Broken RS232 PCB Repair or any other???

[GBeaman]

Hi all... I need an ingenuitive solution here. My 1985 bostomatic 312 is running well on its newer CPU board. All is well except for the file transfer. It will transfer a file out of memory but not into it. Otherwise I only have a Paper Tape reader to access memory. I sent the CPU out to a repair facility and the technician found the problematic part. He referred to it as a "discrete component". I believe it is not an IC but some other component in the circuit. Anyways, he has been at it for a month now and says he is having trouble locating this old component. My initial thought was I need a new repair man! He gave me the run around like this, one other time before. So now what? I guess BTR is an option, but RS232 sure would be easier (and cheaper). I was told by a different person that it might be possible to build a small circuit board with modern parts that would replace the outdated circuit on my CPU. The CPU is dated 1991 by the way. So that gives you a time frame to ancient. Any other thoughts from you technical guru's that know a whole lot more then me. Is there some other cheap way to get a program into and out of memory or a cheap way to get what I have fixed? I am thinking I might mail it out next, but mailing off the CPU means downtime. Which isn't that big a deal but I am going to go nuts if it is another 2 months of looking at this neat money maker that is absolutely worthless without a CPU. Also the repair was supposed to be in the $100 range if parts were available, so I really don't want to drop a grand on a BTR if I don't really need to. Thanks in advance.
-Greg Beaman

 

[roundrocktom]

Greg,

Any idea of what component he is looking for? You're correct a discrete component could be a transistor or diode (both easily substituted), or something really odd.

Years back, to support some obsolete equipment, we used to raid old boards. Heat 'em with a torch, wack the board, and collect the components for future use!

With today's consumer products, it is not uncommon to see IC with a 12 to 18 month production time frame! For Industrial Electronics, more of 5 to 7 years time frame.

There is a whole industry of buying up surplus electronic components items for reselling them.

-Tom

 

[KilrB]

We have a pair of Charmilles Andrew EF22-930 wire edm machines older than that and we can still get refurbished boards on exchange for them.

Surely there is someplace out there that has some of the boards you need on the shelf.

You might try http://www.omegaebr.com/, if that's not who is already looking at it. Found it on Google. We usually deal with EDM Network.

 

[roosta]

It might be the MC1488 and MC1489 chips to the serial port. These things go pop if they get spiked. Easy to change, i've done 'em on Fanuc and Heidenhain motherboards.

 

[GBeaman]

I just spoke with the Kenny the repair guy and he told me the part we are looking for is a "driver" for this board. He said it is an 8 pin dual in line chip with the symbol for "micro" on the top and then the numbers 75150. He may have a lead on a source for one too. This is all greek to me anybody else have any thoughts.
-Greg

 

[emt2688]

I Googled "+75150 + 8 pin"

Here's the first place that come up. http://www.elexp.com/ics_10cn.htm

About 7/8 the way down the page is this:

75150 10 75150 8 pin Dual Line Driver Rs 232 $0.69

There's a shopping cart, just add the item and order.

Hope this helps

Pat

 

[GBeaman]

I had a guy here at work look up the number and we found them on Newark too. They were $1.20 and he found them in about 5 minutes in several different brands. This is making me very disappointed in the repair man. I called him and gave him the number and he sounded like he felt very dumb. Thanks for all of the help. With this proactive approach I should be transferring files in no time.
-Greg

 

[roundrocktom]

Greg,

Little humor... chip was first released by TI in 1971. Datasheet was revised in 1999. I do think that is a record for one of the longest life products as far as IC goes.

Tom

EDIT: SN75150 is the TI part number.
The original (Pb leads) seems to be NLA, but the RoHS version (Pb-free) is coming up available.
Just make sure you get a DIP package, most are SOIC (small outline IC)... you can get you an adapter at Fry's is you need to use that small SOIC.

 

[gar]

GBeaman:

The 75150 datasheet can be found at WWW.TI.COM . It is defined as a dual channel RS232 driver. It is not a descrete device but rather an integrated circuit. In at least one form it is in an 8 pin DIP. RS232 drivers and receivers are very reliable devices when not subjected to stresses outside their ratings. Search on the TI site for SN75150P.

A typical failure cause is excessive external voltage applied to the device from the difference in ground voltage between the source and destination. We sell two products designed to minimize this type of failure. For a discussion of the problem see my web site www.beta-a2.com and the page on NOISE and GROUNDING.

Some machines, such as HAAS, provide reasonable good protection relative to damage from excessive voltage but this does not solve the problem of errors from noise. In HAAS the RS232 connector pin goes thru a 100 Ohm 1/4 W resistor to a bidirectional transient limiter of about +/-18 V. I have not run tests directly on the HAAS circuit but simulated their circuit with a +/-12 V limiter and applied 120 V AC and the 100 Ohm metal film resistor burned out nicely with no damage to the limiter and no excess voltage at the output of the limiter.

The RS232 drivers and receivers are not generally protected at all in personal computers.

.

 

[Old Field Tech]

GBeaman,

Get your board back from your 'repair guy' now
Sheesh! I coulda turned it around in 3 days (gotta wait for UPS)

Next time use OmegaEBR in Arlington,Tx - I do

Disclaimer: I used to work for the above and know their work quality and recieve NO benefits from them

Rod (just repaired a forklift crunched encoder for $50)