Byron, You may find that any noise you have will be remedied by the power supply and audio changes. I owned two different C-Lines over the years: one early and one late. The earlier one was definitely MUCH quieter than the late one I had, and you will probably not need to do a 3rd mixer mod.
I can't seem to find a schematic for the earlier R-4C. Didn't the early ones use 6HS6 mixers? Steve Wedge, W1ES/4 Time flies like an arrow; fruit flies like a banana. All my computers have my signature with various pearls of wisdom appended thereto. From: David Assaf III Sent: Monday, April 01, 2013 8:40 AM To: Byron Tatum ; [email protected] Subject: Re: [Drakelist] R-4C IC Product Detector Byron: we;lcome to the adventure! The 8 KC front end filter is very broad. The previous owner must have been an AM SWL? Please read Sherwood's and Inrad's info on the roofing filter for the radio. The r4c is the radio where the concept of the roofing filter was made back in the 1970's. It transforms a so so radio to a great one. Drake's r4c, stock, was actually a step backwards in performance. Many still claim the B line superior. Modified, as you are doing will erase that doubt. The power supply is a necessary mod. drake simply had one big power supply and when they needed a different voltage they used large resistors. With age, these resistors change and you end up not knowing the actual voltage. The audio and product detectors are a small increment in the performance of the radio. Please consider Sherwood's third mixer mod. I chased the noise in mine till I read his article and it was the second best thing I did for mine (the roofing filters were the first). Cannot tell you the number of third mixer tubes I tried to make the receiver quiet,. Drake had three or four third mixers in the radio. They were aware of the noise, technology was not there to fix it. It is now. I would not pull off the 10 volts on the Balanced modulator. I would do the 12 volts you need from a separate regulator at the power supply. Look at Sherwood's power supply mod. It is all you need for any mod in the radio. The solid state mixer noted above will need that 12 volts as well. One last thing if you do CW. Look into the AGC mod offered by Sherwood. It is well worth the considerable trouble to do. Good Luck! David Assaf, III W5XU On Sun, Mar 31, 2013 at 8:53 PM, Byron Tatum <[email protected]> wrote: Hello- I am in the process of installing some upgrades in my R-4C, an early one (18K SN range) that has the 6HS6's. The INRAD 8 KC 5645 KC first IF filter was in when I bought it, so at least I have a little bit of protection for that second mixer. I upgraded the power supply with the 7812 regulator and better electrolytic caps all around, per WB4HFN info combined with Sherwood info. Today I built the IC product detector using a TL442CN, installed it and appears all is well. I thought I would post this as I believe the TL442CN is an obsolete device. The TI SN76514 is an identical chip, it was used in the Mihuzo 9 Mhz SSB boards as the balanced modulator. One thing, I am powering mine fom the +10 VDC that is provided for BFO, as that terminal was very near the module. Is itnecessary to have the full 12 VDC on the chip? I wish to do the sudio amp upgrade, mostly to get rid of the heat, but also to have a little better audio. I am thinking of going with the LM383T as done by Sherwood, but saw a video of an R-4C sporting a "D-Labs" audio upgrade. I cannot find any additional info on this. Thought I would ask for advice before I proceeded with the audio changes. Thanks, Byron WA5THJ _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist -------------------------------------------------------------------------------- _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
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