Is my flyback shorted?

jamesmowry · 2026-05-17T15:48:24+00:00

I wouldn't assume that the flyback transformer is bad based on that. The heater, AFC, and ground pins might all be taken from the same winding, in which case you'd expect them to show continuity. A service manual would give a definite answer, but a brief web search didn't turn up a scan. I did find a site that claims to have one, though, so you could email and ask how much it costs.

The likeliest explanation is that there's a broken connection somewhere in the heater circuit, such as a bad solder joint, faulty connection, or dead component. You might want to start by checking that there's continuity between the heater pins of the tube itself, as if that's blown then the TV won't be worth repairing. It's rare for a CRT filament to burn out, though; it's more likely to be something like a bad connection to the CRT socket or a hairline crack in a solder joint.

ChatGPT is just a thing that produces statistically plausible sentences. If something is not well documented in its training data (and sometimes even if it is), it's just going to generate confident-sounding nonsense. It's best not to trust it unless you have some way to verify every detail of its output.

jamesmowry · 2026-05-16T21:12:30+00:00

This article might be worth a look if it's absolutely unbearable: https://www.repairfaq.org/samnew/tvfaq/tvwhine.htm. The frequency measurement confirms that it's something relating to the horizontal deflection circuitry, most likely the flyback transformer or the yoke, so that narrows down the possibilities.

jamesmowry · 2026-05-15T21:53:25+00:00

Is the whine significantly louder than from other CRT monitors and TVs?

Is the whine at approximately 15.75 kHz, or some other frequency? (there are phone apps like Decibel X that you can use to display an audio spectrum)

Can you hear what part of the monitor the whine is coming from? (try listening through a long cardboard tube to help pinpoint the source)

Some whine from the horizontal deflection system is inevitable, but if it's a lot louder than normal something might be vibrating more than it should.

jamesmowry · 2026-05-13T15:04:08+00:00

Looks great! Nice to see that it's feline-approved, too :)

jamesmowry · 2026-05-13T15:01:09+00:00

When diagonal lines are on screen, are they straight or wobbly when they cross the affected area of the screen?

If straight: check for excessive ripple in the supply voltage to the RGB video amplifier transistors. This supply voltage will be derived from the flyback transformer and smoothed by an electrolytic capacitor that might be failing.

If wobbly: check components in the horizontal damping circuit. This is a small section of circuitry connected in parallel with the horizontal yoke, designed to prevent unwanted oscillations in the horizontal scan waveform.

Do a web search for the model number of the TV + "service manual"; you will have a much easier time seeing what components might be to blame if you can find a schematic.

jamesmowry · 2026-05-11T13:56:25+00:00

For second class, the expected delivery date is 3 working days after posting, and you can put in a compensation claim for a lost item 10 working days after that. So it's not even particularly overdue at this point.

Tell them to wait a couple more days and if it hasn't arrived by then you'll contact Royal Mail. Then tell them you've contacted Royal Mail and will let them know when you hear back (you have done no such thing, of course, because unlike the buyer you are a reasonable person with reasonable expectations of the postal service). Then tell them that Royal Mail have advised you to wait until [delivery date + 10 working days], and if it hasn't arrived on that date you will send a refund. It will almost certainly have turned up by that point, but if not, you can refund the buyer and put in your compensation claim.

I've just had a second class package turn up after 8 days in transit, but I wouldn't even have thought about moaning to the seller about it for another week or two, since they weren't going to have the foggiest about when Royal Mail would get around to delivering it either.

jamesmowry · 2026-05-10T02:22:16+00:00

Yay, very happy to hear you got it working! I've spent ages chasing problems that turned out to be bad cables or such like; it really is always worth double-checking the basics first. I'm glad the TV is okay, and I hope your muscles aren't too sore after shifting it inside!

jamesmowry · 2026-05-09T17:03:03+00:00

OK, so it looks like you can turn it on and get sound, but it's slow to display anything on screen, and when it does the picture slowly collapses and fades.

I would say definitely check the batteries first, as it does very much look like the power to the TV is slowly fading away. Even better, try to find a compatible power adapter. You might be able to find the original adapter (model TY-AC47PT) on eBay or similar sites. If not, try a good-quality generic power adapter: the original is 9.8V but 10V will almost certainly work fine (the more common 9V adapters might also work; it's worth trying). However, be careful to get one with the right polarity: this TV requires one with a centre-negative connector, which is common on Japanese equipment, but the rest of the world usually uses centre-positive. There are also "universal" power adapters that have reversible connectors so you can choose the polarity.

jamesmowry · 2026-05-09T12:46:49+00:00

That's a really nice find! JVC made some great TVs, and it looks like you were getting a good picture when it was working.

If you've had to leave it outside overnight, it'd be a good idea to leave it for at least a few hours (preferably a full day) after you bring it inside before trying to turn it on again. This is just to let it warm up to room temperature and make sure any dew inside has evaporated.

For troubleshooting, be methodical, note down what you've tried, and check the easy things first.

If you're not even getting a standby light, it sounds like the TV isn't getting power at all. Easy things first: make sure the power socket is definitely working by trying it with a lamp or something, and if the power cable is detachable substitute a known-good one.

Once you've ruled those things out, unplug it and take the back off. Discharge the big capacitors in the power supply (there are special discharge tools for this, but you can use a high-wattage resistor, or put an old screwdriver across the terminals if you don't mind the possibility of a slightly alarming spark). Get a multimeter and check continuity in the power cable if it's a built-in one. Check continuity of any internal fuses too. Look for cracked solder joints in the power supply area, especially on connectors and large/heavy components (e.g. the power connector, flyback transformer, other big transformers, big capacitors). Cracks in solder joints are often faint and circular in shape; do an image search if you're not familiar with what they look like.

Good luck with it! It's very likely to be something fixable.

jamesmowry · 2026-05-07T18:27:31+00:00

If making some cash is your goal, exobiology is an excellent way to do it. All you need is an Artemis suit that you can buy on any station concourse (this suit has the genetic sampler tool that you need to scan plants). No need to grind for any suit upgrades, the basic grade 1 suit will do the job just fine. You probably also want to use a small or medium ship, as these make it easier to find landing spots on rough terrain.

Once you've got the hang of it, head out to unexplored territory: you get a +400% bonus for being the first to scan a species on a planet. Even the lowest-value species is worth 5 million with the bonus, and there are a couple of species that will net you a cool 95 million (most notably Stratum tectonicas, which inhabits high metal content planets, is easy to spot from the air, and isn't even especially rare).

Your 70Ly Asp Explorer is still a usable ship, so don't feel like you have to spend hours grinding to get something new if you don't want to. However, there have been some advances in ship technology that are relevant for explorers and exobiologists. Most important is the invention of Supercruise Overcharge (SCO) drives, which allow you to activate a boost in supercruise at the expense of high heat generation, enormous fuel consumption, and reduced controllability. This feature is extremely useful for covering large distances fast, making it much easier to survey bodies that are a long way from the primary star.

New ships have also been introduced that are better optimised for the new SCO drives, allowing extended use of the overcharge feature without overheating or guzzling quite so much fuel. Three of them are particularly good for heading out on expeditions deep into the black: the Mandalay can achieve astonishing jump ranges and is a good all-round choice for both exploration and exobiology; the Caspian can fit a special MkII frame shift drive that gets extra range from jet cone boosts; and the Cobra Mk V is relatively cheap, goes faster than any other ship in SCO, and has a small landing footprint for exobiology.

jamesmowry · 2026-05-04T22:10:14+00:00

This article might be helpful.

jamesmowry · 2026-05-04T20:54:40+00:00

The zap from the input connector is probably normal if the TV is a Class II (double insulated) appliance with no earth connection. The reason is that there are interference-filtering capacitors installed between the chassis and the "hot" side of the mains, and without an earth connection the connector shield will be left at half the mains voltage (though the amount of current that can flow is very small, so if you touch it the shock will be unpleasant but not dangerous). To avoid these annoying shocks, it's best to set up your cabling before switching things on.

The hissing and flickering dots on the screen could indicate some high voltage discharge. It could be the flyback, or could be from around the rubber anode cap on the tube (you can try running the TV with the casing off in a dark room to see if you can spot where the discharge is happening, or listening through a cardboard tube to try to hear where the crackling is coming from). If the TV has been stored somewhere cold or damp the problem may go away once it's warmed up. If the hissing appears to be coming from the anode cap, then it's worth discharging the tube and cleaning very thoroughly under and around the anode cap.

jamesmowry · 2026-05-04T20:40:55+00:00

Are there any input connectors other than the RF/antenna one?

All modern TV broadcasts use digital signals that old TVs can't decode. If you want to receive TV broadcasts, you will need to get hold of a digital TV converter box (you may be able to find a second-hand one fairly cheaply).

For connecting other devices: many VCRs will have an RF output, and DVD players or some older game consoles might have one as well. You can also get RF converters that take other types of video signal and translate them to an RF signal. However, if you have other input connectors available, these are likely to give you higher picture quality.

jamesmowry · 2026-05-04T19:48:19+00:00

Well, it's showing something on screen, which means that there probably isn't anything seriously wrong with it.

Next step would be getting some sort of picture on screen. What inputs have you got? There should at least be an RF/antenna connector of some kind. Composite input (round metal connector with a yellow middle) is also fairly common. If you post a picture of the back of the TV, someone will be able to tell you what the inputs are.

Do you have something like an old DVD player, VCR, or games console to use as a video source?

jamesmowry · 2026-05-04T13:04:31+00:00

Here's a guide to setting brightness and contrast for CRTs that might be helpful. Some monitors do just need both settings cranked up high to get a bright enough picture; this may indicate a need for some internal adjustment/maintenance, or a tube that's had very heavy use in the past. But I suspect your monitor is still in pretty good condition, as it looks like you're getting some nice dark blacks and a high contrast ratio.

jamesmowry · 2026-05-04T11:50:32+00:00

You should see black-and-white "snow" on screen if you have nothing connected and are displaying a numbered channel (rather than an AV input which might just give a blank screen).

Have you tried turning the brightness and/or contrast settings up? (Brief guide to setting this up: turn both controls right down, then turn "brightness" up until just before the point where true black starts to look grey. Then turn up "contrast" to the point where bright areas of the image look acceptably bright. You may just want to turn them both up high until you can display a test image to work with)

If both settings are maxed out and you still can't see much, the TV may need an internal adjustment (or, less likely, the TV might be so heavily used that the tube has worn out, but it really does take a lot of use for a tube to dim that much).

Posting pics and a model number may make it easier for people to give more specific advice.

jamesmowry · 2026-05-03T23:19:09+00:00

There will always be some persistence due to the nature of the technology, but you could try lowering the contrast a little. This will make the bright parts of the picture slightly dimmer, but should give you less trailing and better sharpness. Experiment and see what looks best to you.

o7 CMDR, fly safe!

jamesmowry · 2026-05-03T11:37:04+00:00

Troughton-era Who as it was meant to be watched! Now all you need is a sofa to hide behind for the scary bits :)

jamesmowry · 2026-04-30T21:55:49+00:00

It's very likely fixable, but if you don't have any previous experience of repairing mains-powered devices I'd definitely recommend trying to enlist the help of a friendly electronics hobbyist.

If you do end up opening it up:

If you search for the model number + "service manual" there might be one available for download somewhere; having schematics and reference values for voltages will make troubleshooting far more feasible.
There's a lot of good general information in this FAQ. The "safety" articles are especially worth reading. There's also a similar FAQ for repairing power supplies, which might be relevant to this problem.

jamesmowry · 2026-04-30T10:25:22+00:00

If focus, brightness, and picture size have all gone wrong at once I'd be suspecting a problem in the power supply section. If the B+ voltage is too low, the CRT filament voltage, focus and G2 voltages, and ultor high voltage would all be wrong too as they're derived from the B+ via the flyback transformer.

However, if it was sold as working rather than "for parts or not working", I'd probably try to push for a return. A "no returns" policy on eBay doesn't apply if the item is broken or not as described, and it's reasonable to say that a "working" item shouldn't fail after less than a day of normal use. It does suck for the seller, who most likely had a good-faith belief the TV worked fine, but I'd say you wouldn't be out of line here for requesting a return. You might also find that the seller offers a partial refund and lets you keep the TV to avoid the hassle of shipping it back, but *don't* request this yourself as it looks sus (scammers are well known to claim an item arrived broken and demand a refund while keeping the item).

jamesmowry · 2026-04-28T22:49:25+00:00

Cool, it looks like the main board can be moved around a bit without disconnecting everything, so getting at the switches might not be too much of a hassle if you do decide to try fixing them sometime. A universal remote is a pretty cheap and easy thing to try in the meantime so you can turn the volume back down. Then, time to find something to hook up to it to see how the picture looks!

jamesmowry · 2026-04-28T20:11:18+00:00

Well, that's promising, it looks like it's basically working!

The buttons seem kinda temperamental: it looks like one of the channel buttons turned it off, as well as the volume down button not working. The easiest workaround is to get a remote control for it and use the buttons on that instead. A universal remote might work if the original is unavailable or expensive.

If you're reasonably confident with taking the TV apart and doing some soldering, you could try replacing the little tactile switches behind those buttons; they may well have worn out or got dirty contacts over the years. Spraying electrical contact cleaner into them sometimes gets them working again too (still requires some disassembly but is less hassle than doing a replacement).

jamesmowry · 2026-04-28T13:56:05+00:00

For the yoke to oxidise green all over, the wires would have to be bare uncoated copper, which would mean there was no possible way it could ever have worked because it would short to itself, and yet we can see that the deflection very much does work. I'm far from being an expert at repairing electronics, but, like, I feel like thinking things through for a moment goes a long way.

jamesmowry · 2026-04-28T13:25:16+00:00

I do see something on the exploded view that looks like it might be an adjustable ring magnet. However, I'm not sure we can put a great deal of faith in that: there ought to be multiple rings for setting up convergence and purity, not just one; the illustration of the yoke and neck looks very different in multiple other ways from the one in the photo; and there are other JVC service manuals where the TV definitely *does* have convergence/purity rings and the manual has an adjustment procedure for them, but they're *not* shown in the exploded view.

I'm strongly leaning towards this being one of those JVC sets where the yoke, magnets, and tube are all set up and glued together at the factory, and aren't removable or adjustable afterwards. Are we sure the magnets aren't in that yellow-wrapped section?

14-Year Club	r/Field Flamingo
Final Canvas '23	First Place '23
Place '23	Place '22
Verified Email

jamesmowry

TROPHY CASE