MODIFICATIONS TO ARGUS
|
VISION UNIT |
|
| HT increased to 300v | To increase contrast and scan drive |
| R17 increased to 10K 5 watts | To increase contrast |
| Screened lead to phase splitter replaced with single core wire | To reduce shunt capacitance |
| R18 doubled to 100 ohms | For cooler running of V6 |
|
SOUND UNIT |
|
| R31/32 replaced with single 470 ohm | Economy measure to reduce HT drain on mains transformer. |
| T2 & T3 replaced with fixed capacitors | Presets unobtainable and unnecessary for tuning |
| C39 replaced by 0.01uF in parallel with 0.022uF + 6K8 | To reduce harshness on sound, increase bass |
|
POWER SUPPLY |
|
| Mains transformer primary under-run | To reduce transformer working temperature |
| Separate heater transformer for timebase heaters | To remove load from mains transformer |
| Half wave HT rectification used from full HT winding | To enable sufficient HT for timebase unit from transformer in stock. |
| C66 becomes 100uF | For adequate smoothing with h/w rectification |
| R73 increased to 4K7 | Found necessary for correct sound unit HT and reasonable economy of HT where it wasn't so critical |
| C65 has 15uF added in parallel | To reduce ripple loading of main component and improve smoothing without overloading rectifier |
| C67 & C68 increased to 22uF | To improve smoothing and take advantage of modern smaller component |
|
TIMEBASE UNIT |
|
| V12 replace by BY206 diode | Reduce heater drain and shunt capacitance on video |
| C44 reduced to 0.02uF | To reduce frame foldover |
| Revised sync separator from Nov '53 issue | Greatly improved picture sync lock |
| C43 reduced to 0.01uF | Correction of article misprint - frame speed was far too slow |
| R33 increased to 4M7 | To preserve higher video frequencies |
| X plates and Y plates connections transposed and tube rotated by 90 degrees | To obtain sufficient width |
| Screened lead from phase splitter to CRT replaced with plain single wire | To reduce capacitative shunt of higher video frequencies |
| R42, R43, R47, R48 reduced in value and uprated for power | To obtain sufficient width |
| 0.01uF added to V17 grid | Trade off, for better interlace at slight cost of vertical linearity |
| 33pF added to V15 grid | To correct irregular line triggering when set stood on conductive surface |
|
EHT/TUBE |
|
| Mu-metal screening used around tube | To remove severe hum on both shape and contrast of displayed image |
| CV2810 tube replaced VCR97 | For a brighter black-and-white picture instead of dim green |
| Grid lead separated from tube feeder cable harness | To prevent capacitative shunt of higher video frequencies |
| V19 replaced with BY206 diode | Easier to fit and less capacitative |
| Above-chassis EHT components mounted below chassis | For greater safety and neatness |
| Triple-tier EHT smoothing replaced twin-tier | To remove hum and increase EHT value |
| Anti-hum mods from Nov '53 issue installed at cathode of tube | To remove slight hum on picture |
| Perspex replaced paxolin for controls' mounting panel | Paxolin not in stock |
| R67 shorted out, R68 reduced to 240K | To increase range of brightness control and maintain correct focus |
| ½ohm in series with tube heater | To reduce tendency to grid emission on tube, which was slightly over-run |
|
MISCELLANEOUS |
|
| Eyetags replaced wires around screws | For more reliable earthing points |