Hello guys i recapped my radio i cannot keep my voltage locked i tryed adjusting l19 viltage will not stay locked.
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Help alignment with 148 gtl
- Thread starter kaos513
- Start date
Sounds like a bad regulator. Depending on the age, it could need this service bulletin applied: http://www.cbtricks.com/radios/cobra/142gtl/graphics/cobra_142gtl_tech_note_1226.pdf
Those China 148 GTL's are problem radios. Was it working before the recap? First make sure that you do not have a Cap in the wrong way. If you did you probably would have heard a pop on fire up though.
If it does have a 3 pin regulator, it is likely a 78XX style regulator, probably 7808 or 7809 if it is supposed to be near 8 volts. If that is the case, unsolder pin 3 from the board, and check that there is +13.8V on pin 1, and that pin 2 is grounded. If those are correct, then test pin 3 for 8 or 9 volts +- 1VDC, depending on if it's a 7808 or 7809 (last digit is the voltage you should see.)
If that passes, then it is probably not the regulator.
If that passes, then it is probably not the regulator.
i adjusted it for spec but when i take meter off and put it back on jumps back to like 4.6 volts on all channels, also i have another 148 gtl works perfect with my meter so its not my meter.
That adjustment is for bias currant. That is done with a milliamp meter. The VCO voltage is on the other side of the radio near the PLL.
You are hooked up to the bias adjustment if you have the jumpers pulled. You should hook your meter to TP9 and adjust L19 for 3.2v. Sounds like you have something mixed up. Read this again you are hooked up to the biased adjustments test points.
Okay I think I misunderstood you I thought I read when you put jumpers back on sorry.
Okay I think I misunderstood you I thought I read when you put jumpers back on sorry.
It is sometimes hard to be sure if a variable inductor is bad or not. You can test to see if it is open or shorted, and it is very difficult to test for a core to coil short without special equipment and good specs, but in my experience with radios, the most common problem with them is the core is cracked/broken due to people using metal or ceramic screwdrivers to adjust them. The ferrite core is very brittle, and will crack very easily, and sometimes it will be difficult to tell without removing the core.
If you suspect the inductor to be bad, disconnect one of the leads and check for continuity, and a fairly small resistance, such as 2-3 ohms. No continuity is a bad inductor. If you have continuity, it is most likely something wrong with the core. If you can still turn the core, turn it until it comes out, and see if there is a crack in the core. If you pull it out, and the core is cracked, you can sometimes pull the core out, remove the broken portion, and insert it in backwards and it will still work to get the output you want. If you can't turn the core from the top, you have to remove the inductor and screw it out from the bottom.
If removing the broken portion and reinserting the core upside down doesn't work, you will likely have to replace the inductor, unless you have spare cores, which is unlikely unless you work on radios and remove the cores from the parts chassis you have.
Anyway, there is more to it than that, but that would cover 95% of all inductor faults.
If you suspect the inductor to be bad, disconnect one of the leads and check for continuity, and a fairly small resistance, such as 2-3 ohms. No continuity is a bad inductor. If you have continuity, it is most likely something wrong with the core. If you can still turn the core, turn it until it comes out, and see if there is a crack in the core. If you pull it out, and the core is cracked, you can sometimes pull the core out, remove the broken portion, and insert it in backwards and it will still work to get the output you want. If you can't turn the core from the top, you have to remove the inductor and screw it out from the bottom.
If removing the broken portion and reinserting the core upside down doesn't work, you will likely have to replace the inductor, unless you have spare cores, which is unlikely unless you work on radios and remove the cores from the parts chassis you have.
Anyway, there is more to it than that, but that would cover 95% of all inductor faults.
