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Michael. ?Try use Gemini ASCOM to see if the fault is the same as with HC.?
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Brendan
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Yes. The solution for me was a new G2 PC board right from Losmandy. I just swapped out and put in the new battery. After making an Ethernet connection, I updated the standard firmware with the Beta Ware from August 2018. Then I simply transferred all my personal settings from the Gemini app. Easy!
Since then, about 6-8 weeks now, I have had no high rev runway Dec slews. All running normally. Michael was sent the old board as he has said.?
Many thanks to Michael, Brendan, Brian, and all who helped with the troubleshooting and recommendations.
Best Regards,
John
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Thank you all...very good pointers.? I'll test each step and see what is likely to be wrong.??
I think it can't be the H bridge...it's driving the motors fine (unless it's flaw is it won't shut off!).? I think it must be the optical encoder detector chip....maybe.? Too many maybes!
Anyways it's a spare board. My own G2 is still working fine.??
Stay well!!!!
Michael
Or H bridge.?
You can compare CRO signals at Ra+ on the PIC and H bridge against moving sidereal west at same points but Ra- pins. ?
As others have said. It¡¯ll be the DSPIC or H bridge.?
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Brendan
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Or H bridge.?
You can compare CRO signals at Ra+ on the PIC and H bridge against moving sidereal west at same points but Ra- pins. ?
As others have said. It¡¯ll be the DSPIC or H bridge.?
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Brendan
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Very good thinking, Les!
I will see if the PC DEC slew works properly.??
Best, Michael
On Sun, Aug 8, 2021, 7:52 AM Les Niles < les@...> wrote: The next obvious guess would be resoldering the hand controller socket. Then start tracing the HC signals to look for something gone wrong. This would be easiest if you have a good board to do an A/B comparison.?
The fact that a bright star slew works makes it seem like a controller input problem rather than a motor/encoder problem. What happens if you initiate a dec movement through the driver or web interface?
? Hi gang!
I received John's questionable G2 mini board, to test it out.??
Symptoms:
It boots up fine.
It slews to an Align Bright Star target fine.
If you press the RA diamond East West button it slews RA fine.
If you let it run Sidereal rate it tracks fine.
If you press the DEC diamond East West button, the DEC motor runs away!?
This is repeatable.
John got a new board from.the factory and his system is fixed...it is definitely a problem with this board, not the cables, motors or handset.??
I'm unsure what to do to try and repair this board...John did try to resolder his DEC socket.??
Any suggestions from the above clues?
Very best, Michael
Was the board repaired at Losmandy?? From experience a runaway flew is a bad motor socket solder join.?
The ICs used are mostly capable of ?minus 20C.? All ICs were chosen to suit this wide temp range spec. Very much doubt it¡¯s that.?
Is I¡¯d all good now ? Has it been repaired ¡if not¡.it¡¯ll come back to bite when you least expect?
--
Brendan
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Ooops this is a G2 ¨C in which case a burnt out motor control PIC. ?
toggle quoted message
Show quoted text
From: David C. Partridge <david.partridge@...>
Sent: 08 August 2021 16:23
To: '[email protected]' <[email protected]>
Subject: RE: [Losmandy_users_io] Gemini-2 momentarily went haywire? Most likely a burnt out PAL decoder for the Dec? channel ¨C you need to program it of course. ? From: [email protected] <[email protected]> On Behalf Of Michael Herman
Sent: 08 August 2021 15:24
To: [email protected]
Subject: Re: [Losmandy_users_io] Gemini-2 momentarily went haywire ? Hi gang! I received John's questionable G2 mini board, to test it out.?? It slews to an Align Bright Star target fine. If you press the RA diamond East West button it slews RA fine. If you let it run Sidereal rate it tracks fine. If you press the DEC diamond East West button, the DEC motor runs away!? John got a new board from.the factory and his system is fixed...it is definitely a problem with this board, not the cables, motors or handset.?? I'm unsure what to do to try and repair this board...John did try to resolder his DEC socket.?? Any suggestions from the above clues? ? Was the board repaired at Losmandy?? From experience a runaway flew is a bad motor socket solder join.?
The ICs used are mostly capable of ?minus 20C.? All ICs were chosen to suit this wide temp range spec. Very much doubt it¡¯s that.?
Is I¡¯d all good now ? Has it been repaired ¡if not¡.it¡¯ll come back to bite when you least expect?
--
Brendan
|
Most likely a burnt out PAL decoder for the Dec? channel ¨C you need to program it of course. ?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> On Behalf Of Michael Herman
Sent: 08 August 2021 15:24
To: [email protected]
Subject: Re: [Losmandy_users_io] Gemini-2 momentarily went haywire ? Hi gang! I received John's questionable G2 mini board, to test it out.?? It slews to an Align Bright Star target fine. If you press the RA diamond East West button it slews RA fine. If you let it run Sidereal rate it tracks fine. If you press the DEC diamond East West button, the DEC motor runs away!? John got a new board from.the factory and his system is fixed...it is definitely a problem with this board, not the cables, motors or handset.?? I'm unsure what to do to try and repair this board...John did try to resolder his DEC socket.?? Any suggestions from the above clues? ? Was the board repaired at Losmandy?? From experience a runaway flew is a bad motor socket solder join.?
The ICs used are mostly capable of ?minus 20C.? All ICs were chosen to suit this wide temp range spec. Very much doubt it¡¯s that.?
Is I¡¯d all good now ? Has it been repaired ¡if not¡.it¡¯ll come back to bite when you least expect?
--
Brendan
|
The next obvious guess would be resoldering the hand controller socket. Then start tracing the HC signals to look for something gone wrong. This would be easiest if you have a good board to do an A/B comparison.?
The fact that a bright star slew works makes it seem like a controller input problem rather than a motor/encoder problem. What happens if you initiate a dec movement through the driver or web interface?
toggle quoted message
Show quoted text
On Aug 8, 2021, at 7:24 AM, Michael Herman <mherman346@...> wrote:
? Hi gang!
I received John's questionable G2 mini board, to test it out.??
Symptoms:
It boots up fine.
It slews to an Align Bright Star target fine.
If you press the RA diamond East West button it slews RA fine.
If you let it run Sidereal rate it tracks fine.
If you press the DEC diamond East West button, the DEC motor runs away!?
This is repeatable.
John got a new board from.the factory and his system is fixed...it is definitely a problem with this board, not the cables, motors or handset.??
I'm unsure what to do to try and repair this board...John did try to resolder his DEC socket.??
Any suggestions from the above clues?
Very best, Michael
Was the board repaired at Losmandy?? From experience a runaway flew is a bad motor socket solder join.?
The ICs used are mostly capable of ?minus 20C.? All ICs were chosen to suit this wide temp range spec. Very much doubt it¡¯s that.?
Is I¡¯d all good now ? Has it been repaired ¡if not¡.it¡¯ll come back to bite when you least expect?
--
Brendan
|
Hi gang!
I received John's questionable G2 mini board, to test it out.??
Symptoms:
It boots up fine.
It slews to an Align Bright Star target fine.
If you press the RA diamond East West button it slews RA fine.
If you let it run Sidereal rate it tracks fine.
If you press the DEC diamond East West button, the DEC motor runs away!?
This is repeatable.
John got a new board from.the factory and his system is fixed...it is definitely a problem with this board, not the cables, motors or handset.??
I'm unsure what to do to try and repair this board...John did try to resolder his DEC socket.??
Any suggestions from the above clues?
Very best, Michael
Was the board repaired at Losmandy?? From experience a runaway flew is a bad motor socket solder join.?
The ICs used are mostly capable of ?minus 20C.? All ICs were chosen to suit this wide temp range spec. Very much doubt it¡¯s that.?
Is I¡¯d all good now ? Has it been repaired ¡if not¡.it¡¯ll come back to bite when you least expect?
--
Brendan
|
Was the board repaired at Losmandy? ?From experience a runaway flew is a bad motor socket solder join.?
The ICs used are mostly capable of ?minus 20C. ?All ICs were chosen to suit this wide temp range spec. Very much doubt it¡¯s that.?
Is I¡¯d all good now ? Has it been repaired ¡if not¡.it¡¯ll come back to bite when you least expect?
--
Brendan
|
Update: this hasn't happened at all in the past couple months.??
Theory: this is temperature related.??
Question: I think I read someone mention (maybe in this thread?) that cold temps does make this more common.? Does it point to a circuit board issue???
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Damn......3.....No wonder you upgraded some equipment
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Brendan
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Update ¨C I¡¯ve actually replaced three of those H-Bridges ? D. ?
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From: [email protected] <[email protected]> On Behalf Of Brendan Smith
Sent: 12 May 2021 04:07
To: [email protected]
Subject: Re: [Losmandy_users_io] Gemini-2 momentarily went haywire ? John I thought I saw some bubbling on the U7 IC but it looks to be just the glue/lacquer Losmandy/Aveox used to glue down the firmware sticker on the DSPIC.
I repaired a similar fault you mentioned.....it was the H bridge in that case.?? I suspect Losmandy would like to see it.??
These PCBs are repairable fully!?? They are designed to be repaired!?? The repairs have spares of this IC and all others on hand in stock.?? David Partridge has replaced one of these (he's in the UK). I'm in Australia, I've done 2 now.?? But Brian Valente (the Losmandy rep) expressed desire to bring it back to their shop.? They have probably replaced plenty. ? So I suggest you sent it to Losmandy.
I mean its up to you but since they asked I think they are interested in analysing this issue...and of course fixing it to component level
Cheers
Brendan
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Brendan
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John I thought I saw some bubbling on the U7 IC but it looks to be just the glue/lacquer Losmandy/Aveox used to glue down the firmware sticker on the DSPIC.
I repaired a similar fault you mentioned.....it was the H bridge in that case.?? I suspect Losmandy would like to see it.??
These PCBs are repairable fully!?? They are designed to be repaired!?? The repairs have spares of this IC and all others on hand in stock.?? David Partridge has replaced one of these (he's in the UK). I'm in Australia, I've done 2 now.?? But Brian Valente (the Losmandy rep) expressed desire to bring it back to their shop.? They have probably replaced plenty. ? So I suggest you sent it to Losmandy.
I mean its up to you but since they asked I think they are interested in analysing this issue...and of course fixing it to component level
Cheers
Brendan
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Brendan
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Brendan,
Here are the shots you were looking for (attached). Hopefully the photographic quality is good enough for what you want to see. Personally I don't see any cracks or burned components anywhere. Previously I tested continuity of the Dec and RA sockets straight through to the far side of the board and they seem fine.
My plan is to replace the board and we'll see if the hiccup goes away. If you or Brian/Losmandy want to examine the old board afterwards, please let me know and I can ship it to you.?
Regards,
John
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That's not how the Gemini H bridge drive works....its PWM....both motor poles are held high (at input voltage aka 12V-18VDC) one pole pulses low at a preset freq (the pulse width is determined by the system...which is to the motor, an avg DC offset, it drives.? It Not only drives it move it does so with good torque due to the drive system PWM design.
The H bridge does have ceramic capacitors on each output and a large electro on its Vin drive power close by (There is another at pwr in).?? The H bridge It is laid out exactly to the design specs of the ICs mfgr.
Any large filter on the motor drive lines will distort the motor power factor.?? This design is basically the same or similar to that in the Gemini 1....just using newer ICs....aka a dual G bridge in SO20 package.
It works there is nothing wrong with the design
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Brendan
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Ceramic cores are fine if properly sized for the application but at very low frequencies the core would not be very effective plus the core would be large and heavy. ?See the ARRL RFI handbook. ? If possible first measure the noise on the DC motor circuit with an Oscilloscope, maybe one of your ham radio or techy friends has one. ?A ?.1mfd ceramic disc capacitor (dot 1 mfd) rated at anything above 50 volts at the dc connection to the motor DC terminals. ?$0.10 . ? ?I have remote controlled DC motors with various decoders not only in my Astro gear but ham radio antenna rotators and WiFi controlled antenna tuners to suppress motor noise. ? Ceramic Ferrite Cores with sufficient inductance would be too large and heavy and are more effective to suppress high frequency noise. ? ?
It would not hurt to add a large filter capacitor across the DC plug to smooth out voltage drop due to motor start surge current . ?Some people have mentioned replacing the power supply but I wonder if that is really necessary , large current surge can be ¡®smoothed¡¯ out with a properly sized electrolytic capacitor across the DC line, such a capacitor is in every power supply ever made , 1000mfd at 50 volts ?but again I like to see the circuit on an oscilloscope for a before and after picture but Non of these components would harm anything ... ceramic disc capacitors are not polarized +/- but Electrolytic capacitors are Polar sensitive, the terminals are marked positive and negative so pay attention to connect positive to positive and negative to negative. ? ?
? ?
Of course proceed at your own risk, all mentioned components are common electronic parts, The electrolytic can be installed anywhere along the DC cable or at a connector just remember positive to positive, negative to negative, thevalue is not critical but the voltage rating should be at least 3 times the power supply output for safety so 35volt or higher rating is Ok, ?The ceramic disc capacitor is very small and should be at the motor terminals. ?A 15 watt soldering iron is best for the job, not 100 watts which could destroy parts. ??
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John
Could you please re-photograph the top of the PCB again particularly U7 DSPic!?? It looks like its bee a little hot on the sticker on top.? The problem here is U7 is DSPic for DEC...the issue is DEC isn't it?
I've worked on Gemini's? that have had runaway issues and odd issues like you said.? Sometimes there sometimes touching a direction arrow causes runaway etc.? Along the food chain of ICs and problems it can be are:
A cracked solder join on the connector to PCB....unlikely with the mini
A bad H bridge U13.??? Yes this can cause the said same issues, usually one channel.
A bad DSPic.?? I'd first attempt to re-flash it to see how that went but the firmware is not available to public.?? Yes this could be the issue...or changing on spec and flashing it.
Or the ARM processor U11.? Which has firmware not publicly available.
PCB cracks....no apart from some motor connectors.? The Gemini uses good leaded solder not that crappy "no lead"....which fractures and needs a furnace to melt/re-flow.
My bet is the H Bridge U13 in one channel.?? Its not easy to replace s the PCB has 4 layers and GND/PWR planes in-between so heat soak is huge.?? You need good equipment and techniques to replace this.
I think its at the point you send it either to Losmandy of one of the repairers.
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Brendan
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On Mon, May 10, 2021 at 01:09 PM, Bill P. wrote:
Noise is not an unusual problem in motor circuits and most often the resolution is cheap and not too difficult, in fact the solution can be made into a cable pigtail for each RA and DEC cable but I won¡¯t go further as I know any electrical engineer knows the answer. ? ?
Bill, No engineer here, but what is this simple solution? I assume you mean a ferrite core noise suppressor which is found on some data cables. I think some of these can be snapped over the outside without cutting and re-soldering the wires. My next step is to replace the Gemini 2 PC board as a whole, not solder in a new chip. My motors and cables appear to be sound, so by elemination the source would be the Gemini unit itself. Thanks, John
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An issue that has never been mentioned on this Gemini forum is electrical circuit noise inhibiting the normal processing of Firmware commands. ?Barring the obvious bad cable/connector/battery/dirty encoder wheel ?DC motors are miniature spark gap radio transmitters and the attached cables are radio transmitter antennas. ?The onboard circuits contain thousands if not millions of radio receivers in the form of Diode junctions that normall act as switches but can act as analog signal rectifiers. ? Its very possible to introduce electromagnetic (EMI) noise into the attached circuits and at sufficient levels this electrical interference is rectified above 0 and/or 1 logic levels to disrupt the onboard computing processes. ?I¡¯m sure everyone is familiar with the MS Windows Blue Screen of Death , the result of a computing problem. ?
When the DC motor is energized the motor winding inductance creates a sufficient EMF noise spike ( a current opposite of the primary source is generated) ?the source of the noise, the duration of the noise spike and amplitude are the culprit. ?Easy to cure. ? ?
Its not hard to determine if EMI is on the cable and most circuit board designs are tested but this is astronomy and who would have thought about such a condition.but at 12 to 18 volts and motor start surge currant this is not a condition to be overlooked.
Noise is not an unusual problem in motor circuits and most often the resolution is cheap and not too difficult, in fact the solution can be made into a cable pigtail for each RA and DEC cable but I won¡¯t go further as I know any electrical engineer knows the answer. ? ??
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Michael Herman
David C. Partridge
Bill P.