Has this bias circuit been modified

[JOEY B.]

Can anyone tell me please if this bias circuit has been modified
Ive looked around and seen pics of others with the added resistor but they could also be modded.
The amp has 447 volts on the plate an idles at 37ma per tube and the tubes are sylvania mesa branded str415.
Does that sound about right It doesent seem too hot but I dont know what is considered the norm with a boogie.
The amps is a simul MKIIC+ with export tranny

Are you saying that all four STR-415's idle at 37mA? If so, then something is not right. The outer sockets(Class-A) should idle at least 25 mA more than the inner pair, with matched 6L6's in a stock circuit. My non-export simul will see high 20 mA on the inner and low 50 mA on the outer sockets, just for reference.

 

[JOEY B.]

No just the two inside ones I will correct the original post , do you think its been modified

Can't say for sure. You really need a current draw measurement for the outer sockets with the STR-415's. This will help to nail it down.

 

[JOEY B.]

No just the two inside ones I will correct the original post , do you think its been modified

Can't say for sure. You really need a current draw measurement for the outer sockets with the STR-415's. This will help to nail it down.

43 ma -44 ma for the outside tubes

Next step would be to measure the negative voltage at pin #5 on each power tube socket. I would think that those outer sockets should be drawing more than 44mA.

 

[stokes]

Maybe the tubes are not matched.Put the outer pair in the inner sockets and the inner pair in the outer sockets and see if you get the same or close to the same ma's.