I have my parts list that I checked at home I'm not there now. I did try it with tr27 removed and I am having the same problem. I will check if I checked those other parts you mentioned if not I will test those thanks.
-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
-
Retevis is giving away Radios for the New Year and Every Member is Eligible. Click Here to see the details!
Another PC122XL TX Problem
- Thread starter Low_Boy
- Start date
The TR27 - it's the limiter, you removed the one thing that would stop any audio - you have a bigger problem. So you may have to backprobe a few spots.
Thinking that although it may TX now, is the TX LED - light on that front panel staying on too?
Then go to LSB or USB mode, TX - check RED TX LED and does the audio cut out then as well?
IF SSB modes work, then the issues is in and around the AM Regulator TR36.
IF this still happens on SSB mode, then there is a power feed line problem.
You may have to double check the front again, those TR31, TR32 and TR33 spots.
Your PA CB switch (very close to that damage)
And that ribbon cable.
Thinking that although it may TX now, is the TX LED - light on that front panel staying on too?
Then go to LSB or USB mode, TX - check RED TX LED and does the audio cut out then as well?
IF SSB modes work, then the issues is in and around the AM Regulator TR36.
IF this still happens on SSB mode, then there is a power feed line problem.
You may have to double check the front again, those TR31, TR32 and TR33 spots.
Your PA CB switch (very close to that damage)
And that ribbon cable.
I was thinking about this on the way home and thinking about scoping from the audio chip. It does happen in AM and SSB. I will take note of the TX RX Light I believe it stayed on all the time.
Also uniden may have changed component brands after the silk screening of the boards. Some transistors are in the wrong way. two of the TR31 thru TR33 I believe two were in the wrong way. They were factory solder joints. I gave seen this before in a couple 148 GTL DX's
Also uniden may have changed component brands after the silk screening of the boards. Some transistors are in the wrong way. two of the TR31 thru TR33 I believe two were in the wrong way. They were factory solder joints. I gave seen this before in a couple 148 GTL DX's
I got sidetracked. Bought a broken Stryker that I wanted to try in my truck. So now that it is working I am back on this.
RX TX light switches like it is supposed to. It is basically doing the same thing on AM and SSB. Different sounds show some swing. but nothing steady. So if it is a feed line problem I tried wiggling the ribbon cable while I modulated and there was no difference. TR 31, 32 and 33 are in the correct way looking at another radio. The silk screen shows them one way but they are actually installed reverse like I mentioned in a earlier post.
AM Regulator is good. I took TR27 out again for testing and same thing. I find it strange that a whistle will show not much of a quick burst of modulation but different tones or sounds will make the scope wiggle and meter move a bit. SSB will show a bit more of a pattern but after the initial burst not enough modulation to put out any power. I rechecked traces and ribbon cable and all look good. I am not sure how to test where the problem lies.
Ok, thinking that the PA CB switch is the hangup. Need to verify that. When in CB mode, the speaker <SHOULD GO> goes quiet. IF the CB PA switch causes the problem - you'd have a ton of feedback, but you're not complaining about it - so when this occurs - put a speaker in the PA jack and see if you have audio when you TX - then we know the front panel is still goofed up.
PA works with a speaker in the PA socket. Speaker does go quiet when switched to CB. Also steady modulation in PA mode not like when in CB mode. PA works perfect.
Ok, and how is the condition of the front panel - the one that had the bad mic socket.
Wondering if we are overlooking something in the front panel?
Because if CB and PA - if one side works, but the audio "dies" on the other...hmmm...
Wondering if we are overlooking something in the front panel?
Because if CB and PA - if one side works, but the audio "dies" on the other...hmmm...
Oh, another question...how is the wattage on the radio.
Waay back earlier in the thread you mentioned R185 - so making sure that R185 is ok...
SSB mode dies too...(D33?)
Waay back earlier in the thread you mentioned R185 - so making sure that R185 is ok...
SSB mode dies too...(D33?)
There are 3 sections dealing with that mic. PA is one, AM is another and SSB the third one - the only common between all three is the mic - which seems to make it to the main PCB, but PA works - so lets presume that is ok, the other two AM and SSB, require the use of TR33, TR32 and TR31 - but they need communication from the FRONT panels USB/AM/LSB switch - so D38 goes hi in TX mode - and mutes the Audio Amp - that seems to work - so the Mic amp - needs 8 volts all the time - so D36 looks back at the PLL - so when you ground Mic pin 3 - the TR32 "looks" to PLL to see if its' in lock - well...is it? You say you get carrier - is it on frequency or just showing stuff on the meter? TX would not go on if PLL is out of lock...
So if TR32 is bad, or PLL out of lock is my only guess...
TR32 is my only last guess, for it is the key to this problem. Mic amp is powered all the time by an 8 volt regulator - so you need to verify the Mic amp "stays" powered - here is a quandary. IT goes back to the front panel - either the CB PA switch one of the poles is "connecting" but the other side isn't. Another factor is the USB/AM/LSB switch - that has two poles and one side switches in 8 volts to turn on a bunch of stuff in SSB mode and puts the AM regulator into full power mode - meaning carrier power in AM mode big time if possible - its' not supposed to.
The olther part of that USB/AM/LSB mode switch toggles the different lines for shift in frequency - and sets AN612 - Using the output of the Mic amp - to send audio in to the TX strip for mixing.
So by your postings you're not having frequency problems - just making it TX again.
You have a TX light but no audio...yet PA works.
Replaced TR31, TR32 and TR33 - got something working...just not audio (at least continuous)and SSB mode you get nothing too...TR27 removed - no effect - replaced.
You'll need to grab a schematic because you need to perform voltage checks to locate a dead section - -this may simply be due to a need for recapping - but when you have physical damage like the front panel shows - there's a lot of tiny work in there that can tear from shearing...
This is a head scratcher?
So if TR32 is bad, or PLL out of lock is my only guess...
TR32 is my only last guess, for it is the key to this problem. Mic amp is powered all the time by an 8 volt regulator - so you need to verify the Mic amp "stays" powered - here is a quandary. IT goes back to the front panel - either the CB PA switch one of the poles is "connecting" but the other side isn't. Another factor is the USB/AM/LSB switch - that has two poles and one side switches in 8 volts to turn on a bunch of stuff in SSB mode and puts the AM regulator into full power mode - meaning carrier power in AM mode big time if possible - its' not supposed to.
The olther part of that USB/AM/LSB mode switch toggles the different lines for shift in frequency - and sets AN612 - Using the output of the Mic amp - to send audio in to the TX strip for mixing.
So by your postings you're not having frequency problems - just making it TX again.
You have a TX light but no audio...yet PA works.
Replaced TR31, TR32 and TR33 - got something working...just not audio (at least continuous)and SSB mode you get nothing too...TR27 removed - no effect - replaced.
You'll need to grab a schematic because you need to perform voltage checks to locate a dead section - -this may simply be due to a need for recapping - but when you have physical damage like the front panel shows - there's a lot of tiny work in there that can tear from shearing...
This is a head scratcher?
Last edited:
All 10v caps are replaced. All caps in audio section are replaced. Possibly the problem lies in the pll section like you said. In the beginning after the first problem was solved I said seems like a cap is flooding charge. Not many original caps left. I will recap the rest of the radio then start voltage checks. The radio is on frequency and has a strong dead key on am. I can turn it up to if I remember 6 or 8 w.
Thanks
Thanks
Ok, make sure the AM power can be adjusted. If AM power can't be adjusted - then the entire issue may be with the regulator itself TR36 - it mixes Bias and audio and feeds the Darlington pair.
As you said and I do agree - a cap or rising voltage somewhere is pinching off the audio.
You had front end (panel) damage - so just about anything goes - even poor ground or a cap shorted and voltage leaks past. (Like the PA - bias can feed into the mic line but it would more distort audio than pinch it off (600 ohm dynamic))
One area that has a cap that gets goofy, is the Mic amp itself - it uses a 100uF 10V and there is also a line filter cap C109/C180 that is a 220uF cap over by the 7808 voltage regulator/Audio amp heat sink flange.
But also - if any works' been done or the damage up front passed into the rear panel in the AM regulator section - this crops up to - no regulation - audio dies too...
So check AM regulator see if any cracks or even shattered diode glass from bending of the board - like a sudden impact - I can see this happening along a side rail...Mic and AM regulator share same side..there is that network back there that feeds in - so if you have carrier great, but if theres' no regulation theres' no audio...
You've got your hands full...
As you said and I do agree - a cap or rising voltage somewhere is pinching off the audio.
You had front end (panel) damage - so just about anything goes - even poor ground or a cap shorted and voltage leaks past. (Like the PA - bias can feed into the mic line but it would more distort audio than pinch it off (600 ohm dynamic))
One area that has a cap that gets goofy, is the Mic amp itself - it uses a 100uF 10V and there is also a line filter cap C109/C180 that is a 220uF cap over by the 7808 voltage regulator/Audio amp heat sink flange.
But also - if any works' been done or the damage up front passed into the rear panel in the AM regulator section - this crops up to - no regulation - audio dies too...
So check AM regulator see if any cracks or even shattered diode glass from bending of the board - like a sudden impact - I can see this happening along a side rail...Mic and AM regulator share same side..there is that network back there that feeds in - so if you have carrier great, but if theres' no regulation theres' no audio...
You've got your hands full...
Some pics to help - X-XYL older radio - note the use of NTE332...
PC122...
PA Mic amp from component side, note the Mic connector pinout and White is Live Audio and Black is Mic Ground.
Mic Amp PA section towards front - FOIL side...
This is Mic amp section...some works' been done to it and needs recapping - kept for reference for moments like this...
AM Regulator - kinda tight in there...
(My version of MAXI MOD - LOL! YEARS ago...SIGH)
:+> Andy <+:
PC122...
PA Mic amp from component side, note the Mic connector pinout and White is Live Audio and Black is Mic Ground.
Mic Amp PA section towards front - FOIL side...
This is Mic amp section...some works' been done to it and needs recapping - kept for reference for moments like this...
AM Regulator - kinda tight in there...
(My version of MAXI MOD - LOL! YEARS ago...SIGH)
:+> Andy <+:
How much for the radio? I have a Ford Focus and there is no room in the thing for much of a radio this would be great if Low-boy doesn't want it let me know.
- No one is chatting at the moment.
