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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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No picture
My Zenith Model SG2037W has lost its picture. Sound is fine. Don't see any
glow from the neck of the picture tube. There is a burn mark on one of the wires leading to the circuit board mounted to the neck of the picture tube. The burn is evidently because the wire was lying against the high voltage lead which has a corresponding burn mark. Does anyone have a schematic of this set they could lend me? |
#2
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check the EHT transistor hasent gone open
or short. "Silver Surfer" wrote in message news:eJ4_c.112160$Fg5.85519@attbi_s53... My Zenith Model SG2037W has lost its picture. Sound is fine. Don't see any glow from the neck of the picture tube. There is a burn mark on one of the wires leading to the circuit board mounted to the neck of the picture tube. The burn is evidently because the wire was lying against the high voltage lead which has a corresponding burn mark. Does anyone have a schematic of this set they could lend me? |
#3
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Sorry for my ignorance on this subject, but what does EHT stand for? I
think I know that HOT stands for horizontal output transistor, but EHT has me stumped. Thanks. "Mr TUBEAMPS" youfinedout@thomuusnonsence wrote in message ... check the EHT transistor hasent gone open or short. "Silver Surfer" wrote in message news:eJ4_c.112160$Fg5.85519@attbi_s53... My Zenith Model SG2037W has lost its picture. Sound is fine. Don't see any glow from the neck of the picture tube. There is a burn mark on one of the wires leading to the circuit board mounted to the neck of the picture tube. The burn is evidently because the wire was lying against the high voltage lead which has a corresponding burn mark. Does anyone have a schematic of this set they could lend me? |
#4
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Where would you recommend that I buy a service manual for this set?
Sams has the paper type as well as a downloadable file. Do you have any trouble working from the electronic manuals? When they are printed are they equivalent to the original paper documents? "Silver Surfer" wrote in message news:E5m_c.371219$%_6.111991@attbi_s01... Sorry for my ignorance on this subject, but what does EHT stand for? I think I know that HOT stands for horizontal output transistor, but EHT has me stumped. Thanks. "Mr TUBEAMPS" youfinedout@thomuusnonsence wrote in message ... check the EHT transistor hasent gone open or short. "Silver Surfer" wrote in message news:eJ4_c.112160$Fg5.85519@attbi_s53... My Zenith Model SG2037W has lost its picture. Sound is fine. Don't see any glow from the neck of the picture tube. There is a burn mark on one of the wires leading to the circuit board mounted to the neck of the picture tube. The burn is evidently because the wire was lying against the high voltage lead which has a corresponding burn mark. Does anyone have a schematic of this set they could lend me? |
#5
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"Silver Surfer" wrote in message news:E5m_c.371219$%_6.111991@attbi_s01... Sorry for my ignorance on this subject, but what does EHT stand for? I think I know that HOT stands for horizontal output transistor, but EHT has me stumped. Thanks. EHT = extremely high tension, high voltage, HV, etc. You said the set is a Zenith though which immediately says don't spend too much time/effort on the thing. Is this one of the direct view sets that usually gets a bad CRT? |
#6
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Well, the reason I'm fooling with this set is that it has become a challenge
for me. Up to now it has given excellent service. Bought it back in '91 for the bedroom so I would have something to occupy my time while recovering from old fashioned type gall bladder surgery. I'm retired now, so there is time available to work on this beast. It might whip me, but not without a good fight. Trouble is I'm an amateur tinkerer; however, I do know that the pros hang out on this board and are an enormous help to "shade tree" technicians like me. Thank goodness there are people like you out there who are willing to share their considerable knowledge and experience with the rest of us. "James Sweet" wrote in message news:6_p_c.630$Q44.607@trnddc09... "Silver Surfer" wrote in message news:E5m_c.371219$%_6.111991@attbi_s01... Sorry for my ignorance on this subject, but what does EHT stand for? I think I know that HOT stands for horizontal output transistor, but EHT has me stumped. Thanks. EHT = extremely high tension, high voltage, HV, etc. You said the set is a Zenith though which immediately says don't spend too much time/effort on the thing. Is this one of the direct view sets that usually gets a bad CRT? |
#7
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"Silver Surfer" wrote in message news:Ost_c.104527$9d6.8043@attbi_s54... Well, the reason I'm fooling with this set is that it has become a challenge for me. Up to now it has given excellent service. Bought it back in '91 for the bedroom so I would have something to occupy my time while recovering from old fashioned type gall bladder surgery. I'm retired now, so there is time available to work on this beast. It might whip me, but not without a good fight. Trouble is I'm an amateur tinkerer; however, I do know that the pros hang out on this board and are an enormous help to "shade tree" technicians like me. Thank goodness there are people like you out there who are willing to share their considerable knowledge and experience with the rest of us. If it's a 25" it's entirely possible the CRT has shorted and taken something else out, guess it won't hurt to fiddle with it if you want though, just beware dumping money into parts that may blow up in short order. |
#8
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This is a 20" TV. Don't know if its CRT is vulnerable to the shorting
problem you mentioned or not. It appears that the filament(s) is(are) not open; however with the socket off the tube there is continuity from the filament (pins 9? and 10?) to pin 12. Doesn't look like pin 12 does much. Not sure why there is continuity there. "James Sweet" wrote in message news:55J_c.2013$PK3.1598@trnddc08... "Silver Surfer" wrote in message news:Ost_c.104527$9d6.8043@attbi_s54... Well, the reason I'm fooling with this set is that it has become a challenge for me. Up to now it has given excellent service. Bought it back in '91 for the bedroom so I would have something to occupy my time while recovering from old fashioned type gall bladder surgery. I'm retired now, so there is time available to work on this beast. It might whip me, but not without a good fight. Trouble is I'm an amateur tinkerer; however, I do know that the pros hang out on this board and are an enormous help to "shade tree" technicians like me. Thank goodness there are people like you out there who are willing to share their considerable knowledge and experience with the rest of us. If it's a 25" it's entirely possible the CRT has shorted and taken something else out, guess it won't hurt to fiddle with it if you want though, just beware dumping money into parts that may blow up in short order. |
#9
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Back in business. A resistor that seems to be for supplying startup 18-volt
power to the horizontal output stage was burned open. Burned beyond recognition. Actual circuit had a diode in series with the resistor in what appears to be a factory modification. Sams schematic showed only a 470 ohm resistor. Zenith schematic showed only a diode. Took a wild shot and put in a 120 ohm resistor in series with diode. OK now. "Silver Surfer" wrote in message news:jsJ_c.379702$%_6.248101@attbi_s01... This is a 20" TV. Don't know if its CRT is vulnerable to the shorting problem you mentioned or not. It appears that the filament(s) is(are) not open; however with the socket off the tube there is continuity from the filament (pins 9? and 10?) to pin 12. Doesn't look like pin 12 does much. Not sure why there is continuity there. "James Sweet" wrote in message news:55J_c.2013$PK3.1598@trnddc08... "Silver Surfer" wrote in message news:Ost_c.104527$9d6.8043@attbi_s54... Well, the reason I'm fooling with this set is that it has become a challenge for me. Up to now it has given excellent service. Bought it back in '91 for the bedroom so I would have something to occupy my time while recovering from old fashioned type gall bladder surgery. I'm retired now, so there is time available to work on this beast. It might whip me, but not without a good fight. Trouble is I'm an amateur tinkerer; however, I do know that the pros hang out on this board and are an enormous help to "shade tree" technicians like me. Thank goodness there are people like you out there who are willing to share their considerable knowledge and experience with the rest of us. If it's a 25" it's entirely possible the CRT has shorted and taken something else out, guess it won't hurt to fiddle with it if you want though, just beware dumping money into parts that may blow up in short order. |
#10
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"Silver Surfer" wrote in message
news:InP%c.270779$8_6.166464@attbi_s04... Back in business. A resistor that seems to be for supplying startup 18-volt power to the horizontal output stage was burned open. Burned beyond recognition. Actual circuit had a diode in series with the resistor in what appears to be a factory modification. Sams schematic showed only a 470 ohm resistor. Zenith schematic showed only a diode. Took a wild shot and put in a 120 ohm resistor in series with diode. OK now. Often when I'm in this situation, I'll put in a flameproof resistor chosen to be dissipating, say, 1/10 watt for a 1/2 watt resistor. Any serious malfunction will take out the resistor safely. If the resistor is feeding a voltage regulator, this can be tricky though - the regulator will have to dissipate more power if the resistor value is too low. Actually, the same would apply to the load circuit if the voltage is unregulated. Hmmm. Mark Z. |
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