2pill 2879 from mostly used parts

[bob85]

this is a 2x2290 box that somebody tried to make into a class c with inch and half transformers

still does not look like it would work from here

i stripped the board and tinned the grounds to improve the current capacity of the thin foil, even though it is double sided board the foil is thin and the throughpins looked puny, this 2879 will draw way more current than the 2290 class c amp it used to be

output transformer only just fits on the board

input transformer soldered in then changed my mind on which side i will ground

used pills and extra ground strapping ready to be soldered

board back in amp realise the wires are scruffy and not wired correctly

biasing almost done, keeping it simple i used a 2 amp 3 leg 9volt regulator

wiring changed and tidied up some, leaves me the old high/low power switch for use as an AB/C biasing switch later on, had to fix shorted transistor in keying circuit.

thats just about it fine tune biasing and make sure it tracks

flux removed and trimmer added to input
UPDATE
tested it yesterday not totally happy but it works ok. i set bias at .625volts and fired her up, idle current is a little over 200 milliamp, will check it when the amp is hot with no fan to see if i have enough thermal tracking, input vswr is 1.7:1 so its time to play with the bird and some caps to get input down, output match seems to be spot on into the dummyload very low vswr, on the plus side on air reports are great with no detectable compression or distortion of my audio when driven to a little over 200w pep on ssb, my buddy says "all it does is lift your signal but your audio does not change", i am not so sure its as smooth as he says untill i hear it myself but at least the bias is working

thanks go to mack for the used 2879's, greg for getting me the transformers and 305 team dm for the bust 2pill amp

 

[mrblue630]

Looking good Bob, be looking forward to the power output results once you got it all finished.
Now all we need to do is come up with a rebuild name for that amp. How does British Steel Amps sound....lol...i like it.

 

[bob85]

tested it on a 25amp psu today, i can only give it 10w deadkey before it trips the psu,

the trimmer sorted the input tuning almost perfect, its down from 1.7:1 to 1:1 and output reflect hardly moves,

with 10w deadkey i see 160w out @12.75volts, thats all the current limit on the 13.8 volt supply will allow which is about 10w more than my class c 2pill under the same limited test conditions,

the biasing is working fine according to my locals theres absolutley no distortion on ssb so to test them i swapped amps for the class c box and first key they jumped on me telling me whatever i did its sh_ _ _ take it off you sound rough as a bears arse :shock:

i will update when i get a chance to give it 14v and more drive.

 

[CDX197]

IS that the ampower box you got for free?

 

[bob85]

yes it is but thats not to say its a bad amp, in fact the am400 is maybe the best sounding class c box i ever tried on ssb and certainly the most powerfull 2pill, its just that anybody using class c on ssb will get grief from other stations round here including me, i just wanted to see if they really could tell a difference if i swapped classes without telling anybody and they could first i talked in class c they were onto me.

 

[AMPOWER]

those pics are NOT of my amp that bob85 has...

AMPOWER