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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Magnavox RPTV
Got one of these (46" '91 model) for peanuts. Had to do a little
tweaking; clean mirrors, lenses, screen and tweak user convergence. The green gun was intermittent, but following advice here, I found and fixed a bad joint on the CRT neck board. The blue crt has the usual contaminated cooling fluid, which I intend to address next (Green has a few floaters, red seems clear...I'll do them all, one at a time to chart the improvement.) My question concerns coolant change advice on the internet; which ranges from 'suck out the fluid, replace after cleaning through the diaphragm hole', to: 'completely remove each CRT, disassemble, clean, reassemble using new O-rings'...from easy DIY job to 'don't even try this yourself'. Is there a middle ground? It doesn't look real easy to clean all that gunk out using remote tools; but pulling the guns, even one at a time, just looks way too involved (sort of like laproscopic surgery). I'm leaning toward sucking out the fluid, removing the lense assembly and cleaning with the tube in place; but even 'that' looks to require quite a bit of cabinet disassembly. The back two screws on the lenses are under a cover which (I think) I need to remove the back of the set, or the else mirror, to access. Any thoughts? The tubes themselves seem to be in good shape. The set might not have gotten a lot of use...plenty bright. The only other issue: the brightness control seems to have little or no effect on the picture. All controls were set at midrange when received, and tweaking yields little improvement. Thanks in advance jak |
#2
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Magnavox RPTV
jakdedert wrote: Got one of these (46" '91 model) for peanuts. Had to do a little tweaking; clean mirrors, lenses, screen and tweak user convergence. The green gun was intermittent, but following advice here, I found and fixed a bad joint on the CRT neck board. The blue crt has the usual contaminated cooling fluid, which I intend to address next (Green has a few floaters, red seems clear...I'll do them all, one at a time to chart the improvement.) My question concerns coolant change advice on the internet; which ranges from 'suck out the fluid, replace after cleaning through the diaphragm hole', to: 'completely remove each CRT, disassemble, clean, reassemble using new O-rings'...from easy DIY job to 'don't even try this yourself'. Is there a middle ground? It doesn't look real easy to clean all that gunk out using remote tools; but pulling the guns, even one at a time, just looks way too involved (sort of like laproscopic surgery). I'm leaning toward sucking out the fluid, removing the lense assembly and cleaning with the tube in place; but even 'that' looks to require quite a bit of cabinet disassembly. The back two screws on the lenses are under a cover which (I think) I need to remove the back of the set, or the else mirror, to access. Any thoughts? The tubes themselves seem to be in good shape. The set might not have gotten a lot of use...plenty bright. The only other issue: the brightness control seems to have little or no effect on the picture. All controls were set at midrange when received, and tweaking yields little improvement. Thanks in advance jak It's not that entailed to pull the tubes. Four 1/4" screws on the frame, pull the kine board, disconnect the deflection yoke plug and the convergence yoke plug from the front and pull the ground wires free. Just did one of that vintage last week, PTV382 and took about an hour that way to do the green and blue. I've never had to do the red since, for whatever reason, red never seems to 'activate' the bacteria. Take the expansion cup off, unscrew the cap, make sure you don't lose the O ring, drain, take apart, clean with denatured alcohol, dry and put together and refill. Make sure you don't underfill and just fill to the base of the cap. May sound like alot of steps but, if you don't try to clear all the bacteria, you're just wasting time and money and will be back in in a couple of months. www.techdata-kicksass.net |
#3
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Magnavox RPTV
I'd have to agree on pulling the tubes. I've got a PTV300 set that I just
changed the fluid in. I rinsed everything out with Windex and put fresh fluid in. Followed the CRT replacement procedure (minus removing the yoke). Afterwards, I adjusted a few of the tabs on the CRTs to bring them back into alignment and tweaked a couple of pots on the convergence board. At least on my set, the user convergence board has a push button switch that brings up a crosshair. I used that to align each of the guns to green and then by using DVD cases to block two of the lenses, used the focus and screen controls to get a clear crosshair of each color with a solid black background. This meant looking at the screen from the back and then moving around to the front for final focus and screen settings. The hardest part was getting the nerve to do it. If your set still has the paperwork for the convergence board, it should be pretty simple to touch up anything that changes. Each of the pots has a specific function. My picture isn't perfect however it's great compared to what it was: dark and red. I have a slight misalignment at the top right that is only visible on the DVD menu screen. Probably won't mess with it... Denatured alcohol sounds good as a cleaner. I'll try that next time. I have a friend with a PTV325 set with a fuzzy picture. If you want new CRT gaskets and fluid, Matt Electronics has kits with new gasket and fluid for about $13 each. Got my fluid from MCM Electronics; slightly more than one 24 oz can was enough for all three CRTs. The fluid in my CRT chambers wasn't terrible; just the color of cider vinegar. Like watching TV through sunglasses... Blue and green were the worst and had the most buildup on the CRT face. Kirk S. "Tech Data" wrote in message oups.com... jakdedert wrote: Got one of these (46" '91 model) for peanuts. Had to do a little tweaking; clean mirrors, lenses, screen and tweak user convergence. The green gun was intermittent, but following advice here, I found and fixed a bad joint on the CRT neck board. The blue crt has the usual contaminated cooling fluid, which I intend to address next (Green has a few floaters, red seems clear...I'll do them all, one at a time to chart the improvement.) My question concerns coolant change advice on the internet; which ranges from 'suck out the fluid, replace after cleaning through the diaphragm hole', to: 'completely remove each CRT, disassemble, clean, reassemble using new O-rings'...from easy DIY job to 'don't even try this yourself'. Is there a middle ground? It doesn't look real easy to clean all that gunk out using remote tools; but pulling the guns, even one at a time, just looks way too involved (sort of like laproscopic surgery). I'm leaning toward sucking out the fluid, removing the lense assembly and cleaning with the tube in place; but even 'that' looks to require quite a bit of cabinet disassembly. The back two screws on the lenses are under a cover which (I think) I need to remove the back of the set, or the else mirror, to access. Any thoughts? The tubes themselves seem to be in good shape. The set might not have gotten a lot of use...plenty bright. The only other issue: the brightness control seems to have little or no effect on the picture. All controls were set at midrange when received, and tweaking yields little improvement. Thanks in advance jak It's not that entailed to pull the tubes. Four 1/4" screws on the frame, pull the kine board, disconnect the deflection yoke plug and the convergence yoke plug from the front and pull the ground wires free. Just did one of that vintage last week, PTV382 and took about an hour that way to do the green and blue. I've never had to do the red since, for whatever reason, red never seems to 'activate' the bacteria. Take the expansion cup off, unscrew the cap, make sure you don't lose the O ring, drain, take apart, clean with denatured alcohol, dry and put together and refill. Make sure you don't underfill and just fill to the base of the cap. May sound like alot of steps but, if you don't try to clear all the bacteria, you're just wasting time and money and will be back in in a couple of months. www.techdata-kicksass.net |
#4
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Magnavox RPTV
Kirk S. wrote:
I'd have to agree on pulling the tubes. I've got a PTV300 set that I just changed the fluid in. I rinsed everything out with Windex and put fresh fluid in. Followed the CRT replacement procedure (minus removing the yoke). Afterwards, I adjusted a few of the tabs on the CRTs to bring them back into alignment and tweaked a couple of pots on the convergence board. At least on my set, the user convergence board has a push button switch that brings up a crosshair. I used that to align each of the guns to green and then by using DVD cases to block two of the lenses, used the focus and screen controls to get a clear crosshair of each color with a solid black background. This meant looking at the screen from the back and then moving around to the front for final focus and screen settings. The hardest part was getting the nerve to do it. If your set still has the paperwork for the convergence board, it should be pretty simple to touch up anything that changes. Each of the pots has a specific function. My picture isn't perfect however it's great compared to what it was: dark and red. I have a slight misalignment at the top right that is only visible on the DVD menu screen. Probably won't mess with it... Denatured alcohol sounds good as a cleaner. I'll try that next time. I have a friend with a PTV325 set with a fuzzy picture. If you want new CRT gaskets and fluid, Matt Electronics has kits with new gasket and fluid for about $13 each. Got my fluid from MCM Electronics; slightly more than one 24 oz can was enough for all three CRTs. The fluid in my CRT chambers wasn't terrible; just the color of cider vinegar. Like watching TV through sunglasses... Blue and green were the worst and had the most buildup on the CRT face. Kirk S. "Tech Data" wrote in message oups.com... jakdedert wrote: Got one of these (46" '91 model) for peanuts. Had to do a little tweaking; clean mirrors, lenses, screen and tweak user convergence. The green gun was intermittent, but following advice here, I found and fixed a bad joint on the CRT neck board. The blue crt has the usual contaminated cooling fluid, which I intend to address next (Green has a few floaters, red seems clear...I'll do them all, one at a time to chart the improvement.) My question concerns coolant change advice on the internet; which ranges from 'suck out the fluid, replace after cleaning through the diaphragm hole', to: 'completely remove each CRT, disassemble, clean, reassemble using new O-rings'...from easy DIY job to 'don't even try this yourself'. Is there a middle ground? It doesn't look real easy to clean all that gunk out using remote tools; but pulling the guns, even one at a time, just looks way too involved (sort of like laproscopic surgery). I'm leaning toward sucking out the fluid, removing the lense assembly and cleaning with the tube in place; but even 'that' looks to require quite a bit of cabinet disassembly. The back two screws on the lenses are under a cover which (I think) I need to remove the back of the set, or the else mirror, to access. Any thoughts? The tubes themselves seem to be in good shape. The set might not have gotten a lot of use...plenty bright. The only other issue: the brightness control seems to have little or no effect on the picture. All controls were set at midrange when received, and tweaking yields little improvement. Thanks in advance jak It's not that entailed to pull the tubes. Four 1/4" screws on the frame, pull the kine board, disconnect the deflection yoke plug and the convergence yoke plug from the front and pull the ground wires free. Just did one of that vintage last week, PTV382 and took about an hour that way to do the green and blue. I've never had to do the red since, for whatever reason, red never seems to 'activate' the bacteria. Take the expansion cup off, unscrew the cap, make sure you don't lose the O ring, drain, take apart, clean with denatured alcohol, dry and put together and refill. Make sure you don't underfill and just fill to the base of the cap. May sound like alot of steps but, if you don't try to clear all the bacteria, you're just wasting time and money and will be back in in a couple of months. www.techdata-kicksass.net Thanks to both of you for responding. I'm still weighing my options, since the set has a pretty good picture as it is. I will definitely be doing at least the blue tube, since it is the one with visible gunk on the face. It sounds like I should probably at least change the fluid on the red tube as well. That was a question I asked earlier, which my isp lost due to a usenet foulup. It sounds like the fluid, even absent any contamination, changes color. That would account for the slightly yellow or amber tint that I've seen on many older RPTV's with otherwise reasonable pictures. jak |
#5
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Magnavox RPTV
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