Pioneer SX-737 No FM

That 5.6 voltage should be for pin 10, not pin 11. Pin 11 goes to the B+ supply and the 13.8 v is correct.

Good luck.

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David Farber
David Farber\'s Service Center
L.A., CA

Dave, thanks for pointing that out. the 13.8 is the only voltage I see on the HA1137. I do not see the input signal of 1.9v on pins 1,2,3 of the chip. I do see the 12.6 v at F2 but nothing after. I will try to replace this fuse? F2 and the HA1137. Does this make sense?

Thanks, Gary

David Farber wrote:

Gary L. Woodruff wrote:

F1 and F2 fuse one of the pairs of wires coming off of the secondary of the power transformer. In the FM section, there is another component which also labeled F2 which appears to be some sort of I.F. filter. You need to tell me if by F2 you mean the fuse or if you mean the filter. You cannot have the

13.8 volts at pin 10 if the fuse is blown. Do you have the correct voltages on Q4?

Good luck.

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David Farber
David Farber\'s Service Center
L.A., CA

Howdy, thanks Dave. Yes I do see 13.7V at the collector, 1.4v Emitter .21v at the base. I do not see anything on the output of the F2 filter (I missed the F2 listing in the tuner part list, and found it listed as a fuse, thanks again).

Thanks, Gary

David Farber wrote:

Gary L. Woodruff wrote:

I believe we've found the problem. I am not in the office at the moment where my schematic is, but if Q4 is reverse biased, that's going to be a dead end for the signal right there.

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David Farber
David Farber\'s Service Center
L.A., CA

Dave, thanks again. What do you think is causing q4 to be reversed biased?

Gary

Sorry I couldn't get back to you sooner. Remove Q4 from the circuit and test it with your multimeter. Also, check the voltage at the base of Q4 were it still in the circuit.

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David Farber
David Farber\'s Service Center
L.A., CA

Dave, I removed Q4 from the circuit and it is OK. I checked the voltage at the base with Q4 out of circuit and get 2.1 V. I resoldered Q4 and checked the base again and still get 2.1 at the base. (I may have misread my previous reading of .21v) I do see 13.7v on the Q4 side of the f2 IF filter but 0v at pin 1 of HA1137. i am thinking I need to replace this F2 if filter?

Thanks, Gary

Well the difference from .21 and 2.1 is quite a difference. That means the transistor is operating correctly. I would replace the HA1137 and see if the voltages come back up. It's not very likely any of those filters are bad. You could remove F2 and see if the voltage comes back up just to see what happens though.

Good luck.

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David Farber
David Farber\'s Service Center
L.A., CA

To all who helped, thank you. I replaced the HA1137 and all is working. Thanks!!, Gary

Used to see a lot of those in the old days!

Mark Z.