You may wish to consider the following:
Solid state mixer mod: The 6EQ7 (I believe) is notoriously prone to microphonics and earlier I had purchased several spare tubes just for this reason. They were hard to get then. They did not last long, so this mod essentially solved the problem and resulted in a much quieter unit. Solid state product detector: The original product detector was a simple and poor design originating to the R blank line; this fixes the unit and makes the detection more robust and less prone to producing noise. Solid state power supply and capacitor kit (actually 2 kits here): many of the mods need a clean and regulated source of DC power. This mod replaces the original capacitors (probably in need of that any way) and PROVIDES A NEW POWER SUPPLY for the radio. Even up to the C line, when Drake needed a voltage less than 250 VDC, they inserted a (generally) big resistor in the line. This was true for the few solid state devices that were in the radio to start with. This cleans it up by providing a clean and regulated source of DC power and allows the radio to run at less DC current on the power supply. Less current, less heat and less "wear" on the power transformer. The best thing you can do for the radio and the modification that wakes up an otherwise lethargic radio is the 600 Cy roofing filter in the first IF. This is the first application (that I know of) of the roofing filter concept for improved CW operation. It is an amazing modification and turns an ok radio into a sprinter. By measurement, the modified R4C has a 2 KC dynamic range of in the 80 dB range. Up until 15 years ago this was a measurement not worth doing as no radio could perform in that regard. You simply accepted what the manufacturer, any, gave you . It took an otherwise good radio and made it a champ. As I work DX only, it made working a pile up or a contest a pleasure instead of a chore. It is truly amazing and essentially is what put Sherwood on the radio map. Incidentally, it was Bob's poor showing using a pair of new R4Cs on the ARRL 160M CW contest that gave birth to the first roofing filter. Since the intro of this mod, the other manufacturers have copied it and offer it in their new designs. It all began here with the R4C mod that Bob Sherwood did in the 60's. The articles in Ham Radio where they were first published are considered classics. If you do but one of the modifications, do this one. Lastly, the audio amplifier tube and circuit can be replaced with a solid state unit. It provides cleaner audio and reduces the heat and current draw even further. The radio I have has some of the home brew items of those articles as well as the modules purchased from Sherwood. I would recommend going the purchase route as all of the chore of mounting and part placement is already worked out in the radio for you. Good luck on your adventure. You will not be sorry. There are other mods that I have considered but not done that would incrementally improve the radio, but do not have them. There are also some simple mods for the T4X as well and I have used some of these as well. There are some that say that such modifications are heresy and should not be done to keep the stable pure and true. I do believe it is because of these mods that Drake is still alive in the contesting field. I would rather take the pleasure of using a modified radio than have a pristine original that I would never use. What you will end up with is a vastly improved radio, beyond what Drake could have imagined. It holds its on with any other radio I have ever used, Yaesu 1000, Orion, Omni 6+ (with the IRC roofing filter), Kenwood. You get the added smell and history and that full bodied sound that only the tube radios have. Keep in touch and go for it! I envy you for the great adventure you are about to embark on! David Assaf, III W5XU From: drakelist-boun...@zerobeat.net [mailto:drakelist-boun...@zerobeat.net] On Behalf Of Steve Wedge Sent: Friday, December 30, 2011 5:49 PM To: AirRadio; drakelist@zerobeat.net Subject: Re: [Drakelist] R4C Sherwood mods Hi, Max - I'd go for the mods that improve on the solid-state circuits. Because of the period when these radios were made, many of the early solid-state circuits that were used in the C's have had significant improvements - particularly the audio chain. I owned a couple of C-Line sets (one early and one late) and both had the Sherwood audio amps - which I consider to be worthwhile. There was another mod that may not have been Sherwood that involved the third mixer and placing an RF choke there (IIRC, it was in the cathode circuit, but we're dealing with a 25-year-old memory here...) - it applied only to the late-production and got rid of much of the hiss in the audio. Bear in mind that a lot of those mods turned the C-Line into contest-ready radios, which - if you're only operating casually - will not return as much value. I used my C-Lines in several CQWW contests and they definitely held their own. 73, Steve Wedge, W1ES/4 Live free or die: Death is not the worst of evils. John Stark. All my computers have my signature with various pearls of wisdom appended thereto. From: AirRadio <mailto:airra...@dsl.pipex.com> Sent: Friday, December 30, 2011 4:28 PM To: drakelist@zerobeat.net Subject: [Drakelist] R4C Sherwood mods I am thinking about doing the full works Sherwood mods on my R4-C. Which are the best to do? I don't mind how far I go with this, I just want the best receiver for my money, I would like it for Top band use but I know it will be good for all frequencies however 160M is where I want to go. 73 Max M0GHQ/W8BX _____ _______________________________________________ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
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