Amp in Ranger 2990

[euhara]

Hello everyone

I have one more problem with a Ranger 2990.
This one has a problem with the little amp at the rear of the radio.
Board number EPA010010A
This was evidently not working when I got the radio. Now the radio works fine but when keyed with the amp plugged in the output power drops instead of increasing. With the amp unplugged the main board signal goes on through with normal wattage. The relay is turning on and off in the amp, and there is about 14 volts at TR903 on the center pin all the time in receive mode. Dont know if it should have voltage on the others or not. Don't really want to pull the 2290s to test them unless I have to. No sign of anything being overheated. Hope I have explained this properly so someone can help diagnose this problem. Otherwise I will answer questions the best I can.

Many thanks,
Jim

[euhara]

Guess ya can't win em all. Thanks anyway guys.

Jim

[timrim]

If there is 12 volts on the collector of the 2SC2290's and you have less power coming out of the amp board, then more than likely they are blown. If you have access to a scope, look at the signal on the base and the collector of the 2SC2290's, the collector should have a much stronger signal, if not, they are fried. If you don't have a scope, then you will need to unsolder them to check them.

[Rick]

Is the fault the same on all modes?
What is the voltage on the Emitter of TR903 in AM mode TX?
What is the voltage on the Base of TR901 and 902 in AM mode TX?
What is the voltage on the Collector of TR901 and 902 in AM mode TX?
Be carefully not to slip with your test probes or may blow the 2SC2290 up.

[euhara]

Thanks to both Timrim and Rick,

Rick Here are the voltage readings you asked about

TR903 Emitter transmit AM 7 volts
Tr901 and 902 both have the same voltage on collector or base in both transmit and receive mode in AM
Base 0 volts on both
Collector 14 volts on both

it now does not transmit at all in any mode with amp plugged in.
R901 has been hot now but is not open, also the little VR (no number on board) standing up in front of TR903 smoked slightly before I unkeyed earlier before these voltage readings. Can you give a number for that or a value and how to set it? Probably will replace both of those parts too if need to replace the 2290's and probably do need that. Right??
Hope this is the correct readings you wanted.
First amp I ever had a problem with.
Thanks , Jim

[ramblingman]

Sounds like the 2290 is shorted.

[euhara]

I agree.

Thanks to all,

Jim

[ramblingman]

Try this before you completely change it out.
Unsolder the collector of the trans.,then plug
the board back in.If you get power though it
now.Then you can be pretty sure it shorted out.