[olaychang]

Dear sir
My fm3 stereo mode was failed.
EMM801 upper eye always open
vol. knob push & pull are always in mono sound.
When I release V71(6BL8/ECF80), the tuner still can work in the mono mode.
I check the component they have no any crack , break
Do any one can help me to solve the problem?
Thanks a lot!!!

[Bill Thomas]

     The problem is somewhere around the 6BL8 tube.  Either a dead 6BL8, or a cold solder joint in the filament connections to the tube are possible candidates.  If the 6BL8 is good, check Voltages around the tube and report back.

     Hope this helps.

Bill

[olaychang]

     The problem is somewhere around the 6BL8 tube.  Either a dead 6BL8, or a cold solder joint in the filament connections to the tube are possible candidates.  If the 6BL8 is good, check Voltages around the tube and report back.

     Hope this helps.

Bill

Hi Bill
Thanks for your suggestion.
I found the filament voltage is too low ---> 5.2Vac
Mybe I need to parallel a 6.3V voltage in the filament of 6BL8.

Thank you very much!!

[baldrick]

Did this fix work?  Did you find anything else wrong?  Have you tried with a new 6BL8 tube?

I think that it is unlikely that the low filament voltage is to blame.

Have you checked that the four germanium diodes are ok?  Have T71 T72 and / or T73 gone out of alignment?  Have you tried to re-align the MPLX section from scratch?