Home brew transistor amplifier, share yours

[Radio Tech]

So who has built any?
I built two for testing purposes.
First was a 1 driving 4.
This week end I built a single 2879 variable in an hour.
All junk parts.

Here is one trick I found.
Used circuit boards.
Cut / remove all components for board. With a sander sand down the board.
Go to Lowes / Home depot and purchase a roll of copper flashing.
This is thin copper but pliable enough to work with. Remove the backing and press onto sanded circuit board material. Now the roll of copper is about 29 bucks. But if you use a lot of circuit boards fro “ugly construction” it works great and cheaper in the long run.

Now where to get old circuit boards from?
Old cb’s, stereos, computers, tv’s, ect.

Share your idea's and discuss.

 

[Radio Tech]

Forgot to mention.
For parts try ICAManufacturing.com - Your One Stop Metal Shop!

Anyway I think this is a good way to learn for anyone.

 

[Moleculo]

Have you done any for 6m or higher, or have they all been for HF?

 

[Radio Tech]

Have you done any for 6m or higher, or have they all been for HF?

So far on for HF. I built several tube amps for VHF/UHF/HF. Still learning the transistor thing. That’s why I been playing around with the excuse the term "cb type amps". But I am so far behind on transistor technology it’s terrible. I am learning the basic steps through trial and error on the cb stuff. What I need to learn now is the filtering and how to make it work efficient.

I am in need of a 6 meter amplifier. Just a few hundred watts with 10 to 14 in. I run a Yaesu FT-726 on 6 meters and love to build a transistor amp with a built in power supply. That may be my next project as soon as I can tie up some loose ends. I love to hear thoughts on this. As in what transistors, transformers, ect one would use.

 

[linearone]

Have you done any for 6m or higher, or have they all been for HF?

"HF"

"medical and educational purposes only"

"10 meter use only"

"Do not remove this jumper or out of band operation may occur"

"MARS/CAP mod"

lol


I love it.

 

[-=PEAKABOO=-]

Good subject, I would elaborate more but I am nursing a solder smoke hangover :laugh::laugh:

 

[Radio Tech]

Good subject, I would elaborate more but I am nursing a solder smoke hangover :laugh::laugh:

Hope that goes well for you

This is a amp I built testing. This was my first attemp at building a transistor amplifier. Now there is no filtering on this. And was built after a cb type amp because that is the circuit I had at the time that was detailed enough to follow.

 

[Hawke77]

Very neat, clean work. I'm not sold on silver mica caps across the output transformers. They tend to heat up and fail over time. Fixed mica compression caps are best and are darn near indestructable.

 

[Radio Tech]

Very neat, clean work. I'm not sold on silver mica caps across the output transformers. They tend to heat up and fail over time. Fixed mica compression caps are best and are darn near indestructable.

I totaly agree with that. I did not use them in this because I had none of the correct requirements. Plus this project was for testing purposes anyway.

And thanks for the kind words. Even though it was mostly made from junk parts I tried to keep it neat. The transformers are home brew also. Ends are basic circuit board material and the brass tubibing came off a garden sprayer:w00t:

 

[linearone]

I totaly agree with that. I did not use them in this because I had none of the correct requirements. Plus this project was for testing purposes anyway.

And thanks for the kind words. Even though it was mostly made from junk parts I tried to keep it neat. The transformers are home brew also. Ends are basic circuit board material and the brass tubibing came off a garden sprayer:w00t:

1) I think this is a fine amplifier. The construction is clean and leaves rom to work in there, and shows it was well thought out especially considering the design limitations of the builders heatsink and case combo. It is nicer than 99% of the cb amps I see. Kudos.

2) I like the use of shielded leads in and out of the unit. while not necessary at this power level and frequency it is nice to see thought was put into it. Good Job.

3) As far as dipped Micas instead of those SEMCo metal micas... I try hard to use dipped micas exclusively. I find that the metal ones shift through heating and cooling cycling loosening them up and the mica can slide around and change its value. I have seen my share of them arced over too, not usually on the transformers but when used for final tuning at the combiner for instance etc. The main limitation of the dipped is current handling and cooling. 1 of these problems is solved with the amplifiers fan typically and the other can be solved by paraleling a couple oif them to get the desired value. for instance i use 2 1000v 500pf caps in paralell instead of one metal 1000pf. a quick out of the box inspection with a capacitance meter will show a much tighter tolerance between dipped caps than the metals always.

4) very cool you made your own transformers as well. I like this.

 

[Radio Tech]

1) I think this is a fine amplifier. The construction is clean and leaves rom to work in there, and shows it was well thought out especially considering the design limitations of the builders heatsink and case combo. It is nicer than 99% of the cb amps I see. Kudos.

2) I like the use of shielded leads in and out of the unit. while not necessary at this power level and frequency it is nice to see thought was put into it. Good Job.

3) As far as dipped Micas instead of those SEMCo metal micas... I try hard to use dipped micas exclusively. I find that the metal ones shift through heating and cooling cycling loosening them up and the mica can slide around and change its value. I have seen my share of them arced over too, not usually on the transformers but when used for final tuning at the combiner for instance etc. The main limitation of the dipped is current handling and cooling. 1 of these problems is solved with the amplifiers fan typically and the other can be solved by paraleling a couple oif them to get the desired value. for instance i use 2 1000v 500pf caps in paralell instead of one metal 1000pf. a quick out of the box inspection with a capacitance meter will show a much tighter tolerance between dipped caps than the metals always.

4) very cool you made your own transformers as well. I like this.

Wow, thanks. I never got a rating like that before. Much appreciated. I was thinking I could had done better.

I spent 2 months thinking the thing out before the first drop of solder was applied. I layed the parts out on the board many times before I was happy.

Did not have the right cabinet at the time. I then remembered the old marage amp for 2 meters I had. The transistors are no longer available so I made use of what I had. One reason the circuit board was not cut down to fit. I may change it later.

As far as the sheilded in/outputs, I figured it would not hurt and be a good idea. Try to keep some of the rf from getting back into the input.

Thanks for the info on the metal caps verses the silver dip. I never thought about those problems. I can see where this would be an issue in a mobile unit when it gets hot.

Thanks agian for the good words. It is always nice to hear what other s say about your work.