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Title: B&W 5100B - Finals wiring error? Post by: KK7UV on November 28, 2021, 07:43:24 PM I acquired this last summer from an estate, where it had been sitting in storage for at least 15 years. All 6146s and the rectifiers were absent.
I am restoring the multiplier/finals module and in the middle of checking values on the original carbon resistors I found a discrepancy between my rig and the schematic. See the attached jpg file. Note how the RFC and parasitic choke are wired into the grids of the 6146's. Is the schematic in error, or is mine wired in error? Also, both 6146 sockets have a 47-ohm resistor from the suppressor pin 4 to ground. This makes no sense since pins 1,4, and 6 in 6146 are common in the tube, and my pin 1 is grounded. My only idea is that the previous owner tried a different tube type in the finals. I was unable to find any such service notes for these differences. Title: Re: B&W 5100B - Finals wiring error? Post by: Pete, WA2CWA on November 28, 2021, 11:50:13 PM I acquired this last summer from an estate, where it had been sitting in storage for at least 15 years. All 6146s and the rectifiers were absent. I am restoring the multiplier/finals module and in the middle of checking values on the original carbon resistors I found a discrepancy between my rig and the schematic. See the attached jpg file. Note how the RFC and parasitic choke are wired into the grids of the 6146's. Is the schematic in error, or is mine wired in error? Also, both 6146 sockets have a 47-ohm resistor from the suppressor pin 4 to ground. This makes no sense since pins 1,4, and 6 in 6146 are common in the tube, and my pin 1 is grounded. My only idea is that the previous owner tried a different tube type in the finals. I was unable to find any such service notes for these differences. The printed schematic is correct. Same circuit and parasitic suppressor components were used in the 5100. Probably included to suppress parasitic radiation from screwing up the TV reception. Final would work fine even if you replaced the suppressor with a wire. 6146 Cathode, pins 1,4, and 6, should go directly to ground with very short connections. |