Search found 432 matches

by The Defpom
Thursday 19th Mar 2009, 10:11
Forum: CB Radio Repair and Troubleshooting
Topic: Cobra 29 No Keyup
Replies: 18
Views: 8405

Re: Cobra 29 No Keyup

Check the voltage at R70, it should be at least 8V, if it is not then there is a problem with the main voltage regulator circuit, D22 TR23.

If the voltage is OK then it could be the 5V regulator circuit, Z10.
by The Defpom
Thursday 19th Mar 2009, 7:20
Forum: CB Radio Repair and Troubleshooting
Topic: Cobra 29 No Keyup
Replies: 18
Views: 8405

Re: Cobra 29 No Keyup

Check the voltage between pin 11 and pin 21 of the PLL, to make sure that it has a supply, it sounds like a DC supply issue at this point. I would also check R124 for 5V from the main 5V supply. It interests me that the meter bulb blew at the same time, I suggest that you check your DC power supply ...
by The Defpom
Tuesday 17th Mar 2009, 14:21
Forum: CB Radio Repair and Troubleshooting
Topic: Cobra 148 GTL PC-416A A Meter Malfunction
Replies: 5
Views: 3306

Re: Cobra 148 GTL PC-416A A Meter Malfunction

Check to see if there is any voltage in the CAL mode, and the S/RF mode, it could be bad wire on the S/RF/CAL/SWR switch. The S/RF and CAL functions get the feeds from different places, I would be surprised if they have both failed. It may also be a good idea to use the earth track of the main PCB f...
by The Defpom
Tuesday 17th Mar 2009, 14:13
Forum: CB Radio Repair and Troubleshooting
Topic: I have made a big mistake! "President Lincoln"
Replies: 2
Views: 2115

Re: I have made a big mistake! "President Lincoln"

It sounds like you have shorted out the MPU, you will have to find another one to replace it with.

In the worst case I would be interested in buying the radio from you for parts.
by The Defpom
Sunday 15th Mar 2009, 11:43
Forum: CB Radio Repair and Troubleshooting
Topic: Cobra 148 GTL PC-416A A Meter Malfunction
Replies: 5
Views: 3306

Re: Cobra 148 GTL PC-416A A Meter Malfunction

You need to find out if it is an electrical or mechanical issue, so measure the voltage that is feeding the meter when you TX, if there is voltage but no movement then the meter is stuck. Usually undoing BOTH the tiny screws 1/2 a turn or so will free it, sometimes you need to go further than that, ...
by The Defpom
Saturday 14th Mar 2009, 17:55
Forum: CB Radio Repair and Troubleshooting
Topic: hr2510 squeals thru speaker
Replies: 2
Views: 1605

Re: hr2510 squeals thru speaker

What test gear do you have available to you ?

Remove the top cover, and touch the IC that is just behind the two vertical PCBs on the main PCB, marked as IC101 (it an NJM2902N), if it feels hot when the radio is on then replace it.
by The Defpom
Thursday 12th Mar 2009, 22:04
Forum: CB Radio Repair and Troubleshooting
Topic: UNIDEN WASHINGTON, no sound(tx,rx,pa)
Replies: 37
Views: 17244

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

It was probably on the back of the pot originally.
by The Defpom
Thursday 12th Mar 2009, 11:22
Forum: CB Radio Repair and Troubleshooting
Topic: UNIDEN WASHINGTON, no sound(tx,rx,pa)
Replies: 37
Views: 17244

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

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 th...
by The Defpom
Thursday 12th Mar 2009, 9:57
Forum: CB Radio Repair and Troubleshooting
Topic: UNIDEN WASHINGTON, no sound(tx,rx,pa)
Replies: 37
Views: 17244

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

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 ...
by The Defpom
Thursday 12th Mar 2009, 0:24
Forum: CB Radio Repair and Troubleshooting
Topic: UNIDEN WASHINGTON, no sound(tx,rx,pa)
Replies: 37
Views: 17244

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

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,...
by The Defpom
Wednesday 11th Mar 2009, 22:25
Forum: CB Radio Repair and Troubleshooting
Topic: UNIDEN WASHINGTON, no sound(tx,rx,pa)
Replies: 37
Views: 17244

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

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 fa...
by The Defpom
Wednesday 11th Mar 2009, 7:03
Forum: CB Radio Repair and Troubleshooting
Topic: UNIDEN WASHINGTON, no sound(tx,rx,pa)
Replies: 37
Views: 17244

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

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 fr...
by The Defpom
Tuesday 10th Mar 2009, 23:31
Forum: CB Radio Repair and Troubleshooting
Topic: UNIDEN WASHINGTON, no sound(tx,rx,pa)
Replies: 37
Views: 17244

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

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 ...
by The Defpom
Tuesday 10th Mar 2009, 23:24
Forum: CB Radio Repair and Troubleshooting
Topic: UNIDEN WASHINGTON, no sound(tx,rx,pa)
Replies: 37
Views: 17244

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

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 ...
by The Defpom
Sunday 8th Mar 2009, 17:45
Forum: CB Radio Repair and Troubleshooting
Topic: UNIDEN WASHINGTON, no sound(tx,rx,pa)
Replies: 37
Views: 17244

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

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...
by The Defpom
Sunday 8th Mar 2009, 15:22
Forum: CB Radio Repair and Troubleshooting
Topic: UNIDEN WASHINGTON, no sound(tx,rx,pa)
Replies: 37
Views: 17244

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

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.
by The Defpom
Sunday 8th Mar 2009, 10:27
Forum: CB Radio Repair and Troubleshooting
Topic: UNIDEN WASHINGTON, no sound(tx,rx,pa)
Replies: 37
Views: 17244

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

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 gav...
by The Defpom
Saturday 7th Mar 2009, 13:53
Forum: CB Radio Repair and Troubleshooting
Topic: Ranger RCI 2950 Non DX Help Please
Replies: 4
Views: 2469

Re: Ranger RCI 2950 Non DX Help Please

Glad to have helped. Have a good one.
by The Defpom
Saturday 7th Mar 2009, 11:28
Forum: CB Radio Repair and Troubleshooting
Topic: Ranger RCI 2950 Non DX Help Please
Replies: 4
Views: 2469

Re: Ranger RCI 2950 Non DX Help Please

There are a few possible causes, I would first check VR2 to make sure it is not cracked or just incorrectly set (VR2 is the SSB signal meter), if that checks out, then check R61 , if that is OK then replace Q15. If the problem is only one LSB or USB (it works on the other sideband) then it could jus...
by The Defpom
Wednesday 4th Mar 2009, 14:20
Forum: CB Radio Repair and Troubleshooting
Topic: Cobra 148GTL, only 2 channels functioning
Replies: 15
Views: 5891

Re: Cobra 148GTL, only 2 channels functioning

The TX alignment issue is probably due to the original clarifier mod, check for correct component values for the resistors that are connected by VR5. On the TX side R187 should be 2.7K, R186 should be 100 Ohm, there should also be diodes in D75 and D52. On the RX side R175 should be 3.3K, R174 shoul...
by The Defpom
Tuesday 3rd Mar 2009, 21:00
Forum: CB Radio Repair and Troubleshooting
Topic: Cobra 148GTL, only 2 channels functioning
Replies: 15
Views: 5891

Re: Cobra 148GTL, only 2 channels functioning

Of course, no CH9.. but yes, check the path and source of the voltage feeding pin 11, if you disconnect it from the ch selector and test the ch selector side for voltage it should say whether the selector is at fault, or if there is a short circuit somewhere (it should be feeding 0V), the PLL pin wi...
by The Defpom
Tuesday 3rd Mar 2009, 20:12
Forum: CB Radio Repair and Troubleshooting
Topic: Cobra 148GTL, only 2 channels functioning
Replies: 15
Views: 5891

Re: Cobra 148GTL, only 2 channels functioning

There is an error with the N codes, the ch1 code should be 1001111, not 1101111, check for problems with the connections for pin 11, try checking the diode matrix that is used for the CH9 funtion, or lifting the wire from the ch selector for that pin.
by The Defpom
Tuesday 3rd Mar 2009, 18:23
Forum: CB Radio Repair and Troubleshooting
Topic: UNIDEN WASHINGTON, no sound(tx,rx,pa)
Replies: 37
Views: 17244

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

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

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