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.
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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.
The "pop" could have come through the speakers and not made by an exploding cap.
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.
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 determined that it will cost me a further $10 to take it to the tip, if it comes to it. Ho hum.
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?
**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:
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Someone there has almost certainly serviced the same model and, perhaps, the same fault.
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.
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.
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.
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.
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The movie \'Deliverance\' isn\'t a documentary!
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.
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.
**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 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.
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!
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.
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.
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.
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.
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The movie \'Deliverance\' isn\'t a documentary!
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.
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.
And crap solder has come full circle, with ROHS.
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The movie \'Deliverance\' isn\'t a documentary!
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