TRC 451 , no receive??

[captian_radio]

Has anyone ever had a radio that developed a problem with no receive?I have a TRC 451 that now has no receive, i have replaced the IC 1182 and now have movement on the meter IE signals but no received audio, I have checked the speaker, tried different mics etc but still no received audio.Anyone have any ideas as this in my onpion is a gerat radio
TNX BOB

[Rick]

If the signal meter is working it is most likely that they is a bad connect or day joint around the Volume control or transistor TR36 is short, this is assuming you have changed IC4 uPC1182H with a new audio amp. Also check you have not soldered two or more connections together.

Rick.

[captian_radio]

Tnx for the info Rick, well i did find a cap that was burned up last nite, c183 10 volt 100uf, replaced it but still no receive audio, checked tr 36 it is still ok, i have replaced 1182 ic 1, i have followed the schematic and c183 is connected to ta75902p but my 451 has a 2902n chip there instead, havent checked that yet.C183 is near where the power leads are soldered to the board,and the protection diode was shot .this one has really got me bugged , i am almost obsessed with trying to get this thing going, as i said it was a really great old radio and worked super before this happened.
Bob

[Rick]

Question is the signal meter work on RX?

If so check the voltages around IC4 and let me know what they are?

If you have a small headphone try connecting it from the hot side of the volume control (R44) and ground you should be able to hear some RX audio.
Let us know how you get on.

Rick.

[captian_radio]

Hi Rick, well i have lots of movement on the s meter , do you mean check voltages from the ic 4 if so what pins and do i use the case a a ground point.I did find a cap that was blown out , it was c183 near the back right corner, replaced it and still the same.
Tnx Bob

[Rick]

You need to give all the voltages at each pin of IC4.

Try a small headphone try connecting it from the hot side of the volume control (R44) and ground you should be able to hear some RX audio.

If you do not know which is the Hot side, look at the volume control from the rear there are 3 contacts one is connected to ground (connect one wire from you headphone to hear) connect second wire from your headphone to to the center connect, by adjust the volume control you should be able to hear some audio. Let us know how you get on.

Rick.

[captian_radio]

Ok Rick , i can do that but i need to know if i use the case of the radio as a ground point when checking each pin of ic 4 , I tried that this am and am getting some voltages on some pins like 1.7 .256 and the rest are very hard to read as they fluctuate almost like ac voltage, i will try the ear piece test later today.
Tnx Bob

[Rick]

Ground well you can use the black wire where the power plug comes in to the radio or any of the tin tuning cans like (L1, L2 and so on). Put the negative probe from you mltimeter on a tin tuning can or the negative wire (Black at power plug) and positive probe on the pins to test and set your multimeter to DC.

Rick.

[captian_radio]

Ok Rick here are the voltages i found pin1,.431 pin2, 1.8 pin3 .420,pin 4.413,pin5 .415,pin6 5.9 pin 7 9.2.i also tried the ear piece with no luck.
tnx Bob

[Rick]

You have a PM.

Rick.

[captian_radio]

Well my thanks go out to Rick in helping me trouble shoot the problem with my Trc 451,Rick has spent a lot of time and effort toward helping fix this radio, in my opinion he has knowledge of radios that is bar none.Great job Rick and again thanks for your patience and teaching that you have taught me with this radio.maybe we can actually talk sometime when the F2 propagation comes back in a few years
Cheers Rick
Bob

[Anonymous]

Rick has helped me out on more times than i can remember he is such a grate guy. I wish there was more like him around. Keep up the good work Rick. Look forward to meeting up with you at the QRP do next month. We all miss you on top band.

73s 51 Tony.

[bbgun]

You have a PM.

Rick.

What did you mean "You have a PM"?