QUAD FM4 always go to prest 2 at power on

[Mooly]

So perhaps yours is a later version in the scheme of things.

I found this:

 

[karvalha]

I allready removed it twice and put in alluminium foil

 

[Mooly]

And just to be sure... without the battery fitted it all works 100% correctly?

 

[karvalha]

without battery is exactly the same

 

[Mooly]

Hmmm. I thought it worked OK tbh without the battery from the earlier post or has the fault changed a little:

without battery goes to tune at power on as it should, with battery back on it behaves as before

So... I think you have to try a chip to prove it one way or the other.

 

[martin clark]

Have you tried the FM4 service manual diagnosis chart?

The Sevice manual is in the public domain, and look at page 9 for a chart of differential daignosis
https://www.dadaelectronics.eu/uploads/downloads/02_Quad-Service-Manuals/Quad-FM4-Service-Manual.pdf

I think the problem lies in this group (extract from chart below), and what follows in the manual are pages of the fine details on assessment and fix.
ATB!

 

[ejp]

pins 12-13 760mV

Voltage across each of the other three input pairs should be zero. Not sure what this pair should do, it's not connected output to inverting input like the others.

D23 should definitely be lit if it's an LED. Replace it if not.

 

[Mooly]

Could we be looking at this all wrong?

Without actually having it front of me its hard to decipher what is happening. The title reads:

QUAD FM4 always go to prest 2 at power on​

That's pretty specific.

First post reads:

I recently purchased a quad fm4 tuner serial 24996, i can manualy tune any station but when i try to save i can do it at preset 2 and it saves it to 1 and 2 with same frequency, then if i try to save a diferent frequency in preset 1 it saves and changes the number 2 as well to same, when switched off no matter what station allways start at number 2 preset.
when i press the preset buttons from 2 to 1 it goes, but not from 1 to 2, i need to press 5 and then i can press 2, if someone had such issue or have possible slution i will apreciate
T:I:A

Could it be something as simple as a problem with the keyscan to the uP? Something like a leaky diode (DI-D4) or a leaky switch or conductive goo on the switches?

Might be worth desoldering the four diodes D1- D4 and also pins 2 and 3 of the uP and seeing how it behaves.

 

[MarcelvdG]

Is C10 in good shape?

 

[karvalha]

Sorry for late repply but had a problem with my net, so, i´ve done everything, changed all diodes changed ic5 dessoldered the pins 2 and 3 and is allways the same. So my guess will be ic1 unfortunately

 

[Mooly]

I think you do have to start to suspect the chip at this point unfortunately Perhaps keep a look out for a damaged FM4 going cheap.

 

[ejp]

I have stock of Quad's new IC1 that also stores 14 stations and eliminates the battery.

Contact me off-list for details.

EJP
Dada Electronics Australia