Realistic TRC-427 Audio Mod 'GoldFinger'

[711]

I’ve been hanging in the shadows here and there . I never did build my Phreaker board , I may A/B/C it in an 880 i have a few of. Been thinking of doing it for the FB group I help . I already injected and Mauldulated that radio. I’m going to build Phreaker’s board and a board I built a few years ago when Bow was talking about his mod. The Mod tranny pumps out a 40 volt peak to peak AC signal where as the darlington pair your Phreaker board does is still limited by the stock supply or 12 volts peak to peak. Run a separate supply like the Mauldulator does to the darlington and you can pump the same numbers out

 

[LeapFrog]

711, waving a big hand from the sand pile.
I bought a 24 Volt Mean Well to help with the voltage differences.

I was going to release my own spin on this, but haven't got the time yet.

Not a lot to it, and it's not some closely guarded secret or anything.

But I could see a mountain of questions being posted so the topic will really need its own thread.


This is the schematic that got me started down this path,
CB Phreaker has helped me out quite a bit along the way.

 

[711]

I was present when Bow did that. I've placed 38 volts on the supply line. If you scrub the datasheets you can learn a lot. I run a beefy cousin of the TIP120 in all my Mauldulator and modulator type circuits. Has lots of gain and can handle the triple the current. I need to build an Australian Mosfet version of this modulator. Suspect itll do the same but be more robust

 

[LeapFrog]

Yes I've been through quite a few datasheets, and tested a few different transistors!

It's a lot of fun, finding what works better..
I learned one lesson the hard way, never trust a random eBay seller to provide OEM parts, a lot of knock-offs and imitation transistors (if they even work) have terrible hFE and fail before the "max" rating in the datasheet.
Quality parts can make a world of difference.

Here is a short clip of a 29 with the mod producing various waveforms.

 

[TheRealPorkchop]

Alllllllll abbbboooooard!!!!

 

[543_Dallas]

There's a negative peak limiting circuit in this thread that may be useful to someone. It also has a filter to prevent excessive bandwidth. 20k wide AM is cool for bragging rights but 10k total bandwidth or 5khz of audio is the starting point of diminishing returns IMO.

http://amfone.net/Amforum/index.php?topic=42552.0

 

[500kpot]

1st time poster here and Ive been researching this thing and I ended up here from youtube and google, How many watts do you get with a 24 volt power supply?

Your video looks cool. I really want to know how to do this, can you post more information about the supporting circuits?

 

[LeapFrog]

That video is not my creation, that was CB Phreaker's work.
I am still waiting on regulators to arrive, so the 24 Volt power supply is just sitting at the moment.
Once I have it running on 24 Volts I will make a video
hi-lighting the details of what is involved.

CB Phreaker apparently doesn't have any interest in marketing this idea (selling a PCB) so I am going to release the complete detailed schematic of my setup, and possibly a PCB file for anyone who wants to build a "custom modulator" for an AM only CB radio.

This has been referred to as an AM regulator mod, Darlington modulator, and other names but I refer to it as the Wabi-Sabi.

The most power I've got at 13.8 Volts was about 4 Watts carrier to 16 Peak, but that was about a year ago.. and seeing as how I didn't need anymore drive than that I left it alone, & simply reduced the carrier a little to increase the amount of positive modulation, and ran with a modified pre-amp.

I really should have created a PDF explaining the process, as I had planned.... but allow me to grab the schematic files and to write up a F.A.Q. document + how to and I will post the details here on WWDX for anyone who wants to try it.

 

[711]

I'm building my Phreaker board now. Gonna install it next my Top Gunn NPC board I made also to side by side compare them. Before anybody reading some previous post about running a 24 volt supply to their radio, keep in mind the 24 volts is only isolated to the darlington. Ok disclaimer put out there , carry on. lol

 

[LeapFrog]

I'm building my Phreaker board now. Gonna install it next my Top Gunn NPC board I made also to side by side compare them. Before anybody reading some previous post about running a 24 volt supply to their radio, keep in mind the 24 volts is only isolated to the darlington. Ok disclaimer put out there , carry on. lol
View attachment 27534 View attachment 27535

I like that NPC board, it is a thing of beauty!

And CB Phreaker's board, is really high quality, he made the holes just big enough for the leads, nothing sloppy about his work! Very tight, and very clean!

I'm typing up a description of the modification process.
This is from my experience and not the end-all be-all of this style of modification, but I figure it can help those who are interested.

Yes thank you for clarifying that, DO NOT run 24 Volts to the input of your radio, unless you have extensively modified the radio for that, the 24 Volts can be regulated with the use of an LM338, to limit the amount of positive peaks with "VR2".

I'm considering a custom input choke and a 7814 or 7812 to power the "Rest of Radio"
(PLL, pre-amp, etc) while the 24 Volts is fed to the 338 and then to the collectors of the modulator.

 

[TheRealPorkchop]

Yes, explain this NPC board you have there, that is a very nice looking board.

 

[711]

I like that NPC board, it is a thing of beauty!

And CB Phreaker's board, is really high quality, he made the holes just big enough for the leads, nothing sloppy about his work! Very tight, and very clean!

I'm typing up a description of the modification process.
This is from my experience and not the end-all be-all of this style of modification, but I figure it can help those who are interested.

Yes thank you for clarifying that, DO NOT run 24 Volts to the input of your radio, unless you have extensively modified the radio for that, the 24 Volts can be regulated with the use of an LM338, to limit the amount of positive peaks with "VR2".

I'm considering a custom input choke and a 7814 or 7812 to power the "Rest of Radio"
(PLL, pre-amp, etc) while the 24 Volts is fed to the 338 and then to the collectors of the modulator.

In the early days of my Mauldulator building, I built many different buck converters, regulating that far down will cook those regulators find a really good heatsink

 

[711]

Yes, explain this NPC board you have there, that is a very nice looking board.

Nothing to it really, just the Ranger darlington setup with both the NPC and Top Gunn modulator circuit in there with the addition of a jumper to remove either from the circuit. Just made it easier for me to test either in my early Mod tranny replacement days. I leave the fancy circuit designing to geniuses like Nomad , I'm just an average hobbyist lol

 

[711]

One of my early schematics to figure out how the Top Gunn modulator works

 

[TheRealPorkchop]

I’ve always wanted to know what was in that TGM under that epoxy or whatever they coat it with.