Dawn
Member
Before it comes up that this radio is old, obsolete or useless, it's actually part of piece of test equipment and not meant for use as a scanner, so I have to troubleshoot the unit.
I have a Uniden service manual for the radio. No problem with the schematics or parts listings and alignment. The manual does not contain any board artwork. The board itself only has markings for some of the components. Does anyone know of any source for any kind or component location.
For the record, the radio was completely dead except for a click on turnon. The culprit was a leaky C 112.
Replacing that cap brought the radio display to life as well as it scanned the wx channels and locked on to them.
Scoping the volume control revealed no audio. Probing the output of the fm detector found audio.
To clear the audio amp, I injected a 1k test signal at the volume control and got audio output, to that cleared the audio stage. Problem is once I did that, I now have audio, but it seems a bit weak. It's hard now to nail down the culprit and which side the problem was. Apparently the strong 1k tone I used probably woke up a 'lytic. It's tedious to try and figure out which caps are which and would be a lot easier if I had some board artwork or component callout which the manual doesn't have.
I don't think SAMS made any photofacts by the time the radio was made. I understand there was a MT or some other publication had known problem component locations from one of Bob Parnass's docs that was posted to usenet years ago.
Anyone can help me here? I'm hoping this unit will die after being shut off for a while so it's easier to scope this out. Right now with it partially working and having no spec in the manual such as a % deviated signal at XX mv should produce x volts ac or full squelch open should produce x volts ac across a load listed in the specs of the manual or any hint of audio stage gain, makes this difficult to troubleshoot.
I have a Uniden service manual for the radio. No problem with the schematics or parts listings and alignment. The manual does not contain any board artwork. The board itself only has markings for some of the components. Does anyone know of any source for any kind or component location.
For the record, the radio was completely dead except for a click on turnon. The culprit was a leaky C 112.
Replacing that cap brought the radio display to life as well as it scanned the wx channels and locked on to them.
Scoping the volume control revealed no audio. Probing the output of the fm detector found audio.
To clear the audio amp, I injected a 1k test signal at the volume control and got audio output, to that cleared the audio stage. Problem is once I did that, I now have audio, but it seems a bit weak. It's hard now to nail down the culprit and which side the problem was. Apparently the strong 1k tone I used probably woke up a 'lytic. It's tedious to try and figure out which caps are which and would be a lot easier if I had some board artwork or component callout which the manual doesn't have.
I don't think SAMS made any photofacts by the time the radio was made. I understand there was a MT or some other publication had known problem component locations from one of Bob Parnass's docs that was posted to usenet years ago.
Anyone can help me here? I'm hoping this unit will die after being shut off for a while so it's easier to scope this out. Right now with it partially working and having no spec in the manual such as a % deviated signal at XX mv should produce x volts ac or full squelch open should produce x volts ac across a load listed in the specs of the manual or any hint of audio stage gain, makes this difficult to troubleshoot.
