qx-949 stereo indicator lite

[john stumpf]

it would appear that my ha1142 chip has bit the dust, as the stereo indicator stays lit continuously. in am fm in fact all the time,its on its own dedicated power supply. it does seem to play well in fm. cant find any on ebay and mtf in a previous mentioned ACME SALES as a source. i cant seem to find the RIGHT acme sales on the web and im scared of nte. anyone know where an ha1142 can be had?

 

[rcs16]

I would not be scared of NTE. In another tuner fix thread someone went with a NTE replacement and it worked out just fine. I just would not recommend NTE discrete semis when you can get the real deal from Mouser.
Socket the part if you change it.
I have some NTE TO-220 drivers in my SX-950, they have been going for >25 years now.

Did you notice the 330 ohm R from the Stereo lamp(5) to ground? Q7-6 through 330 to ground.
I wonder why they did it this way? It would seem to me the lamp is dimly lit all the time.
The stereo indicator in the HA1142 just makes it brighter.

 

[john stumpf]

i dont follow you as i dont see any resistors on q7(6) 0r 5 stereo lamp.i believe you are citing the 949a which sports a different tuner with a ha1156 chip

 

[Watthour]

Follow Pin 13 from the tuner board. I see a 330Ω resistor to ground as well. That may have been to shunt leakage from the open collector in the HA1142 in the event of lamp failure, but that's merely a guess.

As for the dust, a thorough cleaning of tuner boards is never a bad thing if done correctly. A little conductivity and capacitance in RF circuits can go a long way to skew their performance.

 

[john stumpf]

i wasnt really ready to work on this thing but im between jobs waiting on parts so i dimmed bulb this thing and gave it a deoxit treatment fixed a broken knob shaft and made a faceplate glass. it was during the course of all this i noticed the light. i ASSUMED it it could only be a bad ic as it was the only thing in the circuit besides the power supply and the bulb (ASS-U-ME) it turns out it had a led installed in the stereo lite position. i pulled it from its socket but left it connected. i noticed that the light dimmed slightly as it was moved off station,but will not completely turn off. it has 5.9 vdc applied which drops to about 1.4v when tuned off station. but it never (the ic) completely shuts off. i had a used 8v 50ma bulb i replaced it with and it does work better but still the filament glows faintly due to the 1.4vdc being applied. you would never see this through the faceplate.but as the voltage is low under load it wont be very bright. at the risk of appearing ignorant i can only guess that the gate requires a certain amount of load to work correctly. its hard to draw any conclusion's as the thing does have 45 yrs of filth in it but i have seen worse. with an iffy power supply it gets even harder. but i do believe its in the ball park. unfortunately the manual does not list that unregulated output voltage on power supply pin 11. so i suppose the only rational thing to do is note it and see what happens as the rebuilding process progresses. ha1142's dont seem to be available at the moment so there's not much else to be done. i wouldnt mind sourcing one just in case. i dont know what schematic you fella's are using but the one i have DOES NOT SHOW ANY RESISTORS IN the circuit from pin 13. the 949A does. is the equivalent nte1142 or upc554c? i cant find a hitachi cross reference or even a data sheet to compare it to.

 

[Watthour]

This schematic?

 

[rcs16]

it turns out it had a led installed in the stereo lite position.

Remove that 330 ohm R that I spoke of earlier.

 

[john stumpf]

ill be dxxxed! i had to double check to make sure i wasnt hallucinating.that resistor ISNT on the 949 schematic from hi fi engine!!!! i will do it providing i can find where it is. that thing is EXTREMELY crowded.

 

[john stumpf]

its done and has its first led installed CORRECTLY1 works perfectly. it appears identical to a 949a i cant understand why they used an 8v bulb and deliberately installed not only a resistor to ground there is also one in series on the power side! this would only guarantee a dim display. why the schematics are different is also a mystery. thanks fella's!

 

[larryderouin]

PIONEER made the S.M.'s based on prototypes BEFORE production like everyone else. Production line changes wouldn't make the manual, unless you have a SX-626 then you need to know which version you have, so you could get the correct manual, as the early and late SX-626 are totally different. This is the only receiver that I know of that PIONEER did the change 1/2way thru the model years.

But getting back to the 949 and 949A. They are very close, mainly differences are in the matrix and decoding boards, and upgraded transistors in the "A". I had a VERY late 747 that I had to use the 747 and 747A manuals, as they used whatever boards they had in stock.

 

[john stumpf]

it was interesting to note the schematic differences.both the ak data base and hi fi engine were the same. so was the ha1142 unable to handle the power of the stereo light hence the resistors? or was the light to dim and they were later removed? who knows kinda like the chicken or the egg story i guess.the led should remove any worry.i could not find a data sheet on that ic anywhere,nor was there one for sale except in georgia with 50$ shipping and handling thank god i didnt bother! larry ive got a 626 that needs a rebuild,its going to be a christmas present. how does one ascertain the type? its an uc serial number

 

[larryderouin]

Go to the http://www.kallhovde.com/pioneer/Pioneer/Main scan page.html site. Pull everything they have on the 626. Compare your boards with the lists on both manuals, but 1st check your serial with the list from the 1973 manual. If it's higher than the listed serial series then you have a late model 626.
Here's the relevant image from the manual on page 3 or 4. The "UC" code indicates March 1974 so this could very well be a Late model unit. But compare it with the manuals.

 

[john stumpf]

thanks larry its got the round "ic" label and the serial number is 1216XXX so i guess its the later one.