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Cobra 25 ltd newer version parts help
- Thread starter dss56
- Start date
Not C56, C57 per your schematic...the BIG one... by T1 but looks to be SILKSCREENED C550 on the main PCB
Sorry meant c57 I tried on the board layout and cant find.
This is a newer one yr 2013 and cant seem to get the correct schematic for the board. I think the board layout is the same as mine but the schematic might not match. Both were listed as newer 25ltd
This is a newer one yr 2013 and cant seem to get the correct schematic for the board. I think the board layout is the same as mine but the schematic might not match. Both were listed as newer 25ltd
Wild, no wonder why you're having problems!
Man let's get this figured out...you got a headache commin' on with this repair soon enough...
Man let's get this figured out...you got a headache commin' on with this repair soon enough...
Ya I will try the replace the c550 as you mentioned. The site that list the schematics and board layouts had these 2 for the newer 25ltd I did look at the board layout and that seemed to match. A bit hard to see if the schematic matches the board layout.
I going back down to radio and replace the c550 and see what happens BRB
and Thanks Andy
I going back down to radio and replace the c550 and see what happens BRB
and Thanks Andy
You're ok, the radio is not. Lets' keep that separate from each other so we can help you...
The Mod transformer (T1) can also and is correctly identified as Reactance Modulator - we CB'ers just call it the "Mod" transformer - short for Modulation...
So the audio is sent to it, thru that big cap but DC from one side (audio amp) and the DC from T1 are kept from each other using that cap. But audio passes thru it into winds of T1.
So if things are weak and Receiver and PA aren't right - usually the Cap has gone bad and if not replaced can re-damage the Audio amp again!
Remember that Receiver and PA work thru that same part so if they aren't right - you can pretty much isolate it to audio amp and parts around it as a pretty sure bet...
The Mod transformer (T1) can also and is correctly identified as Reactance Modulator - we CB'ers just call it the "Mod" transformer - short for Modulation...
So the audio is sent to it, thru that big cap but DC from one side (audio amp) and the DC from T1 are kept from each other using that cap. But audio passes thru it into winds of T1.
So if things are weak and Receiver and PA aren't right - usually the Cap has gone bad and if not replaced can re-damage the Audio amp again!
Remember that Receiver and PA work thru that same part so if they aren't right - you can pretty much isolate it to audio amp and parts around it as a pretty sure bet...
Andy
Receive audio is great.
I just replaced c550 and still same problem.
If I say Ah in to mike normal voice nothing but if i YELL AHHH in to mike the mod meter external dosy will move up 30-40%
Tried 5 good mikes and all the same results.
So it seems its not getting any modulation amplification with the output carrier modulation is there but no amplification. Racking my brains out , replaced tr10 13 and 17 in local area and same problem.
Receive audio is great.
I just replaced c550 and still same problem.
If I say Ah in to mike normal voice nothing but if i YELL AHHH in to mike the mod meter external dosy will move up 30-40%
Tried 5 good mikes and all the same results.
So it seems its not getting any modulation amplification with the output carrier modulation is there but no amplification. Racking my brains out , replaced tr10 13 and 17 in local area and same problem.
Ok hold on, working with you on this need 5 min to review...may mean D10 and that area along with Final and Driver section too - Carrier power? Do you get 4 watts?
C70 per schematic is the AMC cap - past VR5 - pull that and see if audio returns...that is if C150 failed to provide any changes to the results...
- No one is chatting at the moment.
