2pill 2sc2879 amp build

[fodendaf]

I finished the amp yesterday and wired up the fan today. I was advised to use greater than 2 watts for the feedback resistors so I series paralleled 4.

I removed one ssb delay cap to make it 3300uf which gives a more appropriate delay. I couldn't get the amp to tune with 4 wraps on the input so I went back to 3 wraps and followed the 2 pill small case plans more closely.

I replaced the 2 watt 100ohm variable with a 2 watt 100 ohm resistor. the other leg of the pot is 0 ohms at full output so I didn't replace it with anything.

I installed biasing based on the quick and dirty plans in the homebrew section with all ebay parts. That's why I used the torroid for an inductor.

I relocated the power wires as they did not allow access to the output so239 and I had not soldered a ground. The new location better allows space for ferrites. I did not have grommets to hand so I used epoxy putty to secure the wires where they exit the case.

I am not happy with the input swr which is 2:1 and the output swr which needs 0.56uh added with the tuner. But for the time being I run a tuner on input and output and will do so until I educate myself better to remedy it.

Some were humoured to notice that I used 2 2n2222's in parallel for the relay. This was because one would not supply enough current to switch it.

Output power is strange. On SSB with 50 watts drive the amp puts out 200 but on am with 5 watts deadkey the amp puts out 150 deadkey.
I had one good contact today on lsb who complimented me on my station but as the contact was thoroughly inebriated I cannot be certain sure.

 

[fodendaf]

i was muddled up with the output power. i had hit the amp with 50wpep but dropped it back to 20. the amp output was reading average so thats why it was low.

 

[RADIOOMAN]

good stuff. if you have any comments about not making expensive mistakes or such don't hold back. It looks like I'll have to get a 60 watt soldering iron as my 30 watt is giving cold joints on the pcb.

Sometimes the size and shape of the tip is just as important as the wattage of the iron.
A short fat tip will transfer a lot of heat real fast and let you solder real good real fast.
When you solder you want to solder as fast as you can, that way you transfer more heat to the solder joint and less heat to the components that are associated with the pad that you are soldering to.
You should be able to solder medium sized solder joints in1 second or less.
I juse a tip that is short and fat but is conically shaped so that it is blunted but comes to a point at the very end.
It will let you solder on small and large solder joints.
Please don't assume that I mean to say that you can solder surface mount with it, because it is too large for that purpose.

 

[AudioShockwav]

Most excellent post, the tip of the iron needs enough mass to transfer the heat quickly to the parts to be soldered.
Think of the tip on the iron as a heat storage device.....it must store enough heat to insure the solder is flowing well before the tip cools down below what is needed to make a good connection.


73
Jeff

 

[KAP68]

I use a 45 watt 16th inch chisel tip along with silver-bearing solder. Between the larger surface area of that tip and how well that solder flows, I've never needed any more than 45 watts.

 

[Eireguy]

Nice looking homebrew

 

[CB RADIO FREQ]

This amplifier build is very cool. I once had a two pill amp and ended up killing the pills because of over driving it with 5 1/2 watts. Just take this into mind when using your amp. New pills are VERY expensive.