I have an original master sound 300 B amplifier with a blown transformer. Looking for a schematic or someone that can measure the AC output so I can find something to fit the xfrmr case. The US rep won’t respond. Looks like fixed bias, probably 400-450v. I could probably reverse engineer and take an educated guess but trying to keep the amp as original as possible.
Wrong schematic—
These are the differences
Serial #58
Solid state power supply
5687 driver tubes
Fixed bias
It was sold under Vaic label
These are the differences
Serial #58
Solid state power supply
5687 driver tubes
Fixed bias
It was sold under Vaic label
Last edited:
repairing for a friend...
I build custom
This schematic I found in another thread is closer to the design...https://www.diyaudio.com/community/attachments/300bamp-jpg.767927/
Has the same fixed bias winding but input tubes are a little different.
I build custom
This schematic I found in another thread is closer to the design...https://www.diyaudio.com/community/attachments/300bamp-jpg.767927/
Has the same fixed bias winding but input tubes are a little different.
I have a blown transformer and need voltages
HV to 300b tubes, choke and 6.3vac to drivers I can guess but I have 12-15v for the electronic volume control and another supply that goes to the driver board. It goes thru another bridge with a 400v cap so it must supply the driver tubes but there’s also another supply to driver board tapped from a dropper resistor off the 300b supply.
Mastersound would not help or supply a schematic. US rep took 2 months to respond with no support.
Looking for someone that has a working amp and willing to measure these voltages
HV to 300b tubes, choke and 6.3vac to drivers I can guess but I have 12-15v for the electronic volume control and another supply that goes to the driver board. It goes thru another bridge with a 400v cap so it must supply the driver tubes but there’s also another supply to driver board tapped from a dropper resistor off the 300b supply.
Mastersound would not help or supply a schematic. US rep took 2 months to respond with no support.
Looking for someone that has a working amp and willing to measure these voltages
Attachments
I reversed engineered it
Edcor is building a transformer
400v-6.3v-6.3v-6.3v-230v-12v
Hows that for an oddball transformer!
Edcor is building a transformer
400v-6.3v-6.3v-6.3v-230v-12v
Hows that for an oddball transformer!