Hi to all.
I searched all day for answer and nothing.
I have President Lincoln radio that has had blown output and driver transistor along with copper traces and one bias resistor. I replaced driver 2sc2166 and final 2sc1945 from Eleflow technologies but output is now very weak and RX
is working nice.
After hours of thinkering and soldering I could not find solution. So if anybody has any idea please let me know.
How i troubleshoot it:
1.Turned radio on an measured output and it was very weak (around 3mW)
2.Started measuring DC voltages along chain of output transistors and everything is according to specs.
3.Started measuring AC voltages on bases and collectors on chain of transistors after IC106 and this is where becomes very strange.
Output of IC106(PIN 9) is around 640mV rms
Q134 base(83mV), emitter(90mV)
Q124 base(79mV), collector(340mV)
Q133 base(40mV), collector(170mV)
Q132 base(20mV), collector(150mV)
Output on antenna with connected dummy load is 375mV
(Notice that after each coupling between transistors lot of signal is lost)
4. Started to inspect inductors,chokes and capacitors everything is fine(even removed glue)
5. Changed all el. capacitors in TX
output section and ceramic that are in RF path
6. started to get very frustrated...
Nothing is changed. Everything is the same as it was when i replaced burned components.
I know there are some real gurus here so I would appreciate any help.