2970N2 help

[n4dxx]

Yep, Robb is right on the money. And the SSB output is also regulated thru the AM pass regulator transistor (very poor design). Which is why you couldn't get 12.5V on the SSB APC without adjusting the AM APC to the correct voltage.

What needs to go in there is a TIP36C instead of the 2SB827. And replace the 2SA1869 with a TIP42C.

~Cheers~

The only way i can get the am power down is to drop the apc voltage and that in turn drops the ssb apc...hummm

 

[Robb]

The only way i can get the am power down is to drop the apc voltage and that in turn drops the ssb apc...hummm

You will need to set the APC levels back to 6v and 12.5v respectively for AM and SSB.

Turning them down is neither the problem nor the cure.

When the AM Regulator, or its companion part have gone fault, you will see full AM carrier power on the output. Says it all right there. Been there; done that. That is what you said you saw in your first post - BTW. You still have a bad component that needs replacing. Since you have said that you've already replaced 2SB827 then you probably need to replace the 2SA1869 next to it. Sure bet that one or both of those parts are at fault, as Xit13 said already. . .

 

[n4dxx]

You will need to set the APC levels back to 6v and 12.5v respectively for AM and SSB.

Turning them down is neither the problem nor the cure.

When the AM Regulator, or its companion part have gone fault, you will see full AM carrier power on the output. Says it all right there. Been there; done that. That is what you said you saw in your first post - BTW. You still have a bad component that needs replacing. Since you have said that you've already replaced 2SB827 then you probably need to replace the 2SA1869 next to it. Sure bet that one or both of those parts are at fault, as Xit13 said already. . .

Thanks. I will get to the source ....and will update asap

 

[n4dxx]

Replaced both regulators...No joy,I am seeing only about 2.5v on the collector of both regulators...Puzzled

 

[n4dxx]

Found the issue D90 was installed wrong ...It was sidways and when the machine at the factory soldered it it blobed some joints together and it was pulling the regulator voltage down..Wow what a mess!!I just traded for another one..Think i'll sell it..

 

[ExitThirteen]

Oh wow.... That's some nasty work.... but it doesn't surprise me. I recently worked on a Mirage AM/FM export.... only modulated 1/2W out of the box. Turns out that one of the 52mhz trap coils was completely missing solder on one end.... once I resoldered it, it came right up to 50W.

In all seriousness, that's partly why I hate exports and current models of CB's, like the Galaxy 929/939/959/959/979 radios.... Such awful quality of workmanship, poor soldering, etc.


Glad you found the issue. Hopefully, it'll at least be functioning as it should.... or closer to as it should.


~Cheers~

 

[Robb]

Found the issue D90 was installed wrong ...It was sidways and when the machine at the factory soldered it it blobed some joints together and it was pulling the regulator voltage down..Wow what a mess!!I just traded for another one..Think i'll sell it..

Factory installed wrong; or had someone tried to hack it and failed?

 

[n4dxx]

Nope was not a hack job as one of the pins on the diode has zero solder and a huge blob next to it shorting out some resistors...And the diode was barley hanging sideways on the 3 pen pad..

 

[ExitThirteen]

Were you able to adjust your AM and SSB APC's back to where they should be?


~Cheers~