UNIDEN WASHINGTON, no sound(tx,rx,pa)

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UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Tuesday 3rd Mar 2009, 7:45

Radio Make and Model: uniden washington
PCB Number: PC 385AG
PLL Number: MB8719
Test gear available: multimeter, watt meter...bk2040, 1040
Symptoms: no output on any mode, no rx audio,

What is working: radio lights up perfect, tx/rx light changes when keyed...no rx audio, meter does not move on rx, shows a small dk on AM

What has been tried: replaced ic 4 and ic 5, tr37, d44... replaced the caps in front of 3756(c164, c133)

Did it suddenly happen ?: radio had been setting idle for some years...when fired up...
Anything else that may be of help?: has had the channel mod done to it, very neat job i might add

anybody have any ideas...i have been searching through the forum...for lil tidbits of info on these radios... replacing some parts trying to get some wattage or audio.. no luck

thanks in advance fellas

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by The Defpom » Tuesday 3rd Mar 2009, 14:37

There is a capacitor near the audio amp that can short out when it is old, it kills the audio, check C107.

Also what voltages are you getting on IC5 ?

does SSB TX work at all ? is there an actual carrier getting out on AM ?

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Tuesday 3rd Mar 2009, 17:39

The Defpom wrote:
There is a capacitor near the audio amp that can short out when it is old, it kills the audio, check C107. replaced c107 and a ton of other elect caps

Also what voltages are you getting on IC5 ?

RX TX am TX usb TX lsb
1. 12.48 12.41 12.45 12.45
2. 6.00 5.97 5.99 5.99
3. 0.00 for all modes(rx/tx)
4. 0.00 for all modes(rx/tx)
5. 1.15 1.16 1.16 1.16
6. 1.15 1.16 1.16 1.16
7. 0.00 for all modes(rx/tx)
8. 0.00 for all modes(rx/tx)
9. 6.20 for all modes(rx/tx)
10. 11.75 for all modes(rx/tx)


does SSB TX work at all ? is there an actual carrier getting out on AM ?

no ssb tx. a carrier less than 0.5 of a watt on AM

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by The Defpom » Tuesday 3rd Mar 2009, 18:23

I think you checked IC4 instead of IC5, IC4 is the audio amp, IC5 is the MB3756

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Tuesday 3rd Mar 2009, 18:29

The Defpom wrote:I think you checked IC4 instead of IC5, IC4 is the audio amp, IC5 is the MB3756
you are right
IC5
rx AM USB LSB
1. 8.51 8.45 8.51 8.51
2. 12.47 12.34 12.44 12.44
3. 8.52 8.47 8.53 8.53
4. 0.00(all modes rx/tx)
5.12.47
6. 8.51 0.52 0.56 0.56
7. 0.00(all modes rx/tx)
8. 0.24 8.45 8.51 8.51

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Tuesday 3rd Mar 2009, 18:41

bump for new info

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Sunday 8th Mar 2009, 3:23

anybody??

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by The Defpom » Sunday 8th Mar 2009, 10:27

I kind of forgot about this one..

Have you tried doing an alignment on it, and did you notice anything that seems incorrect during the alignment ?

It is likely to just be a capacitor (or a bunch of them) somewhere that are killing the DC supplies to certain parts of the circuit, the voltages you gave for the MB3756 look ok.

What voltages are you getting on IC3, IC6, TR34, TR35 and TR9, TR10, TR18 ?

I have the SAMS for this radio, so I have the voltage info for just about everything for it.

Your audio amp (IC4) voltages seem off, pin 2 read as 6V, it should be about 3V, pin 5 and 6 are also slightly out, read as 1.15, should be about 1.9V (may be normal though), pin 9 is a touch low, should be 7V, pin 10 read 11.75 but should be about 13.1V

Check the voltage coming out of the radios power supply, I think it is only set to about 12.5V, it should be set to 13.8V, it could be throwing the voltages out a bit.

Replace C112 (4.7uF) to rule that out.

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Sunday 8th Mar 2009, 15:08

The Defpom wrote:I kind of forgot about this one..

Have you tried doing an alignment on it, and did you notice anything that seems incorrect during the alignment ? no not yet

It is likely to just be a capacitor (or a bunch of them) somewhere that are killing the DC supplies to certain parts of the circuit, the voltages you gave for the MB3756 look ok.

What voltages are you getting on IC3, IC6, TR34, TR35 and TR9, TR10, TR18 ?



Your audio amp (IC4) voltages seem off, pin 2 read as 6V, it should be about 3V, pin 5 and 6 are also slightly out, read as 1.15, should be about 1.9V (may be normal though), pin 9 is a touch low, should be 7V, pin 10 read 11.75 but should be about 13.1V

Check the voltage coming out of the radios power supply, I think it is only set to about 12.5V, it should be set to 13.8V, it could be throwing the voltages out a bit( it is showing 11.70, how do i turn it up?).

Replace C112 (4.7uF) to rule that out. replaced earlier

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by The Defpom » Sunday 8th Mar 2009, 15:22

There is usually (but not always) a variable VR on the power supply PCB.

I think I had some notes here for adjusting the voltage when the VR is not present, I will have to have a look.

What is the PCB number on the power supply board, there are different versions.

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Sunday 8th Mar 2009, 16:18

IC6
....RX.....................AM..................USB.................LSB
1..... 0 VOLTS FOR ALL
2. 0.1 .................... 8.14...............7.87..................7.80
3. 0.01.....................8.07................7.44.................7.70
4. 0 VOLTS FOR ALL
5. 0........................8.26.................8.34.................8.34
6. 0 VOLTS FOR ALL
7. 0........................2.86.................2.86..................2.86
8. 0.01....................2.86.................2.86..................2.86
9...... 0 VOLTS FOR ALL
10. 0.......................0.76.................0.74..................0.74
11. 0.......................1.43..................1.42.................1.42
12. 0.......................0.76..................0.74.................0.74
13. 0.......................1.43..................1.42.................1.43
14......0 VOLTS FOR ALL



IC3
.........RX..................AM....................USB...................LSB
1. 3.11.....................1.36...................3.06...................3.06
2. 3.48.....................3.38...................3.42...................3.43
3. 3.47.....................3.34...................3.42....................3.42
4. O VOLTS FOR ALL
5. 6.25.....................6.08...................6.19....................6.26
6. 7.82.....................7.62...................7.74....................7.69
7. 7.89.....................3.83...................4.24.....................4.24

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Sunday 8th Mar 2009, 16:20

The Defpom wrote:There is usually (but not always) a variable VR on the power supply PCB.

I think I had some notes here for adjusting the voltage when the VR is not present, I will have to have a look.

What is the PCB number on the power supply board, there are different versions.
PC-570AB

TR34, 35... are these the final(tr35) and driver(tr34)????

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Sunday 8th Mar 2009, 16:29

TR 9..................RX............................................TX
...............E........C........B.............................E......C......B
USB.........2.32.....1.57...8.36........................0.03.....0......0.56
AM..........2.32.....1.57...8.36........................0.02.....0......0.51
LSB.........2.32.....1.57....8.36........................0.03.....0......0.55

TR10

USB........0.29.....0.98.......8.23......................0.......0.09....0.56
AM.........0.29.....0.98.......8.23......................0.......0.08....0.51
LSB.........0.29.....0.98.......8.23......................0.......0.09....0.55

TR18

USB........1.23......1.96......7.52......................0........0.54....0.55
AM.........1.24......1.98......7.51......................0........0.46....0.50
LSB.........1.22......1.92......7.52......................0........0.54....0.55

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by The Defpom » Sunday 8th Mar 2009, 17:45

All those voltage check out OK...

TR34 and TR35 are the AM modulators, TR34 is a 2SC945, TR35 is a 2SC1419 they are at the rear right corner next to the audio amp.

I am just trying to figure out what could be causing your radios faults, so far everything has checked out, apart from the slightly high voltage on pin 2 of the audio amp, but you replaced that already didn't you.

I think I am going to have to look at this as different faults, not one common one, and try to tackle each in turn.

Replace C92, I have come across that part killing TX audio before, no harm in replacing it.

As there is a lot of things that are unknown I need you to do an alignment, and confirm that the radio is at least on the correct frequencies and the oscillators are all correct etc, so that doubt is removed.

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Sunday 8th Mar 2009, 18:30

just got done changing ALL elect caps..

fired it up... the needle is moving at least now... not swinging very high on ssb but... i will get it on the watt meter later

now for the rest of the voltages

TR 34...........................RX.........................................................TX
...............E..........................C........B.............................E.........................C......B
USB.........0.2(slowly drops).....0.........0.............................37 slowly drops.....0.......0
AM..........0.39(slowly drops).....0.......0..............................same as above.......0.....10
LSB.........0.36 (slowly drops).....0.......0..............................49 slowly drops.....0.......0

TR 35..................RX.................................................TX
...............E.............C............B......................E............C.........B
USB.........12.47.....12.48...8.02........................12.44.....12.45......8.08
AM..........11.93.....12.48...8.02........................7.19......12.41.......7.85
LSB.........12.48.....12.48....8.06........................12.45.....12.45......8.07

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Tuesday 10th Mar 2009, 7:37

very low tx power... less than a watt... it is txing about 20 kHz off freq

the audio amp i replaced the original came out of a used/parts radio, for what its worth

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Tuesday 10th Mar 2009, 13:16

the loop osc freq are high... in the 40 - 50.0000 mhz range

the offset osc freqs are pretty much spot on

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by The Defpom » Tuesday 10th Mar 2009, 23:24

I am a little confused, it is 20KHz off frequency ? if the loop is running in the 40-50MHz range then something is not right if you are getting the TX being only 20KHz off.

Is the loop freq the same (or very close) on TX/RX ?

What loop freq do you get on CH1 at TP1, what freq do you get at TP10 and what voltage do you get at TP9, I can then work out if there is a problem with the Loop circuit (VCO/PLL/Mixer).

Have you tried adjusting the VCO coil (L13) to see if that corrects it ?

I have had VCO issues with this chassis before, so it can happen, a faulty VCO can cause all kinds of weird behaviour.

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by The Defpom » Tuesday 10th Mar 2009, 23:31

frogman296 wrote: the audio amp i replaced the original came out of a used/parts radio, for what its worth
The odd voltage on the audio amp may mean the used one you put in could be faulty as well, if you have a new one try putting that in and re-checking the voltages, if they are about the same and it still has no audio, then the used one may be OK, so dont chuck it out yet.

OK, so what IS working now, and what IS NOT working, just so I know where things are now, obviously changing all the caps has made a difference.

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Wednesday 11th Mar 2009, 1:58

The Defpom wrote:I am a little confused, it is 20KHz off frequency ? if the loop is running in the 40-50MHz range then something is not right if you are getting the TX being only 20KHz off. yes is is 20khz off on the tx

Is the loop freq the same (or very close) on TX/RX ? the readins creep from 33.xxx to 37.44x(am)---- 33.50x to 37.44x(usb)-----33.60x to 33.98x(lsb)

What loop freq do you get on CH1 at TP1( 34.640-34.655), what freq do you get at TP10( 1.7040-1.7080) and what voltage do you get at TP9(1.53, adjusted to 2.00 volts), I can then work out if there is a problem with the Loop circuit (VCO/PLL/Mixer).
Last edited by frogman296 on Wednesday 11th Mar 2009, 6:08, edited 1 time in total.

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Wednesday 11th Mar 2009, 2:04

The Defpom wrote:
frogman296 wrote: the audio amp i replaced the original came out of a used/parts radio, for what its worth
The odd voltage on the audio amp may mean the used one you put in could be faulty as well, if you have a new one try putting that in and re-checking the voltages, if they are about the same and it still has no audio, then the used one may be OK, so dont chuck it out yet.

OK, so what IS working now, and what IS NOT working, just so I know where things are now, obviously changing all the caps has made a difference.
the radfio will fire up and move the needle when keyed on all modes... wattage is very low, less that a watt... rx is there with no noise... rx/ts light changes when keyed

i get ZERO amperage reading at TP7, TP8

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by The Defpom » Wednesday 11th Mar 2009, 7:03

OK, we shall try and fix the loop freq problem first, and go from there.

Because it is a LOOP all parts are incorrect, the frequency drift could be the cause of the voltage shift, or the voltage drifting could be the cause of the freq drift, an easy way to find out if you disconnect the PD output from the PLL which feeds the VCO and inject your own variable voltage to control the VCO frequency, then re-check if the frequency is still drifting at TP10.

So all you have to do is lift one end of R72, and then inject a voltage into TP9, an easy way of doing that is to get a 10K pot and connect each outer terminal pin to 0V and to 8V, at PLL pins 18 (0V) and pin 9 (8V), then connect the middle leg to TP9.

Now check the freq TP10 and see if it is stable when you are injecting each of the following 1V, 3V, 6V.

A common part to fail is C72 or C71, this loads down the control voltage and causes the voltage to fluctuate, or C73, C74 which effect the VCO itself,so if the frequency at TP10 is drifting when a FIXED voltage is injected it could be one of them effecting the VCO, or it could be the mixer transistor that is the problem.

If the freq at TP10 is drifting even with the fixed voltage feed and C71,C72,C73 C74 are definately OK, then check the VCO output at pin 10 of IC1 (the pin that feeds TR19 from the VCO module), and see if that frequency is stable, if it is, or it is better than TP10 (it can get a noisy backfeed), then the mixer transistor or components are likely to be the problem, in which case you need to look at C68,C69,C70 and the transistor itself, TR19, it is also worth checking C75 as well, just in case that is back-feeding noise into the VCO from L14.

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Wednesday 11th Mar 2009, 8:08

The Defpom wrote:
Now check the freq TP10 and see if it is stable when you are injecting each of the following 1V, 3V, 6V.

it does not drift with the fixed voltages

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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Wednesday 11th Mar 2009, 8:15

there is a 20k trimmer and resistor added on the board...looks like some sort of clarifier mod, the red wire you see goes to the clarifier pot

Image
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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by The Defpom » Wednesday 11th Mar 2009, 22:25

frogman296 wrote:
The Defpom wrote:
Now check the freq TP10 and see if it is stable when you are injecting each of the following 1V, 3V, 6V.

it does not drift with the fixed voltages
OK, in that case check for a stable 10.240MHz on pin 7 and pin 8 of the PLL, if it is unstable replace C64, C65, C66, C67 and re-check.

If that still fails to resolve it replace C197, C60, C61, C62, C63 and check R71 (1.5K), R72 (2.7K), R73 (33K), R74 (12K), R75 (33K), R76 (6.8K) and R77 (2.2K), these will all be near the PLL.

I can see a lot of solder flux on the PCB in the pictures, it is a good idea to use some PCB cleaner (flux cleaner) to remove it, especially around oscillators sections, as it can cause problems.

I can also see a couple of questionable solder joints, and there is a smeared solder blob near the end of the yellow jumper wire, which may be bridging to the earth track.

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