UHF Spectra RX Audio problem

ldanna · Post by **ldanna** » Sat Sep 30, 2006 2:21 pm

I am working on a few UHF spectras to move then down to Ham. The help here on the board has been great. Now I am having a weird problem with recieve audio. The reciever un mutes around .25uv but the audio is a low level hum with some digital sounding noises mixed in and only heard if the volume is cranked up. I can hear normal audio from the deteted audio point on the db25 connector. TX audio is fine. With no signal and running squelch down to zero the rx unmutes and the same audio is heard. no normal open squelch noise just what sounds like a carrier with some low level digital artifacts in the background.

Any Ideas welcome.

Thanks
Larry

CTAMontrose · Post by **CTAMontrose** » Sat Sep 30, 2006 4:35 pm

Leaky caps?

Jim202 · Post by **Jim202** » Sat Sep 30, 2006 5:26 pm

Did you check to see if the radio was set up for any
encryption at one time? You may need to install a
jumper to get the audio out of the radio.

Best thing to do is start doing some of the simple
checks. Can't help much with the details, as I don't
have any manuals available.

Jim

jackhackett · Post by **jackhackett** » Sat Sep 30, 2006 6:59 pm

Can you still hear beeps, such as when rolling over from last to first channel, at normal volume?

I've found quite a few Spectras with low receive volume lately, caused by the caps in the control head leaking onto one of the resistors in the volume control circuit, the beeps are mixed in after the volume control so are unaffected.

Also while on the cap subject, I've made a diagram of the cap locations, values, and polarities on a few of the Spectra boards in PDF format (to remind me how they go back in once I've removed the old ones). If y'all are interested I can pass it along, although I don't really have a good place to host it at the moment.

ldanna · Post by **ldanna** » Sat Sep 30, 2006 8:16 pm

Yes Beeps are heard. This is a problem with more than one radio. They were all from the same lot. The encryption post sounds like the next path I should follow Jim. The control head works fine with a 900 meg radio I tested it with (both radios were trunk mount so the control head was not attached.) so I would eliminate that. and the fact that 2 radios have the same condition leads me to believe a common condition. I do believe the radio has securnet and there is a sub board attached to the command board. Is there a missing jumper and where would I it be? I don't have a detailed manual as of today but one is on the way. Is there any software switches to set to bypass securenet? I found one and set it to disable could there be another one I missed?

Larry

ldanna · Post by **ldanna** » Sun Oct 01, 2006 3:20 pm

Here is an update.

Jims suggestion got me going. Aparently the audio path was diverted thru the securenet board. I found a missing resister and a wire jumper that was added. I removed the jumper and replaced the resister and voila normal audio eminates from the speaker. Thanks to all for comments and suggestions.

Regards
Larry