TheRed1
Console Conservationist
I finally found a Fisher TA-500. It's a later model with 5881 output tubes, one of which I am missing. It's also missing 1 knob. (Replacement source?) Otherwise it's in fair condition but it has a wood case unlike others I have seen.
I didn't realize that there were so many versions of this model. I believe the earliest models had EL37s which were replaced by EL34s when they became available. Then came the 5881 model which you see here - serial no. 54087 or 154087, it's hard to tell. (That's my TA-500 timeline theory anyway - based on comparing notes with a few other mono 500 owners and looking at the histories of the tubes themselves.)
Unfortunately, the schematics I have seen available are for the earlier versions and this one appears significantly different. I sat down last night and compared mine to the EL37 version schematic on Tom Bavis' website and noted a number of differences besides the obvious capacitor and resistor value differences. I hope I can find the right one because I don't have the skill to draw one based on what I see.
It has a blown fuse and, as you can see; I have quite a bit of work to do before attempting to bring it up. Here are the output tube sockets from underneath to illustrate some of the thermal issues this old receiver has suffered: (Note the scorched resistors between pins 4 & 6; also the white capacitor with the brown spot on its left, labeled AP 47 20%. It's connected to the yellow wires on the left - one of which is the 16 ohm transformer secondary tap. I thought for sure that must be coupling cap but it appears to be a part of the feedback loop. There's also a .02 capacitor (bottom middle) connected between the AF amp and phase inverter halves of the 12AX7 [I think] that appears to have melted around the insulation on a resistor lead.)
Another thing that caught my eye was the unused pot in the volume control stack (lower right-hand corner). This relates back to another post I did on the 1959 Fisher Ambassador II console in which a TA-500 is used in conjunction with a 30C and a 30A to produce an awkward stereo console. Fisher had your back in case the industry went stereo. I believe it was called the TK-5 modification.
Bird's eye views:
I didn't realize that there were so many versions of this model. I believe the earliest models had EL37s which were replaced by EL34s when they became available. Then came the 5881 model which you see here - serial no. 54087 or 154087, it's hard to tell. (That's my TA-500 timeline theory anyway - based on comparing notes with a few other mono 500 owners and looking at the histories of the tubes themselves.)
Unfortunately, the schematics I have seen available are for the earlier versions and this one appears significantly different. I sat down last night and compared mine to the EL37 version schematic on Tom Bavis' website and noted a number of differences besides the obvious capacitor and resistor value differences. I hope I can find the right one because I don't have the skill to draw one based on what I see.
It has a blown fuse and, as you can see; I have quite a bit of work to do before attempting to bring it up. Here are the output tube sockets from underneath to illustrate some of the thermal issues this old receiver has suffered: (Note the scorched resistors between pins 4 & 6; also the white capacitor with the brown spot on its left, labeled AP 47 20%. It's connected to the yellow wires on the left - one of which is the 16 ohm transformer secondary tap. I thought for sure that must be coupling cap but it appears to be a part of the feedback loop. There's also a .02 capacitor (bottom middle) connected between the AF amp and phase inverter halves of the 12AX7 [I think] that appears to have melted around the insulation on a resistor lead.)
Another thing that caught my eye was the unused pot in the volume control stack (lower right-hand corner). This relates back to another post I did on the 1959 Fisher Ambassador II console in which a TA-500 is used in conjunction with a 30C and a 30A to produce an awkward stereo console. Fisher had your back in case the industry went stereo. I believe it was called the TK-5 modification.
Bird's eye views:
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