TNC145 blowing fuses

[Mike Woo]

AAAAAH help! I have a series 2 interact with a tnc 145 control. Today it wouldnt switch on.
I have traced a blown fuse to the fuse holder in the back of the control box, replaced it and blew it again instantly as i switched the power on at the wall.

I have disconnected the terminals to the vdu screen and the 4 screw on cables that go to the main box on the mill. Blew the fuse..

The only thing that will stop this fuse blowing is to take out the large fuse in the mill box named TFU 2 but i guess this just feeds power to the control box.

It will blow the fuse regardless of whether the stop button is on or off.

I am running out of fuses! Any offers?

Oh and as the handwheel has been getting noticably stiffer and i stripped it hoping to find something wrong but all i managed to do was smash the glass so if anyone has one i need to replace it.

All round a bad day!

Thanks Mike

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[machintek]

Are you talking about the little fuse in the back of the TNC with the voltage dial around it?
If this is blowing, your control is at fault. The control can be removed through the front. The wired in the back are actually plugs that come out sideways. Then the top of the control can be removed exposing plug in boards. It is probably the power supply board that is blowing the fuse. I hope your parameters are backed up.

George

[Mike Woo]

Hi
Thanks George.
Yes it is that fuse. I have had the box out and blown air through it hoping a bit of swarf had got in there.
Guess i will be taking it appart.
Is there anything in particular that fails on the power supply board?
Cheers Mike

[gus]

the PS is common to the 151, and thus supported by heidenhain last I knew.

It is probably caps

[machintek]

I guess there are some things easy to check. Transformer, bridge rectifier/diodes, electrolytic capacitors, etc. Sounds like it is a good short.

George

[Mike Woo]

Thanks for the help so far.

Well sadly it didnt heal overnight so i have now disconnected the feeds from the power board to the rest of the control box and it still blew the fuse so i think this as you say confirms that the problem is on this board.

From now on my knowledge of what i am doing stops.
I cant visually see any problem. There are no burned out bits. The blue label on what may be a transformer looks distorted and wrinkly but thats about all i can make of it.

It has occured to me the machine was left on but not referenced for a day, maybe this caused the problem in the first place?

Are there wiring diagrams available for the board, can anyone fix this one or does anyone have a working one i can buy? I also need a handwheel.

I tried to learn everything about electronics in one night off of the internet but it was heavy going!

Thanks again Mike

[Jukka Honkanen]

Check the two big diodes on the left lower corner of the picture. Those use to burn when I was repairing these some 20 years ago. Check also the diode (if I remember right) which is in the cooling holder next to the diodes.

Good luck
Jukka

[Mike Woo]

Check the two big diodes on the left lower corner of the picture. Those use to burn when I was repairing these some 20 years ago. Check also the diode (if I remember right) which is in the cooling holder next to the diodes.

Good luck
Jukka

Thank you Jukka
Today i tried removing the two other fuses on the center of the board but the fuse blew.
However if i remove any of the 4 (2 red and 2 brown) wires next to the big diodes the fuse did not blow but nothing works.
I will try your advice tomorrow.
Cheers

[Mike Woo]

I have tested the two large diodes and replaced the diode in the heat sink(my neighbour says its thrysistor 2N6505, but i dont understand much of what he says) the new one tested differently and i thought we had fixed it but sadly the fuse still blows.
He says he cant do much else without a circuit diagram for the board which as far as i can see is unavailable.
Heidenhain didnt want to know and wouldnt say if the board for the 151 was the same and they would want the whole 151 box to repair anyway.

I did also discover there is only 2 volts on J9 where it says there should be 24but i dont know if this going into or out of the power control.
Is there anything else it could be before i give up and part with actual funds?
Has any one got one?
Thank you.

[Piki]

tnc 145 manual service