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Goodmans Quadro 902 Composite Video Mod

CRT Module
CRT Module

Here’s the CRT & it’s drive board removed from the main chassis. Nicely modular this unit, all the individual modules (radio, tape, TV), are separate. This is effectively a TV itself, all the tuner & IF section are onboard, unlike in other vintage units I’ve modified, where the tuner & IF has been on a separate board. There’s a 3-pin header bottom centre for the tuning potentiometer, and external antenna input jack. The internal coax for the built in antenna has been desoldered from the board here. here a the usual controls on the back for adjusting brightness, contrast & V Hold, all the other adjustments are trimmers on the PCB.
Unfortunately after 30+ years of storage, this didn’t work on first power up, neither of the oscillators for vertical or horizontal deflection would lock onto the incoming signal, but a couple of hours running seemed to improve things greatly. The numerous electrolytic capacitors in this unit were probably in need of some reforming after all this time, although out of all of them, only 21 are anything to do with the CRT itself.

Anode Cap
Anode Cap

Here’s the anode side of the unit, with the small flyback transformer. The rubber anode cap has become very hard with age, so I’ll replace this with a decent silicone one from another dead TV. The Horizontal Output Transistor (a 2SC2233 NPN type) & linearity coil are visible at the bottom right corner of the board. Unfortunately, the disgusting yellow glue has been used to secure some of the wiring & large electrolytics, this stuff tends to turn brown with age & become conductive, so it has to be removed. Doing this is a bit of a pain though. It’s still a little bit flexible in places, and rock hard in others. Soaking in acetone softens it up a little & makes it easier to detach from the components.

Neck PCB
Neck PCB

There’s little on the neck board apart from a few resistors, forming the limiting components for the video signal, and the focus divider of 1MΩ & 470KΩ feeding G3. No adjustable focus on this unit. There’s also a spark gap between the cathode line & ground, to limit the filament to cathode voltage. The flyback transformer is nestled into the heatsink used by the horizontal output transistor & a voltage regulator transistor.

Tube Details
Tube Details

The CRT is a Samsung Electron Devices 4ADC4, with a really wide deflection angle. It’s a fair bit shorter than the Chinese CRT I have which is just a little larger, with a neck tube very thin indeed for the overall tube size.
Unusually, while the filament voltage is derived from the flyback transformer as usual, it’s rectified into DC in this unit, passing through a 1Ω resistor before the filament connection. I measured 5.3v here. The glow from the filament is barely visible even in the dark.

Electron Gun 1
Electron Gun 1

The electron gun is the usual for a monochrome tube, with 7 pins on the seal end.

Electron Gun 2
Electron Gun 2

The electrodes here from left are Final Anode, G3 (Focus Grid), Accelerating Anode, G2 (Screen Grid), G1 (Control Grid). The cathode & filament are hidden inside G1. In operation there’s about 250v on G2, and about 80v on G3.

Chipset
Chipset

The chipset used here is all NEC, starting with a µPC1366C Video IF Processor, which receives the IF signal from the tuner module to the left. This IC outputs the standard composite signal, and a modulated sound signal.
This then splits off to a µPC1382C Sound IF Processor & Attenuator IC, which feeds the resulting sound through the two pin header at the right bottom edge of the board to the audio amplifier in the chassis.
The composite video signal is fed through a discrete video amplifier with a single 2SC2229 transistor before going to the CRT cathode.
The remaining IC is a µPC1379C Sync Signal Processor, containing the sync separator, this is generating the required waveforms to drive the CRT deflection systems from another tap off the composite video line.
From this chip I can assume the unit was built around 1986, since this is the only date code on any of the semiconductors. Besides these 3 ICs, the rest of the circuit is all discrete components, which are well-crammed into the small board space.
There are 5 trimmer potentiometers on the board here, I’ve managed to work out the functions of nearly all of them:

  • SVR1: IF Gain Adjust
  • SVR2: H. Hold
  • SVR3: V. Size
  • SVR4: B+ Voltage Adjust
  • SVR5: Tuner Frequency Alignment? It’s in series with the tuning potentiometer in the chassis.
PCB Bottom
PCB Bottom

The PCB bottom shows the curved track layout typical of a hand taped out board. The soldermask is starting to flake off in places due to age, and there a couple of bodge wires completing a few ground traces. Respinning a board in those days was an expensive deal! Surprisingly, after all this time I’ve found no significant drift in the fixed resistors, but the carbon track potentiometers are drifiting significantly – 10KΩ pots are measuring as low as 8KΩ out of circuit. These will have to be replaced with modern versions, since there are a couple in timing-sensitive places, like the vertical & horizontal oscillator circuits.

Anode Cap Replaced
Anode Cap Replaced

Here the anode cap has been replaced with a better silicone one from another TV. This should help keep the 6kV on the CRT from making an escape. This was an easy fix – pulling the contact fork out of the cap with it’s HT lead, desoldering the fork & refitting with the new cap in place.

Here I’ve replaced the important trimmers with new ones. Should help stabilize things a little.

Composite Injection Mod
Composite Injection Mod

Injecting a video signal is as easy as the other units. Pin 3 of the µPC1366C Video IF Processor is it’s output, so the track to Pin 3 is cut and a coax is soldered into place to feed in an external signal.

CRT In Operation
CRT In Operation

After hooking up a Raspberry Pi, we have display! Not bad after having stood idle for 30+ years.

Datasheets for the important ICs are available below:
[download id=”5690″]
[download id=”5693″]
[download id=”5696″]

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Topping NX1a Portable Headphone Amplifier

NX1a Amplifier
NX1a Amplifier

Time for another teardown! Here’s a pocket-sized headphone amplifier for use with mobile devices. This unit is powered by a built-in lithium cell, and can give some pretty impressive volume levels given it’s small size.

Audio Connections
Audio Connections

The 3.5mm audio input & output jacks are on the front of the unit, along with the relatively enormous volume knob & power switch. There’s a little blue LED under the switch that lets the user know when the power is on, but this is a very sedate LED, using very little power.

Gain & Charging
Gain & Charging

On the back is the High-Low gain switch, and the µUSB charging port. There’s another indicator LED to show that the internal cell is charging, in this case a red one.

PCB Top
PCB Top

Removing a couple of cap screws allows the internals to slide out of the extruded aluminium casing. Most of the internal space is taken up by the 1Ah lithium cell, here on the top of the PCB secured by some double-sided tape. The volume potentiometer is mounted on a small daughterboard at right angles to get it to fit into the small vertical space in the case.

PCB Rear
PCB Rear

The bottom of the PCB is equally as sparse – the only ICs being the main audio amp in the centre & the battery charger IC at the top.

Amplifier IC
Amplifier IC

The main audio amplifier is a TP9260, I couldn’t find a datasheet on this, so I’m unsure of what the specs are. The row of resistors above the IC are for the gain divider circuit. There’s also a pogo pin on the right that makes contact with the back panel of the case for grounding.

Battery Charger
Battery Charger

Battery charging is taken care of by a UN8HX 500mA linear charging IC, not much special here.

This little amplifier seems to be pretty well made, considering the price point. The only issue I’ve had so far is the audio cables act like antennas, and when in close proximity to a phone some signal gets picked up & blasted into the headphones as interference.

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eBay Special – LED Disco Light With Built In MP3 Player

Here’s an eBay oddity – it’s got the same light & lens mechanism as the cheap “disco light” style bulbs on eBay, but this one is battery powered & has a built in MP3 player.

MP3 Disco Light
MP3 Disco Light

This device simply oozes cheapness. The large 4″ plastic dome lens sits on the top above the cheap plastic moulding as a base, which also contains the MP3 player speaker.

Controls
Controls

There are few controls on this player, the volume buttons are combined with the skip track buttons, a long press operates the volume control, while a short press skips the tracks. Several options for getting this thing to play music are provided:

  • Bluetooth – Allows connection from any device for bluetooth audio
  • USB – Plugging in a USB flash drive with MP3 files
  • SD Card – Very similar to the USB flash drive option, just a FAT32 formatted card with MP3 files
  • Aux – There’s no 3.5mm jack on this unit for an audio input, instead a “special” USB cable is supplied that is both used to charge the built in battery & feed an audio signal. This is possible since the data lines on the port aren’t used. But it’s certainly out of the ordinary.
Top Removed
Top Removed

The top comes off with the removal of a single screw in the centre of the lens. The shaft in the centre that holds the lens is attached to a small gear motor under the LED PCB. There’s 6 LEDs on the board, to form an RGB array. Surprisingly for a very small battery powered unit these are bright to the point of being utterly offensive.

Mainboard
Mainboard

Here’s the mainboard removed from the plastic base. There’s not much to this device, even with all the options it has. The power switch is on the left, followed by the Mini-B USB charging port & aux audio input. The USB A port for a flash drive is next, finishing with the µSD slot. I’m not sure what the red wire is for on the left, it connects to one of the pins on the USB port & then goes nowhere.

Audio Amplifier
Audio Amplifier

The audio amplifier is a YX8002D, I couldn’t find a datasheet for this, but it’s probably Class D.

Main Chipset
Main Chipset

Finally there’s the main IC, which is an AC1542D88038. I’ve not been able to find any data on this part either, it’s either a dedicated MP3 player with Bluetooth radio built in, or an MCU of some kind.The RF antenna for the Bluetooth mode is at the top of the board.
Just behind the power switch is a SOT23-6 component, which should be the charger for the built in Lithium Ion cell.

Lithium Ion Cell
Lithium Ion Cell

The cell itself is a prismatic type rated in the instructions at 600mAh, however my 1C discharge test gave a reading of 820mAh, which is unusual for anything Li-Ion based that comes from eBay 😉
There is cell protection provided, it’s under the black tape on the end, nothing special here.

The main issue so far with this little player is the utterly abysmal battery life – at full volume playing MP3s from a SD card, the unit’s current draw is 600mA, with the seizure & blindness-inducing LEDs added on top, the draw goes up to about 1200mA. The built in charger is also not able to keep up with running the player while charging. This in all only gives a battery life of about 20 minutes, which really limits the usability of the player.