Super heterodyne receiver issue

[Dazoner]

Hi. Does anyone have the voltage measurements for the IC's. I have this awful high pitch squealing that I'm having a hard time tracking down. Thanks.

 

[zgrav]

why not switch back to the cd74hc4046AE chip to see if your original problem with the oscillation returns and the high pitched noise goes away?

that at least will show the underlying issue has not changed. maybe it is the chip, or at least a part that is related to the operation of the chip.

 

[Hexjibber]

why not switch back to the cd74hc4046AE chip to see if your original problem with the oscillation returns and the high pitched noise goes away?

that at least will show the underlying issue has not changed. maybe it is the chip, or at least a part that is related to the operation of the chip.

Hi,

Thanks for the reply, I swapped back to the other IC and my original issue of getting a weird clicking sort of sound returned, in both cases the oscillator doesn’t work as I expect or sound like the videos I’ve watched.

Would be great if the OP of this thread could tell me whether they ever solved the issue and how as the symptoms sound identical.

Will post an update once the new switch arrives from the US and I’ve swapped the old one out.

 

[Hexjibber]

Update on my issue:

I received the new switch from LoveMySwitches, alas it has made zero difference, the constant high pitch note from both the subharmonic and the oscillator remains

I have checked and re-checked my part orientation but as yet cannot see an issue. The fuzz sound seems to function perfectly, it’s only when turning up the sub or osc that I get the high pitched tone/note. Removing the 4046 stops the sound so I presume it is related but I’m getting nowhere really.

Does anyone have any ideas of things to try or potential causes of this issue? Built this for a friend so am keen to get it working. Any help greatly received!

Have attached a photo for reference

 

[Hexjibber]

Ok another quick update, sorry! I've just been scouring the build and noticed one of my CD4017BE chips is actually a CD40174BE which as far as I can tell from the data sheets is not the same thing! Thanks Banzai! Ordered another CD4017BE, fingers crossed!

 

[tcpoint]

That would do it.

 

[BlackNinja]

Hi all !
I have been experiencing the same problem with the oscillator voice and I might have some more input : I've been audioprobing a bit of the circuit and observed that the signal is coming "unaltered" (fuzzy) into the 4046 through pin 14 BUT what comes out of it (pin 4) is the infamous squealing noise. When I remove the 4046 the noise disappears as well, but of course i get no oscillator voice. So it seems to me that the 4046 might be faulty. Gotta try to get a few fresh units for swapping. I'm in Europe also and Musikding have some in stock so I guess I'll be able to give an update quite soon.
Since then, stay the f*** home guys
Cheers

 

[Hexjibber]

Hi all, hope everyone is keeping well out there!

Just to update on my progress with this, finally took delivery of another CD4017BE to replace the incorrect CD40174BE I received from Banzai, and hallelujah it works perfectly! So chuffed! Obviously an obvious lesson there for me, check, double check and triple check those parts! I feel like I'm normally pretty meticulous but just goes to show it can happen at any time!

Anyway, now that's sorted I can breathe a sigh of relief, build report coming soon!

 

[xixaro]

Hello,

I have more information to share with you.

I have removed my "DPDT on-on-on" from the pcb. This makes the high pitch to vanish, indeed.

My "DPDT on-on-on" has the following centre alignment, which actually does not match the one required in the BOM,
View attachment 806

Now,
I have installed the very same "DPDT on-on-on" on the top side of the pcb, as in the picture here below. Before, the swich was installed, welded, on the pcb bottom side, of course.
Any guess about what happens then?
View attachment 807

R. : the noise, high pitch tone, is back!
Hence, it seems the issue is not fully related with the switch being "type 1" or "type 2".

Would you please share, when available, the pcb circuit diagram?

Thank you.

Hello,

12 months after my initial thread about the high pitch noise,
I finally managed to have some spare time to tackle the problem.

So, the 1P8T oscillator switch had some construction flaw, which was at the origin of a missing contact inside the switch, producing the oscillator high pitch!

Issue solved!