
loosened and re-tightened. The two P&B relays in the main electrical cabinet were swapped with no change shown.
There is 30VDC coming from the power supply near the P&B relays and the caps in the power supply have been tested
and are good. The micro switches on the drum switches were all checked and appear to be good. The speed it is going
to is in the normal range and is not tripping the over travel micro switches at each end of the speed range.
Another big clue is that with the motor turned off if I turn the large speed adjust screw by hand the RPM's go up or
down but it always returns the speed to the same spot. If I manually actuate the contactors for raising or lowering
the RPM's the speed will change but again, it always returns to the same speed. And range three doesn't work at all.
I have an HC manual on CD but that doesn't help much for this problem. There is also a blue print electrical
diagram that was in the main electrical cabinet. That is very hard to read and some parts are not legible.
What I need is some direction on where to look and what I should expect to find. Thanks in advance for any good
ideas on how to proceed.
John Mc Cabe
in speed range 1 and 2 but shows no change when shifting to speed range 3. This problem started as an intermittent
problem, coming and going for a few months. Now it seems to have failed completely. It did run for a number of years
with no problem. The power is from a rotary phase convertor but that has all been in place for 15 years and
nothing has been changed. Other machines are operating as normal so I don't think it is the power.
The machine is from some time in the 60's and has rounded corner sheet metal. Here is what has been done so far.
The numbered wires have been checked for continuity from the control panel to the main electrical box and on to
the speed change motor control under the headstock. The speed control pots have been cleaned and checked, they
show a variable resistance across the full range and look good. Same for the pot at the speed change motor which
seems to be used for a sense circuit? The transistors in the control box were "diode" checked and seem OK. They
were also put back in the opposite socket but no change was seen. All screws on the ring lugs on the wiring were
loosened and re-tightened. The two P&B relays in the main electrical cabinet were swapped with no change shown.
There is 30VDC coming from the power supply near the P&B relays and the caps in the power supply have been tested
and are good. The micro switches on the drum switches were all checked and appear to be good. The speed it is going
to is in the normal range and is not tripping the over travel micro switches at each end of the speed range.
Another big clue is that with the motor turned off if I turn the large speed adjust screw by hand the RPM's go up or
down but it always returns the speed to the same spot. If I manually actuate the contactors for raising or lowering
the RPM's the speed will change but again, it always returns to the same speed. And range three doesn't work at all.
I have an HC manual on CD but that doesn't help much for this problem. There is also a blue print electrical
diagram that was in the main electrical cabinet. That is very hard to read and some parts are not legible.
What I need is some direction on where to look and what I should expect to find. Thanks in advance for any good
ideas on how to proceed.
John Mc Cabe