My shed....

OldFoo · Post by **OldFoo** » Mon Aug 18, 2008 6:09 pm

GREAT !!!

many thanks for your help !

I send you a private message !

OldFoo · Post by **OldFoo** » Tue Aug 19, 2008 3:41 am

There isn't much to that board! It shouldn't be too hard to repair.

Do you have an ESR cap meter? If not, you should get one. A lot of the odd power supply problems can be traced back to a cap that fails the ESR tests.

Raymond

OldFoo · Post by **OldFoo** » Tue Aug 19, 2008 6:51 am

Indeed, not much components on that board but I don't have the knowledge necessary to understand the fly-back transformers technology, moreover there are some obsolete components impossible to find on that board like the K422 (Q4) or the EI-22 DC-DC converter, iR9494,etc....

OldFoo · Post by **OldFoo** » Tue Aug 19, 2008 7:10 am

DCE wrote:Indeed, not much components on that board but I don't have the knowledge necessary to understand the fly-back transformers technology, moreover there are some obsolete components impossible to find on that board like the K422 (Q4) or the EI-22 DC-DC converter, iR9494,etc....

2SK422 can be replaced with a 2SK2961 according to Toshiba.

http://www.semicon.toshiba.co.jp/docs/c ... atalog.pdf

IR9494 can be replaced with an off the shelf NTE1729.

The EI-22 is a simple high frequency transformer that can operate to 300khz. Pretty rare for one of these to fail.

Switching type power supplies aren't hard to repair. High speed shottky type rectifiers short out or go leaky... transistors short or go leaky... caps get overheated and the electrolyte dries out. Those caps show up with a high ESR value even if they show the correct uf rating on a meter. That's why you need an ESR meter.

High ESR on a cap will cause the circuits to stop working on a switching power supply. Shotgun all those small electrolytic caps on the right side of that pic and see what happens.

RJ

OldFoo · Post by **OldFoo** » Tue Aug 19, 2008 8:49 am

Many thanks for that usefull informations

I would like to use that opportunity to ask you the equivalents for the others MOSFET presents on that board. There is a H-bridge with four UNS 2SK966 :

and one 2SK1146

But i read that a burned MOSFET has always visible damages ?

I hope you are right, it is probably the small electrolytic capacitors. (it should be cool)

OldFoo · Post by **OldFoo** » Tue Aug 19, 2008 2:53 pm

Check them for shorts with your ohmmeter. Be sure to check between each leg. 1-2, 2-3, and 1-3.... check them in both directions with your meter's leads too.

If a leg combination shows shorted then pull that MOSFET out of the circuit and check it again. If it's still shorted then replace it. If it's not, try to track down why it was reading shorted. Maybe a bad diode somewhere near it or you are reading across a transformer.

If they are bad then we can look for a cross reference.

RJ

OldFoo · Post by **OldFoo** » Sat Aug 23, 2008 11:32 am

Shotgun all those small electrolytic caps on the right side of that pic and see what happens.

I have replaced all the electrolytic caps + transistors + resistors showed in the picture with a yellow point but it is still not working :smt010

OldFoo · Post by **OldFoo** » Sat Aug 23, 2008 3:03 pm

What is the power supply doing? Is it chirping? Is it totally dead? Fuse blown?

Have you checked your input voltages to make sure they are correct?

There are a lot of resistors to check too.

OldFoo · Post by **OldFoo** » Sat Aug 23, 2008 3:48 pm

This board delivers some power to the two FET drivers which are used to control the two motors. Since the problem arrived no supply to both motors.

The fuse is OK, the input voltage is OK.

No schematics and I don't know exactly what this power board must deliver to the FET drivers...

I replaced the Driver board which are used to control the FET drivers, no changes.

No reaction of the two motors and the common point to the both motors is the power board, i suspected directly that board because there was an exploded Triac on it (TR1 = M8GZ46). I replaced this one by a BT138X-800.

I replaced also these components:

R12 = RSF2B - 22ΩJ

R8 & R30 = RSF2B ? 180ΩJ

R3 = RSF2B - 470ΩJ

C7 & C14 = 25V - 47?F - +105?C

C22 & C23 = 25V - 330?F - +105?C

C19 = 50V ? 0.47?F - +105?C

C24 = 50V ? 3.3?F - +105?C

C25 = 10V - 100?F - +105?C

IC1 = 431L

Q2 = C1627

Q3 = TSC 945

OldFoo · Post by **OldFoo** » Sun Aug 24, 2008 4:54 am

Hi sorry for the delay, but i'm BUSY with works....

I'll scan the schematics ASAP, but this will be in Sep. sorry.

IIRC the output should be around 90VDC, I'll go by memory, maybe I remember the G-Loc output voltage.

Remember the 2 motor boards seem the same, BUT it's not, don't know why, but if you swap they wont work!!!

Hope that's help... Andrea