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#176 RSX11M+

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Posted 13 March 2021 - 05:33 AM

Good enough.

 

You understood perfectly - those are 1/4 watt size, a little bigger [as you said] so the only problem is that the cover probably won't close fully. Just don't tighten the cover screws - and that will prevent damage to the resistors and the PCB.

 

Let me know how testing goes. 

 

Replace C1 on the RA board whenever you feel it's exercised enough.

 

 

 

I'm testing some USB-RS232 dongles on the LX200-12 RS232 port. -will advise.

 

Have fun - 



#177 sickozell

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Posted 14 March 2021 - 05:56 AM

I did an all day&night test with no problems.

Only key 1 on HC sometimes worked 50% of times... sometimes 2-5% !!! ... I really need a new HC.

So today I decided to replace C1 on the RA board.

Unfortunately I did a worse job than the DEC one due to the bad position of the board.

I had to rotate the board as you can see from photo to reach better the pins of the connector and keep the pcb still.

Also I had to be very careful not to pull the short wires soldered on the pcb.

 

One question: is there any way to check the good connection of c1? If the RA motor works even without C1, if it's not well connected how would I notice ?

Attached Thumbnails

  • 31 ra board.jpg
  • 32 ra board replacing c1.jpg


#178 astrovoyeur

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Posted 14 March 2021 - 07:56 AM

 

 

One question: is there any way to check the good connection of c1? If the RA motor works even without C1, if it's not well connected how would I notice ?

Simply check continuity between each C1 lead and it's appropriate pcb pad.   Or you may just reflow each solder joint with a fresh dap of solder.   



#179 nitegeezer

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Posted 14 March 2021 - 02:19 PM

The bottom of the two joints looks like a cold solder joint. Try to put the tip of your soldering iron on both the lead and the board pin to see if you can make them flow together.

#180 RSX11M+

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Posted 14 March 2021 - 03:41 PM

...
One question: is there any way to check the good connection of c1? If the RA motor works even without C1, if it's not well connected how would I notice ?


Cold solder joints are seldom diagnosed by actual testing, and then only if they effect the circuit. The customary way is inspection and physical stress. (they "break" easily)

Since C1 has already been shown to be superfluous on the RA board, you wouldn't know if it was well soldered or even bad. You might find out however if it is backwards. storm.gif 



I must agree with astrovoyeur and nitegeezer that this soldering looks worse than previous attempts. "Re-flowing" the joint would be advisable if I thought you needed C1, but since I don't - doing so is a vanity risk.

You have done a really good job not damaging the connecting wires up to this point. You will have to decide how important continuing is to you. The biggest dangers amateurs encounter is damage they cause to their own projects, which is typically worse than the original fault.


You really should practice by reflowing joints on the boards you've been pulling parts from before proceeding on this one. The RA board is critical to scope operation - C1 is not (badly or well soldered)

It appears to me that you are not using solder at all, or if you are - that it is not electronics type. (plumbing perhaps?) Please include a photo of it's label if you plan to proceed.



#181 sickozell

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Posted 14 March 2021 - 04:50 PM

I just checked the continuity and I think I will take no more risks.

I retested the scope all day following objects, so I'll order a new HC at Clearline and Usb adapter too.

I will post again when it will be fully functional.

 

For now I would like to thank  you all very much and hope this thread may help someone else in troubleshooting.


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#182 sickozell

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Posted 06 June 2021 - 04:13 AM

Update:

as mentioned, I bought a new membrane to replace the broken one. It was very difficult to unplug the blue connector from the pcb, being careful not to break anything. It just takes a lot of patience.

You have also to be careful when placing the adhesive membrane, it fits perfectly the hand controller, but it could be easy to fail alignment.

My testings went good.

If you're interested, as suggested from astrovoyeur, I got it from Ron Sampson, please check this site http://www.imjeffp.com/handcontroller/ and email him.

 

I also got a new hand controller for spare from Clearline Technologies.

It works good and it weights less: 240g against 298g of the original one.

They sell it with a cable and a adhesive hook. Maybe the fitting of the membrane in the enclosure is not really really perfect, but it is difficult to notice and does not cause any problem.

For those who need a new hand controller, I really suggest it.

 

In the photo on the left is the old HC with the membrane replaced. On the right is the new HC from Clearline with the hook on the side.

 

From Clearline I also got a USB-toRS232 adapter. I tested it with StarryNight6 and had some initial difficulties. Later I underestood to estabilish connection before the scope alignment, and take care to exactly match the scope and computer time.

Attached Thumbnails

  • 33 hand controllers.jpg

Edited by sickozell, 06 June 2021 - 04:24 AM.


#183 MikeBY

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Posted 06 June 2021 - 01:34 PM

It sounds like excessive current draw on the power supply is causing it to shut down. The behavior is typical of an overdraw on a switching power supply.  There is a very large inrush current when the 18v is first applied to to the telescope due to a large electrolytic capacitor on the control panel board directly across the power connector pins.   I suggest that you connect the supply to the telescope 1st, then plug in the power supply.  This will charge that large capacitor on the telescope.  Then turn on the scope last. 

Regarding capacitor replacements,

I would recommend that you use 10uf 50v electrolytic capacitors with a 105 C rating. Tantalum's are risky when used on the main power supply line.
There are 5 tantalum capacitors that are directly fed +18V from the external power supply, one on each PC board inside the scope and

one in the handset.  Even if these capacitors look ok they can fail from age and there is a tendency for these to fail in a "short" mode that can cause

damage. 

Each board has  an LM7805 voltage regulator and this capacitor is between pin 1 (input side) of the regulator to ground. 

The tantalum on the output side of the regulator does NOT need to be replaced. It only sees the regulated 5v output voltage.

 

The OP's pic of the main board, C3 has  a burn spot. It is failed. 

 

All these boards are double sided and you must be extremely careful when desoldering to not damage the traces on either side of the board and when

installing the new components to be sure that solder has flowed through from the solder side to the component side and that traces on both sides are connected to the capacitor leg. 

On the DEC and RA boards, it is extremely easy to ruin the double sided traces changing the tantalum's. The traces are very very thin. One option is to smash the old tantalum with pliers and then solder the new capacitor to the old legs. 
There are several checks you can make if the board is not running correctly after you've worked on it. If the board is not right you will get runaway motors. 
Also, be very careful of the connections to the photo diodes and leds.  These are very delicate. 
I'd remove the entire motor assembly to work on these then re-install the motor assembly and be sure to put the assembly back exactly where the screws were before. (mark them).
 

1) The transistor looking device next to the capacitor is actually a 7805 voltage regulator.

3) With the wiring disconnected from J1 (six pin connector), check with an ohmmeter from the connector pin 4 (+18v) to pin 1 of the regulator to be sure there is continuity.  The trace runs on the component side from the connector pin to the + leg of the capacitor and then to the regulator pin 1. From there the trace makes it's way to pin 3 of the IC. Removing the old cap, it is easy to damage this trace. 

4) Check continuity from  pin 4 of J1 to pin 3 of U1 (the IC on the board). This supplies +18v to the IC. 

 

When power is applied to this board, there should be +5 volts coming out of the regulator. This can be checked at the resistor R3 which is next to the mounting screw.  The end of the resistor sticking up in the air should read +5v. This voltage supplies the IR LEDs

 

Note that although the circuit boards are the same, the RA motor board also has wires going to the hall effect transistor that are not there on the Dec board.

On J1, the RA board will not have a wire at pin 6, where on the DEC board the connector will not have a wire at pin 3. 

 

On the control panel circuit board, removing the metal panel can be difficult. On the power connector, after removing the metal nut and washer there is a plastic insulator that looks like a shoulder washer.  That plastic piece is actually 2 pieces. It is threaded.  The top threaded piece holds down a thin wedged plastic washer that keeps the connector barrel from touching the panel. I used a small dental pic to turn this small bit of plastic.

For schematics and lots of helpful information I refer you to the site 

http://www.lx200classic.com/

 

Clear skies !!

 

Michael


Edited by MikeBY, 06 June 2021 - 01:39 PM.



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