Low volume PC76XL Philippines

[1jonnyz]

I think I finally got this right. I took the sc2999 out and put in a, 1674 or whatever it was supposed to have. I resoldered the amp and now it seems to be working good. I can hear static and a 1uV signal with no problem at all. I can't hear any static when I have no coax hooked up or when I disconnect the coax from the signal generator, unless I have the NB off. If I hook the coax loosely I get static with the NB on and it's louder when I have the NB off, but nothing when I tighten it up. Does that sound normal? Every other radio I have you can hear static with no coax hooked to it. Thanks for your help!

 

[Robb]

I think I finally got this right. I took the sc2999 out and put in a, 1674 or whatever it was supposed to have. I resoldered the amp and now it seems to be working good. I can hear static and a 1uV signal with no problem at all. I can't hear any static when I have no coax hooked up or when I disconnect the coax from the signal generator, unless I have the NB off. If I hook the coax loosely I get static with the NB on and it's louder when I have the NB off, but nothing when I tighten it up. Does that sound normal? Every other radio I have you can hear static with no coax hooked to it. Thanks for your help!

Sounds about right.
Congrats!

 

[1jonnyz]

I'm not letting you off that easy Robb, LOL!! My Connex 3300HP-ZX has a noise blanker that doesn't work at all. I would like to get it working right before I go back to work next month. Any idea why it makes no difference what position the switch is in? Thanks for your help in the Uniden problem BTW!

 

[Robb]

Start a new thread in the radio repair section and maybe get Xit 13, sonoma, and many others that may have had that issue with that radio. IIRC If that chassis is anything like many other radios, the NB is a convoluted gain stage with a filter out of phase with a with the incoming signal.

Trace that circuit ftom the NB switch with a DMM with the schematic and see if a diode hasn't popped. My guess . . .

 

[1jonnyz]

Thanks Robb!!

 

[DTB Radio]

Be suspicious of 2SC2999's that are currently available. I've been the victim of a couple bad batches. It seems like the original parts are being replaced by cheap copies that aren't as good. Can't say that's the case for all sources. As for your continuing problems, the functioning PA ruled out the audio chip and audio output section completely. I tend to agree that there's a gain or tuning problem between the antenna and de-modulator sections. Could be a cap that's value has shifted over the years, could be a coil that's still not adjusted quite right, could be your 2SC2999 is a cheapo. Put it side-by-side with a known good unit and compare levels at different stages.