DK-3 dual axis controller IC fried, replacement?

[freiform]

Hi,

one of the ICs in my old DK-3 (a clone of Vixen's DD-3) is fried. The component in question sits between the quartz crystal and the motor driver itself. I suppose it creates different clocks depending on the current speed/mode of the controller, so it might be some sort of counter?  As each axis is handled separately, I can exchange the IC and the problem appears in the other axis, so simply replacing the IC should fix my problem. 

The question is, what IC is this? Unfortunately the type is filed off, the dealer does not sell this device anymore and is unwilling or at least unable to help. Does someone know this controller or has any idea how I could find a solution?

Thanks and all the best

Sven

[Dr_Ju_ju]

Before replacing the component, do you know why\how it got fried in the first place ?  I would be a shame to go to all the effort to find a replacement, to only have it fried again...

But looking at your photo, it looks like the component is a motor driver chip, and from the age of the components, I suspect its an LM293 derivative chip. The IC type concealment appears to be some form of paint\polymer so applying a small amount of heat may make it malleable and removable.

 

[freiform]

Hi Julian,

I think the driver is the smaller chip (U2 and U4), the one in question (U3) is located in between the quartz, speed switch and driver. 

Anyway, I already checked for possible shorts and exchanged U1 and U3, with no damage to the functioning chip and function in the corresponding axis. 

Sven

/edit

I already removed the coating from the chip in question, but as I wrote, the top is filed off!

 

[dweller25]

I have the same problem - fried it by putting 12v through it - it should have been 9v !!! doh

[ChrisLX200]

You need someone with an IC identifier, I had one at one time but heavens knows where it is now. If you think it's just a logic chip you may want to take a punt on something like this: http://www.ebay.co.uk/itm/IC-Tester-74-40-45-Series-lC-Logic-Gate-Tester-Digital-led-test-logic-Meter-/181861146112?hash=item2a57c4de00:g:6VQAAOSweW5VM8hB

Just plug your working IC into it and it will (try to) tell you what it is. I used one to check a load of chips I scavenged from scrap boards and built up quite a collection of spares :-)

ChrisH

[Dr_Ju_ju]

Hi Sven,

having another look at the picture and reading around the web, the chip may be some form of PIC controller, as used in the older Skywatcher EQ5 hand controllers. If so, and if you are able to source one, you would then have the problem of reading the code from your working chip and writing the code to the new chip.  

It may be worth asking the Vixen UK importer (https://www.vixenoptics.co.uk/Pages/dd-3_controller.htm) if they are able to supply replacement chips.

 

[freiform]

Oh, if it is a PIC, the outlook is rather bleak. I don't think Vixen is able to provide any help, as the DK-3 is just a cheap knockoff. Also, If you look at pictures of the DD-3's PCB, it is a different design with different chips.

 

 

[Waldemar]

If you are able to identify the IC, and it turns out to be a PIC controller, these guys may be able to help you to retrieve the firmware: http://www.break-ic.com/

Waldemar

[freiform]

Hi Waldemar,

I think this is overkill and most likely considerably more expensive than a new controller. Thank you for the link, though!

Sven

[Dr_Ju_ju]

Hi Sven,

Pondering....  Another way of controlling the mount may be to forget about your broken controller, and instead buy and or build a controller e.g. https://www.astroeq.co.uk/tutorials.php

This can easily be fitted with button control, but also has the ability to be controlled via a computer via EQMod etc....

[freiform]

Hi Julian,

I'm already on to that, but building from scratch using an Arduino with stepper shield. It's more of an educational exercise. I got myself Synscan upgrade for my GP, so I'm all set anyway. I just don't like throwing away stuff that might be repaired, salvaged or put to some other use ;).

Sven