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Old 20th Sep 2023, 4:31 pm   #1
jverschut
Diode
 
Join Date: Sep 2023
Location: Bodegraven, Netherlands.
Posts: 2
Default Sony ICF-7600A & 7601 scale calibration

Hi,

Since I'm new here a short intro. I'm Jasper, I live in the Netherlands, 52 years old and I collect vintage Sony world radio's.

Some of the radio's have the issue that the tuned frequency does not match with the indicator on the scale.

Is there anyone here with experience calibrating the scale to the correct frequency on a Sony ICF-7600A or ICF-7601 radio?

Any help will be very much appreciated.

Jasper
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Old 20th Sep 2023, 7:58 pm   #2
marceljack
Hexode
 
Join Date: Apr 2021
Location: Paris, France.
Posts: 255
Default Re: Sony ICF-7600A & 7601 scale calibration

Hi jverschut,
Welcome on the site.
How big is the difference between the displayed frequency and the received frequency ?
Is it a constant value or somewhat proportional to the frequency ?
If it is a (small) constant value, it could be a misalignment of the IF.
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Old 21st Sep 2023, 12:46 pm   #3
orbanp1
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Join Date: Nov 2009
Location: London, Ontario, Canada
Posts: 678
Default Re: Sony ICF-7600A & 7601 scale calibration

Hi Jasper,

Here is good page on the Sony 7600 series radios:
http://stephan.win31.de/sony76-3.htm#ICF-7601

Regards, Peter
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Old 23rd Sep 2023, 8:02 am   #4
jverschut
Diode
 
Join Date: Sep 2023
Location: Bodegraven, Netherlands.
Posts: 2
Default Re: Sony ICF-7600A & 7601 scale calibration

Quote:
Originally Posted by marceljack View Post
Hi jverschut,
Welcome on the site.
How big is the difference between the displayed frequency and the received frequency ?
Is it a constant value or somewhat proportional to the frequency ?
If it is a (small) constant value, it could be a misalignment of the IF.
Thanks for answering, the difference is quite big and consistent over all SW bands. FM and AM are ok.

Quote:
Originally Posted by orbanp1 View Post
Hi Jasper,

Here is good page on the Sony 7600 series radios:
http://stephan.win31.de/sony76-3.htm#ICF-7601

Regards, Peter
Thanks or your reply, good page.
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Old 23rd Sep 2023, 1:14 pm   #5
orbanp1
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Join Date: Nov 2009
Location: London, Ontario, Canada
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Default Re: Sony ICF-7600A & 7601 scale calibration

Hi Jasper,

I take you have the service manual for your radio, you would need it.
The one on Stephen' s site is OK, but there is around somewhere a version with better resolution, the file size of that version is about 3.6MB.

In any event, look at the block diagram.
The radio is a dual conversion scheme on the SW bands, but the tuning on the SW bands is at the second LO.
The first IF is quite wide, it covers the width of the SW bands. Mixing down to the first IF is done by the first LO, with switched fixed X-tal oscillators.
The second LO is tuneable (the SW band tuning) and produces the second IF of 455 kHz that the rest of the radio processes.
The second LO is implemented by Q7 and its components. Most probably it there where your problem lies, if the oscillator frequency is off, the band coverage for all the SW bands is off.
The service manual describes the adjustment of the 2nd LO under the title "SW2-10/SW1-9 2nd LOCAL (FREQUENCY COVERAGE) ADJUSTMENT".
You adjust LT4 - CT4 for 4.55MHz to 5.25MHz 2nd LO frequencies.

Looking at it, something does not add up!
The first IF on the SW bands is 10.7MHz. Mixing 4.55MHz to 5.25MHz with it does not produce 455kHz!
Is that the mixing is done with second harmonic of the LO? Most probably. Hmm, interesting!
Still, follow the factory adjustment instructions.

Hope this helps.
Regards, Peter

Last edited by orbanp1; 23rd Sep 2023 at 1:23 pm.
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