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

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frogman296
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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Wednesday 11th Mar 2009, 23:31

the tantalum caps, can i replace them with another type?? for instance c63 is a 2.2uF 25v tantalum cap

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

Post by The Defpom » Thursday 12th Mar 2009, 0:24

You will have to use tantalums, as they are critical parts, they form a special filter circuit to smooth out the pulses and steps which are generated by the PLL to control the VCO, using electrolytic caps probably won't work.

You may also want to check C72, that is supposed to be a tantalum as well, and could also contribute to the problem.

Tantalum as almost as prone to failure as electrolytic's, just not as commonly used, so they are always suspects too.

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

Post by frogman296 » Thursday 12th Mar 2009, 1:03

The Defpom wrote:You will have to use tantalums, as they are critical parts, they form a special filter circuit to smooth out the pulses and steps which are generated by the PLL to control the VCO, using electrolytic caps probably won't work.

You may also want to check C72, that is supposed to be a tantalum as well, and could also contribute to the problem.

Tantalum as almost as prone to failure as electrolytic's, just not as commonly used, so they are always suspects too.
i replaced 60 61 62 63 64 65 66 67 with no change

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

Post by frogman296 » Thursday 12th Mar 2009, 9:32

The Defpom wrote:
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.
i cleaned the flux off and replaced all the parts mentioned above still no luck... PA function is working A+

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

Post by The Defpom » Thursday 12th Mar 2009, 9:57

Remove that clarifier mod to return the clarifier to original, and re-do the loop alignment and see if that gives better results, if you have replaced C72 as well and the VCO output is still noisy, then the PLL may be at fault.

The reason I want to get the VCO and loop problem sorted first, is that if it is jumping all over the place rapidly, it could cause the TX freq to jump wildly, resulting in loss of output power and distorted TX audio.

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

Post by frogman296 » Thursday 12th Mar 2009, 10:35

i will try my best to remove the clarifier mod... i will need to see another radio to figure out where they go...unless you can tell me where the 2 outside wires on the pot go to.

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

Post by The Defpom » Thursday 12th Mar 2009, 11:22

One side of the pot goes to R415 (3.3K), which then connects to 0V, the other side goes to the RX only 8VDC supply, as found at the NB switch, and the feed side of the resistor that then connects to the RF gain pot (R417) (there are two, one goes to 0V, the other to the RX only DC).

Once you have the RX side back together, make sure that the TX side is also correct, refer to the partial circuit diagram I have attached which shows how the clarifier and TX only DC supplies are hooked up.
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circuit diagram of clarifier circuit
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Re: UNIDEN WASHINGTON, no sound(tx,rx,pa)

Post by frogman296 » Thursday 12th Mar 2009, 11:43

The Defpom wrote:One side of the pot goes to R415 (3.3K)
are you sure it isnt r145?? i just dont see a 415

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

Post by The Defpom » Thursday 12th Mar 2009, 22:04

It was probably on the back of the pot originally.

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

Post by frogman296 » Friday 13th Mar 2009, 11:30

im the process of getting a first hand account of where the wires go... will keep you updated

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

Post by frogman296 » Thursday 26th Mar 2009, 11:34

finally got the clarifier back to normal... the radio is txing with some watts..1.5 swinging back on AM.. and around 1.5 forward on lsb, and usb

on am... channel 19... it is txing on 27.1859.... i cannot get it onto the exact freq

where to next, scott??

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

Post by frogman296 » Thursday 26th Mar 2009, 12:11

i might add... i Replace 11.1125 crystal with a 11.3258 crystal. and the radio wont do anything...does this mean that the crystal is bad??

the radio had a 11.1125xtal in it when i got it.... technically... it should have been changed in order for the channels to work...am i wrong???

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

Post by frogman296 » Friday 27th Mar 2009, 7:06

this radio never gives up.... now if i turn the volume over 3/4... the speaker squeals, without the mike even keyed..

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