RS232 quit on the cnc mill

Does anybody know details about the related chips
that support RS232? I tried to send from machine to PC today & no go. Nothing either way. Then I replaced the 1488 chip (transmitter I think) and am now able to send TO the PC, but not PC-to-machine which I need to do. There are other components & chips on this card including the UART chip(s).

Any help appreciated....

dan k

1489 is the other I believe

051006-0938 EST USA

dkmc:

PMT is correct the 1489 is the Quadruple Line Receiver. You are correct that the 1488 is a Quadruple Line Receiver. These are specifically TTL to RS232 interface chips.

If you search the Internet for the data sheets on these chips you will find much useful information. The driver outputs are current limited to about 10 ma, but prior to current limiting have about a 300 ohm output resistance.

An important question is why did both fail, and why did not the ones in the PC fail, or did they?

Under normal conditions the 1488 and 1489 are very unlikely to fail.

A usual cause of failure is an excess difference in voltage between the transmitter and receiver. Did you have a lightening storm preceeding the fault, or did someone short a hot ac line to ground, or do you have ground problems?

Our I232 Isolator System will protect your equipment from most electrical faults. It also provides high baud rate capability (115.2 kbaud) at long distance (4000 ft), and good immunity to electrical noise (approximately 2000 v peak). We can run error free with a 1000 v rms (+/-1414 peak volts) 60 Hz sine wave directly to the common of the interconnect cable.

See our web site www.beta-a2.com and the pages on I232, and Noise and Grounding.

gar is correct. The 1489 is the receiver and the 1488 is the driver. The 1488 is repsonsible for the output of the TX (data) signal on pin 2, the RTS signal on pin 4, and the DTR signal on pin 20. The 1489 is responsible for sensing the inputs on the RX (data) signal on pin 3, the CTS signal on pin 5, the DSR signal on pin 6, and the DCD signal on pin 8.

On some model CNC controls, there are tiny fuses that protect the +12/-12v power supplies, so it's possible that you've blown a fuse also. If you replaced the 1488 driver, then when you try to send or receive a file, you should see a positive voltage on the CNCs serial plug on pin #4 and pin #20. You should also see a NEGATIVE voltage on pin #2. If you see voltages on those pins, then the fuses and power supply is OK.

What wasn't mentioned is that you can also use a 75188 as a replacement for the 1488 and a 75189 for the 1489. There is no functional difference.

Guys.....

I don't know -that- much about what all this card does.
Aside from that, there's 2 6821p's and one 6809p on it, along with 8 S/B 88313's and another 16 or so chips.

I have a spare card also, but it didn't help other than that's where I stole the 1488 that seems to work now. (as in- sends a program to the PC) I stole a 75189 off an old PC serial card, no go. Maybe I need a new-good 1489 to be sure its working. Was wondering what other chips it may be that I could try shotgunning....they are all in sockets at least, and I have swapped several at random, but it would be nice to be "in the neighborhood" functionally ......

Edit: My RS232 breakout board shows red LED's on pins 2 & 3 on powerup. No change when I try to send to the machine, not sure what when I transmit to the PC, but it works in that direction, so.....

Edit more:
We've had a couple pretty good storms since I used the machine last.....when RS232 worked fine.
It was plugged in, so maybe a close strike induced thru the ground wire.....????
No RS232 cable plugged into it....and not hooked up to the PC....

thanks!

dan k

The concerns about why the problem occured are quite valid... Those chips are generally pretty robust.

Have you trid connecting 2 PCs together so that you can validate that the PC's serial card isn't a problem?

Also, you should be aware that the PC may not be sending any data (hence the breakout box LEDs not flashing) because the flow control is not working. There are two types of flow control. The first is hardware and hence will be directly affected by your chips. In that scenario, some of the lines are used to tell when the PC should stop sending characters (or vice versa). The other scenario is software. In that mode, the machine will tell the PC to stop sending characters by sending a control code through the transmit line; you only need 3 wires for this technique (transmit, receive, ground).

--Alan

Have you trid connecting 2 PCs together so that you can validate that the PC's serial card isn't a problem?

Click to expand...

Already sent both ways....several times to another
machine yesterday......

dk

051006-1501 EST USA

dkmc:

I do not believe you have mentioned the brand of control.

The storms are the most likely cause of your problem.

Without appropriate test equipment it may be difficult to isolate a particular chip as the cause of the receive problem at the CNC.

If the chips are soldered in and not socketed, then it is hard to use a substitution method.

For some information on troubleshooting RS232 go to the E232 Photo page on my web site previously mentioned.

I have to make some assumptions about the connector at your CNC. These are:

1. The connector on the CNC is a 25 pin male D-connector, and is basically wired the same as Fanuc or HAAS.

2. This means that pin 2 is TxD from the CNC, pin 3 is RxD to the CNC, and pin 7 is signal common.

3. For either hardware or software handshake you generally connect pins 6, 8, and 20 together in the connector that plugs into the CNC.

4. For test purposes you connect pins 4 and 5 together, and also for software handshake.

5. In some cases you could leave 4, 5, 6, 8, and 20 unconnected, but you will have fewer problems testing or running if these are jumpered. There must be no connection between the jumpered 4-5, and the jumpered 6-8-20.

6. If you are running with hardware handshake then 4 and 5 must be appropriately connected between the CNC and computer. Except for certain tests.

7. Since the CNC is using 1488 and 1489 chips we can expect the open circuit rest voltages to be about +/- 10 v relative to pin 7 for the output lines. These are pins 2, 4, and 20. Also the short circuit current for any one of these to pin 7 should be about 10 ma. Open circuit means nothing connected to the CNC connector except the testing voltmeter. In my troubleshooting discussion you will note the high load that the LED tester places on the signal lines. Short circuit means you connect a low resistance between the output pin and pin 7. A milliampere meter is a low resistance.


My assumptions for current and voltage from the computer are the same as at the CNC unless the computer is a laptop.

You can run the same tests at the CNC end of the computer cable, but pin 3 is the TxD output from the computer. Pin 7 is still common.

The rest state (no data being transmitted) for a TxD line is about -10 v. From a laptop this might be about -5 v.

While random data is being sent TxD will average around +/- 1 v.

At the CNC end of the cable from the computer, with it unconnected to the CNC, check the voltage from pin 3 to 7 at rest and while data is being sent. If you can, also check the short circuit current.

Next connect the cable to the CNC, check pin 3 to 7 voltage at the CNC in the rest state, and with the computer sending data. Record these values.

.

051006-1846 EST USA

dkmc:

Some more information.

An important point of my previous discussion is for you to determine if there appears to be data on the TxD line (pin 3) from the computer at the CNC when you are sending data from the computer with the connector unconnected. This test with no connection is so any shorting fault in the CNC is not affecting your test.

If that test passes, then you determine whether the result are affected by connecting the cable to the CNC.

If the connected test looks good, then you are probably looking for a problem in the CNC.

Other background. On a HAAS machine every RS232 signal line and the pin 7 line have a 100 ohm 1/4 w resistor in series with each of these pins. Then on the HAAS control side of the 100 ohm resistor is an 18 v bipolar transient limiter (trade name for one brand is Transorb) from the resistor to common. Common in the machine is tied to pin 1 with no resistor and the the chassis of the machine and in turn to the plant electrical safety ground (green wire in the power wiring). This is a rather good protector for the 1488 and 1489 chips.

Other manufacturers might do the same thing or maybe use a fuse in place of the resistor. In general computer RS232 ports have no protection.

The size of the transient limiters used by HAAS are about the physical size of a 1N4004 diode, maybe slightly smaller. Somewhat bigger than a 1/4 w resistor and made of silicon.

I have run tests on a 12 v Transorb of this size with a 100 ohm 1/4 w metal film resistor. Applying 120 v ac from a 20 amp circuit across the series combination of the Transorb and resistor I burn out the resistor (meaning it opens) and do not damage the Transorb. A maximum voltage of 18 v applied to any input or output pin of an 1488 or 1489 is specified to not damage the chip.

.

Gar,
The control is an Aerotech made in Pittsburg,PA.
Circa 1986.
The PC is a dell.

The chips are all in sockets.

The Resistor/Transorb thing sounds great, however
I think if I just left the thing unplugged from the 3 phase service it would offer the same protection in this case (unless the storm hits when the machine is running).

An important point of my previous discussion is for you to determine if there appears to be data on the TxD line (pin 3) from the computer at the CNC when you are sending data from the computer with the connector unconnected. This test with no connection is so any shorting fault in the CNC is not affecting your test.

Click to expand...

Excellent test.....
I will do it tomorrow.
I had to run today with a relatively short program
keyed in by hand at the machine...took an hour... PITA!!
No up/down keys on the control, just +/- (the cursor worms thru each line).
Another job is up and that program has around 3 pages of code! I NEED to send it RS232.

I plan to retro this machine with MACH III soon.
I need to limp it along a bit longer till the day comes when I can rip out all these old electronics & replace them. Ah, the thoughts of a floppy drive, USB, and full alphanimeric keyboard...with COLOR monitor!!!

You have some neat apparatus on your web site.
Do you have printed catalogs?

dan k

051010-0757 EST USA

dkmc:

Have you been able to isolate the area where the problem may be?

Generally the information in our written material is similar to what is on the web site.

Lightning is not the only way RS232 circuits can be damaged. An electrical short or other voltage source may destroy these components.

Our I232 written material has a diagram and discussion on how a short circuit of the power hot wire to saftey ground can cause very damaging voltages to the RS232 circuits.

.

How long is the cable run from your PC to the machine? And the routing, hopefully not in the same vicinity as arc welding. I have a "vision" that you swap cables around to connect other things to the PC, or maybe not. Did you mention the machine RS232 was not connected to the cable for a long time? Good, if it was connected to the machine and disconnected from the PC it would be a pretty effective antenna. Does seem like exposed pins contacted something, out here in the very arid west static is a constant problem.
ESD can take a long time to surface. Seems likely if it was due to a recent lightening hit other things would of fried too. Strange that the machine RS232 is in trouble with all the protection ckts, that the PC is OK. I'm betting it's from an unterminated line, grounding differential PC/machine, or ESD from handling the chips.
Mike Henry

How long is the cable run from your PC to the machine? And the routing, hopefully not in the same vicinity as arc welding. I have a "vision" that you swap cables around to connect other things to the PC, or maybe not. Did you mention the machine RS232 was not connected to the cable for a long time? Good,

Click to expand...

The cable is around 75! feet long, and has been working fine, still does when I send/recv from the cnc lathe. I unplug it from both pc & machines when not in use......
And it just lays on the floor also.....not a very easy life.
Having a floppy and USB port on the machine is going to be fantastic, and should prevent this dilema in the future.....see below....


Basically, I gave up and entered the program manually. This program is most likely the last one this machine will run with this control.
This machine will get a MACH 3 retrofit
within a month. I've found a guy that will is very knowledgeable on MACH 3 and Koyo PLC's.

Thanks to all for the info & help on the rs22 problem!

dan k