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CRT Flyback / Line Output Transformer Destructive Teardown

Small Flyback Transformer
Small Flyback Transformer

Here’s a small flyback / Line Output Transformer from a portable colour TV set. Usually these transformers are vacuum potted in hard epoxy resin & are impossible to disassemble without anything short of explosives. (There are chemical means of digesting cured epoxies, but none of them are pleasant). This one however, was potted in silicone, so with some digging, the structure of the transformer can be revealed.

Cap Removed
Cap Removed

The cap was glued on to the casing, but this popped off easily. The top of the core is visible in the silicone potting material.

The Digging Starts
The Digging Starts

A small screwdriver was used to remove the potting material, while trying not to damage the winding bobbin & core too badly. The bulge in the casing that I originally thought might house a voltage multiplier turns out to be totally empty. The white plastic bobbin is becoming visible around the core.

Bobbin
Bobbin

After some more digging & a lot of mess later, the entire transformer is revealed. The primary & auxiliary secondaries are visible at the bottom of the transformer, next to the pins. These transformers have multiple windings, as they’re used not only for supplying the final anode voltage of several Kilovolts to the CRT, but many of the other associated voltages, for the heater, grids, focus electrodes, etc. These lower voltage windings are on the same part of the core as the primary.
Above those is the main high voltage secondary winding, which looks to be wound with #38-#40AWG wire (about the thinnest available, at 0.07mm diameter. This is wound in many sections of of a few hundred turns each to increase the insulation resistance to the high voltage. The main anode wire emerges from the top of the bobbin.

Output Rectifier
Output Rectifier

Hidden in a recess at the top is the main HV rectifier, which on this small transformer is a single device (it’s probably not internally, most likely a series stack of diodes to get the PIV rating required).

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Sony Watchman FD-280 Teardown

Sony FD-280
Sony FD-280

Here’s another Sony Flat CRT TV, the FD0280. This one was apparently the last to use CRT technology, later devices were LCD based. This one certainly doesn’t feel as well made as the last one, with no metal parts at all in the frame, just moulded plastic.

CRT Screen
CRT Screen

Being a later model, this one has a much larger screen.

Autotuning
Autotuning

Instead of the manual tuner of the last Watchman, this one has automatic tuning control, to find the local stations.

Spec Label
Spec Label

The spec puts the power consumption a little higher than the older TV, this isn’t surprising as the CRT screen is bigger & will require higher voltages on the electrodes.

Certification Label
Certification Label

The certification label dates this model to May 1992.

External Inputs
External Inputs

Still not much in the way of inputs on this TV. There’s an external power input, external antenna input & a headphone jack. No composite from the factory. (Hack incoming ;)).

Power / Band
Power / Band

The UHF/VHF & power switches are on the top of this model.

Back Cover Removed
Back Cover Removed

Removing some very tiny screws allows the back to be removed. There’s significant difference in this model to the last, more of the electronics are integrated into ICs, nearly everything is SMD.

RF Section
RF Section

There’s the usual RF tuner section & IF, in this case the VIF/SIF is a Mitsubishi M51348AFP.

Tuner Controller
Tuner Controller

The digital control of the tuner is perfomed by this Panasonic AN5707NS.

Deflection / Sync
Deflection / Sync

The deflection & sync functions appear to be controlled by a single Sony branded custom IC, the CX20157. Similar to many other custom Sony ICs, a datasheet for this wasn’t forthcoming.

PCB Top
PCB Top

There’s very little on the top side of the board, the RF section is on the left, there’s a DC-DC converter bottom centre next to the battery contacts. This DC-DC converter has a very unusual inductor, completely encased in a metal can. This is probably done to prevent the magnetic field from interfering with the CRT.

CRT
CRT

Here’s the CRT itself, the Sony 03-JM. The back of this CRT is uncoated at the bottom, the tuning scale was taped to the back so it lined up with the tuning bar displayed on the screen.

Electronics
Electronics

Here’s the electronics completely removed from the shell. There’s much more integration in this model, everything is on a single PCB.

Phosphor Screen
Phosphor Screen

The curve in the phosphor screen can clearly be seen here. This CRT seems to have been cost-reduced as well, with the rough edges on the glass components having been left unfinished.

Electron Gun
Electron Gun

Here’s the electron gun end of the tube. There isn’t a separate final anode connection to the bell of the tube unlike the previous model. Instead the final anode voltage is on a pin of the electron gun itself. This keeps all the wiring to the tube at one end & shortens the high voltage cable.

Electron Gun
Electron Gun

Here’s the gun in the neck of the tube. Again this is pretty much standard fare for CRT guns. It’s more similar to a viewfinder tube in that the anode connection is running from the pins at the back. (It’s the line running up the right side of the tube). I’m guessing the anode voltage is pretty low for this to work without the HV flashing over, probably in the 2-4kV range.