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All the talk about the audio amplifier on an R-4C intrigues me to ask the question, “What are you doing about the speaker?” With a 50 year old speaker in some cases, what are you replacing it

Gary!!! Bravo! I too used a device like that for mine( TDA7377)... I removed the original jensen speaker, used a lower efficiency driver, yet one with better listening specs. My MS-4 has been modified

I've seen that board on Osh Park. I like the purple one. :D "Paul Christensen via groups.io" <w9ac@...> wrote: -- 73 -Jim NU0C

Yeah, that works. The TDA chips are rock stable and practically bulletproof when implemented properly. I have one of the Velleman TDA2002 modules that I acquired some years back for my R4C, I just

The TDA series and LM380 are fine although I wanted lower noise with no detectable hiss at any setting of the AF control when using studio-grade headphones. The image below shows a discrete class AB

Good ideas Jim and I will get at doing that today. It is windy and raining here quite hard. A good job inside hi hi. I will let you know how it goes. Many thanks for the suggestions and help. Jim

It's a waste of time and money to design an AF amp for the Drake. I used a (now) 75cent complete TDA2030 module from china. Like this one:

At this point I am suspicious of that 1.3 MHz reading. That may be a spurious reading. It seems to me that the VCO should not be able to run there. What is the level of the signal? The frequency

FWIW the TR7 uses an LM380. It works pretty well. "Mike Bryce via groups.io" <prosolar@...> wrote: -- 73 -Jim NU0C

Rob, There’s always the possibility of starting over, making the changes to the artwork as necessary to use newer parts and or different parts with different footprints. I have time to do a few…

Using a doubler off the fil line has been done before.? ?We used a doubler (FWD) and used the 5.0 vac fil on the drake L4B fil xfmr sec winding....to obtain? 12.74 vdc (after V drop from? both

Yes Gary I did the ground on RFC505? when looking at the frequency on the counter and it does drop a lot. So I guess you are saying the High VCO is oscillating at 1.3 MHz . If that is the case there

Right now, just a power supply. I am considering letting go of my A Line (late s/n, the transmitter is essentially an T-4XB) and my L7 (has a Harbach board, graphite tubes and I reworked the power

2c. I would also be interested in the R4C printed circuit boards for the Sherman Mods...I've been collecting parts. TNX & 73, Tom Cunningham WA6VZN in Maryland

After I found that Rob's Product Detector could help an R-4B, and heard that it was ok with him to make the kit ourselves, I re-designed Rob's board except using SMD.? My board is therefore smaller

Hi Steve, Oh. What are you looking to part ways with? 73 Stan KM4HQE

With me, it's the AC-4's I have run a switch to the MS-4 to channel to the speaker whichever rig I'm using at the moment. They take up space. The AC-4's sit on the floor and don't complain much ;-)

Hi Stan, All that was ever installed for an R-4B here in the lab were a few PD-4 product detectors. The AMP-4 needs a good 12 to 14 volt supply at several hundred mA that doesn't exist in an R-4B.

I must report with great shame that I have two MS-4s and I hooked one of them to my badly wounded ICOM IC-735. Discraseful, it is like Queen Camilla turning to prostitution to pay her cellphone bill.

I don’t know how it can read 1.3 MHz if not oscillating… Yes, the lo band VCO should change frequency if you pill RFC502 to ground, pulling the varactor drive from ~21 volts to zero volts. Gary