UNIDEN HR2510 (repair help needed)

[221Big D]

This radio has very low tx power. You can hear audio from a nearby radio. All modes are same... I dont know much but I'm trying to learn and figure this out..

Q132 Voltages

Rx
B 0
C 14
E 0

TX
B .766
C 14
E .002

Q133

B 0
C 14
E 0

TX
B 7.95.
C 14
E .001

Base voltage on Q133 during tx is way off... Cant figure out why..

Thanks for any help I can get...

221NC

 

[nomadradio]

Because Q133 has failed. Should never show more than about 0.7 Volts between base and emitter. If it shows nearly 8 Volts, that's because it has failed open between base and emitter.

You should have a look at the driver transistor's bias diode D165. It's also blown open circuit. Don't key it with a new driver before D165 is a good part.

73

 

[221Big D]

Because Q133 has failed. Should never show more than about 0.7 Volts between base and emitter. If it shows nearly 8 Volts, that's because it has failed open between base and emitter.

You should have a look at the driver transistor's bias diode D165. It's also blown open circuit. Don't key it with a new driver before D165 is a good part.

73

I replaced Q133 and D165... Radio is now putting out about 5 watts... Someone has installed a 2sc1969 as the final transistor with 2 of the legs crossed. Going to try to find a alternative for that then see what I got... Thanks for the help you was correct D165 wasnt even installed..

 

[221Big D]

Merry Chistmas everyone... Still working on this 2510. Replaced the 2sc1969 final with a mrf455 mounted to heatsink very short hookup wires. Radio is now doing 12 to 15 watts... When trying to set bias for the final no current is being drawn. Any ideas guys what to look at next.. Thanks

 

[Low_Boy]

Check the bias diode first. I have one with a 455 and it should be doing about 30W to 35W with a nice wave form.

 

[221Big D]

Ok thanks for the help guys... Still working on this old radio... I had all ready replaced bias diodes for final and the driver. I used 1n4001. Output is a little better now almost 20 watts am\30 ssb... Still cant adjust bias on the final. When keyed in USB no power or very little is drawn... Any advice out there on what to look at next?

 

[nomadradio]

Measure the DC voltage at the anode (not-banded end) of the bias diode while you're keyed in SSB.

If it's not at least 6/10 of a Volt there may be additional failed components in the bias circuit.

73

 

[Low_Boy]

Question to nomad. Don't the ceramic disc csps in back of the radio near the big torid usually go bad?

 

[NZ8N]

http://www.cbtricks.com/rogerbird/2510/hp2510_dia.htm

This changes Q134 from a Common Collector (Emitter Follower, or a current amplifier, which has a voltage gain of less than 1) to a Common Emitter (conventional) amplifier (voltage gain now more than 1).
This will increase the RF being fed up the TX chain.