joemango said:
Kale,
Try disconnecting the Rxxx 2.2kohm resistor temporarily near TR28 the 2SA733 emitter (not sure of the component designator since the posted pic is fuzzy and lacking in resolution) . This will diconnect the transistor switch that forces the MPX IC to mono. If that doesn't work, tweak the trimpot near IC08 uPC1173 pin 15, the PLL VCO free-run adjust. Hope you get stereo this time. Don't rely on the stereo LED if you think it is broken. Listen for the usual increase in hiss when stereo engages.
Joe, I keep this what you have written, and I will do this when I got a new upc1173, because I found it and already ordered it(thanks Steve Coy
www.ceitron.com). So firs I will try to change it, and after that try to do what you suggested me. I have one problem on another Sansui G receiver, model G8000, but I will write about this problem on yours PM, if you dont mind?
joemango said:
I think the schematic is screwed again in this area, the 2SA733 base is connected to the supply that is suppose to be for IC05. Args!@#$ It should come from IC07 RSSI pin. IC05 uPC577H supply connection appears to be wrong. Oh well
Those mistakes are
Trade Mark of Sansui Service Manuals. Someone should collect all discovered mistakes until now and collect them on one place:yes:
joemango said:
Of the things you've done, the most critical one is step #3, the dicriminator adjustments and the part for the IC07 HA1137 adjustment (step 1). This is to ensure that the stereo muting coincides with the center of the discriminator for the audio. The rest of the procedure outline in the page is for optimal sensitivity.
Here, what you mean critical step 3 adjustments; on adjusting T03 to 0 Volts or real step 3 Dial Calibrating?
joemango said:
It's odd for the instruction to tell you to physically move the pointer to get the correct tracking at the lower end of the dial. There should be a couple of inductors in the front end that are adjustable for this purpose including the transformer for the LO.
Yes, but for sure, that is another one mistake in that Service Manual, I need advice from someone who already adjusted one G9000/901. It must be one of T01, T02, T03 or T04 in Front End, but I dont know which:scratch2: . I dont wish to touch it if I am not sure!
joemango said:
While you are at it, if you have a signal generator that can drive a 19kHz 1vp-p signal sine or square wave, ac coupled this to uPC1173 pin 2 (the input) while disconnecting the signal from the ratio detector. This will test the 19kHz detector of the uPC1173 and confirm if the IC's pilot detect function is faulty. The trimpot for the PLL VCO may need some adjustment to force the stereo LED to turn on. Leave the previous mentioned 2.2k resistor disconnected when you are doing this.
But, I still dont have Audio Signal Generator (for one month I will get one very good Leader :yes
. That signal generator what I have, only has two FM spot frequency (one is adjusted to 90MHz and another to 106MHZ) on which frequency I can modulate audio sine wave 400Hz OR 1kHz as mono! And that is all! It is good for calibrating FM scale and some other simple test.
ModernClassic said:
Someone mentioned about adjusting the PLL oscillator pot, Have you tried it and still not getting 19K wave at test point? Do not touch the discriminator coil if you don't know what you are doing. If you have tried then it is the IC that is blown. MPX chips often went bad but still give you good mono sound!
Thank you for suggestion ModernClassic, and I decided to wait until I got one upc1173C. And after that we will know much more
Regards!
Kale
