Fried EQ6 board

[StuTodd]

Lost power to my EQ6 mount and discovered the board had fried (yellow circle on attached piccy).

Anyone know where I can get a replacement in Oz or NZ? If not, a supplier elsewhere would be much appreciated!

Out of interest, which component had fried and a possible cause? I have always used the same 13.8v dc battery with no issues up to now. :sadeyes:

Stu

[bojan]

Something around power regulator... better picture may be helpful :)

[Russj]

G'day Stu,
I had a problem with my NEQ6 I spoke to Tasco the distributors in Sydney they sent me a new board under warranty.

NZ distributer for SW should have new boards might be worth ringing them.

Russ

[AndrewJ]

Gday Stu
Its an inductor that has blown up.
You could try cleaning the area around it and then just shorting the gap, but it might have been caused by one of the nearby capacitors going short.

Andrew

[StuTodd]

Thanks and good point about the image Bojan, I have attached a better one!



Thanks, Russ, I will try to find the NZ distributor but it's probably the same people. My EQ6 is out of warranty sadly :sadeyes:



Awesome Andrew, I will give it a clean and have a go at a repair. I have nothing to lose as a new one is going to cost me NZ$220+. Attached a new picture too.

Stu

[bojan]

Yes... as Andrew wrote, cap C45 probably shorted and blown inductor L40.
This is input filter to SMPS regulator (data sheet here (http://pdf1.alldatasheet.com/datasheet-pdf/view/74535/MICREL/MIC2171.html)), so replacing inductor with wire (and removing the remnants of C45) will work as temporary repair.
Try to find suitable inductor and cap as there will be a lot of noise from egulator.

[StuTodd]

Sounds great.

Can you walk me through the fix, i'm good with soldering so that's not an issue, just my lack of knowledge in circuit voodoo.

:)

[bojan]

Just remove fried components, clean PCB with alcohol and place (thin) wire where inductor was.
If the board works after that, you just need to find components with suitable values. I do not have that board, so I am not sure what they should be.. 100nF for caps, couple of /uH for inductor maybe?

[AndrewJ]

Gday Stu
The bottom right corner of the regulator also looks like it has burn marks???
Are they real or just a bit of residue from the inductors BBQ smoke???
If the surface of the regulator is really damaged, shorting the inductor as a test should probably be done using a face mask and goggles :-)
Edit
And looking at the spec sheet i see its a switchmode chip, not a simple voltage regulator.
There are several circuit diags in the datasheets but if the inductor is the one used as part of the feedback loop, vs a simple filter on the incoming voltage, then shorting it wont work.
Maybe see if you can trace the circuit around the chip to see where in the scheme of things the inductor fits

Andrew

Just remembered something
As an aid to tracing his damaged circuitry, a user recently got Synta to provide a schematic for the EQ8 board.
( Its in the files section of the Yahoo EQ8 group )
https://xa.yimg.com/df/SkywatcherEQ8/MC009+Rev+D+Schematic.pdf?token=mnW vmI58YqZNAiFuqFqCPL8bwlr6H_UW_Ss1Ib b208t6hL_EwHE1eaqX7ODvnWO0DmhDPFlzs ONFZiz--VhpODaRzOaDHpKPjhtdQXLASUVLF7skD-Zrm144C0nntw&type=download
This document has a page for the power supply and it is using the same chip, so may be similar.
The only inductor shown there is the feedback one, so its no longer a simple exercise.

[bojan]

Yep... I thought that I would try to use Multimeter instead of inductor, to check current consumption.
Better still, you should use lab power supply, with current limiting.

[StuTodd]

Thanks for the advice Andrew and Bojan.

I'll clean the thing up later and clean then see where I'm at. I have a feeling I'll be shelling out for a new board though.

Stu

[StuTodd]

So the 470nF cap is clean. The only component (I can see) to have been blown is the L40 inductor.

Attached pic of other side. The black was residue and came away.

Having cleaned the burned side away as you suggested Bojan, there is an area of copper revealed where the green protective surface is gone?

Stu

[AndrewJ]

Gday Stu
Just looking, i found my piccies of the reverse side as well.
Looking at them, i see a monster inductor L42a and that is bound to be the main inductor for the switchmode feedback.
As such, i am no longer sure what L40 does, but it can probably be safely shorted, as long as the 5 pin Controller chip didnt show any damage.
The damaged/exposed trace in the latest piccy is under the "power in" socket, which means maybe it is what shorted and took out the inductor.
Easy enough to remove the socket to see if it is damaged and see the traces underneath it.

Andrew

[bojan]

Andrew, L40 is part of filter, it reduces noise emissions from input of the
regulator.

[AndrewJ]

Gday Bojan
I suspected it might be,
I should have realised a small smd inductor would be too small for the switchmode feedback circuit.
That said, if the EQ8 uses the same SMPS chippie, i would have thought it had a similar circuit.
Looking at the linked circuit diags, i cant see where L40 would be used as an input filter.
Only a board trace will show that.

Andrew

[bojan]

Yep, and it is connected to pin 1, which is input into IC.

[ZeroID]

I have an EQ6 board downstairs that no longer works. I replaced it with one from Bintel a year or two back, about $400 IIRC. I'll check to see if the inductor and any associated components are intact. Let you know tomorrow, I can send it down and you can possibly cannibalise any useful parts.

OK, curiosity got the better of me, went and found the board. L40 is intact, board is undamaged in that region. I damaged it somehow playing with an incorrectly wired EQDIR cable so probably chip internal damage.
Pm me with a mail address and I can send it down.

[StuTodd]

Hi Andrew,
I soldered a piece of wire across the "terminals" where the L40 was, with no joy. No power. The controller chip looks undamaged, as does the power input plug and connections.



That's great Brent! I will PM you. I wondered if the board blew due to my mishandling but a fellow EQ6 owner here had the same component go so maybe not :thanx:

[bojan]

Did you measure voltages (pin 1 of regulator, 470uF cap)?

Voltage controller may still be damaged... as well as 470uF cap (at the output of the regulator circuit) could be shorted inside (check with multimeter).

Once you establish what went wrong, regulator chip and caps could be obtained from RS-components, Element14, ebay...
Regulator chip will be very hard to remove from Brent's board without damage (it has a large soldering pad for cooling, which is soldered to PCB, so a lot of heat needs to be applied to remove it - the best way to do it is using heat gun.

[AndrewJ]

Gday Bojan
Using the EQ8 schematic as a guide, i can now see that this regulator is running as a stepup/boost and only provides the "power" inputs to the 4 motor driver chips.
I thought they just ran off the supply voltage, but not so.
It appears to have 2 modes, stepup to 16.2V or stepup to 45.2V.
As such, we have the nasty possibility that a low input voltage will still get stepped up to the required output voltage, but the input current will jump up to compensate. ie brownouts can be worse than suspected????

Andrew

[bojan]

Andrew,
yes, those regulators draw more current at lower input supply voltages...

In this particular case, many thigs could have gone wrong, including intermittent connection with motors.. which may have blown the motor driver.. .which may have damage the L40 (which served as fuse)....

[ZeroID]

ok .....