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uniden washington
- Thread starter kaos513
- Start date
@kaos513 - you're posting with a guy whom used to own one, loved the radio just couldn't keep it - lost in a FC sale when my world blew up in 2008 ~2010.
I can appreciate someone still utilizing the older style systems and in a way , helping me to understand that chassis even more. It helps me, just by talking about it or the many mods I've seen placed in radios and why people complained that they didn't always "track" RX to TX very well. R187 and parts like it, placed in spots along the way to the tuning section - tied in to whatever feedline or RX or whom heaven knows... you now have an answer due to the nature of how they wanted to keep the pot (Voice lock) Linear thru the tuning range - no one ever points out the simpler facts that such designs have divider networks in them and you need to follow thru on the mod to fix all aspects and recover the OEM range once the unlockings' been done. Else TX and RX will "offset" due to the R187 and the like sucking power to feed into the RX line or R187 transferring power from RX line into the Voice Lock Clarifier voltage but not while TX'ing so they get frustrated and screw up a good thing by a slice and dice maneuver.
I can appreciate someone still utilizing the older style systems and in a way , helping me to understand that chassis even more. It helps me, just by talking about it or the many mods I've seen placed in radios and why people complained that they didn't always "track" RX to TX very well. R187 and parts like it, placed in spots along the way to the tuning section - tied in to whatever feedline or RX or whom heaven knows... you now have an answer due to the nature of how they wanted to keep the pot (Voice lock) Linear thru the tuning range - no one ever points out the simpler facts that such designs have divider networks in them and you need to follow thru on the mod to fix all aspects and recover the OEM range once the unlockings' been done. Else TX and RX will "offset" due to the R187 and the like sucking power to feed into the RX line or R187 transferring power from RX line into the Voice Lock Clarifier voltage but not while TX'ing so they get frustrated and screw up a good thing by a slice and dice maneuver.
In regards to the squeal, how are the speaker grounds - are they to the back panel / case or are they to foil ground - as in to RETURNS on the board, not to panel or chassis.
And - check speaker to make sure that it's spyder cage is not shorting itself to the speaker terminals on the speaker itself - for that induces (forms) a ground loop...
To help me further take the photo of the top of that switchboard - which one of them is the CB / PA switch? For the PA switch has two wires off of it going back to the main PCB that grounds the CB Mic amp side using D39 and D40 - BACK TO PIN 5 of the MIC SOCKET. So if works been done - recheck the mike socket.
This "talkback" sounds like EXT and PA speaker crosswired.
Now there are mods for using the PA jack and EXT Sp jack, together, to make talkback.
So if that is the squeal you're getting - it can be from a BOTCHED rewire when they tried to fix it before you.
Again back to that Blue wire from Pin 4 of Audio Amp. But also for Nomads' reference to the Mic amp - if that is still going - the PA side of the switch network may need a little more re-work.
And Pin 6 of the MB3756 - that is the RX toggle - the RX uses an audio pre-amp TR36 gets it's power from R114 a 1K into the supporting circuit - then goes to Pin 4.
So if volume - ever so slightly bumped up - means that you're speaker output is feeding back into the Audio amp.
That is your feedback squeal...or tone so it may be from bad caps of wrong value or you have some caps still needing replacement in the Audio Amp TA7222AP section. That also includes the PRE-AMP TR36.
And - check speaker to make sure that it's spyder cage is not shorting itself to the speaker terminals on the speaker itself - for that induces (forms) a ground loop...
To help me further take the photo of the top of that switchboard - which one of them is the CB / PA switch? For the PA switch has two wires off of it going back to the main PCB that grounds the CB Mic amp side using D39 and D40 - BACK TO PIN 5 of the MIC SOCKET. So if works been done - recheck the mike socket.
This "talkback" sounds like EXT and PA speaker crosswired.
Now there are mods for using the PA jack and EXT Sp jack, together, to make talkback.
So if that is the squeal you're getting - it can be from a BOTCHED rewire when they tried to fix it before you.
Again back to that Blue wire from Pin 4 of Audio Amp. But also for Nomads' reference to the Mic amp - if that is still going - the PA side of the switch network may need a little more re-work.
And Pin 6 of the MB3756 - that is the RX toggle - the RX uses an audio pre-amp TR36 gets it's power from R114 a 1K into the supporting circuit - then goes to Pin 4.
So if volume - ever so slightly bumped up - means that you're speaker output is feeding back into the Audio amp.
That is your feedback squeal...or tone so it may be from bad caps of wrong value or you have some caps still needing replacement in the Audio Amp TA7222AP section. That also includes the PRE-AMP TR36.
Turn up the squelch until it turn on (if it does) when the volume is turned down low like that - should be completely quiet.
If not, that is related to TR13 (1st AF amp from conversion and TP3 output) and TR15 and TR14 (Squelch amp section)
So if Squelch mutes, then that is a TR36 and or Volume Control issue...Volume control is shielded cable - so if works been done - all routing needs to be checked - not just connection point to point but routing of cable itself.
Usually signifies a tweak or two but I'll wait for you to decide where and what to do next..
Tweaks are more of a last resort - so do the above test and I'll see what else we can offer to help.
If not, that is related to TR13 (1st AF amp from conversion and TP3 output) and TR15 and TR14 (Squelch amp section)
So if Squelch mutes, then that is a TR36 and or Volume Control issue...Volume control is shielded cable - so if works been done - all routing needs to be checked - not just connection point to point but routing of cable itself.
Usually signifies a tweak or two but I'll wait for you to decide where and what to do next..
Tweaks are more of a last resort - so do the above test and I'll see what else we can offer to help.