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draganm
Joined: 08 Mar 2006
Posts: 8990
Location: Colorado
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| Posted: Wed May 20, 2009 5:16 am Post subject: What was this supposed to be? |
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OK, here's another great example of "yeah, I can solder"  Not sure what happened here, looks like someone thought they found a bad transistor which burned up the resistor before it? Transistor has been replaced but the problem remains. At any case, why would you leave the old one in there and bridge the new one up 1 inch up off the board? this the green channel on a marquee Ultra FGM
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tommo2
Joined: 03 Jun 2006
Posts: 226
Location: Ireland
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| Posted: Wed May 20, 2009 6:37 am Post subject: |
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First off, unless the old resistor is totally fried, the new resistor will not do much good.
If the old resistor is not totally fried (ie complete open circuit), then (and assuming the new resistor is of equal value) the resistance of both resistors in parallel will be half the required resistance.
This will give you an overvoltage across the transistor or load it is feeding, damaging the transistor or some other downstream component (and even upstream component)
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Wed May 20, 2009 7:19 am Post subject: |
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A chin up bar for smurfs
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draganm
Joined: 08 Mar 2006
Posts: 8990
Location: Colorado
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| Posted: Wed May 20, 2009 4:33 pm Post subject: |
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| tommo2 wrote: | | If the old resistor is not totally fried (ie complete open circuit), then (and assuming the new resistor is of equal value) the resistance of both resistors in parallel will be half the required resistance. |
yup, but it looks like the old one and new one are both cooked. I hope I have the FGM schematic at home and i'll give this one a try but it might wind up going ot Curt. I don't really like board repairs.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed May 20, 2009 4:54 pm Post subject: |
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| draganm wrote: | | yup, but it looks like the old one and new one are both cooked. I hope I have the FGM schematic at home and i'll give this one a try but it might wind up going ot Curt. I don't really like board repairs. |
I feel your pain. I myself have seen my share of booger jobs, some even by repair shops that charge for that crap.
I'm pretty sure I have the print for that board so if you need a copy just let me know.
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akajester
Joined: 09 Jul 2008
Posts: 934
Location: Wisconsin
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| Posted: Wed May 20, 2009 5:04 pm Post subject: |
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| AnalogRocks wrote: | | A chin up bar for smurfs |
oh, that's just too funny. lmao.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed May 20, 2009 5:29 pm Post subject: |
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What is that location id? I cant quite make it out....
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Heywood Jablome
Joined: 12 Mar 2006
Posts: 1548
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| Posted: Wed May 20, 2009 7:40 pm Post subject: |
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| akajester wrote: | | AnalogRocks wrote: | | A chin up bar for smurfs |
oh, that's just too funny. lmao. |
Naah... Smurfs are three apples tall. That's clearly a limbo bar for hampsters, voles, or mice. Was this Richard Geres' projector? 
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-- Baron Alexander von Humboldt: 1769-1859
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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draganm
Joined: 08 Mar 2006
Posts: 8990
Location: Colorado
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| Posted: Wed May 20, 2009 8:53 pm Post subject: |
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| Nashou66 wrote: | Dragan, what is the board doing or not doing?
Athanasios |
I haven't actually tested it yet, the machine was exhibting a lack of vertical Pincusion and occasional set shut-down.
| macgyver655 wrote: | | What is that location id? I cant quite make it out.... |
marquee focus module, close to the big heat sink and right next to the bi-polar caps.
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed May 20, 2009 10:45 pm Post subject: |
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| draganm wrote: | | macgyver655 wrote: | | What is that location id? I cant quite make it out.... |
marquee focus module, close to the big heat sink and right next to the bi-polar caps. |
I meant the resistor location number. R2??. On the board. I cant make out the number in the picture. 
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jkruger
Joined: 24 Oct 2007
Posts: 2435
Location: Carlsbad, CA
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| Posted: Wed May 20, 2009 10:49 pm Post subject: |
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Looks like R235 to me.
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Wed May 20, 2009 11:10 pm Post subject: |
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Hey, look on the bright side, any size alligator clip will fit on that resistor.
It's not uncommon to solder (temporarily) a replacement resistor on top of the original smoked one, I do that all the time if I'm not sure that the board is repaired 100%. Once the board is repaired though, then you always take out the original one and solder in the replacement.
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Clarence
Joined: 08 Mar 2006
Posts: 3827
Location: Smith Mtn Lake, VA
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| Posted: Wed May 20, 2009 11:28 pm Post subject: |
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| Heywood Jablome wrote: | | That's clearly a limbo bar for hampsters, voles, or mice. Was this Richard Geres' projector? |
Speaking of Hampsters doing bad things, didn't Hampster go d!%!#@|? 
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draganm
Joined: 08 Mar 2006
Posts: 8990
Location: Colorado
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| Posted: Thu May 21, 2009 6:03 pm Post subject: |
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| Curt Palme wrote: | | It's not uncommon to solder (temporarily) a replacement resistor on top of the original smoked one, I do that all the time if I'm not sure that the board is repaired 100%. Once the board is repaired though, then you always take out the original one and solder in the replacement. |
ahhh, thanks curt, that makes sense now. I noticed the transistor to the right was replaced and that work looked good. I guess someone started this but gave up and simply never finished.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Thu May 21, 2009 6:47 pm Post subject: |
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| draganm wrote: | | Curt Palme wrote: | | It's not uncommon to solder (temporarily) a replacement resistor on top of the original smoked one, I do that all the time if I'm not sure that the board is repaired 100%. Once the board is repaired though, then you always take out the original one and solder in the replacement. |
ahhh, thanks curt, that makes sense now. I noticed the transistor to the right was replaced and that work looked good. I guess someone started this but gave up and simply never finished. |
I would agree with this process but as I hope Curt would agree, I usually at least clip one end of the resistor to take it out of circuit in case it had some resistance left it it. I dont see that in that picture and its easier then trying to keep testing it up into K or M ohms to be sure its open and not affect the circuit when clipping the temporary resistor in for testing.
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draganm
Joined: 08 Mar 2006
Posts: 8990
Location: Colorado
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| Posted: Fri May 22, 2009 12:15 am Post subject: |
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| macgyver655 wrote: | | I would agree with this process but as I hope Curt would agree, I usually at least clip one end of the resistor to take it out of circuit in case it had some resistance left it it. I dont see that in that picture and its easier then trying to keep testing it up into K or M ohms to be sure its open and not affect the circuit when clipping the temporary resistor in for testing. |
that'sa good point too, the old one was obviously damaged so it's not like your losing anything by clipping it from the circuit. hopefully I have better results with the board then the previous attempt. At any rate it will look better 
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