Despite lacking expertise, someone asked me to see if I could determine why a Rotel RA-1412 is not working. It has dual power supplies and my first thought was to look there. My skills are rudimentary and with some coaching, it appears that both power supplies are OK.
The amplifier's problem is no audio output. The first thing I noticed was two 8 amp rail fuses were missing on the left channel's power supply board. Replacing them cause a DBT to glow brightly. I checked rectifer diodes, stabilizer transistor and output transistors.
Two of the four left side outputs are blown which are 2SD426. The internet searching I did this afternoon identifed two potential replacement candidates. MJ15022 and MJ21194. Limited quantities of both are on hand at a major supplier.
I am poor at reading data sheets.
Both of those tentative replacements claim audio amplifiers as an application. But most if not all their numbers exceed those of a 2SD426.
I understand that within some parameters, more can be inconsequential or perhaps even better. My hope is that someone here can either vouch for an MJ15022 or MJ21194 as being suitable or suggest an altogether different one.
At this time, my intention is replacing all four 2SD426 outputs on the left channel only. Being dual power supplies, my thought was to leave the right channel's functioning 2SD426 outputs in place.
The amplifier's problem is no audio output. The first thing I noticed was two 8 amp rail fuses were missing on the left channel's power supply board. Replacing them cause a DBT to glow brightly. I checked rectifer diodes, stabilizer transistor and output transistors.
Two of the four left side outputs are blown which are 2SD426. The internet searching I did this afternoon identifed two potential replacement candidates. MJ15022 and MJ21194. Limited quantities of both are on hand at a major supplier.
I am poor at reading data sheets.
Both of those tentative replacements claim audio amplifiers as an application. But most if not all their numbers exceed those of a 2SD426.
I understand that within some parameters, more can be inconsequential or perhaps even better. My hope is that someone here can either vouch for an MJ15022 or MJ21194 as being suitable or suggest an altogether different one.
At this time, my intention is replacing all four 2SD426 outputs on the left channel only. Being dual power supplies, my thought was to leave the right channel's functioning 2SD426 outputs in place.
Those devices will replace 99% of TO3 audio outputs. The other 1% are germanium or a rare instance where the original is some super high fT type you can’t get anymore (and most of the time the 21194 works anyway if the driver circuit is competently designed).
