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SX 626 no FM or AM.

Stereoboy70

Stereoboy70

Active Member
A friend gave me an SX 626. It’s a newer model with the tuner gang that’s part of the tuner board. Not like the older ones where the tuner gang was separate. I went through it and recapped it and cleaned it up. The aux , tape and phono all work great. I have no radio. No AM or FM. I recapped the tuner board entirely and replaced the HA 1137 IC chip which was super corroded
2 new 535 transistors and still absolutely nothing. Could it be one of the other IC chips? I’m not really set up to test the tuner with a frequency generator etc…. Maybe I’m missing something. My friend said it just stopped working one day. The AM went and then the FM. No sound . Nothing. Pushing the stereo / mono button does nothing. The other functions all work fine. Thanks in advance.
 
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SInce it's both AM and FM, I would suspect something common to both. Do you have the 12.5v supply at the tuner board? Are there any grounded mounting screws that might be oxidized?
 
I’ve checked some voltages on the IC chips and some of them are not what the service manual shows. I’ll check for proper V again
Stay tuned. (Pun intended)
 
This could be as simple as a dirty selector switch or broken wire. The voltage from the power supply comes to the tuner board on pin 4. It's filtered and sent out to the selector switch on pin 7. The switch energizes parts of the AM or FM circuitry through pins 16 & 20 respectively. You'll see this on the block diagram on page 18 of the SM.
 
Pin 4 has 1.8v on FM and 13.1v AM. I know there are two different setups for this receiver as far as the tuner board goes. I have the AWE-031 board. Pins 16&20 are dead.
 
TomSc said:
This could be as simple as a dirty selector switch or broken wire. The voltage from the power supply comes to the tuner board on pin 4. It's filtered and sent out to the selector switch on pin 7. The switch energizes parts of the AM or FM circuitry through pins 16 & 20 respectively. You'll see this on the block diagram on page 18 of the SM.
Click to expand...
Also Ive cleaned the switches thoroughly. I recorded all the V on all the pins as well as the IC chip pins. I will post results. Some of the V seem off. I know some of the V change when you switch from AM to FM
Seems odd that the AM went out first and then the FM. All of the sudden
 
Your not giving much to go on.
Start by making sure the chips have the required supply voltage where its supposed to be.
Pin 20 is the common 13.5 volt feed to the three chips. It branches off. Follow the voltage through that circuit. The voltage is reduced with resistors. Keep chasing it to the chips?
 
zebulon1 said:
Your not giving much to go on.
Start by making sure the chips have the required supply voltage where its supposed to be.
Pin 20 is the common 13.5 volt feed to the three chips. It branches off. Follow the voltage through that circuit. The voltage is reduced with resistors. Keep chasing it to the chips?
Click to expand...
Hello again. I’ve found a possible issue with the V on pin 5 from the power supply board to pin 6 on the EQ board. My schematics show 30v but I’m only getting 12.8-13 v. Since the tuner board also runs through this board could this be an issue ? Again my aux input is full volume but my radio (am/fm) I have to crank it up to hear anything. Thanks again
 
Did you try using a source in the aux input?
It sounds like a amp issue with low supply to both amps?
The +30 volt supplies the amps (Both amps).
Try a different a input source and confirm that the receiver is also weak.
Or:
Rebuild the PS using three KSC2383YTA for Q1 through Q3. Pay close attention to the leg placements the 2383's are ECB.
Replace the caps as a good measure.
 
zebulon1 said:
Did you try using a source in the aux input?
It sounds like a amp issue with low supply to both amps?
The +30 volt supplies the amps (Both amps).
Try a different a input source and confirm that the receiver is also weak.
Or:
Rebuild the PS using three KSC2383YTA for Q1 through Q3. Pay close attention to the leg placements the 2383's are ECB.
Replace the caps as a good measure.
Click to expand...
PS board is rebuilt with new caps and transistors. My board is the AWR 029B not the older one. All the diodes check ok
 
zebulon1 said:
Did you try using a source in the aux input?
It sounds like a amp issue with low supply to both amps?
The +30 volt supplies the amps (Both amps).
Try a different a input source and confirm that the receiver is also weak.
Or:
Rebuild the PS using three KSC2383YTA for Q1 through Q3. Pay close attention to the leg placements the 2383's are ECB.
Replace the caps as a good measure.
Click to expand...
The supply V to the amp board at pin 3 is 59v. This is good. Something on the board is dropping the v to pin 5 (30v). I’m reading 13 v. I’ll investigate further. Thanks
 
Desolder the pin and wrap from pin 5 and recheck the voltage at the pin solder pad. Check for the 30v.
If its there then a short on the amp or EQ.
 
To all the people who helped me troubleshoot my SX626 tuner issue. I’m currently suffering from HIA syndrome. After hours of tinkering and many sleepless nights I finally found the problem.
I had replaced the transistor at Q2 on the PS board (AWR029B). The pin out was EBC, NOT ECB!!! Dammit Man!!!!! Volume is at full and all is good. The simplest thing can wreck your month. Thanks again to all who chimed in and gave me some guidance. I count this as a success because right or wrong, I learned something. I’m no electronics guru by any stretch of the imagination but I’m learning every time I open up a unit to repair. I’m currently on some self medication for the Head In Ass problem. Haha. Cheers!!
 
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