A few items to cross off the ‘matters arising’ at our next Committee meeting. Les G1LQB and Stuart M7RSF finished off the refurbishment of the trailer; it looks like new now. Alistair M0TEF, Stephen M5SJM and Si M0SIY repaired and put the Doublet back up And Alistair and Stephen fitted the new capacitor to the Gap Eagle; it will be tested at Fir Park over the weekend.
Continue reading →It isn’t always plain sailing when we put on Special Event Stations. On the way back to the shack after Fir Park our trailer which Les was towing had a blow-out and had to have a new tyre. Today wheels with decent tyres were fitted ready for our next Special Event Station at Boultham Park Fair on 13th July. Pictured doing the work Peter 2E0FGA, Stuart M7RSF and Andy 2E0OYQ
Continue reading →After serious thought on the layout of the components on this Linear Amp especially the placement of the filament transformer and the position of the RCA 813 valves for cooling, I decided that the best thing to do was to remove everything and reposition it better within the chassis. Initially my thoughts were to sort the amp out and get it working keeping the same layout, but as I progressed I was not happy with the layout, so this has now actually turned into building a 1kw Linear Amp from some recycled parts as I am now modifying a lot … Continue reading →
Because of finding dangerous faults during this project, this Linear Amp was not a refurbishment but a complete rebuild. I would advise others not to do this work unless they are experienced in what they are doing, as inexperience could result in DEATH as LETHAL VOLTAGES are involved. For reference, this linear is not pretty and is being brought back to life as a working project and will only be used safely in my shack, it will not be entered into any beauty contest. I changed the way the valve bases had been fitted to provided better ventilation by removing … Continue reading →
Refurbishing the Linear Amp was still in progress, and because I was changing the old filament transformer for a proper center tapped transformer suitable for the amplifier, I had to change the circuit to take this into account. Another modification to the amplifier was the cathode bias circuit as the old circuit did not have one. R5 is a 50K 10 Watt resistor that biases the valve at cut of when not transmitting keeping the valves cooler and D5 is a 5 volt 10 Watt Zener Diode which biases the valve for transmission. For those not familiar with the grounded … Continue reading →
This is a series of articles doing a step by step refurbishment on an old homebrew HF linear amplifier. It has to be taken into consideration that when the Linear Amp was built everything at that time would be valves which were more forgiving unlike the transistors of today. The amp was 2 X RCA813 valves wired in grounded grid configuration and the input was fed directly to the cathodes of the valves with no matching network. (this was common in the old valve days) The first step was a visual examination of the linear and I was suspicious about … Continue reading →
Electrolytic’ Capacitors may smooth out our ripples but they do need some TLC or they will blow your equipments main fuse. They do benefit from a regular top up of electricity but some are neglected and need a little bit of extra TLC to bring them back to life. This short article is covering the poor neglected electrolytic capacitors that have not had an electron pass through them for a very long time and is to give you advice on giving them that extra TLC. More information on electrolytic capacitors can be found on the Wikipedia. While this topic is … Continue reading →
A recent conversation with Des G4UHZ prompted me into writing this post about the changing ways of today’s Radio Amateur. For those who are wondering what a Boat Anchor is, in radio terms all vintage electronic valve equipment becomes encompassed with the term because it is a heavy piece of equipment with large transformers and tied with rope is suitable for mooring a boat. This is theoretical and I am pleased to say that vintage equipment it is not normally used for this purpose. This post is not about restoration, but more on the loss of essential skills that are … Continue reading →
Built during 1956 – 1962 the Eddystone 730/4 is a professional commercial receiver based on the 680X with 15 valves, 2 RF stages, 2 IF stages (450kc/s), BFO, IF cathode follower output, variable IF selectivity, xtal filter, xtal calibrator, adjustable scale, noise limiter, S-meter, audio filter for CW, fully tropicalised. Cost at time of manufacture £230. This receiver was ordered by the Ministry of Defense in large quantities and used by the Royal Signals The opportunity arose for me to purchase an Eddystone 730/4 spares or repair from the family of a Silent Key at a reasonable price, so I … Continue reading →
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