Sriskie
Well-Known Member
I've been struggling a bit with a G-7500. I think I have it mostly sorted out but am unsure of some things. I've been wading through numerous threads, particularly Anderslober's epic 27 pager and still have some concerns.
Without getting into every detail I'll get right to where I'm at now. The unit idles perfectly and is stable. This is the first time I've monitored the bias while playing music so I don't know what's "normal". As I increase volume, bias rises proportionately. I've seen conflicting posts on this and am searching for some clarification. At a fairly high volume (around 11:00), the bias is rising to about 40mv and drops right back down with the volume. It does this on both channels equally. I've read that the bias should rise with signal and also that it's a problem. I'm a little confused here. Perhaps it should rise slightly but not that much?:scratch2: The outputs and emitters are staying cold as well as 2 of the drivers. TR 17/18 (MJE15033G) run about 10 degrees warmer.
There was a mention about runaway bias being caused by the same drivers I've used, but they've been recommended several times. I'll list all of the subs I have in there now in case there's something that's amiss.
Drivers;
2SD381-MJE15032G
2SB536-MJE15033G
Outputs;
2SA1106-NJW0302
2SC2581-NJW0281
Others;
2SD313-MJE15032G
2SC2071-KSC3503D
2SA939-KSA1381
2SB507-MJE15033G
2SA992-KSA992
2SC1845-KSC1845
All of the E.C.s, 10D2 diodes, and N.I.R. resistors have been replaced and all of the other resistors checked so I'm thinking I may have made a poor choice somewhere on the TR subs if it's not behaving itself like it should.
Without getting into every detail I'll get right to where I'm at now. The unit idles perfectly and is stable. This is the first time I've monitored the bias while playing music so I don't know what's "normal". As I increase volume, bias rises proportionately. I've seen conflicting posts on this and am searching for some clarification. At a fairly high volume (around 11:00), the bias is rising to about 40mv and drops right back down with the volume. It does this on both channels equally. I've read that the bias should rise with signal and also that it's a problem. I'm a little confused here. Perhaps it should rise slightly but not that much?:scratch2: The outputs and emitters are staying cold as well as 2 of the drivers. TR 17/18 (MJE15033G) run about 10 degrees warmer.
There was a mention about runaway bias being caused by the same drivers I've used, but they've been recommended several times. I'll list all of the subs I have in there now in case there's something that's amiss.
Drivers;
2SD381-MJE15032G
2SB536-MJE15033G
Outputs;
2SA1106-NJW0302
2SC2581-NJW0281
Others;
2SD313-MJE15032G
2SC2071-KSC3503D
2SA939-KSA1381
2SB507-MJE15033G
2SA992-KSA992
2SC1845-KSC1845
All of the E.C.s, 10D2 diodes, and N.I.R. resistors have been replaced and all of the other resistors checked so I'm thinking I may have made a poor choice somewhere on the TR subs if it's not behaving itself like it should.