Re: Pioneer SX-737 No FM

David Farber wrote:
Gary L. Woodruff wrote:
David Farber wrote:
Gary L. Woodruff wrote:
Howdy all, I have a vintage Pioneer receiver. It will pick up AM
stations but is dead on FM. I do not get any deflection on the
tuning meters and no static. I do have a print. I do have b+
into the board and have good voltages at the HA1156.
I do not see anything at the HA1137, with the exception of 13.8v
at pin 11 (should be 5.6v). There is only a coil in series with
a cap to gnd between b+ and this pin. I do not have a way to
measure inductance on the coil but have measured the cap .047
microfarads is spec and I get .055. I am tempted to try to
replace the IC (HA1137) but am
concerned about the amount of voltage I see on pin 11 of the IC.
Any and all advice is GREATLY appreciated.


Thanks, Gary
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.
Gary L. Woodruff wrote:
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


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.
Gary L. Woodruff wrote:
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



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.
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.


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
.

Relevant Pages

  • Re: Pioneer SX-737 No FM
    ... a cap to gnd between b+ and this pin. ... concerned about the amount of voltage I see on pin 11 of the IC. ... F1 and F2 fuse one of the pairs of wires coming off of the ... Remove Q4 from the circuit and test ...
    (sci.electronics.repair)
  • Re: Pioneer SX-737 No FM
    ... a cap to gnd between b+ and this pin. ... concerned about the amount of voltage I see on pin 11 of the IC. ... F1 and F2 fuse one of the pairs of wires coming off of the ... Remove Q4 from the circuit and test ...
    (sci.electronics.repair)
  • Re: power supply?
    ... pin, and the ground on 1 pin then your ok there. ... Your procedure for checking voltage levels is correct, ... You can connect an ammeter in series with a load to measure current ... Look inside the supply for a fuse on the 5V output. ...
    (comp.sys.cbm)
  • Re: power supply?
    ... pin, and the ground on 1 pin then your ok there. ... Your procedure for checking voltage levels is correct, ... You can connect an ammeter in series with a load to measure current ... Look inside the supply for a fuse on the 5V output. ...
    (comp.sys.cbm)
  • Re: Pioneer SX-737 No FM
    ... cap to gnd between b+ and this pin. ... F1 and F2 fuse one of the pairs of wires coming off of the secondary ... I.F. filter. ... dead end for the signal right there. ...
    (sci.electronics.repair)
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