CR-800 Tuner 12V Chasing

[milo63]

My FM is dead, I'm not getting 12V to the left side of the FM board (FB, GR, AGC) but the right side has +12 and -12. Trying to trace back where it originates through the switchology is making my head hurt.
Oh, and where's the RF Front End (TR1-TR4)?

 

[Sparkplug]

Check the function board too when switching to FM, +12V and FB both go through there. Dirty switch? Bad connection?



Yes, Tr1 to Tr4 are the RF front end where the RF signal from the antenna is first processed.

 

[avionic]

Oh, and where's the RF Front End (TR1-TR4)?

Probably snuggled up next to the tuning air variable capacitor.

 

[milo63]

Probably snuggled up next to the tuning air variable capacitor.

You sir, are correct. Buried in the cap case and pretty much unavailable.

 

[milo63]

Check the function board too when switching to FM, +12V and FB both go through there. Dirty switch? Bad connection?

View attachment 3853692

Yes, Tr1 to Tr4 are the RF front end where the RF signal from the antenna is first processed.

Thank you for the red trace, something weird is happening.
Going to the RUSH concert tonight so I'll be poking at it again tomorrow.

 

[milo63]

Back to the bench..I chased the brown wire back to the switch and found a break. Break repaired, FM works great..
I really like the "tackle box" engineering of the CR-800 but I guess it comes with risks.