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uniden washington
- Thread starter kaos513
- Start date
As I mentioned my technical knowledge is extremely limited. I do own a Washington, and Madison and have experienced other difficulties similar but not exact as the one you're mentioning. I couldn't read all the replies as there are so many, but sometimes going for the simplest troubleshooting issue is the best way to go. I'm going to assume you do not have another microphone wired for the Washington. I'm only assuming that because I would suspect it would have been something you would have mentioned. I would suggest either borrowing a 5-pin Uniden wired microphone (4 pin for the first edition. I think?) or checking out the mic cord connections at the plug, and the ones at the microphone. In all honesty I don't know if this is good advice. But I can't tell you how many times I've been driven crazy trying to figure out what might be wrong with a transceiver, and its audio issue turned out to be a simple microphone wiring one. I hope this helps although I know it's probably a long shot, and most likely has been suggested in some of the other reply. Or you have already went that route. I hope that you inform everyone what the issue was when you eventually find it. I have little doubt that you will. Especially with all the excellent radio hobbyist with an abundance of knowledge that congregate right here on this form. The total knowledge of these guys must equal about a thousand years of experience. 73's ps. Sometimes one is better off finding someone willing to call you and walk you through certain steps. I don't know if loose Cannon has the time or wouldn't mind doing so. But there are other people who are extremely knowledgeable about the Washington who I'm sure would help you better in a private message or telecommunicating situation. Ask somebody if they're willing to private message you. If so send them your phone number. Most if not all or close to 99% of the people on this form are good honest people. I've gotten help from so many of them that I have lost count. I have even sent equipment out to members who were glad to repair whatever it was I needed for a fair fee. LooseCannon is a wizard with the Madison. So I wouldn't be surprised if his knowledge on the Washington is equal to that of the Madison. I hope looseCannon don't get angry at me for throwing his name out there. LOL very good people.
I read your original post. When you say there is no carrier but 100% modulation what exactly do you mean? When you key the microphone I get what you're saying there is absolutely no dead key output. But when you say 100% modulation is achieved when modulating are you substituting 100% modulation for pep power? I'm assuming that you are getting pep. When you modulate on AM what is your pep output and what type of meter are you using in order to get your output readings? And just to clarify when you key the microphone on USB/LSB and modulate into the microphone you are showing appsolutely no output?
i do get am power such as 3 1/2 watts on am receieve is good because i have test radio when i talk on test radio i hear my self perfect on my uniden washington just dont have modulation at all.
Ok, back to the section we had problems with before. When you had some type of "squeal" when you turned up the volume control.
Now, you have no modulation to the TX but you have carrier...
Is carrier adjustable? IF so good!
- Recheck that spaghetti mess where the RX Speaker wire that goes to CB/PA switch - leads to, it's a giant set of pads with TONS of wires running out between the EXT speaker and PA Speaker jacks...The radio should show a short from that pad (Output of C118 goes into this) to CB PA switch, and FROM CB side of the Switch - back to the board towards EXT Speaker - and then to the Internal Speaker - THEN - FROM INTERNAL SPEAKER - back to that OTHER pad, that then has wires that route to other spots including the MIC jack Pin 5 - for the speakers ground - BACK to that area for Pin 5's Ground.
- We just may have a FAILED cap or a wiring issue - with the Microphone's Pin 5 wire - it routes here to ground the RX side of the speaker - because when you key the Mic, not only does the MB3756 toggle it's output to stop RX and turn on TX (Pins 3 and 4 of the Mic short) - Those LED's turn from Green to Red - Pin 5 opens up to turn off that speaker, then the radio is forced to send the Audio Amp output thru the big cap (C118) , into the little cap (C119) and into the Darlington pair - with a little help along the way...
- Pin 4 of the Mic - goes to Ground - it's your COMMON on the switch that handles the MB3756 and Speaker ground., The SHIELD - is for Pin 2 - and it's a separate ground location - to handle Audio from Pin 1 of the Mic handset
If not - thats' bad - for that means we have to take a look at that "Darlington Pair" and see which one of them is blown - or both because the one took the other out and it's shorted...
That means you have to remove and physically test TR34 (2SD1419 / 2SA1012 or 2SB754 - PNP Heavy duty TO-220 style case) and TR35 2SA945 or equivalent...Then also check to see if Cap 120 is ok 10uF 16V may need to be replaced with a 50V 10uF instead...
Yes it tx's in upper and lower sideband but no audio.when I key up the meter jerks a little bit still no audio on all bands.
More than once we have seen a radio that has had the limiter transistor TR32 removed. We put a 2SC945 back in at TR32 and now there is no AM transmit audio. Take the center leg of TR32 loose, and the AM modulation comes back.
Closer inspection reveals that a resistor has been cut, probably because someone thought this would boost the AM modulation. When TR32 was gone, it had no effect. But when we put that limiter transistor back, it caused TR32 to reduce the AM moculation to zero.
If you remove the solder from the center leg of TR33 so that it's loose and doesn't touch the foil pad, does the AM modulation come back?
If so, you could just leave it that way. Won't cause trouble setting the ALC modulation limit for sideband, but the AM audio would have no limiting.
Easy to try, at least.
73
Closer inspection reveals that a resistor has been cut, probably because someone thought this would boost the AM modulation. When TR32 was gone, it had no effect. But when we put that limiter transistor back, it caused TR32 to reduce the AM moculation to zero.
If you remove the solder from the center leg of TR33 so that it's loose and doesn't touch the foil pad, does the AM modulation come back?
If so, you could just leave it that way. Won't cause trouble setting the ALC modulation limit for sideband, but the AM audio would have no limiting.
Easy to try, at least.
73
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Did you ever check that D39/D40 stuff - D41 is also involved in that - in RX it is supposed to quiet the Mic line so you don't get crosstalk or a squeal...turns on Limiter to quench the line so you don't pick up "open mike night" underneath a noisy apartment or a "buzz" - bad transformer from some source of noise...
So whatever you did to fix the squeal, let's investigate...
So whatever you did to fix the squeal, let's investigate...
kaos,
the things im going to suggest are separate from what others are helping you with because i don't want to de-rail anyone else's troubleshooting advice.
so, my advice may just be a repeat of what someone else said, and i may ask you to do something that you have already done. if that's the case, just let me know you've already been down that road.
TO THE OTHERS who are helping kaos with this problem, please don't let my posts interfere with what you are trying to accomplish.
admittedly i have not read all of the posts, but i do believe that the radio is working somewhat normal, but has no modulation in any mode.
if there are other issues or weirdness, please tell me.
first thing's first, please confirm that the mic you are using is good and works on other MB8719 radios.
next, you need a scope. i think you already have one, but please confirm that too.
with all of the mods and crap that was done to this radio, i believe that the highest probability for why the radio still isnt working is that you have a wiring issue in one of the places where you were working on putting the radio back to stock.
the first thing i will ask you to do is check the areas where you had to re-wire things, like the switch PC board, the speaker section, and the mic jack inside the radio.
get your schematics, and some colored markers and trace out the wires using different colors, then re-check that you ran all the wires to the correct traces.
all that is ok?
lets start right at the mic jack. radio off for this test.
set your multimeter to ohms, and put one lead on the NEGATIVE lead of C121, and the other lead to pin 1 of the mic jack.
you will read a resistance here, and i would like to confirm that this resistance moves up and down evenly when you turn the DYNAMIKE control.
i like to use an analog meter for this so you can see any irregularities in the movement.
this is good?
remove the solder from the middle (collector) leg of TR32 and confirm that it is not making contact with the PC board trace.
now check your audio again. the reason is that if TR32 is shorted C to E or if C192 has gone short, that will shunt all your audio right to ground.
if the audio came back with the Collector of TR32 removed, then check it and C192.
if the audio did not come back, leave TR32 collector unsoldered for now to keep that part of the circuit out of the equation.
next step is to get your scope probe and put it on the middle leg (collector) of TR29, and speak into the mic. do you see the signal moving around on the scope (modulating)?
I don't know for sure that the signal is measurable on the scope at this stage, but i would think it is, i just don't know how sensitive you will have to set your scope, so try different settings to see if you can get a reading.
(some of the others here may be able to help with that)
let's stop there and see what you do or don't get.
im just trying to come at this from a different direction.
LC
the things im going to suggest are separate from what others are helping you with because i don't want to de-rail anyone else's troubleshooting advice.
so, my advice may just be a repeat of what someone else said, and i may ask you to do something that you have already done. if that's the case, just let me know you've already been down that road.
TO THE OTHERS who are helping kaos with this problem, please don't let my posts interfere with what you are trying to accomplish.
admittedly i have not read all of the posts, but i do believe that the radio is working somewhat normal, but has no modulation in any mode.
if there are other issues or weirdness, please tell me.
first thing's first, please confirm that the mic you are using is good and works on other MB8719 radios.
next, you need a scope. i think you already have one, but please confirm that too.
with all of the mods and crap that was done to this radio, i believe that the highest probability for why the radio still isnt working is that you have a wiring issue in one of the places where you were working on putting the radio back to stock.
the first thing i will ask you to do is check the areas where you had to re-wire things, like the switch PC board, the speaker section, and the mic jack inside the radio.
get your schematics, and some colored markers and trace out the wires using different colors, then re-check that you ran all the wires to the correct traces.
all that is ok?
lets start right at the mic jack. radio off for this test.
set your multimeter to ohms, and put one lead on the NEGATIVE lead of C121, and the other lead to pin 1 of the mic jack.
you will read a resistance here, and i would like to confirm that this resistance moves up and down evenly when you turn the DYNAMIKE control.
i like to use an analog meter for this so you can see any irregularities in the movement.
this is good?
remove the solder from the middle (collector) leg of TR32 and confirm that it is not making contact with the PC board trace.
now check your audio again. the reason is that if TR32 is shorted C to E or if C192 has gone short, that will shunt all your audio right to ground.
if the audio came back with the Collector of TR32 removed, then check it and C192.
if the audio did not come back, leave TR32 collector unsoldered for now to keep that part of the circuit out of the equation.
next step is to get your scope probe and put it on the middle leg (collector) of TR29, and speak into the mic. do you see the signal moving around on the scope (modulating)?
I don't know for sure that the signal is measurable on the scope at this stage, but i would think it is, i just don't know how sensitive you will have to set your scope, so try different settings to see if you can get a reading.
(some of the others here may be able to help with that)
let's stop there and see what you do or don't get.
im just trying to come at this from a different direction.
LC