Cobra 148 gtl no tx in am rx ok. SSB RX and TX ok

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Cobra 148 gtl no tx in am rx ok. SSB RX and TX ok

Post by speedracer6g » Wednesday 10th Jun 2009, 3:11

Radio Make and Model: Cobra 148 GTL D
PCB Number: PC-332
PLL Number: 8719
Test gear available: Motorolla r-220b service monitor, Freq counter, Scope, Digital and Analog VOM, ect.
Symptoms: This Radio had the ERF2030 mod and I guess it never worked and that is why i ended up with it. I got everyting back to factory and had a bad am regulator TR41. I replaced the part and now i am getting sideband but no AM TX. Rx is working fine on all formats. I took some voltage measurements and replaced a few parts around while i was checking them just in case they were intermittent. they were C174, R228, D63, TR42, R193. I dont have alot of measurement data in the service manual. But i did check the voltage on TR41 and TR42. They are not rite but this is what i have.

TR41 RX B 5.8v C 13.8v E 13.8v
TR41 TX B 5.6v C 13.8v E 13.8v

TR42 RX E 5.8v C 13.8v B 5.6v
TR42 TX E 5.8v C 13.8v B 5.6v

if any one has any ideas please let me know.


What is working: Am RX, SSB RX and TX.

What has been tried: parts and diagnostics.

Did it suddenly happen ?: Result of an Ekl Mosfet mod gone bad.

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