Hi, this old novice is attempting to fix an old friends Model 22 that has multiple problems. I am usually lurking in Vintage SS, Sansui or new Kenwood forums since that is the gear I have. With AK members help I have refurbished, fixed and modified my receivers. So, I have some experience with recaps, the basics of control & front end cleaning, testing components in and out of circuit and doing some mods. This unit is a challenge due to the number of problems. A Fluke 179 and Dim bulb tester are my main test instruments.
Although it will play, there is a weak FM signal problem and no stereo Beacon. But, the first problem is in the left channel Amp Board (P600).
There is an overheating 100 ohm 1W resistor (R650) issue to resolved first. Looking at the schematic I am led to believe that this resistor supplies -34 V to the C of driver (H610)2SA497, and B of (H004) TO3 Output SJ2000. Specs call for -34V on those legs. I measure about 26V across this 100 ohm 1w resistor, I think that works out to over 6watts. There is only -8V on the C & B legs, specs call for -34V. I replace the resistor (R650), that had visual burn signs and tested at 165 ohms. Also replaced 2SA497 with same, but no help. Now I suspect the the SJ2000 is the problem.
So, my first question is; am I on the right part i.e, SJ2000? If so what is the substitute for the Power Output Transistors SJ2001 (PNP) & SJ2000(NPN)? Only info I can get is that they were made specifically for Marantz by Motorola and a possible sub may be MJ15024/ MJ15025.
I have attached a close up of the left channel(P600), hope one of the Marantz gurus can help me.
Although it will play, there is a weak FM signal problem and no stereo Beacon. But, the first problem is in the left channel Amp Board (P600).
There is an overheating 100 ohm 1W resistor (R650) issue to resolved first. Looking at the schematic I am led to believe that this resistor supplies -34 V to the C of driver (H610)2SA497, and B of (H004) TO3 Output SJ2000. Specs call for -34V on those legs. I measure about 26V across this 100 ohm 1w resistor, I think that works out to over 6watts. There is only -8V on the C & B legs, specs call for -34V. I replace the resistor (R650), that had visual burn signs and tested at 165 ohms. Also replaced 2SA497 with same, but no help. Now I suspect the the SJ2000 is the problem.
So, my first question is; am I on the right part i.e, SJ2000? If so what is the substitute for the Power Output Transistors SJ2001 (PNP) & SJ2000(NPN)? Only info I can get is that they were made specifically for Marantz by Motorola and a possible sub may be MJ15024/ MJ15025.
I have attached a close up of the left channel(P600), hope one of the Marantz gurus can help me.
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