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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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19th Nov 2020, 5:38 pm | #1 |
Tetrode
Join Date: Sep 2020
Location: Johannesburg, South Africa
Posts: 85
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Sony ICF-7600AW radio, short wave and AM soft
Afternoon need some guidance above radio. FM is smooth as ice cream but am and sw is like phoning the deepest jungle very faint and you can only hear some sound with headphones on FM is again boom box quality must I look at caps etc because it looks like someone worked on the PCB prior to my purchase
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19th Nov 2020, 7:15 pm | #2 |
Octode
Join Date: Sep 2020
Location: Thetford, Norfolk, UK.
Posts: 1,731
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Re: Sony ICF-7600AW radio, short wave and AM soft
Hi,
Almost certainly surface mount capacitors; they go high ESR and even open circuit. I have repaired a number of these sets and they almost always need completely re-capping. Regardsm Adrian. |
20th Nov 2020, 5:50 pm | #3 |
Tetrode
Join Date: Sep 2020
Location: Johannesburg, South Africa
Posts: 85
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Re: Sony ICF-7600AW radio, short wave and AM soft
Thanks Adrian
Not s ure of where I can get a schematic for this as radiomuseum is hell to downloaded I will clean PCB Saturday and do visual inspection Hope u receive the 3 attachments Adrian |
20th Nov 2020, 8:08 pm | #4 |
Heptode
Join Date: Jan 2011
Location: Croydon, London, UK.
Posts: 767
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Re: Sony ICF-7600AW radio, short wave and AM soft
You'll find the service manual at Electrotanya:
https://elektrotanya.com/sony_icf-76...wnload.html#dl Paula |
22nd Nov 2020, 12:36 pm | #5 |
Tetrode
Join Date: Sep 2020
Location: Johannesburg, South Africa
Posts: 85
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Re: Sony ICF-7600AW radio, short wave and AM soft
Thanks so much Paula I did clean PCB corrosion with alcohol still looks in need of more detox .the radio side by side with another the songs output is about 30%lesser sound it looks tricky to remove PCB?I have component tracker I Will use to see if some caps are gone but I don't want to damage PCB or surrounds removing it?
radio |
24th Nov 2020, 6:15 pm | #6 |
Tetrode
Join Date: Sep 2020
Location: Johannesburg, South Africa
Posts: 85
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Re: Sony ICF-7600AW radio, short wave and AM soft
Struggling to remove PCB on this I have removed all six screws on PCB unclipped the clips and wangled earphone socket and leftside almost out but then I struggled to go any further as I did not want to force and break something
I cleaned PCB with bicarbonate soda and it made a difference with removing the corrosion Is there any hidden drew or clip which maybe hindering the removal of the PCB? |
24th Nov 2020, 11:40 pm | #7 |
Octode
Join Date: Jan 2003
Location: Guildford, Surrey, UK.
Posts: 1,958
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Re: Sony ICF-7600AW radio, short wave and AM soft
The ICF-7600A manual contains dismantling instructions. I recall that you have to tape the tuning drive cord in place on the lower gear wheel, mark the gear positions where they mesh (to help reassembly) and remove the fixing screw and lift off the gear before the pcb will come out. It's best to read that dismantling page before diving in.
I recall a slight problem when removing the pcb from the cabinet, the speaker was stuck to its mounting flange on the cabinet, so the pcb would not lift out for some reason I have forgotten. Take care not to damage the cone if your speaker is stuck. Ron Last edited by ronbryan; 24th Nov 2020 at 11:53 pm. |
25th Nov 2020, 9:51 am | #8 |
Tetrode
Join Date: Sep 2020
Location: Johannesburg, South Africa
Posts: 85
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Re: Sony ICF-7600AW radio, short wave and AM soft
Many thanks Ron i will proceed carefully so I will forget the hammer and tong approach maybe I just connect external amp in speaker connector ? But that would count as a non repair!
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2nd Dec 2020, 9:34 pm | #9 |
Octode
Join Date: Sep 2020
Location: Thetford, Norfolk, UK.
Posts: 1,731
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Re: Sony ICF-7600AW radio, short wave and AM soft
Sorry for delayed response - I have been away from my computer for a week.
The problem with removing these sets from their cabinets, is often the speaker has become 'glued' to the front of the case. Look and proceed with caution, looking to see if the speaker is stuck, as any force will tear the cone. From your description and work thus far, it is almost certain that the caps need replacing; I have found it fairly common for them to leak and cause the sticky residue on the PCB. |
3rd Dec 2020, 8:26 pm | #10 |
Tetrode
Join Date: Sep 2020
Location: Johannesburg, South Africa
Posts: 85
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Re: Sony ICF-7600AW radio, short wave and AM soft
Thanks Ron had almost removed the board and yes
The cone housing did tear off I did try and reassemble but there was an obstruction so I have it on my bench ready to try again! at least the radio still works on FM and sw plus am! But now the short wave band switch moves fine but.... But i am Picking up the same Swahili station on all bands so the switch short wave is not changing bandwidth I have put the small white worm gear in and out and played with it keeps falling off after a while Next to the band selector indicator and no joy there! Maybe I should go back and first sort out the sound and faulty caps I see someone has worked on the PCB before me! |
27th Jan 2021, 6:55 pm | #11 |
Tetrode
Join Date: Sep 2020
Location: Johannesburg, South Africa
Posts: 85
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Re: Sony ICF-7600AW radio, short wave and AM soft
Anyhow I have assembled ad resembled this Analog radio I checked the voltages on the ic op amp and they seem to be fine!So now I have to work backwards to find a component that is common to the MW/Sw band being soft but audible! The FM band is fine so it can't be the op amp 8 pin? I have not yet scoped this Sony it does mention on the schematic an other Ic Ha12413 on the schematic but not sure where it is !the Pc has no smd caps and has about 20 radial capacitors and its not the greatest Pcb to work on any guidance? Please
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28th Jan 2021, 3:51 pm | #12 |
Octode
Join Date: Sep 2020
Location: Thetford, Norfolk, UK.
Posts: 1,731
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Re: Sony ICF-7600AW radio, short wave and AM soft
I am surprised that it doesn't use smd caps. Can you post a couple of photos of the PCBs?
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29th Jan 2021, 10:46 am | #13 |
Tetrode
Join Date: Sep 2020
Location: Johannesburg, South Africa
Posts: 85
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Re: Sony ICF-7600AW radio, short wave and AM soft
Thanks bit awkward to show components! Hope you can see these images
I will check corrosion on the PCB and as mentioned previously. Someone else has worked on the PCB! Question is will the voltages stay the same across all three band's FM MW and sw?where will the FM and Am plus Sw signals meet to go out of the op amp 8 pin ic regards |
29th Jan 2021, 11:04 am | #14 |
Octode
Join Date: Jan 2003
Location: Guildford, Surrey, UK.
Posts: 1,958
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Re: Sony ICF-7600AW radio, short wave and AM soft
If you are searching for corroded tracks causing weak reception, you will have to remove the screening cover over the HA12413 and have a good look around.
The block diagram shows FM output signals and AM output signals merging on pins 9 and 12 of the HA12413. There may be coupling components around this point, joining the signals, but the tracks are pretty fine and may well be corroded through. I use 30AWG wire-wrap wire for bridging as it is not too bulky and is insulated. Ron Last edited by ronbryan; 29th Jan 2021 at 11:17 am. Reason: Added last paragraph. |
29th Jan 2021, 11:43 am | #15 |
Octode
Join Date: Jan 2003
Location: Guildford, Surrey, UK.
Posts: 1,958
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Re: Sony ICF-7600AW radio, short wave and AM soft
I've had a look at the circuit diagram now I've found it and there is a possibly suspect 0.47uF electrolytic capacitor C51 in series with the AM output from the HA12413 as well as a load of other filtering components (C50, C76, C42, R73 and R49) but a corroded track in that area is still a strong possibility in my view.
Ron |
29th Jan 2021, 11:47 am | #16 |
Octode
Join Date: Sep 2020
Location: Thetford, Norfolk, UK.
Posts: 1,731
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Re: Sony ICF-7600AW radio, short wave and AM soft
Ah - not the model I was first thinking of, but I have repaired many of these.
The good news - you don't have smd components to work with The bad news - these sets can suffer from PCB rot, where tracks can go open circuit for no apparent reason. Panasonic sets from the same vintage suffer the same problem. Clearly you have identified that the problem is in the early AM stages. As Ron says, you will need to remove the screening cover so you can get at the IC. I have never had failure of ICs in these sets, so the issue will either be coupling components or more likely open/high resistance PCB tracks. Have you got a scope? That would be the easiest way to track the problem. Start at the HA12413 and work back. From experience, the most common PCB tracks to cause problems are the ones carrying the power supply to the various areas, so if you don't have a scope then start by ensuring enough voltage is getting everywhere. Good luck. |
29th Jan 2021, 5:20 pm | #17 |
Tetrode
Join Date: Sep 2020
Location: Johannesburg, South Africa
Posts: 85
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Re: Sony ICF-7600AW radio, short wave and AM soft
Many thanks gents I do have two scopes and an old octopus tracker so its back to school for me and start fault finding !I will let you know ja there is a lot of corrosion on the PCB which I cleaned! at least all the bands are still working I will keep going with this repair.
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30th Jan 2021, 10:15 am | #18 |
Tetrode
Join Date: Sep 2020
Location: Johannesburg, South Africa
Posts: 85
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Re: Sony ICF-7600AW radio, short wave and AM soft
Here is an image of circuitry around their circuitry
I did clean it with bicarbonate soda as the reply s suggest I must begin to hunt for the faulty track /components |
30th Jan 2021, 10:19 am | #19 |
Tetrode
Join Date: Sep 2020
Location: Johannesburg, South Africa
Posts: 85
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Re: Sony ICF-7600AW radio, short wave and AM soft
Images
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31st Jan 2021, 12:27 pm | #20 |
Tetrode
Join Date: Sep 2020
Location: Johannesburg, South Africa
Posts: 85
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Re: Sony ICF-7600AW radio, short wave and AM soft
I have written down voltages on the Bands sw mw fm
With ac adaptor on to me a few things stand out but pin 3 of 5 volts on FM but zero volts on MW and sw bands!all voltages are DC! Does it make sense? |