Wiring Schematics wrong for G250.

[Dougal]

A quick warning to those who are about to wire up any gecko G250s.

There are some wiring diagrams out in circulation (official gecko diagrams) which show the wrong pinout on pins 26 and 28. Using these diagrams will kill your stepper cards, I have killed two by following this diagram.

The incorrect diagram I downloaded from geckos website in late august, the current one for download is correct but the revision number has not changed so it is not obvious whether you have the right wiring diagram.

Here's how you tell.
On page #1 the written descriptions are correct on both instruction sheets.
On page #2 the diagram in the dodgy sheet contradicts the description on page 1.

If your description and diagram agree (the correct version is pin 26 - no connection and pin28 - step) then you're good to go.
The wrong version has these two pins reversed.

I have emailled gecko my dodgy diagram and told them that following their pinout has killed two of my G250's. I have yet to get a response from them.

[CarveOne]

Thursday was Thanksgiving holiday in the USA and the Gecko folks may (or may not) have taken Friday off as well. I wouldn't expect a reply until Monday. It's remotely possible that one of the employees will check in here over the weekend.

CarveOne

[poordumbbastard]

Dougal,

How is it possible to blow up a G250 by connecting a logic signal to the wrong pin?

I don't mean to say you are telling a whopper but it sounds fishy to say the least.

What is pin 26 anyway?

The Gecko guys should be around here and answer you pretty quick so don't worry.

PDB

[CarveOne]

Looking at the rev.4 manual, page 1, it says that pin 26 is "Reserved", and pin 28 is the STEP input pin. Reserved usually means that it is not connected to anything. However, page 2 says "Do not Use". I take that to mean that it MAY actually have something connected to it inside the board. Without the schematic it is hard to know for sure. I didn't find that yet. Mariss will clear this up.

CarveOne

[Mariss Freimanis]

The original G250 manual had pins 26 and 28 transposed on page 2 while it was correct in the text on page 1. The current manual on our website is correct on both pages.

The "Do not use" pin 26 is actually +12VDC and we use it in the G540 to power the HCPL-2531 STP/DIR optoisolator detector side.

The +12VDC regulator in the G250 is designed to blow open a 33 Ohm surface mount resistor if that pin is overloaded (>60mA). This limits the damage to one resistor and protects the rest of the drive. Replacing that resistor restores the drive.

Please return the G250s for repair.

Mariss

[CarveOne]

Mariss,

Thanks much for the clarification. Especially on your "time off".

Seems that I saw mention of this somewhere (Yahoo Groups?) but things don't stick in my mind like they used to.

CarveOne

[Dougal]

Originally Posted by Mariss Freimanis The original G250 manual had pins 26 and 28 transposed on page 2 while it was correct in the text on page 1. The current manual on our website is correct on both pages. The "Do not use" pin 26 is actually +12VDC and we use it in the G540 to power the HCPL-2531 STP/DIR optoisolator detector side. The +12VDC regulator in the G250 is designed to blow open a 33 Ohm surface mount resistor if that pin is overloaded (>60mA). This limits the damage to one resistor and protects the rest of the drive. Replacing that resistor restores the drive. Please return the G250s for repair. Mariss

Thank you for your reply.
I really hope I haven't damaged my CNC Brain.

Unfortunately I'm in New Zealand so returning the geckos for repair is going to take weeks and cost me a similar amount in postage to new drives and I really don't want to lose those weeks.

Is it possible to replace these resistors myself?
Can you send me a schematic to find them?

When I say "replace myself" I mean I have people who do such jobs, but pointing them in the right direction on the board will save a lot of time at this end.

[Dougal]

Originally Posted by poordumbbastard Dougal, How is it possible to blow up a G250 by connecting a logic signal to the wrong pin? I don't mean to say you are telling a whopper but it sounds fishy to say the least. What is pin 26 anyway? The Gecko guys should be around here and answer you pretty quick so don't worry. PDB

There goes your answer. Pin 26 is +12vdc.

Really hoping it hasn't damaged anything else.

[Dougal]

The CNC Brain seems to still work okay with one of my remaining G250's.
Big relief, there must be some decent internal protectin inside that thing.

[poordumbbastard]

Dougal,

Well that explains everything.

Gecko should pay for the shipping and replace all the damaged parts including your CNCBrain since it was a mistake on there part.

From what I have been reading here on the Zone they take care of all there customers no matter what.

PDB

[Mariss Freimanis]

The 33 Ohm safety resistor is on the extreme edge of the pcb under the big (8mm dia) blue capacitor. It is immediately adjacent to the regulator thru-hole pad and it is marked '330' meaning it's 33 Ohms. Read it with an Ohmmeter; if it is blown, it will read substantially more than 33 Ohms. Replacing this resistor will restore the drive to proper operation.

The G250 is safetied in as many ways as possible for a price-sensitive drive. The 33 Ohm resistor is one example. The 60mA current necessary to burn open the resistor is below a level that would have harmed any logic connected to it.

Mariss

[Dougal]

Originally Posted by Mariss Freimanis The 33 Ohm safety resistor is on the extreme edge of the pcb under the big (8mm dia) blue capacitor. It is immediately adjacent to the regulator thru-hole pad and it is marked '330' meaning it's 33 Ohms. Read it with an Ohmmeter; if it is blown, it will read substantially more than 33 Ohms. Replacing this resistor will restore the drive to proper operation. The G250 is safetied in as many ways as possible for a price-sensitive drive. The 33 Ohm resistor is one example. The 60mA current necessary to burn open the resistor is below a level that would have harmed any logic connected to it. Mariss

Yes I have found it.
My blown drives show between 0.5-1.5 kohm across these resistors, my healthy drive show ~33ohms.

Thank you for that, I will now be able to at least get it running.
But I still haven't received a response from my emails to gecko just over a week ago now. I want to get some new drives and relegate these two (once repaired) to spares.