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Equipment Discussions >> Classic Telescopes

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orion61

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Reged: 10/20/07

Loc: Birthplace James T Kirk
Help getting Tracker Fixed new
      #5605037 - 01/04/13 03:34 PM

Anybody know where I can get my Dyna Tracker fixed?
Or does anybody here fix them reasonably? I'm on Disability and things are kind of tight right now, waiting for my next surgery from getting run over by a car!
I've got a great old Sandcast C8 that is fantastic and looks like the day it was made...


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dgreyson
scholastic sledgehammer
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Reged: 11/06/12

Loc: South Carolina
Re: Help getting Tracker Fixed new [Re: orion61]
      #5605077 - 01/04/13 03:55 PM

They are pretty simple, I have one myself. Is it totally dead or what?

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orion61

*****

Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: Help getting Tracker Fixed new [Re: dgreyson]
      #5605129 - 01/04/13 04:16 PM

yep pretty much, plugged it in to use from a battery and smelled THAT smell, looked down and saw a bit of smoke..
now it's ka-put


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starman876
Postmaster
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Reged: 04/28/08

Loc: VA
Re: Help getting Tracker Fixed new [Re: orion61]
      #5605338 - 01/04/13 06:26 PM

These electronic things stop working when you let the smoke out. Every electronic thing I have ever had stopped working after the smoke was let out.

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orion61

*****

Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: Help getting Tracker Fixed new [Re: starman876]
      #5605353 - 01/04/13 06:38 PM

Somethin like rubbing a lamp and Genie? but mine wouldn't look like Barbara Eden (Memba her WOW)
Mine would look like Curley (Jerome) Howard (The 3 Stooges)
and let the smoke out of my tracker as he tripped over it
Nyuck Nyuck....


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dgreyson
scholastic sledgehammer
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Reged: 11/06/12

Loc: South Carolina
Re: Help getting Tracker Fixed new [Re: orion61]
      #5605506 - 01/04/13 08:18 PM

usually in vintage electronics, the Electrolytic capacitors fail due to age and short out which burns a resistor. Hopefully one of the driver transistors hasnt blown. I will pull the cover on mine and see what the circut looks like.

Rather than just plugging it in and switch it on when it's been sitting a long time unused, you plug it into a variac transformer and slowly bring up the voltage over a day or so to Rejuvinate the capacitors. But some wont form correctly coz they are too dried out and old and blow anyhow. The usual procedure is to replace all the electrolytic capacitors, check for burnt or open resistors and check the transistors and that fixes 90% of the usual problems with such things.

Your smoke came from the Main unit, not the hand controller right?


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dgreyson
scholastic sledgehammer
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Reged: 11/06/12

Loc: South Carolina
Re: Help getting Tracker Fixed new [Re: dgreyson]
      #5605696 - 01/04/13 10:40 PM

Had it been in regular use by you and failed or did you just buy it with your new scope? Same things would go bad, capacitors have a limited lifespan. just curious.

I pulled the covers off mine and took a look, I would think it should cost less than $20 dollars in parts to fix it, maybe $25 ish if both the power transistors are blown.

The hand controller has a 12v adjustable oscillator made from small signal transistors and ought to be just fine. It pulses 12v through the two power transistors into a transformer that steps it up to near line voltage to drive the motor. I can fix it if no one is closer to you as I'm an electronics tech if you want.

If you have a small phillips screwdriver, unplug the power cord from the wall and pull the main box's lid to see if you can see one of the 3 grey electrolytic capacitors bulged or leaking and if one or more of the three black rectifier diodes have burned.
Hopefully the orangeish large power resistor next to and below the diodes is unburnt as it goes to the power transistors. Also, check the handbox plug to make sure a wire isnt loose or shorted at the plug. the plug cap unscrews if you want to check it but be gentle, dont force it if it's stuck. Has the fuse blown or is it intact?


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DAVIDG
Post Laureate
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Reged: 12/02/04

Loc: Hockessin, De
Re: Help getting Tracker Fixed new [Re: dgreyson]
      #5606374 - 01/05/13 11:24 AM

I have repaired many telescope electronics over the years, just ask TIM53 about all the stuff I fixed for him. Since you said it happened while running off of the battery that sugguests that it is not the AC/DC rectifier used to allow it to run off 110VAC.
What I have found is about 90% of the time on these type of drive correctors is that one of the power transistors has gone bad and is now shorted to ground. This causes all the current to be dumped into the secondary of the transformer, which causes things to heat up and then let the smoke out.
The other common problem is that a wire breaks in the hand controller. The hand controller contains parts which form the oscillating circuit. If the circuit doesn't oscillate what happens is one power transistor is turn on all the time and again all the current is now flowing thru the secondary of the transformer and things get hot.
As Dgreyson sugguests pull the cover off and see what looks damaged and if you can post some pictures I'm sure that we can get a good idea of what went wrong and how to repair it.

All the Best,
- Dave


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dgreyson
scholastic sledgehammer
*****

Reged: 11/06/12

Loc: South Carolina
Re: Help getting Tracker Fixed new [Re: DAVIDG]
      #5606627 - 01/05/13 01:25 PM

Ah hah, I missed he said he was running on batteries, we are good from the line cord to the 12v socket then.

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orion61

*****

Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: Help getting Tracker Fixed new [Re: DAVIDG]
      #5606644 - 01/05/13 01:38 PM

Thank you all so very much for your help. I have it packed away, I bought a Dynamax DX6 a little over a year ago and it came with it. The first time I tried it, it blew, it looks to have never been used.
I admit I dont know a resistor from a Flux-Capacitor!
I am recovering from my 6th surgery after getting hit by a car, then getting Staff infection,and a Hear attack after a surgery and I threw a blood clot. I thought it would be a good time to have it looked at. I'll try and dig it out.
BTW dont laugh about the Dynamax, it has superb optics!


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DAVIDG
Post Laureate
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Reged: 12/02/04

Loc: Hockessin, De
Re: Help getting Tracker Fixed new [Re: orion61]
      #5606767 - 01/05/13 02:54 PM

Many years ago I heard that Criterion made a mistake when they either designed the drive corrector or when it is built and the power resistor for the power transistors was the wrong value. It could have been defective right out the box and you were the first to plug it in. In any case I'm sure that a bunch of us that know electronics can pretty quickly figure out what died and how to fix it.
If it isn't working off the battery then it the odds are low that it will work off the 110 VAC house current since all the rectifier circuit does is take the 110AC and make 12 volt DC, just like the battery is providing. When you hook it up to the battery the rectifier section is out of the circuit.
Anybody got a schematic ? The guys at Criterion were pretty smart and they also got many of their ideas from the literature of the day so I bet the circuit is pretty close to the Saxon circuit publish in Jan 1975 Sky and Tel.

- Dave


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orion61

*****

Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: Help getting Tracker Fixed new [Re: DAVIDG]
      #5607121 - 01/05/13 06:31 PM

Thinking about it it really does look and untill it Smoked
smelled like brand new, the paint and rubber smelled brand new, and the cords were still sealed in bags.
It fried the first time. Also wont work on AC
possibly should toss it


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dgreyson
scholastic sledgehammer
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Reged: 11/06/12

Loc: South Carolina
Re: Help getting Tracker Fixed new [Re: orion61]
      #5609852 - 01/07/13 10:06 AM

Not when you can fix it for 10 or 20 dollars. another one with shipping still is going to likely cost more than shipping and fixing this one I would guess, unless you get a good deal on it. In that case never pass up a good deal. I think parcel post would be $12 if you dont know how to use a solder gun or a volt-ohm meter and have neither. As a vendor you should have access to discounted shipping rates anyhow. But time is money I know, it is often better to buy another rather than tie up time you dont have to spare.

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DAVIDG
Post Laureate
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Reged: 12/02/04

Loc: Hockessin, De
Re: Help getting Tracker Fixed new [Re: dgreyson]
      #5631427 - 01/19/13 11:55 AM Attachment (10 downloads)

I sent Larry a note that I would be happy to take a look at his Criterion E-6 controller. I have been doing electronics since I was kid and also as part of my job for the last 27 years as a research engineer. I've built a number of drive controller and CCD camera system from scratch and helped Richard Berry with his "CCD Camera Cookbook". I'm not trying to brag just saying that I know which end of a soldering iron to hold without burning myself, most of the time. I'm also a big Criterion fan and I wanted to see how this controller worked. I heard many years ago that Criterion had either made a mistake in the design or when it was assembled which caused the power resistor to easily fail on these units.
Larry packed it up and sent to me and when it arrived I pulled the cover of the unit and took a look. Larry had said that as soon as he plugged it in that it smoked. It didn't take long to see what part had fried. It was the power resistor. Actually it cracked in half it got so hot. Here is a picture showing it still installed in the circuit.

- Dave


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DAVIDG
Post Laureate
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Reged: 12/02/04

Loc: Hockessin, De
Re: Help getting Tracker Fixed new [Re: DAVIDG]
      #5631433 - 01/19/13 11:57 AM Attachment (10 downloads)

I dissassembled the case to get to the cooked resistor. I replaced it with Ohmite ceramic one of much better quality.
Here is what was left of the cooked one.

- Dave


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DAVIDG
Post Laureate
*****

Reged: 12/02/04

Loc: Hockessin, De
Re: Help getting Tracker Fixed new [Re: DAVIDG]
      #5631466 - 01/19/13 12:14 PM Attachment (13 downloads)

The next step was to determine if the AC/DC rectifer circuits was OK. I unsoldered the DC connection to the main power transistors and unplugged the hand controller. The oscillator circuit was located in the hand controller and it's job is to turn on and off each power transistor. If the hand controller had a problem or one the power transistor was bad, would usually happens is that one of the power transistor is conducting all the time dumping all the current in the transformer. All the current has to go thru the power transistor which is suppose to limit the current. If it is the wrong size it fries.
So with the transistors out of the circuit I powered up the unit. The rectifier section had no problems and was making 16 volts of clean DC.
The next day I brought the hand contoller into work so I could use the test equipment in my lab. I dissassembled the unit to see what was going on. I flipped over the circuit board and discovered the another resistor was cooked and broken in half. This thing took a real hard hit. Luckly I was able to take the pieces of the resistor and look at them under a microscope and was able to see the what was left of the color coding strips that determine it value. It was 680 ohm and the one right next was also of the same value. I replaced both of them.
Here is a picture of the back of the circuit board and the inside of the case showing were the resistor had burned the paint off the inside of the box and the two new resistors installed on the board.

- Dave


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DAVIDG
Post Laureate
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Reged: 12/02/04

Loc: Hockessin, De
Re: Help getting Tracker Fixed new [Re: DAVIDG]
      #5631471 - 01/19/13 12:22 PM Attachment (14 downloads)

I carefully power up the hand controller and was hoping to see two nice sqaure waves coming out of each channel but it was still dead. I little more digging and discovered at 6 volt Zener diode was shorted so it was replaced. Also all the Mylar capacitors looked strange. I never had seen one of these types go bad but on the outside of all of them they had would looked like salt crystals growning on them. Mylar caps are "dry" type so they don't use any liquid electrolyte so I had no idea what was going on. Since I have a ton of spare parts at home, I replaced all the caps. I found one 4.7uf electrolytic cap that when I tested it had 1/2 the value that it should.
Here is a picture of the hand controller board will all new caps and a Zener diode.

- Dave


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Bill Griffith
professor emeritus


Reged: 08/12/09

Loc: Ca.
Re: Help getting Tracker Fixed new [Re: DAVIDG]
      #5631477 - 01/19/13 12:27 PM


Dave, you are the epitome of the classic forum! You certainly have given good advise to me.

Congrats Larry,

I'm sure Dave won't stop until the controller is better than new!

Bill

Edited by Bill Griffith (01/19/13 12:57 PM)


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DAVIDG
Post Laureate
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Reged: 12/02/04

Loc: Hockessin, De
Re: Help getting Tracker Fixed [Re: DAVIDG]
      #5631498 - 01/19/13 12:39 PM

With the hand controller still not working, then the issue has to be with one of the transistors. The unit was designed in the late 60 to early 70's and is based on analog radio technology. How it works is that is uses a resistor/capacitor circuit as a time base. By using a variable resistor the user controls the frequency that the unit puts out. The first RC sections fires a transistor which controls another RC/transistor section to make two timing pulses that are 180 degree out of phase. In simple terms when one is on when the other is off. Those two signals then feed another two transistor based circuit that length the pulses to make them squares wave. It these two square waves that turn on and off the two power transistors in the main box of the unit. Those power transistor pulse 12 volts into a secondary of transformer. The transformer then steps up the voltage to 120VAC to make the AC needed to run the motor in the telescope.
The problem is that the transistor (2SB187) used are vintage Japanese germanium units that at one time were very commonly used in radios but not any more. Luckily EBAY comes to the rescue and I found a cheap source there. So when they arrive I'll replace them and I hope that will get this section up and running.

- Dave


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orion61

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Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: Help getting Tracker Fixed new [Re: DAVIDG]
      #5633129 - 01/20/13 12:47 PM

I cant tell you how much i thank you.
Dave you really know what you are doing!
There are people in this world I admire, People loke Dave, also Guys that can do Body Work. I've tried and it come out looking like someone threw a handfull of mud on the fender...
Thanks again Dave.. Like you I also Love Criterion I have a great old RV6!
The DX6 Dynamax that tracker came with has outstanding optics, and is in mint "cosmetic" condition. Like that Dyna Track is.. Sure was a lot of smoke coming out of that thing.


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