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Hitachi SR 303L

binbash

binbash

New Member
Good morning from Uruguay, i register in the forum searching info about a old Hitachi receiver. I buy the receiver for 30 USD untested, because it is in very, very good external condition; all knobs, no scratches, serigraphy ok.

I turned the receiver on, and all lights on the panel are off, i put an mp3 player on Aux and a FM antenna.

The receiver works fine on Aux, only minor clics and noise on volume knob, loudness and source-tape buttons.

But the FM section emits no sound, the signal panel works fine and detects the stations tuned but no sound nor noise on speakers. The MW section emits a continuos noise added to a faded voice or music of station selected.

the model is Hitachi SR303L, Any ideas? Thanks in advance.
 
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Hola, binbash. Do you get any sound from the FM section if you set the "FM MUTE" switch to "OFF"?

Cheers,

chazix
 
Hola, yes i tried, and no difference in either off or on positions. Thanks

Sorry for my english, i don't speak english very well, only spanish. I use google translator a lot.
 
Your English is certainly better than my Spanish.

I think the most likely cause of the problem is that some component has failed in the circuitry that "detects" the audio from the FM section, or in the stereo decoder. I can't find a schematic for your receiver, so it is difficult to make a more specific guess.

Can you identify the "chips" (integrated circuits) that are on the same board as the tuning capacitor? The chips should be marked with "HA" and some numbers. For example, "HA1196" is a stereo decoder chip made by Hitachi.
 
Bueno! Can you locate TP4 on the tuner board, and touch it with your finger? (There are no dangerous voltages on the tuner board.)

If the HA1196 and the remainder of the FM audio path were working normally, I would expect that you would hear a faint hum from the speakers when you touch TP4.

(If you have an audio signal generator, you could connect its output to TP4 instead of your finger. If you use a generator, start with a very low output.)
 
I don't have a signal generator, but when i touch TP4 with the finger, both speakers emits a hum, like "MMMMMMMMMMMMMMMM"
 
Interesting. The hum is evidence that most of the FM audio path is working.

I believe the SR-303L has only a signal strength meter, so when you say the receiver "detects the stations tuned", I think you mean that the meter deflects higher when the receiver is tuned to a station. Is that correct? That would indicate that part of the HA11211 chip is working, but it doesn't indicate whether the part that de-modulates FM signals is working.

Do you have a DMM (digital multimeter)? If so, can you connect the DMM to read the voltage between TP2 and TP3?

If the FM demodulator is working correctly, the voltage between TP2 and TP3 should change from slightly positive to slightly negative as the receiver's tuning is moved back and forth around the center of a strong station.
 
I don't know if I made a mistake and i was working with MW or LW, not FM the first day; but now the signal meter doesn't move in FM (when turn the tuning knob) in MW works.

In addition, stereo led indicator never lights.

Yes, i have a multimeter , i will try to read the voltage betwenn TP2 y TP3.
 
First thing I always do with old analog tuners is clean the trimmers on the tuning gang. The usual suspects are FM Oscillator which is usually on top of the gang and FM Muting. In my experience nearly all old receivers that have come through the door had tuning issues. About three our of four come back to life with a simple cleaning.
 
SoCal Sam's advice makes sense in general, but in this case the total lack of sound (even with muting off) indicates that the IF section isn't working.

If the signal meter doesn't move in FM, there is no need to check TP2 and TP3.

It is not 100% certain, but the most likely problem is that the HA11211 chip has failed.
 
chazix said:
SoCal Sam's advice makes sense in general, but in this case the total lack of sound (even with muting off) indicates that the IF section isn't working.

If the signal meter doesn't move in FM, there is no need to check TP2 and TP3.

It is not 100% certain, but the most likely problem is that the HA11211 chip has failed.
Click to expand...

I will defer to your technical expertise. However, I have had plenty of low power receivers that are not worth taking to my excellent tech. IME, it is worth a try if only for economic reasons. I would point out if Muting is set to reject everything, the OP will get no sound. Also make sure all tuner controls are clean. This eliminates the easy DIY stuff after which technical care is called for.
 
The receiver was stored unused for years before i purchased it in a garage sale. The big variable capacitor was very dusty, i blow a compressed air spray on it two days ago. Can i clean it with "contact cleaner" for a more deep cleaning? or i can damage it?

I'am computer technician, and compressed air and isopropyl alcohol helps certain dusty boards, cpu's and slots to begin operating. I am not a audio technician only have basic understanding, i buy the receiver for personal use because i like the vintage design of it, and it would be nice to fix it myself.

Worse, in my country it is hard to find a good old technician. Nowadays if a electronics equipment fail, people will throw away not repairs it.
 
The first note in this thread is a good description of cleaning the variable capacitor. (I have not read the rest of the thread.):

http://www.audiokarma.org/forums/index.php?threads/how-to-clean-a-tuner-analog.144163/

SoCal Sam mentioned the "trimmers" that make fine adjustments to the variable capacitor. Look for screws on top of the variable capacitor frame, or in some cases down on the daughter PC board. I agree that sometimes the trimmers need cleaning. (They do not affect the muting function, however.) If you move any of these trimmer, make note of the original positions and return them to those positions.

I am reasonably certain that none of the above steps will fix the major problem with this particular receiver, but they might help after the major problem has been resolved.
 
I did the cleaning and i got a great improvement in MW reception, now is near perfect, much better than a modern radio. The FM remains with no sound.
 
If you can obtain a new HA11211 chip, my suggestion would be to replace it.

Replacing that chip should be followed by an alignment procedure, as described in the service manual. But even if an alignment is not possible for you, I think the receiver will still be in better condition than it is now.
 
I'm a stupid, i realized today that on friday when i test the FM, the signal meter didn't move because.... i didn't connect the FM antena........ In summary, the signal meter in FM yes show the station tuned.

And if i put the volume to the max, i can hear a very faint music.

Anyway the stereo led indicator not lights.
 
Oh! That changes the picture. Can you measure the voltage at pin 17 of the HA11211 when the receiver is tuned to a strong FM station (with an FM antenna connected)?

Also, I would again be interested to know whether the voltage difference between TP2 and TP3 changes polarity as you tune above and below the station.
 
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