pchilson
Active Member
Hi,
I know this subject has been broached before without closure. It may be that it can't be solved.
This is a barn find. It was full of dirt and debris from sitting for 30 years. It was stated it blew a channel and off to the barn it went. Well it may have blown a channel at one time as there is only one original output transistor remaining, the others have been changed and the original driver boards have been changed out to the F-6013 boards. Once cleaned up a bit and the switches and pots addressed the unit works in all functions except anything to do with FM.
I know nothing about FM circuitry other than to leave it alone if it is working. Well it isn't, so... I have been trying to discover the problem sporadically for about 2 weeks now and I am finally at the end of what I can comprehend.
I have printed the 5000 schematic, cut and taped the pages together so I have a good working copy. However, I have boards in my unit that are not listed in any of the 5000 model schematics or service manuals. All of these list the muting circuit board as the F-1120 and my unit uses the F-1098 muting circuit board so given that I can't be sure my working copy of the 5000 schematic is absolutely correct for my unit.
I may not find a solution to this and you guys may not be inclined to cipher it out but I'm going to try.
What I can say is all areas of the unit work as they should with the exception of the FM. All voltages given on the schematic, which are few, check out as they should. I can't find a discrepancy in the stated voltage and what I get at the given points. Mostly the schematics don't list voltages so when that is the case who knows if what I read is good or not?
I do hear static from FM with the muting off and silence with muting on. I never get any activity on the signal strength meter while in FM. The signal meter works as it should in AM. I have never seen the tuning meter as much as twitch because AM doesn't employ it and obviously there is no signal to tune in FM.
I don't know what else to try. Short of taking it to a tech or just selling it, is there anything I can test to see where in the chain the fault could lie?
Thanks for any pointers you might think of.
Attaching 3 photos of the schematic. The first is a full shot to give perspective. The second is the left (input) side of the FM and the third is the right (output) side of the FM.
I know this subject has been broached before without closure. It may be that it can't be solved.
This is a barn find. It was full of dirt and debris from sitting for 30 years. It was stated it blew a channel and off to the barn it went. Well it may have blown a channel at one time as there is only one original output transistor remaining, the others have been changed and the original driver boards have been changed out to the F-6013 boards. Once cleaned up a bit and the switches and pots addressed the unit works in all functions except anything to do with FM.
I know nothing about FM circuitry other than to leave it alone if it is working. Well it isn't, so... I have been trying to discover the problem sporadically for about 2 weeks now and I am finally at the end of what I can comprehend.
I have printed the 5000 schematic, cut and taped the pages together so I have a good working copy. However, I have boards in my unit that are not listed in any of the 5000 model schematics or service manuals. All of these list the muting circuit board as the F-1120 and my unit uses the F-1098 muting circuit board so given that I can't be sure my working copy of the 5000 schematic is absolutely correct for my unit.
I may not find a solution to this and you guys may not be inclined to cipher it out but I'm going to try.
What I can say is all areas of the unit work as they should with the exception of the FM. All voltages given on the schematic, which are few, check out as they should. I can't find a discrepancy in the stated voltage and what I get at the given points. Mostly the schematics don't list voltages so when that is the case who knows if what I read is good or not?
I do hear static from FM with the muting off and silence with muting on. I never get any activity on the signal strength meter while in FM. The signal meter works as it should in AM. I have never seen the tuning meter as much as twitch because AM doesn't employ it and obviously there is no signal to tune in FM.
I don't know what else to try. Short of taking it to a tech or just selling it, is there anything I can test to see where in the chain the fault could lie?
Thanks for any pointers you might think of.
Attaching 3 photos of the schematic. The first is a full shot to give perspective. The second is the left (input) side of the FM and the third is the right (output) side of the FM.
