Realistic TRC-453, no modulation on AM, but SSB is ok.

[Satelitte]

Hello everyone.
I've got a problem with my Realistic TRC 453 (simillar to Uniden PC-122 Radio).

It has no modulation on AM mode (carrier only), but on SSB mode everything is allright and modulated.

So I am asking you. How I can fix it up?

Driver, and PA transistors are OK.
I picked a new capacitor 47uF near to the NE612 modulator and trying to resolder the area around.
Turning the VR of AM mod changes nothing.
:headbang

Any ideas?

73!

 

[sp5it]

Replace TR544
Mike

 

[Satelitte]

That's it!
After a quick measurement I see it can be broken.
(Drivers of it seems to be ok)

Will be replaced soon.

Dzięki Michał. 73

 

[Robb]

The NTE equivalent part for the original 2sa1012-0 ('TR-544') is a NTE-153 - IIRC.
It is a more sturdy part than the original . . .

http://www.nteinc.com/specs/100to199/pdf/nte152.pdf

http://www.cbtricks.com/radios/realistic/trc_453/index.htm

http://www.cbtricks.com/radios/realistic/trc_453/graphics/realistic_trc_453_sm_pg44_45_sch.pdf

 

[Satelitte]

I'd rather put BD912 there. No problems with availability.

 

[Satelitte]

Hi guys it's me again.

After replacement - it still doesn't work.
There's about 8V when transmitting, on every single electrode of this transistor.
It heats very much too.

And there's only carrier and no mod.

 

[sp5it]

Check TR36, 37, 38, D42.

But first of it all remove C166 and check if there is any audio on R135.
Mike

 

[Satelitte]

Still nothing... Can it be some issue with AM transformer? The carrier on AM is sometimes discontinuous.

Thanks