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Polar Scope Illuminator on Vixen GPDX

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#1 Avitam

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Posted 22 January 2025 - 03:07 AM

Hello All,

 

I just received a Vixen GPDX. I am trying to get the Polar Scope Illuminator to work, but no luck so far. 

 

The LED itself is working confirmed using the diode test on a multimeter , but for some reason I cannot get it to work after install the AA batteries. 

 

Does someone have a similar polar illuminator on their Vixen mount and can me through it so I can understand what is wrong/missing with my polar scope illuminator? What can I test?

 

PXL_20250122_065748357.jpg

 

Full Gallery is here: https://www.cloudyni...pe-illuminator/

 

Thanks!

 

Avi


Edited by Avitam, 22 January 2025 - 03:21 AM.


#2 mazdak

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Posted 22 January 2025 - 08:05 AM

Apparently some modification has done on your mount . My GP-DX mount do not have a DC input jack. 

Am I seeing correctly?



#3 39cross

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Posted 22 January 2025 - 08:41 AM

I see two copper plates or tabs that look like they were used for grounding, with solder on them but no wires attached at the solder points.  Is there something missing here?  My guess is yes.



#4 Avitam

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Posted 22 January 2025 - 09:02 AM

I see two copper plates or tabs that look like they were used for grounding, with solder on them but no wires attached at the solder points. Is there something missing here? My guess is yes.


Those copper plates are just the retaining clips for the AA battery. I have absolutely no idea why there is solder on them though

#5 ngc7319_20

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Posted 22 January 2025 - 09:02 AM

The external power adapter looks like a DIY modification.  The solder joints at the battery clip / wire connection are dodgy, and you wouldn't want bare solder acting as battery contacts. 

 

The rest looks like a nice printed circuit board.   It would be interesting to see a picture of the underside with the printed circuit traces.  Maybe something was modded there. The original owner may have disabled the internal battery capability, either intentionally or accidentally.

 

As @39cross mentions the solder on the two copper tabs that retain the batteries makes no sense electrically.  This solder appears unnecessary.  No wires need be connected there.

 

Maybe try reversing the batteries.  I know they are supposed to go the way you show, but maybe the diode got flipped around when they were modding.

 

The black round thing at the top is a variable resistor with a switch attached.  Is there a knob sticking out somewhere on the reverse side? Maybe check if the switch is in the circuit and simply in "off" position.  Or might have been disabled.


Edited by ngc7319_20, 22 January 2025 - 09:07 AM.


#6 39cross

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Posted 22 January 2025 - 09:19 AM

I wondered if those metal tabs were for securing the batteries, but being made out of metal instead of plastic, I wasn't sure. 

 

As @ngc7319_20 writes, it would probably be useful to see the other side.  Maybe they cut the battery connection.  It would be nice if you could see what a working example looks like.  I'm guessing you've measured the voltage going to the diode and see nada?  And with batteries reversed?

 

Since it's just two batteries to light up a diode it should be a simple circuit, but you may have to undo the mods.



#7 Avitam

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Posted 22 January 2025 - 01:22 PM

Hi All,

 

Some updates. I added more pics to the gallery album: https://www.cloudyni...pe-illuminator/

 

  1. The previous owner (or the original owner....not sure who did the mod) certainly made some funky mods. I reached out to someone else who has the same polarscope illuminator and the pics he sent me show a stark difference. All those extra soldered wires extra are clearly add-ons/modifications. : https://www.cloudyni...al-illuminator/
  2. Good news: I got it to work. I think there was crud on the Cu contacts that prevented proper contact with the battery. The previous owner had left the batteries in there and they had leaked and deposited  a lot of residue/crud on the contacts. I cleaned them off with sand-paper and the LEDs are now lighting up. 
  3. But I think the custom mods that were made are interfering somewhat with the operation of the potentiometer. For e.g., after turning on the potentiometer dial, the LED does not light up until the potentiometer travel is close to 60-70% of it's full travel range. So the intensity control is really limited. Maybe that was the intent behind the mods: to control the intensity range? Not sure. There is a ~1 kOhm resistor that has been added. I am tempted to disconnect those extra wirings to see if it restores normal operation. 
  4. The little white box to the side....that is also missing in the reference pic I received and I really can't tell what it's purpose is. 

Someone has clearly gone through some pain to make these mods, so I feel that must have been with a specific and educated intent. smile.gif


Edited by Avitam, 22 January 2025 - 01:28 PM.

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#8 Avitam

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Posted 22 January 2025 - 03:04 PM

Final update. 

 

I removed the solder connections and both wires related to the custom mod and it did exactly nothing. smile.gif Didn't influence the operation of the illuminator in anyway. 

 

I have a video here: https://avishekaiyar...aring/e6fsl1T7l

 

Anyway.....I think this is resolved, but I am left with the mystery of what the person who made the mods was attempting.....maybe operating it using an external power source? That seems plausible since replacing the batteries means removing the RA axis every time. I can see that being problematic....not because of the extra effort, but more because I don't like to leave batteries in there for a long time because they do tend to leak and cause contam issues.


Edited by Avitam, 22 January 2025 - 03:08 PM.

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#9 Astrojensen

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Posted 22 January 2025 - 03:48 PM

 

I don't like to leave batteries in there for a long time because they do tend to leak and cause contam issues.

Yeah... That has happened to the GP-DX mount I bought used a while back. The illuminator circuit was toast, when I opened the mount to inspect. undecided.gif

 

Currently trying to decide how to proceed.

 

 

Clear skies!

Thomas, Denmark



#10 ngc7319_20

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Posted 22 January 2025 - 03:57 PM

I think the purpose of the mod was mainly to run external power -- probably 6V or 12V -- to the illuminator.    I think disassembly to change batteries would have been a major pain.  And forgotten batteries are like a ticking time bomb waiting to ruin a nice mount.   Was the "white box" merely the input jack for the external power?  Interesting exercise...


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#11 Avitam

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Posted 22 January 2025 - 04:08 PM

I think the purpose of the mod was mainly to run external power -- probably 6V or 12V -- to the illuminator.    I think disassembly to change batteries would have been a major pain.  And forgotten batteries are like a ticking time bomb waiting to ruin a nice mount.   Was the "white box" merely the input jack for the external power?  Interesting exercise...

I didn't look closely enough inside the white box, but presumably it houses contacts from whatever jack is meant to be used on the external port that was installed on the outside. 

 

the modifications are fairly simple I think....simply copies the existing circuit but redirectors the supply to a source outside the illuminator housing. The resistor is a 1 kOhm resistor, whilst the OEM one is closer to 0.5 kOhm. Maybe the radio jack (or whatever it is ) simply connects to one of these : https://www.digikey....cB&gclsrc=aw.ds

 

Seems like a cool and really relevant idea. 


Edited by Avitam, 22 January 2025 - 04:09 PM.


#12 Avitam

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Posted 22 January 2025 - 04:15 PM

Yeah... That has happened to the GP-DX mount I bought used a while back. The illuminator circuit was toast, when I opened the mount to inspect. undecided.gif

 

Currently trying to decide how to proceed.

 

 

Clear skies!

Thomas, Denmark

uh oh....that is unfortunate....luckily for me the damage was contained to just the Cu terminals....could have been a lot worse. I must say that it's not the best design for battery replacement. I think the person who made the mods did something really nice. 

 

I need to figure out what that external connection is though....the smallest DC plug I have is a 3.5 mm x 1.35 mm one and even that seems too big. 



#13 Astrojensen

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Posted 22 January 2025 - 04:41 PM

Now I've ordered a Sky-Watcher external illuminator for the GP-DX. I'll just remove the old one and not bother with it. 

 

 

Clear skies!

Thomas, Denmark



#14 Avitam

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Posted 22 January 2025 - 04:55 PM

Not to digress from this topic, but wondering which epoch your reticle goes to.....from what I can tell the OEM reticles only goto 2010....so do you just extrapolate from there on? How does that work?



#15 ngc7319_20

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Posted 22 January 2025 - 05:15 PM

If you go with AA batteries, you could use something like Energizer Ultimate Lithium AA.  They are supposedly leak poof.  I'm using them in all my high-end gear.   I've never had one leak.


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#16 Astrojensen

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Posted 22 January 2025 - 05:46 PM

Not to digress from this topic, but wondering which epoch your reticle goes to.....from what I can tell the OEM reticles only goto 2010....so do you just extrapolate from there on? How does that work?

I've not tested it yet, so I don't know. I'll probably extrapolate, at least for now. There are replacement reticles available for the older EQ-5 mounts and they should fit the GP finderscopes, too. 

 

https://www.teleskop...polsucher-15367

 

 

Clear skies!

Thomas, Denmark


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#17 Avitam

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Posted 24 January 2025 - 11:20 AM

I think the purpose of the mod was mainly to run external power -- probably 6V or 12V -- to the illuminator.    I think disassembly to change batteries would have been a major pain.  And forgotten batteries are like a ticking time bomb waiting to ruin a nice mount.   Was the "white box" merely the input jack for the external power?  Interesting exercise...

This is timely as I am building my 12v battery box right now and have room to add on customizations. 

 

I thinkig off adding on a cheap buck converter to drop the voltage from 12V to 3V. 



#18 ngc7319_20

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Posted 24 January 2025 - 01:42 PM

This is timely as I am building my 12v battery box right now and have room to add on customizations. 

 

I thinkig off adding on a cheap buck converter to drop the voltage from 12V to 3V. 

Gee, I dunno.  Buck converter seems like a lot of trouble for 3V and 20mA to run the LED.  A simple 470 ohm 1/4 watt resistor would do the same job.  If I'm reading the color code off the old resistor correctly it is brown - black - red - brown or 1000 ohms.  You could check it with the multi meter.   That would work also, just a tiny bit less bright.  Nothing to buy.  If you needed 1A then I'd say sure, get a buck converter.  But for this a resistor is fine.


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#19 Avitam

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Posted 24 January 2025 - 08:53 PM

Gee, I dunno.  Buck converter seems like a lot of trouble for 3V and 20mA to run the LED.  A simple 470 ohm 1/4 watt resistor would do the same job.  If I'm reading the color code off the old resistor correctly it is brown - black - red - brown or 1000 ohms.  You could check it with the multi meter.   That would work also, just a tiny bit less bright.  Nothing to buy.  If you needed 1A then I'd say sure, get a buck converter.  But for this a resistor is fine.

you are totally correct. I was thinking buck converters because I am going to install them on the OnStep board that I am planning for the GPDX, but that is way down the line. I think for now, I am just going to with the resistor and the 12V supply. 




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