Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Misc Schematics and Layouts => Topic started by: Jalmeida on October 05, 2023, 06:48:19 pm
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Hey folks,
I spent some time going over my AC50/2 amp chassis and decided to put together a layout. This is a V1 diagram and I have gone over it, but another set of eyes are appreciated if any of you see anything missing or a mistake. This is stock layout quirks and all. The wire colors don't seem to follow a standard like the older ones. And looking over other similar period amps show some different colors. So left many colors default. Hopefully this of help..
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And schematic
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Well done, that’s great work!
You’ve even got the old British red black green mains cable :icon_biggrin:
One discrepancy is that the schematic shows switch then fuse, whereas they’re swapped over on the layout.
When I refurbed my friend’s MkII, the 56k DCCF cathode resistors put me in a quandary. The stock 1W resistors overdissipate and drift up in value, I think they both were up around 75k.
Plus the valves were well over their Vh-k limit.
The solution I came up with was to increase the HT droppers to those stages to 22k, which brought the cathode voltage down to around 200V. I think I also used 2W 56k resistors, so they weren’t idling up at their limit.
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Well done, that’s great work!
You’ve even got the old British red black green mains cable :icon_biggrin:
One discrepancy is that the schematic shows switch then fuse, whereas they’re swapped over on the layout.
When I refurbed my friend’s MkII, the 56k DCCF cathode resistors put me in a quandary. The stock 1W resistors overdissipate and drift up in value, I think they both were up around 75k.
Plus the valves were well over their Vh-k limit.
The solution I came up with was to increase the HT droppers to those stages to 22k, which brought the cathode voltage down to around 200V. I think I also used 2W 56k resistors, so they weren’t idling up at their limit.
I just double checked mine, and it is the way I drew it. However, mine has had the Voltage selector removed as well as the Power transformer replaced. I agree that it doesn’t match the schematic. I will look a bit into other pictures of original amp before I change it to be sure. Not sure if it is worth drawing in the voltage selector into this layout.