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Hi all, rebuilt one of these but went off the 7247 schematic instead of the 6C4/6AV6 schematic regarding the power supply rebuild, the difference being the inclusion of an 80 ohm resistor before the screen and plate supply cap and the 310 v rail. In other words, same cap input (40 uf) followed by the 80 ohm then 40 uf and the 33K 20 uf 310 v rail. The original was 40 uf that was the plate & screen followed by 33k and 20 uf for the 310 v rail. So, a bit more capacitance and a CRC supply, rather than just C. All voltages are on point except the cathode, its at 11.8 voltages rather than 15 on the 7247 schematic, and I have no voltage numbers for the 6C4/6AV6. Sounds good at this point, thanks!
310v rail voltage is way too low. The source voltages should be 360v,350v,and 320v. This would also explain your lower cathode voltages.
Was this originally the 6C4/6AV6 amp or don't you know?
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Hi, Michael, and thanks! This was originally the 6AV6/6C4 version that someone in the past had wired up the PS to be the version with the 7247, don't really see a problem with that. The plate and screen is right on the money, the rail after the 33K is 281 v, whereas the schematic notes 310, this is for the 7247 version, don't know what the voltages are supposed to be for the 6C4/6AV6 version (this voltage feeds the front end tubes) Also, the cathode for the 6BQ5 is 11.6 v, once again I don't know what it should be for the 6C4/6AV6 version, but the 7247 schematic it is 15 volts. Thanks, Randy
There is no reason to believe that the voltages would differ. The triode in a 6AV6 is the "same" as those in a 12AX7. The triode in a 6C4 is the "same" as those in a 12AU7. The 7247/12DW7 is 1/2 'X7 and 1/2 'U7.
BTW, the 2 tiny diodes in the 6AV6 would be grounded out.
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