Brian May Deacy Amplifier Build Part 2 - Circuit Board Assembly and Discussion

This is the second in my series of three videos in which I make a replica of Brian May’s legendary Deacy amplifier which was assembled by Queen bass player John Deacon in the early 1970s. In this video I unbox the Knight Audio Technologies (KAT) custom kit of electronic components and assemble it, discussing their key characteristics as I progress.
00:03 - Musical introduction: Dreamer’s Ball by Queen.
00:14 - Introductory remarks.
00:40 - Opening the KAT kit main box.
01:50 - Presenting the components in the kit.
03:46 - Unboxing and discussing the interstage (T1) and output stage (T2 transformers.
05:02 - Discussing the Deacy amplifier circuit (Supersonic PR80 transistor radio and Mullard Reference Manual of Transistor Circuits).
06:05 - Presenting the main tools and equipment - Weller WD1 soldering station, Peak Atlas LCR45 inductance, capacitance and resistance test meter and Peak Atlas DCA55 semiconductor component analyser.
07:08 - Unbagging, testing and sorting the resistors.
08:15 - Installing the resistors onto the circuit board.
09:59 - Soldering the resistors (sequence shortened).
10:23 - Unbagging, testing and sorting the capacitors.
11:38 - Discussing the lead solder and soldering conditions while soldering the capacitor legs (sequence shortened).
12:07 - Discussing, loading and soldering the bias trim potentiometer assembly.
12:33 - Installing the transformers onto the circuit board.
12:57 - Soldering the transformer legs (speeded up) and reviewing the circuit board assembly.
13:22 - Mounting the aluminium and copper heat sink assembly.
13:55 - Soldering the heatsink legs to the PCB track.
14:09 - Testing the vintage TO-1 germanium transistors.
14:47 - Installing the two AC128 transistors.
16:06 - Soldering the AC128 transistor legs (real time).
16:30 - Preparing, installing and soldering the AC126 transistor.
17:04 - Preparing, installing and soldering the AC125 transistor.
17:42 - Reviewing the main components installation.
18:04 - Installing the power supply link wire.
18:21 - Installing and soldering the six VERO pins to allow external input jack socket, speaker and 9V power supply wires to be soldered in place.
18:46 - Soldering the external input jack socket, speaker and 9V power supply wires.
19:05 - Attaching the 470R test resistor.
19:09 - Testing the amplifier output current is between 5 and 6 mA with a Fluke multimeter.
19:26 - Connecting the Deacy amp replica board to a Guyton RS Transporter type guitar and KAT/Fryer Ringmaster treble booster.
19:55 - Illustration of ground interference.
20:06 - Playing some individual notes and distorted chords through an ELAC 6RM/186 speaker rated at 15 Ohms to test the unit.
20:54 - Closing remarks and outro.
Thanks to Nigel Knight for developing the KAT products illustrated in this video and supporting my projects over the years and Mark Reynolds for helping me source some of the items required for this build.
Part 1 - Introduction to the Deacy Amplifier
• Brian May Deacy Amplif...
Part 3 - Making the Cabinet and Final Assembly
• Brian May Deacy Amplif...
Demonstration
• Brian May Deacy Amplif...
Please take a look at my other UA-cam videos on Brian May’s Red Special guitar and musical equipment and visit my website, dsgb.net for further information on the Deacy amplifier and my other Brian May related guitar projects.
#BrianMay #Deacy #Deacyamp #JohnDeacon

[@xavvdb666]

I just discovered the story of this amp, it's completely crazy !!! I need to try one !
😀

[@dsgb]

Definitely find one and give it a try, the sound is unique. 👍🏻😀

[@Maxxeleven]

Great video

[@dsgb]

Thanks Martin! 🙏🏻💜😀

[@davejackson8376]

Although there’s no chance I’ll be in the market for one of these it was an interesting video and… before I’d ever heard of the Deacy amp (we’re talking late 1970s) I made something very similar from an old hifi speaker. I didn’t construct the amp from parts though, I think it was a commercially available unit that just needed the addition of a mains power supply, which I cobbled together without killing myself. Happy days!

[@dsgb]

Happy days indeed. I didn't need to make a Deacy amp replica but I learned a lot by eventually fulfilling a desire and curiosity to make one. 😀👍🏻 I'm pleased that you got some interest from my Deacy video(s) because they took a lot of effort to produce.

[@ValBoschi-ix9cd]

Do you know what ohm of speaker load the circuit needs to see, please?

[@dsgb]

It is always best practice to contact the vendor (KAT) to resolve any technical queries.

[@ValBoschi-ix9cd]

@@dsgb yes, perfect response, thanks