Sony CFS-5000S radio cassette player no FM reception

[mikey5791]

Hi forum members,

In the past i have had many helpful hints from generous forum members in diagnosing and solving issue related to most of my electrical things.

Fyi, i have been keeping this unit of Sony radio cassette player as the cassette belting has worn off but the radio has been working fine before. Recently, out of a sudden i found out i can't get any radio reception at all (no signal from FM,MW or SW band) except some buzzing warp noise from the speakers.

I opened the casing inside and checked for any dry solder, burned component or loose wires but there is none found. Connected the external rod type antenna and adjust to many other direction but i can hear some warbled noise, not very clear but i think those are radio signal. Somehow i believe this could be due to a deteriorating FM ic or some component that i missed.

Hopefully someone experience enough in radio frequency detection can kindly guide and help me to diagnose and find the lost radio signal. Hope to revive this radio instead of throwing to the dump.

[lotas]

Re: Sony CFS-5000S radio cassette player no FM reception

There is a problem in the switches themselves (contact in groups disappears), you need to puff into the hole from a spray can from the "Contact Cleaner" series.

[Devil_rider]

Re: Sony CFS-5000S radio cassette player no FM reception

Definitely start with contact cleaner in the switches then look for power on the tuner ic , check power supply for ripple that would affect oscillators and create noise

[mikey5791]

Re: Sony CFS-5000S radio cassette player no FM reception

Definitely start with contact cleaner in the switches then look for power on the tuner ic , check power supply for ripple that would affect oscillators and create noise

Hi lotas and Devil_rider,

Thanks for reply. Done spraying with electronic contact cleaner but still no signal. My next step as suggested is voltage testing on tuner ic LA1260 at which after removing the whole board and connect wires manually. Then power on and put dmm black probe on pin 4 and red probe on pin 6 vcc. But no dc voltage detected.

In addition, i also done voltage check on equalizer ic LA3600, dmm black probe on pin 16 and red probe on pin 4 and then on pin 14 vcc. Too bad there is no voltage detected. From the above test, i kind of suspect both the tuner ic LA1260 and equalizer ic LA3600 are faulty.

I googled for both the ic but there is no local online seller except from ebay. Later i found out local seller suggest to use newer type single chip radio tuner RDA5807M in a diy kit which i might consider. Any comment or suggestion? Kindly advise.

[R_J]

Re: Sony CFS-5000S radio cassette player no FM reception

You are missing your vcc supply voltages, check the voltage on Q302 (+6v regulator) You should have 9V on the collector and 6v on the emitter.
Download the service manual for the schematic

[mikey5791]

Re: Sony CFS-5000S radio cassette player no FM reception

You are missing your vcc supply voltages, check the voltage on Q302 (+6v regulator) You should have 9V on the collector and 6v on the emitter.
Download the service manual for the schematic

Hi R_J,
By putting my dmm black probe on primary ground(-9vdc connector), red probe on left side Q302 being c1815 npn transistor emitter, i did not detect any voltage. But when i put red probe on middle of Q302 the collector, i got 9vdc. Is this indication Q302 is open and faulty?

[R_J]

Re: Sony CFS-5000S radio cassette player no FM reception

Hi R_J,
By putting my dmm black probe on primary ground(-9vdc connector), red probe on left side Q302 being c1815 npn transistor emitter, i did not detect any voltage. But when i put red probe on middle of Q302 the collector, i got 9vdc. Is this indication Q302 is open and faulty?

No, this indicates Q302 is not turned on. (or there could be something shorted on the emitter side)
Check if there is voltage on the base, you may have a shorted D302 zener diode

You need to put your negative meter lead on chassis ground IE: D301 anode

[mikey5791]

Re: Sony CFS-5000S radio cassette player no FM reception

No, this indicates Q302 is not turned on. (or there could be something shorted on the emitter side)
Check if there is voltage on the base, you may have a shorted D302 zener diode

You need to put your negative meter lead on chassis ground IE: D301 anode

R_J,

Q302 emitter is connected to R216 a 220 ohm (red,red,brown,gold) resistor . On dmm, it reads 198 ohm and not shorted. By the way, there is no voltage on base of Q302. Then i trace further to Q202 on top pcb(but silk printed Q203 on the back) with marking 603 42R which is a NPN Darlington transistor, same also with Q102(silk printed Q103 on the back).

Looking at pdf datasheet of ztx603 it is emitter on left side ,base is mid pin and collector on right side. Voltage test on both Q202 and Q102 on all the pins while my negative ground is on anode of D301 shows no voltage at all.

Fyi, D302 zener diode seems like for led display power on purpose. It is lit on red dim light whenever i turn the switch to radio tuner.

[R_J]

Re: Sony CFS-5000S radio cassette player no FM reception

I made a typing mistake, the zener I am talking about is D301, (not D302 led) on the base of Q302. See the schematic.
R216 connects to Q203 emitter NOT Q202. (Q202 is a line out amp)

So can you measure the voltage on Q302 emitter, base and collector and post the results.

Does D302 LED light up? If it does R308 should have 9V on one side

I have marked the transistor and diode so there should be no mistakes

[mikey5791]

Re: Sony CFS-5000S radio cassette player no FM reception

I made a typing mistake, the zener I am talking about is D301, (not D302 led) on the base of Q302. See the schematic.
R216 connects to Q203 emitter NOT Q202. (Q202 is a line out amp)

So can you measure the voltage on Q302 emitter, base and collector and post the results.

Does D302 LED light up? If it does R308 should have 9V on one side

I have marked the transistor and diode so there should be no mistakes

Hi R_J,
The zener diode D301 by dmm diode test reads 714 on one side and 607 on other side if i flip the probe. Does the reading seems to indicate shorted diode? I saw marking of "02" on the zener diode. Should i replace this first?

Following your picture guide on new ground point near ic 202, i did voltage test on Q302 being the c1815 trans. The left side pin being emitter reads no voltage.(no 6vdc) So is the right pin being the base(no 6.7vdc). Only the middle pin being the collector has 9vdc.

Fyi, during D302 led light up, i measured resistor R308 and got 9vdc on one side while my negative ground is on anode of D301.

[Devil_rider]

Re: Sony CFS-5000S radio cassette player no FM reception

How did you measure the diode? Ohm setting or diode setting on dmm? Check r307 if open. As rj said use anode of Zenner as reference for voltage measurements.

[R_J]

Re: Sony CFS-5000S radio cassette player no FM reception

Hi R_J,
The zener diode D301 by dmm diode test reads 714 on one side and 607 on other side if i flip the probe. Does the reading seems to indicate shorted diode? I saw marking of "02" on the zener diode. Should i replace this first?

Following your picture guide on new ground point near ic 202, i did voltage test on Q302 being the c1815 trans. The left side pin being emitter reads no voltage.(no 6vdc) So is the right pin being the base(no 6.7vdc). Only the middle pin being the collector has 9vdc.

Fyi, during D302 led light up, i measured resistor R308 and got 9vdc on one side while my negative ground is on anode of D301.

Here is what you measured, correct? No base voltage = NO emitter voltage, so NO vcc to the tuner ic's

[mikey5791]

Re: Sony CFS-5000S radio cassette player no FM reception

Hi Devil rider and RJ,

On D301 zener diode, while power still off if i use dmm ohm setting i got reading of "1" while other side reads "-0.672" after flipping probe. If i use diode setting i got reading of "1" while other side reads "-670" after flipping probe.
R307 with color green,blue,brown,gold which is the 560 ohm resistor reads 443 ohm on my dmm.
R325 with color brown,red,red,gold which is the 1.2k ohm resistor reads 672 ohm on my dmm.

To answer RJ, my results on post no.10 remains the same. Using the anode of D301 as negative ground, while power on only the middle pin of Q302 collector has 9vdc. No base voltage and no emitter voltage.
Kindly continue to assist. I appreciate very much.

[R_J]

Re: Sony CFS-5000S radio cassette player no FM reception

LOOK AT THE SCHEMATIC. If there is 9 volts on the collector and 0 volts on the base either there is a short across D301 OR R307 is OPEN. D301 is a 6.8 volt zener diode. Remove Q302 from the circuit and then check if there is 6.8 volts on D301

Is this an autoranging meter? Are you sure you are measuring 443 ohms and not 443 MEG ohms across R307

[mikey5791]

Re: Sony CFS-5000S radio cassette player no FM reception

LOOK AT THE SCHEMATIC. If there is 9 volts on the collector and 0 volts on the base either there is a short across D301 OR R307 is OPEN. D301 is a 6.8 volt zener diode. Remove Q302 from the circuit and then check if there is 6.8 volts on D301

Is this an autoranging meter? Are you sure you are measuring 443 ohms and not 443 MEG ohms across R307

RJ,
Yesterday i desoldered off the cathode side of D301 zener diode. My dmm on diode test reads 606 on one side and reads "1" on other side after probe flipping. I also desoldered one leg off the resistor R307 and set dmm on 2k ohm scale. Got reading of 564 ohm.

Fyi, my dmm is a manual setting type, not auto range type. From above tests, it sort of concludes both D301 and R307 are still good. Correct me if i am wrong. Btw, i did voltage test on c119 and c122 while putting my black probe on anode of D301 as ground. Both caps positive side reads about 9vdc.(as per schematic)

After removing Q302 off circuit, i got 6.8vdc on D301 zener diode. This confirm the zener diode receiving proper voltage but it doesn't reach the emitter or base of Q302. Wonder which part is at fault now.

[R_J]

Re: Sony CFS-5000S radio cassette player no FM reception

C119 and C122 are not part of this regulator circuit.

After removing Q302 off circuit, i got 6.8vdc on D301 zener diode. This confirm the zener diode receiving proper voltage but it doesn't reach the emitter or base of Q302. Wonder which part is at fault now

then either C306 is shorted or R325 is open. I would replace C306. In this test with Q302 removed, and you have 6.8v on D301, C306 should charge to 6.8v through R325.
With C306 replaced you should have 6.8v going to Q302 base connection. If this is true, then reinstall Q302 and you should then have 6.8 On the base and 6V ON the emitter.

C306 is a 220µf/10v but not that critical, If you don't have that value on hand any value close should be ok to test the circuit.

The circuit could not be simpler (6 components), they use this type of regulator in many circuits, even to this day.

[mikey5791]

Re: Sony CFS-5000S radio cassette player no FM reception

C119 and C122 are not part of this regulator circuit.

then either C306 is shorted or R325 is open. I would replace C306. In this test with Q302 removed, and you have 6.8v on D301, C306 should charge to 6.8v through R325.
With C306 replaced you should have 6.8v going to Q302 base connection. If this is true, then reinstall Q302 and you should then have 6.8 On the base and 6V ON the emitter.

C306 is a 220µf/10v but not that critical, If you don't have that value on hand any value close should be ok to test the circuit.

The circuit could not be simpler (6 components), they use this type of regulator in many circuits, even to this day.

RJ,
Desoldered c306(220uf10v cap)and it was detected as a 0.07 ohm resistor on an esr meter. Then i replaced with an Elite 220uf25v cap. Put in the Q302(c1815 trans). Now the emitter has 6vdc, collector is 9vdc and the base is 6.7vdc.

The FM audio signal is still noisy with lots of buzz, i hardly can hear any clear reception. Tested voltage on tuner ic LA1260 by dmm black probe on pin 4 as ground and red probe to pin 6, my digital dmm reads about 6vdc. The voltage is about the correct one according to datasheet. Also, i tried reposition my external arial antenna for better fm reception but still could not get anything clear. I did try touching my antenna slightly to touch pin 8(fm output pin) of LA1260 tuner ic, but still no fm reception.
Any suggestions? Kindly guide with thanks.

[mikey5791]

Re: Sony CFS-5000S radio cassette player no FM reception

RJ,
Thanks for your earlier tip on replacing C306 which is defective and restoring the proper voltage to Q302(c1815 transistor). After power on for like 30 minutes, all the three pins of Q302 will be super hot to my finger touch. I was trying to tune in FM station but so far i can't hear any clear signal yet. Just static buzzing. Can this be caused by a faulty FM oscillator or some component related to FM frequency? I had tried pressing on few locations of the tuner board side to check for any crack or loose solder while tuning in to FM but there is still no audible signal.

Later on i tried change to MW band, i can hear some faint audible vocal from one station. Not crisp clear but i can hear the words clearly. Fyi, this Sony tuner has radio band selection switch of FM,MW and SW (short wave).

Looking forward to your further diagnosis if possible. Thanking in advance.

[R_J]

Re: Sony CFS-5000S radio cassette player no FM reception

Did you ever download a service manual? I hope you did NOT try adjusting any of the coils etc.?
If C306 was that bad, I suspect there are others just as bad.
A scope would make quick diagnosis but I doubt you have one, so you would need to start replacing caps. I doubt the ic's or transistors are at fault but the caps have dried up over time.

Start by replacing C30 (10µf/16v) Then replace the audio coupling caps, C40[FM] & C41[AM] (0.47µf/50v)

You can also just place another cap in parallel with the one on the board so you don't have to remove them, for example C30 could be bridged with another 10µf to see if it improved the operation, if it didn't then that cap is not the problem. C40 and C41 could be bridged with a 1µf to see if FM or AM level improved.

Do you have another FM receiver to check what FM stations are operating in your area?

[mikey5791]

Re: Sony CFS-5000S radio cassette player no FM reception

RJ,
For this tuner, i have not download the service manual and have not adjust any of the coils.
Appreciate your advice on replacing c30,c40 and c41 but in my model i can't seem to locate those caps position. Fyi, i did tried your suggestion on bridging and placing another cap in parallel. I started with c29,c32,c36,c33,c32,c34,c13,c25 and c21 but reception didn't improve.
Instead,. I desoldered all the above 9 caps and tested for esr and eventually found out c32 is faulty (it was detected as a 0.03ohm resistor). Replaced c32 and voila! Now the tuner works like new, the reception is crisp clear.

Thank you to all who assist and help in reviving this tuner. Another tuner saved from the dump.