Skywatcher HEQ5 Pro New Mainboard?

[malc-c]

Once this thread is updated to confirm the replacement MOSFET resolved the issue and no other issues occurs then I might request the mods to split this thread from FabInSpace's post in February last year and merge it with the large thread on blown motorboards

[TrevaP]

I get that Malcolm and I'm taking a punt that the mount may be on the edge of overvoltage at ~13.5V.

If it's something else so be it; it's a cheap fix to try before buying another MB - anyway I'll let y'all know how it goes.

[malc-c]

Skywatcher state on their website that the power requirements are 11-15v DC @2 amps, so providing 13.5 or even 13.8v as many use bench top supplies at this voltage should be well within the voltage range.  Unless this is more applicable to the older PIC mico based boards and the new MC020 ARM based boards are more voltage intolerant 

[Skipper Billy]

4 hours ago, TrevaP said:

I get that Malcolm and I'm taking a punt that the mount may be on the edge of overvoltage at ~13.5V.

A fully charged '12 volt' lead acid battery is ~13.7 - 13.9 volts.  Nothing to worry about.

 

[TrevaP]

OK - nothing else is jumping out at me and troubleshooting boards like this isn't my strong point so we'll just replace the transistor and see what happens.

There's one thing - while removing the RA connector from the board when I did the Rowan mod, I may have damaged one or more of the soldered connections.  I managed to pull the entire connector from the board this time (replacing the bearings with SKF) and resoldered it. Whether or not those connections were dodgy after my first intrusion I have no idea - likewise the possible consequenses.

The mount was working just fine up til the Meridian Shift, load was nothing heavy (WO GT81) and there were no cable snags.

[malc-c]

Normally if a repair hasn't been done right it either goes open or closed circuit.  In this case I would have suspected that the motor for RA wouldn't work as having a short across the coils or if the coils are open circuit would prevent it from running.  On the new board it's clear to see the four tracks from the driver chip to the connector, so it would be very easy to repair any damaged tracks.  If you could post up a picture of the repair we could then comment further.  

Did you also get my PM ?

[malc-c]

@TrevaP I've dropped you a couple of PMs regarding close up pictures of U7, hopefully you can oblige.   In the mean time any news on the repair, did the replacement FET work?

If anyone else has one of these new MC020 board and could take a close up image I would welcome a PM from you.

[TrevaP]

Just to let you know - replacing Q3 did the trick 👍

How many people have forked out $250 for a new MB without knowing that a $2 transistor will get it going?

Edited March 24, 2023 by TrevaP

[malc-c]

Excellent news, well done.

Now the conspiracy theorists would say that the manufactures of the board knows that a $2 MOSFET is its built in weakness in order to generate sales of replacements costing hundreds of pounds / dollars as a result of Q3 failing / blowing.

 

[TrevaP]

🙂 That did occur to me.

[ozarchie]

Hi Malc, and TrevaP

I think there are a lot of people on different forums with MC015 and MC020 boards that would appreciate any info you can share.

Both these boards share a lot of common power supply circuitry (including the now notorious Q3).

The MC020 contains a Q4 (unpopulated) with similar circuitry for the +12V supply line.

I have been working with Andrew Johansen (also from Oz) in researching the Q3 circuitry.

Similar faults have been reported on the groups.io site https://groups.io/g/SkywatcherEQ8/topic/94480706#5424 which also references a similar problem on the Cloudy Nights forum.

While I have a preliminary version of the circuitry,  it is only based on the photos that Malc sent me.

If you can share any insights, I will try to incorporate them with the circuit and perhaps jointly publish a note for all forums.

Cheers

Archie

 

[malc-c]

Hi Archie,

I think part of the problem is most forums seem to have policies that remove links to other forums and discussion groups.  SGL seem to be more understanding, but yes I think we need to get the word out there that motor board can be fixed, and sometimes by replacing a cheap transistor.  

Reverse engineering boards is quite a challenge, especially when you only have photos to go by, so if anyone has already ordered a replacement and still has the faulty ARM based board that they can donate to the cause I'm sure it will be a great help.  I'm guessing that these new boards are multi-layer, so if anyone has access to a new board and a means of having it X-rayed that really would be the icing on the cake 🙂   I know Australia is a huge place, but maybe TrevaP could loan his board to you so you get a hands on and tweak the schematic if needed.