Advice Needed Technics st-gt650 fm tuning issue

Darryl

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And does anybody know the info on this part its value etc
 

Channel Hopper

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Darryl

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Thanks for your reply.
I do have that from the service manual but cant find any online
 

jeallen01

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I was on the idea that ferrite is ferrite and just replace the core screw considering it only screws through a coil
There are many grades of ferrites with different permettivities - some are optimised for low frequencies, some for medium frequencies - and so on.!
 

Darryl

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So if I try a few that will fit and it brings the discriminator value down to a close 0v would that be ok?
 

jeallen01

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I'm guessing but I suspect that you need a coil - and thus core - that is optimised for the frequency range over which the discriminator operates.

Never delved into how those work but this page seems to indicate that it might be about 300-1300Hz - if so, then you need a coil/core suitable for that range, and thus not from a superhet receiver IF filter (e.g. 455-465kHz, 10.7MHz, etc...)????
 

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You could take one out of another FM radio, anything from the 80-90s should be suitable.
 

Darryl

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I do have in the loft the complete board from a 28" Toshiba model 2873DB there maybe a few on that
 

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A few screen shots of my damage.
I guess I should have used the correct tool and last night I thought why the dam didn't I use a matchstick to try and not a jewelry Phillip's Screwdriver
You should use a non-metallic, or non-ferrous adjustment tool on any ferrite cored coil, the metal tool will affect the outcome.

What is normally used is a square tip (or other type tip) plastic/nylon tuning tool, or if you can find one now days a ceramic tuning tool.

As for a replacement coil or ferrite, try here if you know the value.......
Code:
https://www.coilcraft.com/en-us/products/rf/tunable-rf-inductors/
 

Darryl

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You should use a non-metallic, or non-ferrous adjustment tool on any ferrite cored coil, the metal tool will affect the outcome.

What is normally used is a square tip (or other type tip) plastic/nylon tuning tool, or if you can find one now days a ceramic tuning tool.

As for a replacement coil or ferrite, try here if you know the value.......
Code:
https://www.coilcraft.com/en-us/products/rf/tunable-rf-inductors/
Looks like a good side but I just dont know the value of the damaged one.
If Anybody is will to accept the service manual from me by email might help identifying the little bugger lol
 

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Darryl

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Service manual attached
 

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Darryl

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I make have struck Gold so bear with me I'm having a look at this.

Ohhh thanks for everybody's help
 

Darryl

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Darryl

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False alarm still nothing
 

Darryl

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No that's ok.
One thing I have tried in the manual it says tune to 100.10mhz and set discriminator to 0v which I did with ariel in loft connected but when I tuned back to 97.00fm ( Heart Plymouth) the 0v is now showing more like -1.32 etc what should I do set the 0v on 97.00 with or without atrial connected and be done with it?
 

Darryl

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I have done that I set to 97.00fm heart plymouth then I bought it down to 0v but if I turn the tune dial the voltage varies then.
Plus I broke the core in the discriminator canister but radio is receiver as it should now and not .05mhz out of range.
Can a replacement core be screwed into place Jack?
I did connect the multimeter to the 2 points but what I would like to know is there are 2 resistors after the coil on the board and which side of them should I test.
 

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