[NJARC] Heathkit AR-29

[stevecafiero2 at gmail.com]

> Greetings,
> 	First let me say that my first NJARC meeting was in September, and the club makes a new member feel very welcome.  Maybe someone can offer some assistance with a problem I am having.
> 	While doing an FM alignment on my Heathkit AR-29 stereo receiver (I had to “fix” something that was working!), the FM gradually died out.  First the adjustments had no effect, then the stereo light stayed on, then it died, and finally the entire FM went dead.  Voltage measurements showed that the 12 VDC, which powers the FM circuitry, was about 2 volts.  The 12 VDC powers the AM/FM board, multiplex board, and the tuner.  If all of these are removed I get 12.4 VDC.  If any one of these is installed, the 12 volts drops to about 2.  Transistors Q4, Q5, and Q6 regulate the 12 VDC.  These all check out good (using an ohm meter).  Resistors R7,8,9,11,12,and 13 all check out good too.  All of the caps are brand new.  The 50 VDC, B+, and B- voltages are good, and aren’t affected by whether or not the FM is powered.  When unloaded, all voltages on the power supply board are good.  When any one of the FM boards or the tuner is connected, I get:
> Q6 emitter - very low, about 2
> Q5 base - very high, about 33.8
> Q4 base - very low, 1.5
> It seams to me that the power supply makes 12 volts, but can not maintain it with a load.
> The schematic and power supply description are attached.
> Any guidance is appreciated.
> Stephen Cafiero
> 
> 
> 
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