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malc-c

HEQ5 - Blown mainboard ?

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Due to an accident last summer I've not used the telescope in the observatory over the winter period.  A few weeks back I gave the observatory a spring clean, and checked the scope was still operational by driving it through RA and DEC using EQMOD on the PC, it was fine so parked the scope and that was that.

Today I thought I would see how the sun looks, so powered up the mount from the Fusion 13.8v bench PSU, booted the PC, placed the solar filter on the scope and slewed to the sun.  I needed to do a small adjustment using the gampad and that's when I first noticed something nor quite right, the mount began to track at the adjustment speed on the same axis, so I re-targeted in DCD and it locked on.  A few moments later I could smell electrical burning coming from the area of the PC / PSU - I bent down to check the PC and as I did glanced at the PSU to see that it was still showed nothing untoward such as a massive current draw, which it wasn't,  showing little over an amp being drawn.  However the PSU then went POP and the display went out.  I disconnected the wires to the mount and removed the unit.  Opening it up the smell of cooked electronics was striking - but there was no sign of anything obvious, no smoke, no scorched components or anything burst open.  The only thing I could find was a wet patch on the board which looked like it had sweated or a viscous fluid had leaked - but none of the capacitors had vented, unless it was from underneath.  OK so I need a new PSU.  But I need to power up the mount and park it so I don't loose all the sync points in EQMOD.

I got a 12v -2amp wall block PSU from an old network switch and connected that to the mount.  Where EQMOD was upset and displayed  Time Out Comms issue, it now displayed Long / Lat/ RA / DEC info etc, so the mount was communicating with the PC, but I couldn't hear that audible high pitch whine from the mount, and using the gampad or PC the mount fails to move.  I do however hear that initial clunk you get when you first power on the mount, so power is getting to something, although manually turning the motors there is no difference in resistance when power is turned on or off.  I've tested with a DVM and I'm getting 5v (or close enough) on the main board connectors at various pins.

So I'm at a turning point.  Do I shell out the £100+ for a new main board, plus another £30 for PSU, or is there a possible simple fix.  I've been involved in electronics for over 30 years and you would seldom find that a complete board has failed, and that it's often a small descrete component that has failed (diodes, or regulator) - seldom a PIC or driver chip.  The thing is I'm not sure if the communications come from the main board which would suggest the PIC micro is running, or if it comes from the power board where the handset and power connectors are.

Any suggestions ?

 

Malcolm

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Hi Malc,

If you still have the handset laying around, try to connect it and see if it displays any error messages during startup. When my motherboard was fried (due to 12V contact issues related transients) it displayed "Both Axes No Response" which I cured by replacing the motherboard. The small pcb where the 12V & ST-4 comes in, if I remeber correctly there are no parts there that could cause your symptoms. 

As for feeding the mount from a PSU, I would still have a small led-acid battery near the mount. It will eat most of the transients if the PSU should misbehave. In fact, I am so superstitious after my incident that I now have a 1 ohm resistor in series with the 12V line, and a short-circuiting switch over the resistor. I always keep the switch open when I power or un-power the mount.

Ragnar

 

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Thanks for the comments.  Regretfully as the mount is permanently set up in an observatory I no longer have the handset, so have no other means of testing.

As the mount requires an external USB to serial adaptor, this does indeed suggest that the communications is handled by the PIC micro, which would in turn suggest that the issue is driver chip related rather than processor.  But the fact that 90% of the board is surfaced mount components diagnosing what needs to be replaced will be hard.

It really peeves me that there is no easily replaced protection components on these boards, and power spikes, glitches etc can cause such a main component to fail - and at £100 a pop (no punn intended :) ) 

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3 hours ago, malc-c said:

The thing is I'm not sure if the communications come from the main board which would suggest the PIC micro is running, or if it comes from the power board where the handset and power connectors are.

Any suggestions ?

 

Malcolm

Comms come direct for the PIC's uart. If you are getting position display on EQMOD then it is communicating and the PIC is running fine.

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1 hour ago, chrisshillito said:

Comms come direct for the PIC's uart. If you are getting position display on EQMOD then it is communicating and the PIC is running fine.

Thanks Chris for the confirmation that I'm on the right lines... so what do you think cold be the issue,  or how to go about diagnosing the main board

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Does anyone know what the part number of the four 24 pin driver chips are on the mainboard are

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Well, thanks to a recommendation from a fellow SGL forum member, I contacted a guy on the East Midlands Stargazers forum.  It was suggested that I replace two capacitors on the board as these seem to be very sensitive to voltage drops / spikes and fail.  I didn't have the right can size as the ones I had in my electronics box were 35v rated rather than the 25v rated fitted by synta, but they were persuaded to fit, and as it isn't as if anyone is  going to see it !

Well I'm pleased to say the mount is now fully operational :)

 

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2 hours ago, malc-c said:

Well, thanks to a recommendation from a fellow SGL forum member, I contacted a guy on the East Midlands Stargazers forum.  It was suggested that I replace two capacitors on the board as these seem to be very sensitive to voltage drops / spikes and fail.  I didn't have the right can size as the ones I had in my electronics box were 35v rated rather than the 25v rated fitted by synta, but they were persuaded to fit, and as it isn't as if anyone is  going to see it !

Well I'm pleased to say the mount is now fully operational :)

 

Wow, you are lucky - congratulations ! By the time I replaced my board I took this picture of it.

pcb.jpg.f5c71edb74130afbac67360a632dfa23.jpg

Can you please tell which capacitors you replaced (never mind the notes on this old pic) ? I might replace mine and get myself a workin spare board.

 

 

Edited by lux eterna

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Hi,

 

No problem.  It was the two 470uf 25v caps (top right of your picture).  There was nothing physically obvious with them (no bulging or leaking) - I have no idea what part they play in the circuit, but swapping them out resolved the issue for me.

Good luck

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16 hours ago, malc-c said:

Well, thanks to a recommendation from a fellow SGL forum member, I contacted a guy on the East Midlands Stargazers forum.  It was suggested that I replace two capacitors on the board as these seem to be very sensitive to voltage drops / spikes and fail.  I didn't have the right can size as the ones I had in my electronics box were 35v rated rather than the 25v rated fitted by synta, but they were persuaded to fit, and as it isn't as if anyone is  going to see it !

Well I'm pleased to say the mount is now fully operational :)

 

Glad you resolved your issue ,good job :thumbsup: 

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The Micrel MIC2171 is a 2.5A switch-mode power controller. The data sheet has several sample circuits, showing 470uF capacitors as the main smoothing capacitors. Without adequate capacitance, voltage ripple may well affect the circuitry downstream of the regulator.

Geoff

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Geoff, thanks for the explanation.  I was guessing it was more PSU related as the charge pump caps would seem to be the four smaller caps near the PWM driver chips

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It seems the capacitors on both the EQ5 & 6 boards fail on quite a regular basis, reading reports over the last few years. I often thought of buying a spare board for my Avalon, which incidentally has the same board as the EQ6. But at £100 for a board which costs a few pounds to make grieves me. I'll purchase a few capacitors - Just in case...

Great to see you got it fixed Malcolm.

Steve

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I just received an e-mail from OVL, they contacted a "skywatcher engineer" who gave the following response

Quote

It looks like that the motor control board is damaged and the PC cannot talk with it.

 

1.       If the power LED on the mount’s panel can still light up, it means the PIC MUC is still partially working and the voltage regulator on the motor control board is normal. In this case, one or both of the PIC MCU on the board might be damaged.

2.       If the power LED does not light up, it might means a broken ferrit bead or inductor on the power feeding path. I would suggest to check along the power feed path to the 7805 voltage regulator.

I gave them the full diagnosis as posted here, so to say that the PC is failing to talk to the motor control board is strange given Chris confirmed if communications are working then the PICs are running and talking to the PC.

I have replied to OVL stating how the board was fixed, and included Geoffs comments on the effects of these capacitors have on the power controller chip.  My reply was polite and professional, but I doubt that I will receive any follow up e-mail from either OVL or the engineer.  I just hope that anyone new to these mounts reads this thread if they find their mount starts behaving the same way, and that (provided the mount is out of warranty) replacing these capacitors will fix the issue and give the board a new lease of life.

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Hello,

sorry for "pin up" to this post but i maybe have a similar problem.

In HEQ5 i tried to connect via EQMOD and Bluetooth EQMOD adapter connected to mount. (prior to this connection, everything worked fine - and i haven't change anything in my setup). On connection EQMOD reply that is a "Timeout" error. 

When i connect handset - everything works fine (no errors, RA and DEC works perfectly, tracking also). 

I double check COM number of BT Adapter and, like i said - everything works fine till now. When i connect BT adapter to other HEQ5 mount - everything works fine.

Right now i don't have a clue what is wrong (capacitors mentioned above?). 

Can you help me in any way? :-)

Best wishes

Pawel

 

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Wow, that's a strange one.  The fact the mount works fine with the handset would suggest the main board is fine, and its an issue with the EQDIR / BT adaptor.  But you say that they both work with a second mount ?? - very confusing.  Do you have an other PC that hasn't been used with the adaptors and try and install EQMOD and Ascom on that, then connect up the EQDIR cable and see if it communicates with the mount.  If it does then the issue is with the original installation on the main PC.  This may be port handling within Windows, or simply a corrupt driver that needs re-installing.

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Hi,

thanks for answer. It happen to me for the first time. I'm really suprised by this situation. I used other PC and results are the same - on one mount i cannot connect with EQMOD - timeout error.

Currently i use only BT EQDIR adaptor, but i must do more more test - connect the mount with EQDIR cable and see what happend.

I was worry that mainboard is broken in any way...

 

Thanks

Pawel

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I think that there would be little chance the main board has the same fault as mine as the mount is fully functional when used with the handset.  I personally prefer a direct cable connection. Bluetooth has always seem flakey in my experience

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6 minutes ago, malc-c said:

Bluetooth has always seem flakey in my experience

You are right. I use BT for about a year and i haven't any problems with that... till today.

 

7 minutes ago, malc-c said:

I personally prefer a direct cable connection

I hope that on direct cable this mount will work. 

Thanks.

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On 23/09/2018 at 23:10, Pav1007 said:

Hello,

sorry for "pin up" to this post but i maybe have a similar problem.

In HEQ5 i tried to connect via EQMOD and Bluetooth EQMOD adapter connected to mount. (prior to this connection, everything worked fine - and i haven't change anything in my setup). On connection EQMOD reply that is a "Timeout" error. 

When i connect handset - everything works fine (no errors, RA and DEC works perfectly, tracking also). 

I double check COM number of BT Adapter and, like i said - everything works fine till now. When i connect BT adapter to other HEQ5 mount - everything works fine.

Right now i don't have a clue what is wrong (capacitors mentioned above?). 

Can you help me in any way? :-)

Best wishes

Pawel

 

Hello Pawel

I have an identical - and I mean IDENTICAL - issue with my HEQ5! Just wondering if you got your issue sorted.

Mine is a well-used HEQ5-Pro I got recently. Tracks reasonably well with handset (though should be better), motors smooth and quiet, but the thing completely refuses any communication at all with BT unit or Shoestring EQMOD cable. Both of these operate fine on my friend's mount; likewise his computer works fine on his mount, but not at all on mine. My bet is it's the comm port itself, but I haven't cracked it open to check it just yet.

I don't have the time to try to fine-diagnose the board or replace caps, but if replacing the motherboard is the answer, then I'm ok to do that.

Was seriously considering getting a brand new mount at incredible expense, but it occurs to me that I need to get this current one working anyway in order to sell it. So, I need a fix.

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Guys, no expert, but here's my 2p worth

If you can control the mount via the handset, but not with any EQ-direct cable then the issue isn't with the motor control board, it's an issue with the comms board (the smaller board where the handset plugs in).  If both the BT module and Shoestring cable work with another mount but not yours then this would suggest it's the serial port on that board that mount that is to blame.  I've never been a fan of the Shoestring & BT modules, preferring the use of a direct cable connection based on a 5V FTDL USB cable.   When EQMOD reports com errors it's either because the settings are wrong, the port on the computer is mis-configured, the connections aren't perfect, or the cable is at fault.  If  you are positive that these options have been explored then I have no other suggestions, especially as the handset communicates with the mount perfectly.  One possible option is to buy one of the cables that plugs into the handset and set the handset to PC-DIRECT mode - this would confirm if there is simply a compatibility issue with your mount and the shoestring cable / BT module.  

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Hello all,

I know that this is a rather old post!

My HEQ5 (with Pro kit upgrade) started giving the error "Both Axes No Response". It's pretty old now - 14 years or so. The hand controller still connects to a laptop ok, and I have re-flashed the memory just in case. The error still shows though. I took a look at the motor board. Nothing obviously wrong. I replaced the two 470uF capacitors but I', still getting the same error. 

I cant really afford a new board at £120 until the new year. Any suggestions of what else it may be?

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If you have a USB to serial lead, try connecting to the mount directly, by-passing the hand controller, & see if that will drive the mount motors....

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They won't be ceramics, as the 470 uF capacitor values are too large. They will be electrolytic capacitors.

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