Saturday, August 16, 2014

Eddystone EC10 communication receiver restoration and PSU add-in

Recently I got vintage Eddystone EC10 MK1 communication receiver from friend of mine and it is completely dead when it comes to me. EC10 MK1 is one of Eddystone's very early solid state communications receivers and it use 10 PNP Germanium transistors. This receiver cover 550 kHz to 30 MHz and come up with BFO for CW and SSB receptions.

Restored EC10 MK1 HF communication receiver

The main problems which I noticed in my EC10 is corroded wires, components and PCB. I did restoration step-by-step and most of the steps are listed in my qsl.net page.

Other than repairing, this article covers details of power supply which I integrated into EC10 communication receiver. The schematics and photographs are available at the same article.

After repairing and above changes EC10 starts to work again and with some external antenna is performs quiet well. Most of the times I use this receiver to listen to 40m 4S7RS net on 7060kHz.

Sunday, August 3, 2014

Panasonic RX-5090T power amplifier repair

Panasonic RX-5090T is quiet old combo box from Matsushita Electric and its most notable feature is powerful three band SW tuner. Recently I got some RX-5090T unit and its problem is distorted audio output.

PCB and mechanical component distribution of Panasonic RX-5090T combo box

After careful examination we identify C128 (100µF / 10V) and C224 (3.3µF 25V) as defective components. In this unit, VR103/203 (20KΩ) potentiometer is also defective and because of that we got some random distortions when we try to change the volume of the receiver. To fix this issue we disassemble the potentiometer and clean it using isopropyl-alcohol (this potentiometer is not available in local market and only option is to clean it and use it again). After these two fixes receiver starts to work again.

Mainboard of Panasonic RX-5090T combo box

Schematic diagram of Panasonic RX-5090T is quiet difficult to find in the web and we share copy of it in here.