Charles, I'm excited to start this project. I've disassembled a spare R-390a. I plan to make the Solid State Tubes from PC board that I will machine on my computer controlled CNC. I will also use surface mount components. I've found tube socket pins on eBay. I've also ordered as many of the parts as I can identify from your videos. Thanks for the inspiration and some great videos.
Good deal Mack. Just so everybody knows, Mack is an expert on R390's and has refurbished many of them. He has now completed his conversion project and has it in daily use. He is using plug-in "tubelets" that he invented that use a printed circuit board mounted vertically on a tube type base. His radio really looks professional. He has done instrument checks on his radio and compared it to his working tube models and found them to have exactly the same sensitivity. He loves the instant-on feature. There are many advantages. No heat, no tubes, no high voltage, no more resistor burnouts, no electrolytics to worry about and a little less weight. The conversion is permanent and should last for generations without repair. Way to go Mack.
Great job! I appreciate your work, ideas (...wall plugs) and effort. I am courious to hear what your motivation was? Thanks and kind regards from Fürth/Nuremburg Germany
Great work. Surprised to see that the IF cans etc dont need any change as the transistors would presumably have different output/input impedance values than the tubes ?
Each FET is matched to the IF transformer using a choke/capacitor combination. The FET and the transformer are both happy with this method. All the coils in the converted radio tune exactly like the tube model.
Hi Charles, I just was given an R-390A in non-working condition. It looks like it hasn’t been tech-terrorized, so am hopeful to get it running. Your (&Mack) solid-state conversion looks really intriguing, and would allow the RX to be run continuously for cheap! How can I contact you for the document? I did not see an email, nor know your call to look at QRZ. Tnx & 73… 😊
What's the downside? Besides, of course, not being original and possibly not easily reversible. Obviously, lifespan and power consumption would be much much better, but what suffers as a result? Both of my receivers, a R390 and a R390A, are remarkably sensitive and sound top notch. But, I crave another R390A full restore, but with a kick. Maybe a solid state conversion? What do you lose? I'd love to see more technical details and schematics of what you've achieved.
The converted radio is a match to the original tube unit except for 3 minor things. The signal strength meter will not have exactly the same linearity but works just fine, The limiter will not take out strong spikes without inventing a true blanker circuit and the balanced line audio has less output (useless item anyway). Reception in all modes is great. Equally sensitive. W4AX is an expert on 390's and he loves his converted radio. There is a conversion manual available. You can contact me using the email at the end of the video for more discussion.
Hi guys. Great respect for your skilled work! BUT that agressive background hissing I cant stand. I had a german Telefunken E863, also transistor based. I sold it just because of that hissing and love my R390 and R390A not to speak of my Hammarlund SP600. Hours of listening with headphones on. No way with transistor receivers. Gets me headache.
When swapping between the tube radio and the SS radio you will notice the hiss is the same. It is atmospheric noise. It disappears when the antenna is removed. Notice also that the bandwidth control is in the 16KC position which is even noisier than the narrow positions. I have not seen a tube radio that does not receive atmospheric noise, including the R390 and the SP600.
I have restored MANY R390/R390A receivers over the last 25 years. I am intrigued with the work you have done so far. Generally, I like to keep things more or less stock but I do a product detector mod and several audio updates with the usually replacing caps, out of spec R's etc. I also have a good inventory of decent 3TF7 replacements mode by an engineer in Germany. To me your SS 390A has more dynamic range, a little less muddy and less fatiguing to listen to. I see in the notes that Mack has some SS replacements on the way but that doesn't address the AC concerns you mentioned. Or maybe it will later. One thing I really don't like on stock 390's or A's is how they sound tuning across a CW station. I solved this here by running the audio through an outboard 6V6 PP amp. Now it sounds rick much like a Hallicrafters, a SX 101 or National HRO 500. Mr Charles, if you have time, could you record some CW as you tune through several signals slowly. Maybe a couple minutes with your SS 390A. This is one area I am most interested in. Thanks for sharing your engineering progress. You have established a benchmark for others going forward !! Either way, these are great receivers. Maybe not as sexy as a 51J4 or 75A4 but they're GREAT and no problems getting parts.
Hello Glenn, Sorry I cannot reproduce good enough sound with my camera's built in mike to do any justice to a CW video. Believe me however, the CW is very clear and readable and produces good tone. The audio is crisper than the tube model because of the audio amp I'm using. It does not have the muffy sound of the tube model. You would not be disappointed with the reception. There are a few things that don't match the tube model perfectly such as the DB meter and the line audio level. Also the noise limiter does not work as well. Converting to transistors in a radio designed for tubes will always have some areas that don't perfectly match. However, reception is very strong and vibrant. Mack, W4AX has perfected the "tublet" plug-ins and his 390A is in regular use. If you really love the 390A and want to convert one you will not be disappointed. I have added some clarifications and extra schematics to the manual to make it easier for the next person. If you want a manual send me an email.
Thanks for sharing this solid state conversion. Well done. VK6ADA
Charles, I'm excited to start this project. I've disassembled a spare R-390a. I plan to make the Solid State Tubes from PC board that I will machine on my computer controlled CNC. I will also use surface mount components. I've found tube socket pins on eBay. I've also ordered as many of the parts as I can identify from your videos. Thanks for the inspiration and some great videos.
Good deal Mack. Just so everybody knows, Mack is an expert on R390's and has refurbished many of them. He has now completed his conversion project and has it in daily use. He is using plug-in "tubelets" that he invented that use a printed circuit board mounted vertically on a tube type base. His radio really looks professional. He has done instrument checks on his radio and compared it to his working tube models and found them to have exactly the same sensitivity. He loves the instant-on feature. There are many advantages. No heat, no tubes, no high voltage, no more resistor burnouts, no electrolytics to worry about and a little less weight. The conversion is permanent and should last for generations without repair. Way to go Mack.
Great job! I appreciate your work, ideas (...wall plugs) and effort. I am courious to hear what your motivation was? Thanks and kind regards from Fürth/Nuremburg Germany
Great work. Surprised to see that the IF cans etc dont need any change as the transistors would presumably have different output/input impedance values than the tubes ?
Each FET is matched to the IF transformer using a choke/capacitor combination. The FET and the transformer are both happy with this method. All the coils in the converted radio tune exactly like the tube model.
@@charlessmith833 That makes a lot of sense. Did you say that you have a 30 page manual/schematcis that you could share ? TIA
@@yannistzavaras4343 Malista
Hi Charles, I just was given an R-390A in non-working condition.
It looks like it hasn’t been tech-terrorized, so am hopeful to get it running.
Your (&Mack) solid-state conversion looks really intriguing, and would allow the RX to be run continuously for cheap!
How can I contact you for the document? I did not see an email, nor know your call to look at QRZ. Tnx & 73… 😊
My name, call letter and email address appear at the end of the video. I also mention my call KV4JT in the video.
@@charlessmith833 Aha, the jokes on me; I ended the video too soon!
Thanks! 😊
What is the weight of this solid-stated 390A? I hope it's less than 60 lbs!
This is fantastic, Charles.
Did the overall weight of the receiver change? Hopefully, it is somewhat easier to lift the solid-stated radio!
Yes it is lighter but don't cancel your fork lift purchase.
Super ! Best 73
What's the downside? Besides, of course, not being original and possibly not easily reversible. Obviously, lifespan and power consumption would be much much better, but what suffers as a result? Both of my receivers, a R390 and a R390A, are remarkably sensitive and sound top notch. But, I crave another R390A full restore, but with a kick. Maybe a solid state conversion? What do you lose? I'd love to see more technical details and schematics of what you've achieved.
The converted radio is a match to the original tube unit except for 3 minor things. The signal strength meter will not have exactly the same linearity but works just fine, The limiter will not take out strong spikes without inventing a true blanker circuit and the balanced line audio has less output (useless item anyway). Reception in all modes is great. Equally sensitive. W4AX is an expert on 390's and he loves his converted radio. There is a conversion manual available. You can contact me using the email at the end of the video for more discussion.
Hi guys. Great respect for your skilled work! BUT that agressive background hissing I cant stand. I had a german Telefunken E863, also transistor based. I sold it just because of that hissing and love my R390 and R390A not to speak of my Hammarlund SP600. Hours of listening with headphones on. No way with transistor receivers. Gets me headache.
When swapping between the tube radio and the SS radio you will notice the hiss is the same. It is atmospheric noise. It disappears when the antenna is removed. Notice also that the bandwidth control is in the 16KC position which is even noisier than the narrow positions. I have not seen a tube radio that does not receive atmospheric noise, including the R390 and the SP600.
I have restored MANY R390/R390A receivers over the last 25 years. I am intrigued with the work you have done so far.
Generally, I like to keep things more or less stock but I do a product detector mod and several audio updates with the usually replacing caps, out of spec R's etc. I also have a good inventory of decent 3TF7 replacements mode by an engineer in Germany.
To me your SS 390A has more dynamic range, a little less muddy and less fatiguing to listen to.
I see in the notes that Mack has some SS replacements on the way but that doesn't address the AC concerns you mentioned. Or maybe it will later.
One thing I really don't like on stock 390's or A's is how they sound tuning across a CW station. I solved this here by running the audio through an outboard 6V6 PP amp. Now it sounds rick much like a Hallicrafters, a SX 101 or National HRO 500.
Mr Charles, if you have time, could you record some CW as you tune through several signals slowly. Maybe a couple minutes with your SS 390A.
This is one area I am most interested in. Thanks for sharing your engineering progress. You have established a benchmark for others going forward !!
Either way, these are great receivers. Maybe not as sexy as a 51J4 or 75A4 but they're GREAT and no problems getting parts.
Hello Glenn, Sorry I cannot reproduce good enough sound with my camera's built in mike to do any justice to a CW video. Believe me however, the CW is very clear and readable and produces good tone. The audio is crisper than the tube model because of the audio amp I'm using. It does not have the muffy sound of the tube model. You would not be disappointed with the reception. There are a few things that don't match the tube model perfectly such as the DB meter and the line audio level. Also the noise limiter does not work as well. Converting to transistors in a radio designed for tubes will always have some areas that don't perfectly match. However, reception is very strong and vibrant.
Mack, W4AX has perfected the "tublet" plug-ins and his 390A is in regular use. If you really love the 390A and want to convert one you will not be disappointed. I have added some clarifications and extra schematics to the manual to make it easier for the next person. If you want a manual send me an email.