Hi all, I bougt an used DC-5 and when I opened it i fund a strange modification. The circuit differs from the schematic I found in internet: The anode connection of valve V4a (pin 1 of V4) is connected in a different way. In particular, instead of a 100k resistor connected to the 287V output of the power supply (output D), it is connected through a 150K to the 450V (outpt C). It is certainly a mod because in the printed circuit there is a vacant place for the 100k resirtor and the "new" 150k resistor is artificially added with a soldering on an uncovered strip of the printed circuit. On the other hand it is also strange that the resistor used is exactly of the same type of the other resistors used in the rest of the amp, so that it looks like such mod was made by Mesa Boogie (?) (there are more recent models of the DC5 with a slightly different preamp schematic so that this could be an "intermediate" model fabricated using the old printed circuit board). The old possessor bought it new and he says he did not make any mod. Anyhow, the amp seems to work fine and I don't know whether to restore it to the "original"(?) circuit or not.
Does anybody know anything about such mod?
What it does and why it was made?
Is it possible that Mesa Boogie made this modification after the fabrication of the printed corcuit board?
Do you suggest to restore to the original circuit?
Thanks to everybody in advance.
Does anybody know anything about such mod?
What it does and why it was made?
Is it possible that Mesa Boogie made this modification after the fabrication of the printed corcuit board?
Do you suggest to restore to the original circuit?
Thanks to everybody in advance.
