Cross-talk in 800b?

I have an 800b that I fully restored except for the FM de-emphasis mod.
I switched over to my tape input and had had no sound from my RTR. I accidentally had the DBX switch box on the wrong tape input. Before seeing this I turned up the volume and could hear the FM faintly in the background.
Does anyone else have this? Is is just acceptable to have this in an old receiver due to design? Before I open it up again to look at lead dress, shielding, etc. I was just curious if anyone else had this issue in their 800?

Thanks
Glenn

Not sure about the Fisher 800 specifically, but many older amps did this. The selector switches did not ground the un-used sources so you could get some bleed-through from another source when in tape or aux or whatever mode.

I've gotten FM Bleed thru on my old 400 and do on my 800C. Very minor, but still there. You get used to it. If you have any source RCA's that aren't used, ground them with a RCA JACK that has the center pin and the outer case connected together. Some DIY Jacks from Ratshack, and some solder will do it. You can even put a piece of stiff wire in there across the case to pin, and use it as a handle to remove them when needed.

Larry

Are you using the tape monitor or the tape head input? If you are connecting to the tape head input, don't! It is a low voltage input with special filtering. I wouldn't be surprised if you could hear aliens from that input.

The tape monitor input can suffer from crosstalk if the selector switch is on one of the radio settings. Fisher turns the power off to the radio tubes when another input is selected.

However, the tape monitor switch is not part of this scheme. Turn the switch to a non-radio position (such as the tape head input) and the FM crosstalk should disappear.

Thanks everyone, I thought it might be just due to the vintage design.

Drew jogged my memory, I did experience this when using the tape monitor switch. I'll have to try switching the input to something other than FM to see if it goes away. I know about not using the tape head input from reading this forum

I like the idea of grounding the unused jacks, I'll probably do that also.

Thanks again everyone for the replies.
Glenn

vfr800fiman said:

Thanks everyone, I thought it might be just due to the vintage design.

Drew jogged my memory, I did experience this when using the tape monitor switch. I'll have to try switching the input to something other than FM to see if it goes away. I know about not using the tape head input from reading this forum

I like the idea of grounding the unused jacks, I'll probably do that also.

Thanks again everyone for the replies.
Glenn

Click to expand...

Fisher grounds unused inputs on the selector switch. They already did it for you. Grounding RCA's are nice but not necessary.

Sounds like you need to clean your selector switch with Deoxit. The selector switch has a wafer to ground the unused inputs. Maybe your contacts are dirty so the grounding is not happening.

That's probably a good thing to do since I'm going to have the bottom cover off anyway. Time to check the bias on the JJ's again

Drew called it, this only happens with the tape monitor switch. If I turn the input selector to some unused input, I don't get the bleed through. I also don't have any issue if I'm using the "Tape input" directly.

Thanks Drew!