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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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Rank Arena Widescreen CRT
I bought this on Ebay for $5.50 on the off chance that I could fix it.
It was described as having lost picture with a "pop", and with the observation that a TV repairman said it sounded like it could be a power supply issue. I've determined that the sound works OK, as does the tuner and video signal stage - it outputs the composite video on an AV out socket. It's clear what produced the "pop" noise. http://members.optusnet.com.au/sylviae/tv1.jpg http://members.optusnet.com.au/sylviae/tv2.jpg Presumably this diode shorted out. It's on a board close the EHT circuitry. But what are the chances that that's all that's wrong with it? Just getting the board out to gain access to the underside will be a fairly major exercise. Sylvia. |
#2
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Rank Arena Widescreen CRT
Sylvia Else wrote:
I bought this on Ebay for $5.50 on the off chance that I could fix it. It was described as having lost picture with a "pop", and with the observation that a TV repairman said it sounded like it could be a power supply issue. I've determined that the sound works OK, as does the tuner and video signal stage - it outputs the composite video on an AV out socket. It's clear what produced the "pop" noise. http://members.optusnet.com.au/sylviae/tv1.jpg http://members.optusnet.com.au/sylviae/tv2.jpg Presumably this diode shorted out. It's on a board close the EHT circuitry. But what are the chances that that's all that's wrong with it? Just getting the board out to gain access to the underside will be a fairly major exercise. Sylvia. Um, strike that. Once I started pulling it apart, it was apparent that that's actually a diode with an inductive bead on its lead. Sylvia. |
#3
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Rank Arena Widescreen CRT
Sylvia Else wrote:
I bought this on Ebay for $5.50 on the off chance that I could fix it. It was described as having lost picture with a "pop", and with the observation that a TV repairman said it sounded like it could be a power supply issue. I've determined that the sound works OK, as does the tuner and video signal stage - it outputs the composite video on an AV out socket. It's clear what produced the "pop" noise. http://members.optusnet.com.au/sylviae/tv1.jpg http://members.optusnet.com.au/sylviae/tv2.jpg The diode *looks* OK. Though it seems like there might be a wire or maybe some "glue fibers" draped across it? Presumably this diode shorted out. It's on a board close the EHT circuitry. I'd look at the switching transistor (HOT) first. But what are the chances that that's all that's wrong with it? Just getting the board out to gain access to the underside will be a fairly major exercise. grin You should see what a nuisance some of the high end Sony monitors are (were?) to service! : |
#4
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Rank Arena Widescreen CRT
D Yuniskis wrote:
Sylvia Else wrote: I bought this on Ebay for $5.50 on the off chance that I could fix it. It was described as having lost picture with a "pop", and with the observation that a TV repairman said it sounded like it could be a power supply issue. I've determined that the sound works OK, as does the tuner and video signal stage - it outputs the composite video on an AV out socket. It's clear what produced the "pop" noise. http://members.optusnet.com.au/sylviae/tv1.jpg http://members.optusnet.com.au/sylviae/tv2.jpg The diode *looks* OK. Though it seems like there might be a wire or maybe some "glue fibers" draped across it? Presumably this diode shorted out. It's on a board close the EHT circuitry. I'd look at the switching transistor (HOT) first. But what are the chances that that's all that's wrong with it? Just getting the board out to gain access to the underside will be a fairly major exercise. grin You should see what a nuisance some of the high end Sony monitors are (were?) to service! : As far as I can see, and despite the numerous headers, it's impossible to remove the circuit board from this TV without desoldering some wires from it. I rather think it was never intended to be repaired. However, with some of the unpluggable wires unplugged, there is just enough slack in the remainder to prop the circuit board up into a vertical position. Based on the described "pop" symptom, I was looking for something showing physical trauma, but if there's any visible, I'm missing it, and I've spent a good while looking. I've established that the HT (190V) is present at the powersupply. The switching transistor seems OK Sylvia. |
#5
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Rank Arena Widescreen CRT
Meat Plow wrote:
On Tue, 10 Nov 2009 17:11:45 +1100, Sylvia Else wrote: D Yuniskis wrote: Sylvia Else wrote: I bought this on Ebay for $5.50 on the off chance that I could fix it. It was described as having lost picture with a "pop", and with the observation that a TV repairman said it sounded like it could be a power supply issue. I've determined that the sound works OK, as does the tuner and video signal stage - it outputs the composite video on an AV out socket. It's clear what produced the "pop" noise. http://members.optusnet.com.au/sylviae/tv1.jpg http://members.optusnet.com.au/sylviae/tv2.jpg The diode *looks* OK. Though it seems like there might be a wire or maybe some "glue fibers" draped across it? Presumably this diode shorted out. It's on a board close the EHT circuitry. I'd look at the switching transistor (HOT) first. But what are the chances that that's all that's wrong with it? Just getting the board out to gain access to the underside will be a fairly major exercise. grin You should see what a nuisance some of the high end Sony monitors are (were?) to service! : As far as I can see, and despite the numerous headers, it's impossible to remove the circuit board from this TV without desoldering some wires from it. I rather think it was never intended to be repaired. However, with some of the unpluggable wires unplugged, there is just enough slack in the remainder to prop the circuit board up into a vertical position. Based on the described "pop" symptom, I was looking for something showing physical trauma, but if there's any visible, I'm missing it, and I've spent a good while looking. I've established that the HT (190V) is present at the powersupply. The switching transistor seems OK Sylvia. The "pop" could have come through the speakers and not made by an exploding cap. Yes. I also have to confess to wondering whether I've been suckered in, with the pop being just to give the impression that it might be easily fixable. The guy wasn't even very interested in his $5.50, and said that he really just wanted to get rid of of the TV which turned out to be so heavy it requires two to lift. There seems to be a lack of sync signals making me suspect that the fault lies at a low power section where component failure is unlikely to make a noise. Turns out that "Rank Arena" is a brand name that is transferred between companies. The one using the name at the time no longer exists. I've heard a lot of pops, snaps, cracks, etc...over my lifetime in the industry and as a rule pops are generated by older electrolytic caps as they now have a safety valves built in and only hiss. When I repaired my first CRT 51" TV it seemed a daunting task with all the interconnecting boards and other things in the way of the convergence amp board. But I was driven by necessity. In your case the $5.50 you paid should be an incentive as long as you remain curious. I've determined that it will cost me a further $10 to take it to the tip, if it comes to it. Ho hum. Perhaps I should try to sell it on Ebay. Sylvia. |
#6
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Rank Arena Widescreen CRT
Sylvia Else wrote:
D Yuniskis wrote: Sylvia Else wrote: I bought this on Ebay for $5.50 on the off chance that I could fix it. It was described as having lost picture with a "pop", and with the observation that a TV repairman said it sounded like it could be a power supply issue. I've determined that the sound works OK, as does the tuner and video signal stage - it outputs the composite video on an AV out socket. This is A Good Sign. The diode *looks* OK. Though it seems like there might be a wire or maybe some "glue fibers" draped across it? Presumably this diode shorted out. It's on a board close the EHT circuitry. I'd look at the switching transistor (HOT) first. But what are the chances that that's all that's wrong with it? Just getting the board out to gain access to the underside will be a fairly major exercise. grin You should see what a nuisance some of the high end Sony monitors are (were?) to service! : As far as I can see, and despite the numerous headers, it's impossible to remove the circuit board from this TV without desoldering some wires from it. I rather think it was never intended to be repaired. However, ....like many *cars*! :-/ with some of the unpluggable wires unplugged, there is just enough slack in the remainder to prop the circuit board up into a vertical position. Based on the described "pop" symptom, I was looking for something showing physical trauma, but if there's any visible, I'm missing it, and I've spent a good while looking. I've established that the HT (190V) is present at the powersupply. That's *mains* voltage (rectified and filtered?). Are you sure the flyback is working? The switching transistor seems OK |
#7
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Rank Arena Widescreen CRT
D Yuniskis wrote:
Sylvia Else wrote: D Yuniskis wrote: Sylvia Else wrote: I bought this on Ebay for $5.50 on the off chance that I could fix it. It was described as having lost picture with a "pop", and with the observation that a TV repairman said it sounded like it could be a power supply issue. I've determined that the sound works OK, as does the tuner and video signal stage - it outputs the composite video on an AV out socket. This is A Good Sign. The diode *looks* OK. Though it seems like there might be a wire or maybe some "glue fibers" draped across it? Presumably this diode shorted out. It's on a board close the EHT circuitry. I'd look at the switching transistor (HOT) first. But what are the chances that that's all that's wrong with it? Just getting the board out to gain access to the underside will be a fairly major exercise. grin You should see what a nuisance some of the high end Sony monitors are (were?) to service! : As far as I can see, and despite the numerous headers, it's impossible to remove the circuit board from this TV without desoldering some wires from it. I rather think it was never intended to be repaired. However, ...like many *cars*! :-/ with some of the unpluggable wires unplugged, there is just enough slack in the remainder to prop the circuit board up into a vertical position. Based on the described "pop" symptom, I was looking for something showing physical trauma, but if there's any visible, I'm missing it, and I've spent a good while looking. I've established that the HT (190V) is present at the powersupply. That's *mains* voltage (rectified and filtered?). I'm in Australia, mains voltage 240V RMS. Are you sure the flyback is working? At this stage, I'm reasonably sure that it's not, but due to a lack of appropriate input signals. I'm somewhat aghast at the sheer complexity of the board that's creating the horizontal and vertical scanning outputs, and the anode voltage. It has two LSI circuits, including one that contains a programmable processor, and no less than six transformers (I don't think any are chokes, but don't quote me), not including the EHT transformer. OK, so it's implementing the functions of a multi-sync monitor (the set has an XVGA input), but even so.... Whatever happened to circuits that just contained a couple of valves? Sylvia. |
#8
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Rank Arena Widescreen CRT
"Sylvia Else" wrote in message ... Whatever happened to circuits that just contained a couple of valves? **There never were any "circuits that just contained a couple of valves". When they first arrived, TV sets were mindbogglingly complex devices compared to anything that preceded them (in domestic appliance-speak). They were also fabulously unreliable. You could figure that the average TV set would require several repair jobs every year. Your incredibly complex, LSI controlled, TV set is likely to be vastly more reliable. You've probably found the first fault it has ever had. BTW: If you post your request on aus.electronics, with the appropriate model and chassis numbers, you may gain more of an insight. Even better, you could join these guys: http://www.ceta.org.au/ Someone there has almost certainly serviced the same model and, perhaps, the same fault. -- Trevor Wilson www.rageaudio.com.au |
#9
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Rank Arena Widescreen CRT
Trevor Wilson wrote:
"Sylvia Else" wrote in message ... Whatever happened to circuits that just contained a couple of valves? **There never were any "circuits that just contained a couple of valves". When they first arrived, TV sets were mindbogglingly complex devices compared to anything that preceded them (in domestic appliance-speak). They were also fabulously unreliable. You could figure that the average TV set would require several repair jobs every year. Your incredibly complex, LSI controlled, TV set is likely to be vastly more reliable. You've probably found the first fault it has ever had. Well, OK, but the use of a programmable LSI chip makes it rather hard to determine whether the chip outputs are what was intended, particular in the absence of a schematic, and with the manufacture apparently out of business. BTW: If you post your request on aus.electronics, with the appropriate model and chassis numbers, you may gain more of an insight. Even better, you could join these guys: Well, the model number is RK-32HDP81. Not sure where I'd look for the chassis number - it doesn't really have a chassis. The serial number is RK00000027, making me wonder how many of these were sold, though I suppose the guy I bought it from could have been an early-adopter. I've added aus.electronics, as per you suggestion, so to summarise the situation as I perceive it now: There is no picture, but sound works. The receiver side of the video clearly works because it outputs to an AV output socket[*], and plugging a suitable screen into that gives a picture. The horizontal and vertical scanning outputs appear to be present. At least, there are substantial signals there - whether they're the right shape I couldn't say. The most evident issue is that the EHT switching transistor, which itself appears intact, has no base drive, and so far I haven't been able to find a signal by backtracking. The one good thing I have to say about the boards in this TV is that they have component numbers on the soldered side of the board. http://www.ceta.org.au/ Someone there has almost certainly serviced the same model and, perhaps, the same fault. I couldn't see any sort of public forum, and I wouldn't qualify for membership. Sylvia. [*] The signal remains even when the TV is in standby mode. You can't change channels in that mode, but the channel the TV was tuned to is still available. Maybe this is common - I've never looked at other TV outputs in standby mode, but it doesn't suggest the minimum possible power consumption in that mode. |
#10
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Rank Arena Widescreen CRT
Trevor Wilson wrote: "Sylvia Else" wrote in message ... Whatever happened to circuits that just contained a couple of valves? **There never were any "circuits that just contained a couple of valves". When they first arrived, TV sets were mindbogglingly complex devices compared to anything that preceded them (in domestic appliance-speak). They were also fabulously unreliable. You could figure that the average TV set would require several repair jobs every year. Your incredibly complex, LSI controlled, TV set is likely to be vastly more reliable. You've probably found the first fault it has ever had. It sounds like they only sold crap in Australia, and that you've never seen the very low parts count in a Muntz TV. My parents had three service calls in 15 years. Two of those were due to lightning taking out the front end in the VHF tuner. The third was a bad electrolytic in a voltage doubler that took out a fusible resistor. That isn't a couple times a year. -- The movie 'Deliverance' isn't a documentary! |
#11
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Rank Arena Widescreen CRT
Sylvia Else wrote:
I bought this on Ebay for $5.50 on the off chance that I could fix it. It was described as having lost picture with a "pop", and with the observation that a TV repairman said it sounded like it could be a power supply issue. I've determined that the sound works OK, as does the tuner and video signal stage - it outputs the composite video on an AV out socket. It's clear what produced the "pop" noise. http://members.optusnet.com.au/sylviae/tv1.jpg http://members.optusnet.com.au/sylviae/tv2.jpg Presumably this diode shorted out. It's on a board close the EHT circuitry. But what are the chances that that's all that's wrong with it? Just getting the board out to gain access to the underside will be a fairly major exercise. Sylvia. I've given up on this anyway. Having run out of other ideas, I pulled apart the box mounted on the neck of the tube, to see whether the reported "pop" might have come from there. Nothing of note inside, except yet more large heat-sinks. Anyway, I decided that putting it back together again was going to be more trouble than it's worth. So it's off to the tip tomorrow. Sylvia. |
#12
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Rank Arena Widescreen CRT
Michael A. Terrell wrote:
Trevor Wilson wrote: "Sylvia Else" wrote in message ... Whatever happened to circuits that just contained a couple of valves? **There never were any "circuits that just contained a couple of valves". When they first arrived, TV sets were mindbogglingly complex devices compared to anything that preceded them (in domestic appliance-speak). They were also fabulously unreliable. You could figure that the average TV set would require several repair jobs every year. Your incredibly complex, LSI controlled, TV set is likely to be vastly more reliable. You've probably found the first fault it has ever had. It sounds like they only sold crap in Australia, and that you've never seen the very low parts count in a Muntz TV. My parents had three service calls in 15 years. Two of those were due to lightning taking out the front end in the VHF tuner. The third was a bad electrolytic in a voltage doubler that took out a fusible resistor. That isn't a couple times a year. It must be thirty or thirty five years ago that my family in England got one of the early fully transistorised Philips colour televisions, with teletext. This was our upgrade from B/W. We rented it, rather than bought it, which was just as well, because it frequently broke down. Indeed, the first occasion was within days of its arrival, with an intermittent fault that the service company never did track down[*]. Often repairs involved fixing dry joints. So Trevor's comment does fit my own experience. Televisions have become more reliable. But I wonder whether that's because of improved construction and quality control, rather than because of the circuitry now in use. If individual components are very reliable, and they're fixed properly to the circuit board, then the result can be reliable. That doesn't mean that the design doesn't use an excessively large number of components. [*] The fault had the dual effect of killing the sound, and making the picture about twice as wide as it should be. Years later, I obtained the schematics for the set, and it was quite obvious where the fault had to lie. I can only assume that the technicians who came to fix it either didn't understand the circuit, or just couldn't be bothered. After they fiddled with the set a bit, the fault would go away. Later I found that a good thump on the cabinet would work just as well as calling the technician. Sylvia. |
#13
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Rank Arena Widescreen CRT
"Michael A. Terrell" wrote in message m... Trevor Wilson wrote: "Sylvia Else" wrote in message ... Whatever happened to circuits that just contained a couple of valves? **There never were any "circuits that just contained a couple of valves". When they first arrived, TV sets were mindbogglingly complex devices compared to anything that preceded them (in domestic appliance-speak). They were also fabulously unreliable. You could figure that the average TV set would require several repair jobs every year. Your incredibly complex, LSI controlled, TV set is likely to be vastly more reliable. You've probably found the first fault it has ever had. It sounds like they only sold crap in Australia, and that you've never seen the very low parts count in a Muntz TV. **Very possibly. Don't forget: We are talking about the mid-late 1950s. Valve TV sets were not very reliable. Dunno about foriegn sets. I never saw one. My parents had three service calls in 15 years. Two of those were due to lightning taking out the front end in the VHF tuner. The third was a bad electrolytic in a voltage doubler that took out a fusible resistor. That isn't a couple times a year. **My parents first transistorised set was very reliable. It developed a fault in 1967 (I was 14 years old). My dad took it to the service guy and was horrified at being asked to pay $50.00 for a quote. He brought it back home and asked me if I wanted to have a go at it. I diagnosed the fault at a dead rectifier in the power supply. I caught the train into the city to buy a rectifier diode, soldered it in and the thing has operated perfectly ever since. My dad figured that buying that multimeter for my 13th birthday was an excellent investment. Valve sets, OTOH, were not very reliable. The first Aussie made colour sets (all solid state) from Kriesler were basically a large box-full of dry solder joints. Great picture, but crap reliability. -- Trevor Wilson www.rageaudio.com.au |
#14
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Rank Arena Widescreen CRT
On 11 nov, 08:37, Sylvia Else wrote:
Sylvia Else wrote: I bought this on Ebay for $5.50 on the off chance that I could fix it. It was described as having lost picture with a "pop", and with the observation that a TV repairman said it sounded like it could be a power supply issue. I've determined that the sound works OK, as does the tuner and video signal stage - it outputs the composite video on an AV out socket. It's clear what produced the "pop" noise. http://members.optusnet.com.au/sylviae/tv1.jpg http://members.optusnet.com.au/sylviae/tv2.jpg Presumably this diode shorted out. It's on a board close the EHT circuitry. But what are the chances that that's all that's wrong with it? Just getting the board out to gain access to the underside will be a fairly major exercise. Sylvia. I've given up on this anyway. Having run out of other ideas, I pulled apart the box mounted on the neck of the tube, to see whether the reported "pop" might have come from there. Nothing of note inside, except yet more large heat-sinks. Anyway, I decided that putting it back together again was going to be more trouble than it's worth. So it's off to the tip tomorrow. Sylvia. you shouldn't give up yet. Any static on screen? what happens if you raise the g2/screen pot on the line o/p transformer? have you got volts on the RGB o/p stage on the CRT neck pcb? have you checked for open resistros in the frame circuit feed (very common 'black screen' cause)? have you checked components in the line driver cct? these are all fundamental first steps - I think your troubleshooting has not been very systematic if you haven't done 'em! -B |
#15
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Rank Arena Widescreen CRT
Rank Arena were old UK names, the Rank/Bush/Murphy brands were all
used in the 60s and 70s. Likely bought out by some chinese/turkish firm, as have other former respected names like Dual, wharfefdale, and Sansui. -B |
#16
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Rank Arena Widescreen CRT
b wrote:
On 11 nov, 08:37, Sylvia Else wrote: Sylvia Else wrote: I bought this on Ebay for $5.50 on the off chance that I could fix it. It was described as having lost picture with a "pop", and with the observation that a TV repairman said it sounded like it could be a power supply issue. I've determined that the sound works OK, as does the tuner and video signal stage - it outputs the composite video on an AV out socket. It's clear what produced the "pop" noise. http://members.optusnet.com.au/sylviae/tv1.jpg http://members.optusnet.com.au/sylviae/tv2.jpg Presumably this diode shorted out. It's on a board close the EHT circuitry. But what are the chances that that's all that's wrong with it? Just getting the board out to gain access to the underside will be a fairly major exercise. Sylvia. I've given up on this anyway. Having run out of other ideas, I pulled apart the box mounted on the neck of the tube, to see whether the reported "pop" might have come from there. Nothing of note inside, except yet more large heat-sinks. Anyway, I decided that putting it back together again was going to be more trouble than it's worth. So it's off to the tip tomorrow. Sylvia. you shouldn't give up yet. Any static on screen? what happens if you raise the g2/screen pot on the line o/p transformer? have you got volts on the RGB o/p stage on the CRT neck pcb? have you checked for open resistros in the frame circuit feed (very common 'black screen' cause)? have you checked components in the line driver cct? these are all fundamental first steps - I think your troubleshooting has not been very systematic if you haven't done 'em! -B The switching transistor for the EHT transformer has no base drive. I traced backwards through a transformer, another bibolar transistor, a pair of FETs, a pair of bipolar transistors and ultimately reached two outputs from the programmable LSI circuit. So the reason there was no EHT was that the outputs from the LSI were unchanging. I surmise that it had probably detected some fault, and disabled the EHT for that reason, but since it's programmable, I have no way of determining what it might be objecting to. I couldn't find any dead transistors, or capacitors that were evidently faulty, and the low resistance resistors that I measured were all within tolerance. Nothing had obviously burnt out. Anyway, it's in the car now. Given how heavy it is, there's no way it's moving from there other than at the tip. Sylvia. |
#17
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Rank Arena Widescreen CRT
Meat Plow wrote: On Tue, 10 Nov 2009 22:46:14 -0500, "Michael A. Terrell" wrote: Trevor Wilson wrote: "Sylvia Else" wrote in message ... Whatever happened to circuits that just contained a couple of valves? **There never were any "circuits that just contained a couple of valves". When they first arrived, TV sets were mindbogglingly complex devices compared to anything that preceded them (in domestic appliance-speak). They were also fabulously unreliable. You could figure that the average TV set would require several repair jobs every year. Your incredibly complex, LSI controlled, TV set is likely to be vastly more reliable. You've probably found the first fault it has ever had. It sounds like they only sold crap in Australia, and that you've never seen the very low parts count in a Muntz TV. My parents had three service calls in 15 years. Two of those were due to lightning taking out the front end in the VHF tuner. The third was a bad electrolytic in a voltage doubler that took out a fusible resistor. That isn't a couple times a year. My dad always bought RCA even though the RCA tube guy seemed to visit monthly. (color sets) I did TV repair for about 20 years, and never saw anything that bad. Most customers got three or four years out of a new set before the first service call. By the time a set needed a lot of repairs, it was cheaper to replace. I went on some calls on Zenith sets that were almost 20 years old, and it was the first service call. The cost of 12 service calls in one year would be higher than a new TV set. Only tubes I deal with these days are in guitar amps. Whoopie. I won't touch tube sets, unless they get a full overhaul. I no longer work with multiple 65 KW Klystrons, or transmitter tubes made with beryllium oxide ceramics. Have you ever used a water cooled power tetrode with two, 1000 A, 1.5 volt filaments? The AC had to match to a few millivolts, or it would modulate the output current. You had to use an open ended wrench to adjust the length of a copper buss bar. Its resistance went up as it was stretched. This was in the RCA TTU-25 series UHF transmitter. -- The movie 'Deliverance' isn't a documentary! |
#18
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Rank Arena Widescreen CRT
Trevor Wilson wrote: "Michael A. Terrell" wrote in message m... Trevor Wilson wrote: "Sylvia Else" wrote in message ... Whatever happened to circuits that just contained a couple of valves? **There never were any "circuits that just contained a couple of valves". When they first arrived, TV sets were mindbogglingly complex devices compared to anything that preceded them (in domestic appliance-speak). They were also fabulously unreliable. You could figure that the average TV set would require several repair jobs every year. Your incredibly complex, LSI controlled, TV set is likely to be vastly more reliable. You've probably found the first fault it has ever had. It sounds like they only sold crap in Australia, and that you've never seen the very low parts count in a Muntz TV. **Very possibly. Don't forget: We are talking about the mid-late 1950s. Valve TV sets were not very reliable. Dunno about foriegn sets. I never saw one. Most american made TVs did much better. We really didn't see sets with high failure rates until the early japanese sets arrived on US soil. Everything was crammed in so tight to reduce the size and weight for shipping that they ran way too hot. 'Madman Muntz' built things with as few components as possible so he could sell the sets cheaper than anyone else. My parents had three service calls in 15 years. Two of those were due to lightning taking out the front end in the VHF tuner. The third was a bad electrolytic in a voltage doubler that took out a fusible resistor. That isn't a couple times a year. **My parents first transistorised set was very reliable. It developed a fault in 1967 (I was 14 years old). My dad took it to the service guy and was horrified at being asked to pay $50.00 for a quote. He brought it back home and asked me if I wanted to have a go at it. I diagnosed the fault at a dead rectifier in the power supply. I caught the train into the city to buy a rectifier diode, soldered it in and the thing has operated perfectly ever since. My dad figured that buying that multimeter for my 13th birthday was an excellent investment. I have one of the first Motorola Quasar TVs shipped. My dad bought it while I was in Jr. High School. It has been repaired a half dozen times, since the mid '60s. Once was to replace the original 23EGP22 CRT with a top of the line Channelmaster 25VAP22 black matrix CRT when the TV was nine years old. People didn't believe it was the same tv. The 23EGP22 was the first, and worst rectangular color CRT. The 25VAP22 black matrix CRT was one of, if not the best produced for consumer use. It cost 1/3 of the original cost of the TV and required modifications to the cabinet to install but it was well worth it. I had another set like it that i converted into a color monitor for my shop so i could service early video gear. Valve sets, OTOH, were not very reliable. The first Aussie made colour sets (all solid state) from Kriesler were basically a large box-full of dry solder joints. Great picture, but crap reliability. And crap solder has come full circle, with ROHS. -- The movie 'Deliverance' isn't a documentary! |
#19
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Rank Arena Widescreen CRT
And crap solder has come full circle, with ROHS.
I'm bothered about buying expensive products with non-lead solder. |
#20
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Rank Arena Widescreen CRT
Michael A. Terrell wrote:
snip Have you ever used a water cooled power tetrode with two, 1000 A, 1.5 volt filaments? The AC had to match to a few millivolts, or it would modulate the output current. You had to use an open ended wrench to adjust the length of a copper buss bar. Its resistance went up as it was stretched. This was in the RCA TTU-25 series UHF transmitter. Was that adjustment in one direction only (to increase resistance)? How much range did it have before the copper would need replacement? Michael |
#21
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Rank Arena Widescreen CRT
"b" wrote in message ... Rank Arena were old UK names, the Rank/Bush/Murphy brands were all used in the 60s and 70s. Likely bought out by some chinese/turkish firm, as have other former respected names like Dual, wharfefdale, and Sansui. **Dual was purchased by Thorens. Thorens is still a European made product. -- Trevor Wilson www.rageaudio.com.au |
#22
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Rank Arena Widescreen CRT
On 11 nov, 12:19, Sylvia Else wrote:
The switching transistor for the EHT transformer has no base drive. I traced backwards through a transformer, another bibolar transistor, a pair of FETs, a pair of bipolar transistors and ultimately reached two outputs from the programmable LSI circuit. So the reason there was no EHT was that the outputs from the LSI were unchanging. I surmise that it had probably detected some fault, and disabled the EHT for that reason, but since it's programmable, I have no way of determining what it might be objecting to. if you had checked the RGB and frame stages, I'm sure you would have found something amiss causing the set to prevent the EHT starting. This sounds like a classic case of 'don't look for the fire, look for the boy with the matches' . Still, another one for landfill :-( -B |
#23
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Rank Arena Widescreen CRT
On 11 nov, 21:51, "Trevor Wilson"
wrote: **Dual was purchased by Thorens. Thorens is still a European made product. Sorry, not true. In the last 4 years, have seen the Dual name, including the logo, on chinese made DVD player and a Turkish vestel TV. -B |
#24
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Rank Arena Widescreen CRT
msg wrote: Michael A. Terrell wrote: snip Have you ever used a water cooled power tetrode with two, 1000 A, 1.5 volt filaments? The AC had to match to a few millivolts, or it would modulate the output current. You had to use an open ended wrench to adjust the length of a copper buss bar. Its resistance went up as it was stretched. This was in the RCA TTU-25 series UHF transmitter. Was that adjustment in one direction only (to increase resistance)? How much range did it have before the copper would need replacement? The originals were still in the transmitter, and it was built in 1952. Backing the bolts off allowed some change in length, so they were backed off and then set to a minimum torque. The new tube was installed, and the voltage measured. Then each was tightened to the recommended filament voltage. A new tube would last a couple years, so it didn't have to be done very often. What bugged me was 3 KW of electricity was used to get 25 KW out of the tube. -- The movie 'Deliverance' isn't a documentary! |
#25
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Rank Arena Widescreen CRT
b wrote:
On 11 nov, 12:19, Sylvia Else wrote: The switching transistor for the EHT transformer has no base drive. I traced backwards through a transformer, another bibolar transistor, a pair of FETs, a pair of bipolar transistors and ultimately reached two outputs from the programmable LSI circuit. So the reason there was no EHT was that the outputs from the LSI were unchanging. I surmise that it had probably detected some fault, and disabled the EHT for that reason, but since it's programmable, I have no way of determining what it might be objecting to. if you had checked the RGB and frame stages, I'm sure you would have found something amiss causing the set to prevent the EHT starting. Well, perhaps. But by the time I'd got the metal box partly apart, which required desoldering, I'd already managed to cut myself on it, and I wasn't feeling particularly goodwilled towards the set. There was also the question of what I was going to do with it if I managed to fix it. It was rather bigger than I envisaged when I bid for it, so it wasn't really going to suit my living room. I wouldn't feel entirely comfortable about selling a TV that I'd taken a soldering iron to the insides of. So if I'd fixed it, it might have ended up on the tip anyway Sylvia. |
#26
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Rank Arena Widescreen CRT
"b" wrote in message ... On 11 nov, 21:51, "Trevor Wilson" wrote: **Dual was purchased by Thorens. Thorens is still a European made product. Sorry, not true. In the last 4 years, have seen the Dual name, including the logo, on chinese made DVD player and a Turkish vestel TV. **Dual was STILL purchased by Thorens. Thorens may have recently on-sold the name. Or not. It is not beyond the realms of possibility that the Chinese are illegally using the name. -- Trevor Wilson www.rageaudio.com.au |
#27
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Rank Arena Widescreen CRT
On Thu, 12 Nov 2009 00:05:44 -0500, "Michael A. Terrell"
wrote: msg wrote: Michael A. Terrell wrote: snip Have you ever used a water cooled power tetrode with two, 1000 A, 1.5 volt filaments? The AC had to match to a few millivolts, or it would modulate the output current. You had to use an open ended wrench to adjust the length of a copper buss bar. Its resistance went up as it was stretched. This was in the RCA TTU-25 series UHF transmitter. Was that adjustment in one direction only (to increase resistance)? How much range did it have before the copper would need replacement? The originals were still in the transmitter, and it was built in 1952. Backing the bolts off allowed some change in length, so they were backed off and then set to a minimum torque. The new tube was installed, and the voltage measured. Then each was tightened to the recommended filament voltage. A new tube would last a couple years, so it didn't have to be done very often. What bugged me was 3 KW of electricity was used to get 25 KW out of the tube. Amazing, isn't it! g What was used to measure the filament voltage with that accuracy? |
#28
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Rank Arena Widescreen CRT
Meat Plow wrote: On Wed, 11 Nov 2009 14:01:33 -0500, "Michael A. Terrell" wrote: Meat Plow wrote: On Tue, 10 Nov 2009 22:46:14 -0500, "Michael A. Terrell" wrote: Trevor Wilson wrote: "Sylvia Else" wrote in message ... Whatever happened to circuits that just contained a couple of valves? **There never were any "circuits that just contained a couple of valves". When they first arrived, TV sets were mindbogglingly complex devices compared to anything that preceded them (in domestic appliance-speak). They were also fabulously unreliable. You could figure that the average TV set would require several repair jobs every year. Your incredibly complex, LSI controlled, TV set is likely to be vastly more reliable. You've probably found the first fault it has ever had. It sounds like they only sold crap in Australia, and that you've never seen the very low parts count in a Muntz TV. My parents had three service calls in 15 years. Two of those were due to lightning taking out the front end in the VHF tuner. The third was a bad electrolytic in a voltage doubler that took out a fusible resistor. That isn't a couple times a year. My dad always bought RCA even though the RCA tube guy seemed to visit monthly. (color sets) I did TV repair for about 20 years, and never saw anything that bad. Most customers got three or four years out of a new set before the first service call. By the time a set needed a lot of repairs, it was cheaper to replace. I went on some calls on Zenith sets that were almost 20 years old, and it was the first service call. The cost of 12 service calls in one year would be higher than a new TV set. Only tubes I deal with these days are in guitar amps. Whoopie. I won't touch tube sets, unless they get a full overhaul. I no longer work with multiple 65 KW Klystrons, or transmitter tubes made with beryllium oxide ceramics. Have you ever used a water cooled power tetrode with two, 1000 A, 1.5 volt filaments? The AC had to match to a few millivolts, or it would modulate the output current. You had to use an open ended wrench to adjust the length of a copper buss bar. Its resistance went up as it was stretched. This was in the RCA TTU-25 series UHF transmitter. I have seen a TV transmitter, a Doppler radar transmitter and a huge mercury vapor rectifier. Have seen a walkin klystron but only in pictures. Ever seen a klystrode? -- The movie 'Deliverance' isn't a documentary! |
#29
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Rank Arena Widescreen CRT
PeterD wrote: On Thu, 12 Nov 2009 00:05:44 -0500, "Michael A. Terrell" wrote: msg wrote: Michael A. Terrell wrote: snip Have you ever used a water cooled power tetrode with two, 1000 A, 1.5 volt filaments? The AC had to match to a few millivolts, or it would modulate the output current. You had to use an open ended wrench to adjust the length of a copper buss bar. Its resistance went up as it was stretched. This was in the RCA TTU-25 series UHF transmitter. Was that adjustment in one direction only (to increase resistance)? How much range did it have before the copper would need replacement? The originals were still in the transmitter, and it was built in 1952. Backing the bolts off allowed some change in length, so they were backed off and then set to a minimum torque. The new tube was installed, and the voltage measured. Then each was tightened to the recommended filament voltage. A new tube would last a couple years, so it didn't have to be done very often. What bugged me was 3 KW of electricity was used to get 25 KW out of the tube. Amazing, isn't it! g What was used to measure the filament voltage with that accuracy? An RCA VTVM on the lowest AC scale. If the needle moved at all, it was out of spec. Yo connected it to the filament end of the pair of copper resistors and adjusted for zero volts, like a Whetstone bridge. That transmitter was built in 1952. -- The movie 'Deliverance' isn't a documentary! |
#30
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Rank Arena Widescreen CRT
Meat Plow wrote: Michael A. Terrell wrote: Ever seen a klystrode? And you need to know why? Then that's a NO. The Klystrode 'was' the replacement for Klystrons in UHF TV transmitters, but was short lived because new designs switched to all solid state. They were more efficient than the Klystron, and cut the electric bill by thousands of dollars a month. A technology between the two tubes was to add a 'Pulser' to a Klystron to lower the electric bill. -- The movie 'Deliverance' isn't a documentary! |
#31
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Rank Arena Widescreen CRT
Meat Plow wrote: On Fri, 13 Nov 2009 19:29:38 -0500, "Michael A. Terrell" wrote: Meat Plow wrote: Michael A. Terrell wrote: Ever seen a klystrode? And you need to know why? Then that's a NO. Wouldn't matter one way or the other because you were going to tell me about a klystrode regardless. The Klystrode 'was' the replacement for Klystrons in UHF TV transmitters, but was short lived because new designs switched to all solid state. They were more efficient than the Klystron, and cut the electric bill by thousands of dollars a month. A technology between the two tubes was to add a 'Pulser' to a Klystron to lower the electric bill. I'll remember that the next time I apply for an engineer position at a UHF TV station. They will laugh in your face if you aren't familiar with the new Harris solid state transmitters. BTW, I found four high power GE X Ray heads yesterday. They use about 100 KV DC to power them. Heavy *******s, with cooling fans. I wonder if the store has any idea what they are really work, or just how dangerous? -- The movie 'Deliverance' isn't a documentary! |
#32
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Rank Arena Widescreen CRT
Michael A. Terrell wrote:
Meat Plow wrote: On Fri, 13 Nov 2009 19:29:38 -0500, "Michael A. Terrell" wrote: Meat Plow wrote: Michael A. Terrell wrote: Ever seen a klystrode? And you need to know why? Then that's a NO. Wouldn't matter one way or the other because you were going to tell me about a klystrode regardless. The Klystrode 'was' the replacement for Klystrons in UHF TV transmitters, but was short lived because new designs switched to all solid state. They were more efficient than the Klystron, and cut the electric bill by thousands of dollars a month. A technology between the two tubes was to add a 'Pulser' to a Klystron to lower the electric bill. I'll remember that the next time I apply for an engineer position at a UHF TV station. They will laugh in your face if you aren't familiar with the new Harris solid state transmitters. BTW, I found four high power GE X Ray heads yesterday. They use about 100 KV DC to power them. Heavy *******s, with cooling fans. I wonder if the store has any idea what they are really work, or just how dangerous? If its just the heads they could be worth more for the lead in them ! -- Best Regards: Baron. |
#33
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Rank Arena Widescreen CRT
Baron wrote: Michael A. Terrell wrote: BTW, I found four high power GE X Ray heads yesterday. They use about 100 KV DC to power them. Heavy *******s, with cooling fans. I wonder if the store has any idea what they are really work, or just how dangerous? If its just the heads they could be worth more for the lead in them ! What lead? This is the aluminum waveguide & tube part. The lead is part of the moving arm and holds the X ray assembly. They still weigh about 5o pounds each for the smaller pair. I didn't know it was legal to dispose of these outside the medical electronics industry. I would think they would be rebuilt, like all the other types. -- The movie 'Deliverance' isn't a documentary! |
#34
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Rank Arena Widescreen CRT
Michael A. Terrell wrote:
Baron wrote: Michael A. Terrell wrote: BTW, I found four high power GE X Ray heads yesterday. They use about 100 KV DC to power them. Heavy *******s, with cooling fans. I wonder if the store has any idea what they are really work, or just how dangerous? If its just the heads they could be worth more for the lead in them ! What lead? This is the aluminum waveguide & tube part. The lead is part of the moving arm and holds the X ray assembly. They still weigh about 5o pounds each for the smaller pair. I didn't know it was legal to dispose of these outside the medical electronics industry. I would think they would be rebuilt, like all the other types. Oh ! I'm thinking about the wrong bit. I've seen a couple in scrap metal yards. Didn't have a tube in them though. -- Best Regards: Baron. |
#35
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Rank Arena Widescreen CRT
Baron wrote: Michael A. Terrell wrote: Baron wrote: Michael A. Terrell wrote: BTW, I found four high power GE X Ray heads yesterday. They use about 100 KV DC to power them. Heavy *******s, with cooling fans. I wonder if the store has any idea what they are really work, or just how dangerous? If its just the heads they could be worth more for the lead in them ! What lead? This is the aluminum waveguide & tube part. The lead is part of the moving arm and holds the X ray assembly. They still weigh about 5o pounds each for the smaller pair. I didn't know it was legal to dispose of these outside the medical electronics industry. I would think they would be rebuilt, like all the other types. Oh ! I'm thinking about the wrong bit. I've seen a couple in scrap metal yards. Didn't have a tube in them though. No problem. -- The movie 'Deliverance' isn't a documentary! |
#36
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Rank Arena Widescreen CRT
Michael A. Terrell wrote: Baron wrote: Michael A. Terrell wrote: BTW, I found four high power GE X Ray heads yesterday. They use about 100 KV DC to power them. Heavy *******s, with cooling fans. I wonder if the store has any idea what they are really work, or just how dangerous? If its just the heads they could be worth more for the lead in them ! What lead? This is the aluminum waveguide & tube part. What about the high voltage leads? seems like that would be pretty handy for various hi-voltage projects, but I haven't seen anything like defunct medical x-ray stuff at the local scrap yard for many years. I'd like to get 10 or 20 feet of that HV cable to go on a tree root zapper. The lead is part of the moving arm and holds the X ray assembly. They still weigh about 5o pounds each for the smaller pair. I didn't know it was legal to dispose of these outside the medical electronics industry. It's not, the Dept. of HHS supposedly tracks all medical and dental x- ray tubes through out their life. I would think they would be rebuilt, like all the other types. -- The movie 'Deliverance' isn't a documentary! (que Dueling Banjos 8^O) |
#37
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Rank Arena Widescreen CRT
mike wrote: Michael A. Terrell wrote: Baron wrote: Michael A. Terrell wrote: BTW, I found four high power GE X Ray heads yesterday. They use about 100 KV DC to power them. Heavy *******s, with cooling fans. I wonder if the store has any idea what they are really work, or just how dangerous? If its just the heads they could be worth more for the lead in them ! What lead? This is the aluminum waveguide & tube part. What about the high voltage leads? seems like that would be pretty handy for various hi-voltage projects, but I haven't seen anything like defunct medical x-ray stuff at the local scrap yard for many years. I'd like to get 10 or 20 feet of that HV cable to go on a tree root zapper. There were no cables with these assemblies. The lead is part of the moving arm and holds the X ray assembly. They still weigh about 5o pounds each for the smaller pair. I didn't know it was legal to dispose of these outside the medical electronics industry. It's not, the Dept. of HHS supposedly tracks all medical and dental x- ray tubes through out their life. These were still in the boxes & packing material. The only date I found on any of them was 1977. -- The movie 'Deliverance' isn't a documentary! |
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