Fisher X-202-B Phono Section Access.

[richiem46]

I am in the process of restoring a Fisher X-202-B that I recently obtained. I have done most of the restoration work but in the phono section the left channel is not working. Tubes not an issue and normally I could just trace through the circuits and find the issue. The phono section of the X-202-B however is VERY busy. I am attaching photos for reference. It looks like a previous owner has tried to access the coupling caps in this section without success. It looks like this section is on a separate sub-chassis based on the screws etc. that I see. Does anyone have any insight as to how best to get access around the switch to the underlying components?


Thanks for any help offered!

 

[larryderouin]

Take a picture of the topside at that location. Maybe the section lifts up after removing a few screws???

 

[richiem46]

It looks like if I remove the screws on top, on the side and through the front panel the input selector switch and Phono section will be freed up. I am not sure with all the attached wiring that will have to be disconnected/re-connected if that is a good idea.
I will have to stare at it for a while to see if I want to give that a go.

 

[gadget73]

any chance you've got a set of those tube test adapters that bring the pins out topside? That would get you access without having to actually disturb anything.

 

[richiem46]

I don't have the tube test adapters but I have socket savers I use with my tube tester. I probably could use them with a little fiddling around.

I removed all the screws etc. holding in the phono section. It moves but there are so many connections to it that it is still pretty rigid with all the chassis screws removed. Will leave it alone and go with plan "B"

 

[tonyg88]

Does it have a magnetic tape option at the input selector like the 800c has? Just curious if the channel is still out on that option since I think the circuitry runs through similar parts.

 

[richiem46]

Yes it has a tape head option with equalization settings for 3.25 and 7.5 ips. All are inoperative on the left channel.

 

[richiem46]

Update: Plan B worked! I spent several hours poring over the phono section visually and taking resistance measurements, comparing the working right channel with the inoperative Left channel visually and with the ohm meter. I saw a wire soldered to ground that looked wrong. It was spot-soldered to the chassis and then to pin 2 of the 12AX7 phono pre-amp effectively shorting the grid to ground bypassing R19 the 4.9M resistor. I am attaching a marked-up picture showing the wire partially obscured behind the cable shielding. Not sure how/why the wire was placed there but the phono pre-amp now works. After poking around the area I am pretty sure I can manage to replace the .022 and .047 coupling caps so I will do that tomorrow. Guess the old adage persistence pays is true!

 

[gadget73]

Sometimes the things found in old gear are just baffling.

 

[tonyg88]

Is this something you think happened at the factory and the original owners sorta just lived with it?

 

[richiem46]

No, When I removed the wire it was just tac-soldered to the tube lug. I suspect it was done in an attempt to replace one of the components in the phono section.