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Hitachi Sr 804 no Fm signal or sound

secrets

secrets

Member
Just picked up a Hitachi Sr 804 and it plays beautiful except for the fm , I get no sound or signal from the meter when switched to fm .what I did notice is the tuning meter drops just a little from center when switched to fm and that's about it . I tested for voltage here and there and I see it but would like if any one out there can give me any ideas on what to check on this unit .
http://www.hifiengine.com/manual_library/hitachi/sr-804.shtml
forgot to mention I don't even get static while on fm
I feel there might be a fusible resistor somewhere ?
 
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secrets said:
I feel there might be a fusible resistor somewhere ?
Click to expand...

I take it you think there might be a problem with the power supply to the FM section. That seems sensible to me, but note that the AM section runs from essentially the same power supply. So, if AM works, it's not very likely that the FM problem has to do with power. (That isn't 100% certain, though - there are a few places where power for parts of the FM section is routed through some filtering components that could conceivably fail.)

I would think the voltages to check to decide if you have a power problem are on the power pins of the IF and MPX chips. That would be pin 11 of the HA11211 and pin 1 of the HA1196, respectively. Both pins should be between 11 and 12 volts DC. Be very careful probing those pins so as not to make a short circuit with adjacent pins.

Hope this helps,

chazix
 
Tested pin 11 of HA11211 set on dc volt on multimeter read 5.2v and pin 1 of HA1196 set on dc volt on multimeter read 11.5v @chazix
 
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secrets said:
Tested pin 11 of HA11211 set on dc volt on multimeter read 5.2v
Click to expand...

If you are confident that you tested the correct pin, then this reading indicates that there is either a problem with R220 or L203 (such that they limit the power supply current available to the HA11211), or perhaps a problem with the HA11211 itself (such that it is trying to draw much more power than it should - in this case, I would expect both the HA11211 and R220 to be very noticeably warm).

There are other possibilities, such as a bad solder connection, but they are relatively rare (in my experience).

If you can locate R220 (a 56 ohm part according to the hifiengine manual), it might be a good idea to measure the DC voltage on both of its terminals.
 
grounded lead to chassis set to dc tested l203 either leg 11.32v tested r220 with test lead on chassis and one leg read 11.33v and the other read 12.99v seems like the ic might be bad but what could cause it? have the unit on and neither is warm or hot. on the ha11211 i tested the pin next to the one that read 5.19v and it reads 11.36v
 
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I think you have established that the power supply for the tuner is OK.

I forgot to ask what I should have asked first: Do you get any sound when the MUTE switch is set to OFF?

Also, does the AM function work?
 
chazix said:
I think you have established that the power supply for the tuner is OK.

I forgot to ask what I should have asked first: Do you get any sound when the MUTE switch is set to OFF?

Also, does the AM function work?
Click to expand...
No sound from fm while pressing the mute switch I tried with it on and off but when I press it I can hear a small thump very lightly .the am works fine and while on am the meters function as they should meaning the tuning and signal meter . when switched to fm the tuning meter drops a very small amount . Now I feel as the mute is causing the fm not to work but I tested the switch and the voltage changes when pressed on and off .
 
I'm afraid I can't think of any more relatively simple checks. I think the best way forward is for someone who understands the signal paths in the tuner section to do some hands-on troubleshooting.

Except for the power supply, almost any repair to the tuner section should be followed by an alignment, so that is another indication that some help from a local expert is needed.
 
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