Sony ICF PRO 80

[eugen_b]

Sony ICF PRO 80

Hi,

I replaced the electrolytic capacitors and cleaned the PCB with alcohol!
FM reception works!
AM on LW, MW and KW no reception, only noise.
As stated, I set the generator to 11.8 KHz, Mod. 400
but nothing to hear, no mod. tone! (ICF also at 11.8 KHz AM)

Can someone please tell me how to do it or what I'm doing wrong.
Tried to set the filters ... it was unfortunately a mistake, because there was no sound to heard (400 Hz).
Vias can also be affected by the broken electrolytic capacitors to be pulled ?
I fed the signal on IC_TA7761F pin 16 and in via a capacitor
Signal (tone 400 Hz) perceived. I appreciate every help, thank you.
Eugene
Sorry...regret my English is not so good!
i try a translator!!!

[orbanp1]

Hi Eugene,

Welcome to the forum!
Your English is just fine, do not worry about it!

The Pro-80 had different versions, Type-1 to Type-4, with different frequency coverage - which one is yours?

First point is that neither versions of it receives AM at 11.8kHz!
Coverage starts at 150kHz, so adjust your sig generator accordingly!

As a ground rule, do not adjust any settings, unless you do know what is that adjustment doing and what is it you want to achieve.
It is a lot harder to bring back everything in alignment after such an event!

Also, if you do not have it, download the service manual of the Pro-80, it is on the net.
Once you have that I can help you with fixing your radio, I have worked on the Pro80 "remotely" (helped someone, who successfully repaired his scanner).

Regards, Peter

[ms660]

11.8MHz.

Lawrence.

[eugen_b]

Hello,
I'm happy that someone wants to help me!
I mistyped it should be 11.8 MHz.
The radio goes from 150 KHz to 108 MHz (SW 30 MHz)
Unfortunately I have attempted to reconcile the recipient.
It is also difficult for me to interpret the answers, but with your help Peter I hope that it will work well. Nice evening from Augsburg, Eugen

I have a service menual
and try to follow the tips. thank you

[Goldieoldie]

With the radio set to receive am ,any frequency .Try with your generator set to 455 kc/s ( the am if frequency ) inject the signal via the ferrite aerial.You don’t need to touch the aerial just put the output near it
If you get a sound then the if circuits are ok so it could be the local oscillator
Cheers,Pete

[ms660]

So far as I can make out it's dual conversion on AM.

Lawrence.

[eugen_b]

Hello,
I'll try ... unfortunately I only have time at the weekend!
I'll let you know as soon as I know something
Thank you and have a nice day, Eugene

[Goldieoldie]

One fault I had on one of these was an open circuit on the am detector transformer T11
This was because the electrolyte had leaked from the adjacent capacitors and corroded the windings
Also the same leakage can corrode the connections from one side of the board to the other

[eugen_b]

Hi,
Good morning Peter
I followed your advice and found the following:
1. 455 KHz can be heard when I bring my generator nearby.
2. Still have to check T 11, but when I put my generator over T11 the sound is very loud!
3. The 11.8 MHz signal is unfortunately still not working !!!
4. The core of T11 has a crack and cannot be moved.
What else can I do?
Is the T11 available as a replacement?
See you soon and have a nice day.
Greetings from Augsbuerg and thank you, Eugene

[ms660]

Is the 3 volts being switched to the LW/MW/SW 1st mixer VCO?
According to the schematic there should be approx. 3 volts on the collector of Q227.

Can you check to see if the 2nd mixer oscillator is working? The manual shows a frequency counter being used to check it's frequency (55.39MHz)

Lawrence.

[orbanp1]

Hi Eugene,

You are getting some good advice here!

Here is a short summary how the radio works on the AM bands, also some info on the FM mode as well. This should help you follow the signals and find where does it fail.

The reception on AM, from LW to VHF, is double conversion heterodyne mode.
The SW and VHF reception starts with the RF amp, that is implemented by Q4 and Q5, a cascade amplifier. That amplifier is followed by selectable low-pass filters, for SW the break point is above 30MHz, for VHF it is at about 70MHz. Those filters are based on L7, L8, L9 for VHF, and L10, L11, L12 for SW. The filters are switched by diodes.
The LW and MW RF signal is also tied to that point, it is coming from the BC-RF amp circuit using Q6, Q12, Q13. The signal from there is also switched by diodes. (Look at the gray arrows.)
The selected RF signal goes to a balanced mixer, implemented by Q7 and Q8 FETs. The LO signal is coupled to the source of the mixer FETs by T7. The LO signal is coming from selectable VCOs on the PLL board.
The first IF filter is implemented by T8, XF1, and T9. The first IF frequency is around 56MHz. The filtered IF signal goes to the NBFM chip, IC1, pin 16. Again, follow the gray arrow.
On the AM bands the signal is routed back from IC1 to IC2, that is an AM/FM chip, and it works in the AM mode.
In IC1 the AM-IF signal (it also includes VHF) is mixed down to the 2nd IF frequency, and that is 455KHz. The 2nd LO is a fixed frequency, it uses an X-tal, X2. The 2nd LO frequency can be measured at the test point at L19. Do check if that signal is present!
The mixer output is on pin 3 there is the first 455KHz filter, T13. It is followed by selectable ceramic filters, CF6, CF7, for wide and narrow bandwidths. The filters are selected by diode switches.
The output from the filter is amplified by Q21. The signal from the collector of Q21 goes to pin 5, the NBFM IF amp and quadrature detector for NBFM reception. In NBFM mode the audio (in VHF) comes out on pin 9 of IC1.
For AM reception the 455KHz signal from the collector of Q21 also goes back to pin 19 of IC2, the AM/FM chip. The AM oscillator in IC2 is not running, the signal is already mixed down to 455KHz, the mixer serves just as amp. The AM audio comes out at pin 12.
In SSB mode there is a separate SSB decoder implemented by Q27 (BFO osc), mixer diodes D26, D27, and audio amp Q28.
The audio signals are also selected by diode switches according to the mode.
In AM mode the S-level detection still works in IC1, as it also gets the signal, and is used for squelch.

Regards, Peter

[eugen_b]

Hi Lowrence,
Hi Peter,

So Q227 has the 3 V, unfortunately the 2nd mixer (55.390MHz) does not work!
for whatever reason!?
IC 1 defective?
Peter I say thank you for the information, thanks to Lowrence now I know more.
Unfortunately I'm on the weekend Grandpa (63) and my granddaughter is looking forward to playing with me! so the radio has to wait.
Wish you both a nice weekend. I'll let you know if I know something new.
All the best from Augsburg and stay healthy!

[Goldieoldie]

From my experience most of the faults after replacing the capacitors( have you double checked your work ) Is damage cause from the old leaking capacitors
This can be the traces going open circuit to the little link throughs that link one side of the board to the other ( common ) Going open circuit
Also the little coils and transformers going open circuit from corrosion from the old capacitors
So check around the capacitors for this sort of damage and check those components

[orbanp1]

Hi Eugene,

Have fun with your granddaughter on the weekend, the radio for sure can wait!

Do check the 2-nd LO according to the service manual, as listed on Page 19, titled "Second Local Oscillator Alignment".
Check the signal with a scope too, use a 1:10 probe, or the 1:10 probe setting, if the probe is adjustable (the input capacitance is only about 10pF - 15pF for a 1:10 probe or setting as opposed to 60pF to 70pF in the 1:1 mode).
You should verify the existence of the signal with a scope and not just with a frequency counter!!
The 2-nd LO oscillator circuit is implemented by parts of IC1. To read up on it, download the TA7761 datasheet:
https://www.alldatasheet.com/datashe...BA/TA7761.html
The 2nd LO oscillator is a crystal Pierce-oscillator, the X2 crystal is most probably a 3rd overtone crystal.
An overtone crystal has resonances, in addition to the fundamental frequency, at odd multiples of the fundamental frequency too. The cut of the crystal is optimized to produce these overtones.
For a crystal oscillator circuit to run at an overtone frequency and not at the fundamental frequency there usually is an LC tank circuit tuned to the required overtone frequency.
In the Pro-80 2nd LO it is L18 and the capacitors around it that implements that tank circuit. If that tank circuit is maladjusted it might make the oscillator not to run.
If the 2nd oscillator is indeed not running you could try adjusting the tank circuit (L18).
First mark the original location of the L18 coil setting, attach the scope to the test point "B", as listed in the 2nd LO adjustment section. Tune L18 to maximum output.
If that adjustment does not make the oscillator run, put back the L18 slug to the original marked position. Chances there is something else amiss in the circuit.
The advice to check PCB traces and coils for continuity is spot on, the PCB and coils in those Sonys are really fragile! My friend whom I helped fix his scanner also had issues with bad traces and coils!

Regards, Peter

[eugen_b]

Hi Peter,
thanks for your answer, will check the PCB and measure for interruptions.
But if the quartz is defective or the L19 where can I buy spare parts ... I have replenished and unfortunately find nothing! Do you know where?
Happy Sunday, Eugen Boros

[orbanp1]

Hi Eugene,

As mentioned, those Sonys are really fragile, so do be careful with the repairs!
A "repair" can make some damage!

Finding replacement parts for that radio will not be easy!
A good bet is to find a faulty similar radio.
You could try Sony too!

The crystal is probably special order, even for Sony!
Coils could be cannibalized from similar vintage Sony Walkman's. Chances are that you might need to rewind those coils, but that is doable!

T11 is the AM-IF detector coil. Leave that alone for the time being, chances are that it is still in "reasonable tune".

You could try injecting 455kHz AM modulated signal starting backward from the AM-detector stage. Use a 10nF DC blocking capacitor to couple the signal. Follow the schematics!
The overall 455kHz IF-amp gain is probably around 40dB - 50dB, give and take, this is a dual conversion radio, so there is gain in the first IF-stage as well.
The demodulated output audio signal is probably in the 10mV to 100mV range.

If the 455kHz IF-stage works fine at all stages, "move backwards" again, inject into the first IF-stage AM-modulated signal.
As mentioned before, the first IF frequency is around 56MHz. I would have to dig a bit deeper as to what is the exact frequency. But that should be close enough to find the faulty stage.
This would also tell you if the second conversion works, but do check the 2nd LO too!

It helps if your sig gen has a calibrated output attenuator...

Regards, Peter

[Goldieoldie]

Did you replaced all the electrolytic capacitors ?
There are two hidden in the screen can on the bottom board ,they are for the dc to dc converter Circuit
You have to unsolder from the bottom board underneath the LCD board.Be careful of the flexi board linking the two boards
A bit fiddly but ok to do

[henrymarpla]

The DC to DC converter caps are very important, since they generate the voltage of the Varicaps.

[eugen_b]

Hello everybody,

I replaced all capacitors! The DC / DC also brings the right voltage. Everything points to the quartz, which is so hard to get. A friend who is a radio amateur has gotten a quartz with 55.5 MHz ... or I don't know how it works with the switch, because he will give me the quartz in two weeks bring when he comes back. An acquaintance recommended the company ASWO but they are only accessible to specialist workshops!
Icw will try and let you know if something new arises.
Thank you all for your help (the Germans are not all ready to help)

[eugen_b]

Hello everybody,

I cleaned my problem child again and the solder joints on the L19 and quartz
re-soldered. Yes a miracle is seen the radio works again.
Did a new comparison and all OK!
Whether it was cleaning the circuit board or re-soldering the solder joints was the cause
I can not say it!
But the quartz was not broken!
It works and I'm happy.
Thank you all for your help.
Greetings from Augsburg, Eugen