AZEQ6 capacitors

[PadrePeace]

My AZEQ6 motherboard capacitors have blown and I need to replace them. Does anyone know what specification they are and where I might get some?

I have annotated the capacitors in question with a blue line. C11; C12; C34; C38; C46; C47.

thanks for your support.

Chris

[Dr_Ju_ju]

Why do you think they are blown, as they are just simple suppressor caps, even available on eBay, or Farnell\RSComponents.....

[Adam J]

Those are surface mounted, difficult to replace normally you would need a hot air rework station. There is such a thing as a capacitance meter but even that would not help much as if they are blown you can't measure them.

[rl]

I would very much doubt if so many capacitors have spontaneously failed. In fact I'd be surprised to see one. 

There would have to be a very good reason (like gross overvoltage) and the silicon bits would probably pop first. How did you get into this situation?

 

[Dr_Ju_ju]

Surface mount caps are easy to replace, if you have a good soldering iron with small bits, I do it all the time....  But you still haven't answered why do you think they are blown, what doesn't work ??

[PadrePeace]

All. Thanks for contributing.

I have the MB with a circuit board technician who has tested the board and reported the fault listed here. 
This occurred I think from using  a  laptop power supply (15v 4amp) that was reverse polarity. The stalling started after that. I’ve since realised that surprisingly A lot of Astro gear and SW mounts have no built in protection against this or over voltage and so I have got to source new components. 
The mount will run at slew speeds up to 7 but stalls above that. 
Hope this helps. 
 

[PadrePeace]

15 hours ago, Dr_Ju_ju said:

Surface mount caps are easy to replace, if you have a good soldering iron with small bits, I do it all the time....  But you still haven't answered why do you think they are blown, what doesn't work ??

Given your experience in this area have you any advice on how to identify the spec of the capacitors?

[PadrePeace]

15 hours ago, rl said:

I would very much doubt if so many capacitors have spontaneously failed. In fact I'd be surprised to see one. 

There would have to be a very good reason (like gross overvoltage) and the silicon bits would probably pop first. How did you get into this situation?

 

My technician says he has found a direct short showing on the motordriver side capacitors for both RA and Dec. He says a reverse polarity feed would cause this. 

[Dr_Ju_ju]

IF you are saying they found a short on the Output side of the chips, and he tested for a short with the motors connected, then he was seeing the motor coil winding resistance which is quite low.....

To Identify the capacitors, you'd need a magnifying glass to read what is printed on the capacitor, and yes it will be there....

I still don't know what caused you to start looking at the motherboard in the first place, no movement ???    Just saw your post above, and if it works at slow slew rates and tracking ?? I'd be more inclined to look at the power supply side of the board, where there is an on board regulator, which may well have issues, (I blew one on mine).

Edited March 28, 2020 by Dr_Ju_ju

[PadrePeace]

Power Supplies.

I started off using the battery connector that came with the mount and. 90aHr leisure battery which supplies 12-13 v and amps as necessary (I recorded the mount pulling 2.89amps in this system). Being within the mount spec this should have Been sufficient but got a flashing power light which indicates low power. 

I then tried a Toshiba Mains 15v 4amp rated supply. The mount would not run in this supply so I went back to the battery. This was when I then stared having a permanent flashing power light and fast slew issues with motors stalling. 
 

Finally, I bought a Nevada bench power supply rated at 13.8v and 5-7amps as recommended by many on this site as the sweet spot for big mounts.  The slew issues continued and we are now where we are. 
 

[PadrePeace]

10 minutes ago, Dr_Ju_ju said:

IF you are saying they found a short on the Output side of the chips, and he tested for a short with the motors connected, then he was seeing the motor coil winding resistance which is quite low.....

To Identify the capacitors, you'd need a magnifying glass to read what is printed on the capacitor, and yes it will be there....

I still don't know what caused you to start looking at the motherboard in the first place, no movement ???    Just saw your post above, and if it works at slow slew rates and tracking ?? I'd be more inclined to look at the power supply side of the board, where there is an on board regulator, which may well have issues, (I blew one on mine).

That’s really helpful. He has tested with stepper motors connected so this will be useful. I’ll pass your comments on.

Can I just Google the spec etched on the part to find it or do I need to go direct to a specific retailer such as RS Components?

[Len1257]

Could be my eyes but the caps look to be connected across pins 17 & 18. In which case they are filtering noise on the sense resistors. Those resistors are possibly the 270R resistors (although these seem on the high side?) and control the drive current. So maybe what your tech saw as a short may just be the 270R resistors. The value given in the datasheet for the cap is suggested to be a standard 0.1uF (100nF) and won't be polarity sensitive. So wouldn't have blown for a reverse polarity. Datasheet of the A3959SLBT is available on the web but won't solve your problem. 

Are you sure you haven't got a mechanical limiting your slew speed?

[Dr_Ju_ju]

Don't be fooled by current drawn, the published value is just an indication of the maximum the mount will draw when slewing, as this is the time both motors are working 'flat out', and in normal operation will be consuming a lot less....  What you have to ensure is that when the maximum current is being drawn, the supplied voltage doesn't drop below approx. 11v.

I've also inadvertently run my mount off a 19v Samsung monitor supply, with no ill effects...   

[PadrePeace]

22 minutes ago, Len1257 said:

Could be my eyes but the caps look to be connected across pins 17 & 18. In which case they are filtering noise on the sense resistors. Those resistors are possibly the 270R resistors (although these seem on the high side?) and control the drive current. So maybe what your tech saw as a short may just be the 270R resistors. The value given in the datasheet for the cap is suggested to be a standard 0.1uF (100nF) and won't be polarity sensitive. So wouldn't have blown for a reverse polarity. Datasheet of the A3959SLBT is available on the web but won't solve your problem. 

Are you sure you haven't got a mechanical limiting your slew speed?

There is no mech limiting. I can slow slew 360 deg on both axis but when I use higher slew speeds than 7 I get stalling in both axis. As per the posted video. 

Edited March 28, 2020 by PadrePeace

[Dr_Ju_ju]

Its not Mechanical limiting, Len's point that they could be across the 270ohm resistors, would indicate that the system is current limiting (stepper motors work on current pulses NOT voltage per se), so that at the requested higher slew rates, the appropriate current is not being delivered by the driver chips....   

[PadrePeace]

That’s where I am with my understanding. So in that case should we be looking at the regulator as mentioned earlier?

[Dr_Ju_ju]

I think that may be a better starting point....   Its also relatively easy to source and easy to change.

Edited March 28, 2020 by Dr_Ju_ju

[PadrePeace]

2 hours ago, Dr_Ju_ju said:

I think that may be a better starting point....   Its also relatively easy to source and easy to change.

Many thanks. I’ll pass this on to my tech.

[Starflyer]

I'd say 15v probably wouldn't be enough to damage the MB.  If it was reverse polarity it shouldn't work at all, with L1, amongst other things being blown open.

I know it's been said before and you've discounted it, but I'd put my money on a mechanical issue, namely the worm mesh being too tight.  This would still allow the mount to slew at lower rates without stalling but would stall at faster rates.  Refit it, back off the worm mesh and set it up again to test.  Changes in ambient temperature can make enough of a difference to cause stalling, I've set up an EQ6 outside in the cold, once brought inside and tested the next day it would stall at high speeds.

If you're convinced it's the MB then depending what your tech is charging you you may be better off just buying a new MB. I think Modern Astronomy stock them, or have access to them.

 

Edit; I can't see L1 on your MB. On the EQ6 MB's there is a small inductor that gets blown with reverse polarity, that's why it stops working completely. I'd expect to see it on that MB too.

Edited March 28, 2020 by Starflyer

[blinky]

Totally agree with whats being said on this thread - those caps wont blow due to reverse polarity and it would take a significant over voltage to blow them.  As Strarflyer said, I would be looking for something mechanical, reverse polarity will blow the board and it would not work at all. If its stalling at high speed, I would be looking at the mesh and backing it off ever so slightly.

[PadrePeace]

I backed off both axis so that I can feel slightly more backlash than it came with and the speed limit on both axis persisted. That’s where I am with my understanding. I’ve even removed both belts and rotated each worm by hand and found no resistance.  

So in that case should we be looking at the regulator as mentioned earlier?

It’s curious that the mount runs so most of the board is happy. It’s just not getting on with both axis demands above slew 7. To be clear it worked fine, if with a flashing power light, before I got involved with mains power supplies. Now I have a flashing power light even with the mount at rest. This seems odd As there must be enough power at rest to satisfy the Low power warning circuitry surely? 

Edited March 28, 2020 by PadrePeace

[Adam J]

1 hour ago, PadrePeace said:

I backed off both axis so that I can feel slightly more backlash than it came with and the speed limit on both axis persisted. That’s where I am with my understanding. I’ve even removed both belts and rotated each worm by hand and found no resistance.  

So in that case should we be looking at the regulator as mentioned earlier?

It’s curious that it turns so most of the board is happy. It’s just not getting on with both axis demands above slew 7. To be clear it worked fine, if with a flashing power light, before I got involved with mains power supplies. 

Did you try slewing at max rate without the belts attached? If so that definitively removes a mechanical issue as the cause.

Adam

Edited March 28, 2020 by Adam J

[Adam J]

9 hours ago, Len1257 said:

Could be my eyes but the caps look to be connected across pins 17 & 18. In which case they are filtering noise on the sense resistors. Those resistors are possibly the 270R resistors (although these seem on the high side?) and control the drive current. So maybe what your tech saw as a short may just be the 270R resistors. The value given in the datasheet for the cap is suggested to be a standard 0.1uF (100nF) and won't be polarity sensitive. So wouldn't have blown for a reverse polarity. Datasheet of the A3959SLBT is available on the web but won't solve your problem. 

Are you sure you haven't got a mechanical limiting your slew speed?

If that is correct then you could easily test it as the resistance across the capacitor would just be 270R would it not?

[PadrePeace]

1 hour ago, Adam J said:

Did you try slewing at max rate without the belts attached? If so that definitively removes a mechanical issue as the cause.

Adam

No unfortunately. I tried it with no weights or scope attached. At the time I thought that should be sufficient. 

Edited March 28, 2020 by PadrePeace

[Adam J]

4 hours ago, PadrePeace said:

No unfortunately. I tried it with no weights or scope attached. At the time I thought that should be sufficient. 

Probably was sufficient, it's a bit of a long shot anyway.