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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 22nd Mar 2020, 12:36 am   #1
tareqam
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Smile Sanyo RP-1270 circuit help

Hi all.

I want to make my own Sanyo RP-1270 based on the circuit design I found on the internet.

I used to listen to it when I was kid and want to make it now as a circuit building practice and piece of history to keep.

I have some stuff I don't understand about the circuit like where is the ferrite rod antenna? How do I make one? Where is the variable capacitor?

Attached is the circuit if anyone can leave some comments on it please.

Thanks a lot.

Last edited by AC/HL; 22nd Mar 2020 at 2:17 pm. Reason: Copyright schematic removed
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Old 22nd Mar 2020, 2:16 pm   #2
Herald1360
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Default Re: Sanyo RP-1270 circuit help

Radio museum isn't usually happy about their documentation being publicly posted...... or didn't used to be for sure.


If you're building this from scratch your biggest problems will be the mixer and IF transformers, otherwise it's all pretty standard stuff for the period.



How T3 does anything useful feeding a shorted primary in that IF transformer is beyond me- I can only assume it's a misprint and there's a missing capacitor!
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Old 22nd Mar 2020, 2:18 pm   #3
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Default Re: Sanyo RP-1270 circuit help

As above, the schematic is available on radiomuseum.org.
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Old 23rd Mar 2020, 12:03 am   #4
tareqam
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Thumbs up Re: Sanyo RP-1270 circuit help

Quote:
Originally Posted by Herald1360 View Post
Radio museum isn't usually happy about their documentation being publicly posted...... or didn't used to be for sure.


If you're building this from scratch your biggest problems will be the mixer and IF transformers, otherwise it's all pretty standard stuff for the period.



How T3 does anything useful feeding a shorted primary in that IF transformer is beyond me- I can only assume it's a misprint and there's a missing capacitor!
Thanks a lot for the reply and comments on the circuit

What is a mixer? Is it the same as oscillator?
Why you would be worried about them? Do you mean they are not manufactured anymore?
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Old 23rd Mar 2020, 11:30 am   #5
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Default Re: Sanyo RP-1270 circuit help

tareqam.

Members here are always willing to offer help, but you could help yourself by reading about (Superhet)erodyne Receiver theory.
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Old 23rd Mar 2020, 12:05 pm   #6
tareqam
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Default Re: Sanyo RP-1270 circuit help

Quote:
Originally Posted by Station X View Post
tareqam.

Members here are always willing to offer help, but you could help yourself by reading about (Superhet)erodyne Receiver theory.
Will do. thanks!
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Old 23rd Mar 2020, 1:08 pm   #7
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Default Re: Sanyo RP-1270 circuit help

It's unlikely that the specific mixer and IF transformers could be obtained new, now, and the same will go for all parts of the set though generic small components (resistors, capacitors, transistors etc) that would fit an original circuit board are readily available. Parts like the transformers with multi pin connections will be more difficult to source unless you are not constrained by originality in appearance and fitting.

Specific answer to mixer/oscillator question (do follow Station X's recommendations though):

The (local) oscillator provides a variable frequency signal differing from the frequency of the signal being received by a fixed amount. This constant difference frequency is produced when the signal and oscillator frequencies are combined in the mixer. It's done that way because it's much easier to provide high gain and selectivity in a tuned amplifier at a fixed frequency than at a variable frequency depending on the station. The process brings its own ragbag of new problems (mostly spurious responses and frequency tracking problems) but overall it's worth doing.

The mixer is simply the device which mixes the two frequencies together. Just for added confusion, most consumer product radios (as does this one) have a combined mixer and oscillator stage where one device carries out both functions!
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Old 24th Mar 2020, 11:29 am   #8
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Default Re: Sanyo RP-1270 circuit help

I am not worries about the parts being original. just want to replicate the circuit.

Herald1360, Your comment is very informative. thanks a lot 💚📻💚
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Old 25th Mar 2020, 5:39 pm   #9
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Default Re: Sanyo RP-1270 circuit help

Hi!

The "AM Radio" kits offered by the Far Eastern vendors use almost identical components to the ones originally used by Sanyo to make the RP–1270, down to the a.f. input and output transformers!

https://www.ebay.co.uk/itm/184213280368

You'd be hard pushed to tell the difference between these components and the ones Sanyo used, apart from the cosmetic items of course!

Chris Williams

PS!

You'd probably be able to get a set from another Member that may be too bad cosmetic–wise to be worth restoration in it's own right for the coils, ferrite rod, tuning gang, etc., etc., ask on here!
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Last edited by Chris55000; 25th Mar 2020 at 5:44 pm.
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