So I decided to get myself a couple of old CRT TVs. Unfortunately, one does not work... I really want to get it fixed someway, but these things can be very dangerous...
The TV that doesn't work is Philips, model number 14PT136A/01W. The problem is that there is no picture (no static feeling either), no sound from speaker, only some loud squeaking sound coming from somewhere inside. Apparently there can be several causes to this kind of issue...


And I know that these are dangerous, there can be many kilovolts of voltage even after unplugging! Could someone help anyways? Also, you can recommend me some repair places if you know and trust any.

A loud squeaking coming from inside the TV sounds like it could be a high voltage issue. Maybe the high voltage connector for the CRT got disconnected and is ow arcing to something. This could be a fix as simple as reconnecting it, but the arcing could have also caused internal damage to other components that need replacing as well. Or it could be something else, IDK I am not a CRT expert.

Try finding a Finnish old radio or TV forum. Trouble shooting a CRT TV as an unexperienced (assuming, not knowing here) person is nearly impossible.

Did you grow up with CRT TVs? A 15625Hz whine is completely normal for those things and it is quite loud in some TVs. Especially for people in their late teens/early 20s who still have their full range of hearing, but were not accustomed to it, it might be too loud to their ears.

No sound, no picture so practically dead plus squeaking from inside sounds to me like a short circuit on some output of the power supply. The short circuit causes the operating frequency of the power supply to drop into audio band and the transformer then emits noise.

Now it must be some branch which normally uses to use high power, otherwise it would either smoke the power supply or in decent equipment designs blow a fuse on the affected branch in a short time.

What was a kind of most frequent cause of such troubles was deteriorating electrolytic capacitor in the base drive of the horizontal deflection circuit, with consequent destruction of the deflection transistor.
So you may start to Ohm the circuit from there - the transistor is some 1500V 5..15A (depends on the picture tube size and deflection angle) has its collector connected to the HV transformer and then via some capacitors and inductors (some with a permanent magnet stuck on them) to the horizontal deflection coils. Very likely you will find the transistor as shorted.
Be aware, replacing just the transistor may seem to fix the TV, but the shorted transistor is just a symptom, not cause, you have to check all electrolytic capacitors (mainly their ESR) mainly around its base drive, but I would generally sweep all involved in anything related to power. Also beware many of them need to be of the low ESR / high ripple current rated types, so replace with properly rated types (look for the series and their datasheets).

The TV that doesn't work is Philips, model number 14PT136A/01W. The problem is that there is no picture (no static feeling either), no sound from speaker, only some loud squeaking sound coming from somewhere inside. Apparently there can be several causes to this kind of issue...

Loud sqeaking may mean CRT lose vacuum ant there is sparking inside between 2nd anode and some ground. At first, I'd try to wiggle CRT neck/socket by hand a little. If it indeed does move, CRT is of course broken.

The are other possibilities like dead short somewhere in secondary circuits like a rectifier diode, or horizontal output transistor.

I think I have brought back to life some hundreds of CRT monitors and TVs back in time when it was profitable, so certainly can suggest a repair. But many times you need a service manual (look at electrotanya.com for example) and oscilloscope and quality soldering iron, plus the ability to use them.
 

Thanks for the responses...


Here is a small video if it helps anything: [size=78%]https://www.youtube.com/watch?v=35qHSMrbywI[/size]

Last resort option would be to get a new control board. There are still manufacturers in China who make universal analog boards for CRTs, along with speaker control. Again, this is a last resort as these boards may not fit inside the TV or may be low quality.

What I hear is the demagnetization rumble just at the power ON and then a transformer whine. Otherwise clearly no activity at all.
To me it still corresponds to some output of the power supply shorted.
Not the diode, nor any part of the power supply part itself, as that would prevent it from even whining this way. Shorted secondary diode shorts out the phase when the switching transistor is ON, so preventing the magnetic buildup in the transformer, so no whining, maybe just some buzz or clicking noises.
If some lower power branch was shorted, the power supply would initially start over that, so there will be some activity (filament glow, some noise from the sound part,...).
But this looks like the supply circuit has no problems when the switching transistor is ON, but it takes forever for the magnetic field to disappear (the feedback is waiting on that moment to restart a new cycle) when off, indicating no voltage buildup on the load side, so a shorted output (behind its rectifier diode) branch.

Now if the power supply was OK but for instance the tube was cracked, practically whole circuit will be alive, just a lot of arcing and mainly smoke from the tube and the HV transformer (HV is generated not by the power supply part itself, but by the horizontal deflection circuit). That would definitely leave overheating marks around the HV transformer.

I would really take it apart, identify the power supply rectifier diodes (various diodes around the non-HV transformer) and try to "diode test" them.
Plus also "diode check" the C-E and C-B of the horizontal deflection transistor (the power transistor on a rather significant heatsink near the HV transformer).

Be aware, some Philips sets tend to have the power supply configured as a nonisolating Buck topology for the highest power output (the main horizontal deflection circuit), all the lower power parts are then supplied by additional windings on the inductor (forming a transformer with the required insulation for the signal side power), so the transformer in the power supply remains rather small.
So that means the big part of the horizontal deflection, include the deflection coils on the tube, are on the mains side of the power supply, so with the mains voltage on it. Only the lower power parts are insulated.
So better use an insulation transformer, like with a hot schassis set.
Plus of course the regular High Voltage TV stuff...

Now I got it to make different squeaking noise, like this: https://www.youtube.com/watch?v=xWgRQQcosw4
One of my friends says it would be normal, but is it?

I wasn't hearing anything, but if it was the 15kHz whine, that is normal (even when sometimes quite loud) and also likely today I would not be able to hear it anymore.

Wasn't the picture waking up? My impression was I've seen there the typical static noise picture. Dark (compare to the ilumination of tge filming), but present.
If yes, what may have happened was some of the electrolytic capacitors degraded into essential short circuit, but by you messing with it and trying to turn it on the capacitor recovered, so the thing just started working.
The dark picture may heal itself as well - the tube may got contaminated by gas releases and even ingestion (e.g. Helium can pass the glass wall, messing with it around vacuum devices is a best receipe to kill them in a short time), which may get cleaned out after some hours of operation.
But it would still mean the capacitors are on their last leg before dying...

I don't think it would be that high as 14kHz...


Maybe it's just best to get rid of the TV... but I can tell exactly what has happened. So I somehow managed to snap a small part of the PCB, luckily it only had like 3 lines (or whatever you call them). I soldered some jumper wires, and apparently by accident, put one into wrong solder pad, that's what caused the sound in the first video. Then I fixed that, and now it makes the sound that it's currently doing. I know that it can be very dangerous to solder those jumper wires, but I think I managed to do it correctly now. I can show photos of the PCB if that helps at all...


But still, no photo, no static feeling, no audio. Only that whine. Or could it just take longer to come on if it hasn't been on for a long time? I mean, I had it on for several minutes, and absolutely nothing.
Also, any idea of how the buttons on the front work?


Or should I just stop attempting to fix it before something bad happens?