Bozo
journeyman
Reged: 09/03/08
Posts: 6
Loc: Alto, Michigan
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Well I am glad I found this forum. Incredible amount of talent and info here. Now for the question: I acquired a Classic for free and have just about completed repairing it when it showed it had the DEC runaway. After searching the forum I found the fixes for it last night and tried the jump wire solution. Well it was late and I should have waited till the next day.
Don't ask how but the jumper arced across one of the solder points of the Hbx plug and shut the hbx down. After reading I think I fried the hbx. I will have to research that problem.
However when I checked the power supply it only had .5 volts at the plug end. When i split the connector just before the fuse it had 19.4 volts. With the fuse removed and checked across the fuse holder and the plug end ground it was .5 volts.
What the heck? 
Where did the 19 volts go?
Any ideas?
Thanks
Bozoni
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Bozo
journeyman
Reged: 09/03/08
Posts: 6
Loc: Alto, Michigan
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It turned out to be a blown line fuse. The fuse looked good and so I did not put the OHM meter on it.
Live and learn.
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skynut
sage
Reged: 09/24/05
Posts: 243
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The earlier LX 200's used 18 volts to power the scopes. My buddy tried to use 12 volts -- it worked for a while, but burned up the mobo in the base. Hope this helps a little
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KnightDiver
member
Reged: 03/21/08
Posts: 34
Loc: SE Michigan
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Quote:
The earlier LX 200's used 18 volts to power the scopes. My buddy tried to use 12 volts -- it worked for a while, but burned up the mobo in the base. Hope this helps a little
From my reading about this, I believe that the LATER LX200's were the ones that used 18 volts. And I don't think there is a way that 12 volts into that circuit can burn up the MOBO. It is regulated down to 5 volts in both systems.
Probably just a coincidence.
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Kolenka
professor emeritus
Reged: 06/01/08
Posts: 600
Loc: Seattle Area, WA, USA
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The Classics use 18V, the later models like the GPS/ACF use 12V. You are right that it shouldn't be able to 'burn up' the mobo though.
The reason for the high voltages is the motors I believe. The 18V input was probably to drive some motors that were rated for 18V.
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Meade 10" LX200R
Orion 80ED
Nagler 7T6, 9T6, 13T6, 17T4, 26T5
Canon XSi (Modded), TIS DMK 31AF03
Northwest Astro Photoblog
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rmollise
Carpal Tunnel
Reged: 07/06/07
Posts: 1662
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Quote:
The earlier LX 200's used 18 volts to power the scopes. My buddy tried to use 12 volts -- it worked for a while, but burned up the mobo in the base. Hope this helps a little
The motherboard in his base may have burned up, but it was not the 12volts that did it. Not only was 12volts safe to use on the 18v classics, they were usually more reliable when operated that way.
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Uncle Rod
Watch for Rod's New Book:
Choosing and Using a New CAT--coming in December!
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KnightDiver
member
Reged: 03/21/08
Posts: 34
Loc: SE Michigan
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Quote:
The Classics use 18V, the later models like the GPS/ACF use 12V. You are right that it shouldn't be able to 'burn up' the mobo though.
The reason for the high voltages is the motors I believe. The 18V input was probably to drive some motors that were rated for 18V.
I meant to say that the later LX200 *Classics* were 18 volts. The earlier LX200 *Classics* were 12 volts.
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Arctic_Eddie
super member
Reged: 12/30/07
Posts: 131
Loc: St. Petersburg, FL
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Motors are designed for a particular voltage. When operated differently they can draw excessive current for either over or under voltage. The excess current has to pass through copper traces on the circuit board from the direction switching transistors. Also, the trace widths are designed for a max current. Exceeding this rating will overheat the traces and burn the board.
Always operate at the design voltage and with a regulated power supply. Wall-warts are usually not regulated and have an unloaded voltage 41% higher than the rated value.
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The shortest distance between one point is an infinitely small circle.
73's de KF4JU
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southmike
Carpal Tunnel
Reged: 11/22/04
Posts: 2821
Loc: Fayetteville, NC
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the original classics were designed origionally to run on 12v but they didn't repond well ie the motors lacked torque.
bumpingthe voltage up to 18 was meades cure. as far as i knoe none were sold at 12volts....not counting the lx5 or 100's I have no idea what they run at.
( i am talking about ones with big square boxy hand controler, not auto star series)
18v worked well except for the fact that the early classics were not fully grounded and suffered from some spikes.
also the yellow tantium capacitors could some times pop.
mostly an easy repair except for one in the handbox under a thin ribbon , when that popped it cut the ribbon.
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group scope pic
my refractors
LX200 10"-St120
LX200 8" f6.3-Orion 80ed
LX200 8" f10-Orion 90 Mak setup pic
Meade 102ED LXD650
Sky Watcher 100 ED Triplet prototype
Nexstar 5
etx125
etx70's
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Bozo
journeyman
Reged: 09/03/08
Posts: 6
Loc: Alto, Michigan
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I just had one of the tantulum's pop on the RA board.
Not to mention my power supply operates 19 to 21 volts. Time for a regulated supply.
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JAT Observatory
Space Freak
Reged: 02/20/05
Posts: 5656
Loc: Eastern PA
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Quote:
The reason for the high voltages is the motors I believe. The 18V input was probably to drive some motors that were rated for 18V.
My understanding is the motors actually run on a voltage differential of 1.5 to about 3 or 4 volts between one side of the motor and the other. So it is not the 18 volts taht directly power the motor.
If there is 12.5 volts on one side and 11.0 volts on the other (coming from the motor controller board) the motor sees the differential 1.5 volts and will run at sidereal rate. You can power the motor directly with a 1.5 volt battery which is a common troubleshooting technique.
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-Marcus
The problem with free speech is even the stupid have a voice.
http://jatobservatory.org
12" LX200R on a Paramount ME
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