high final bias current on 139xlr

[loosecannon]

im confused by the bias current on the final in the 139xlr i am aligning.

this radio was completely stock when it came to me. i have moved the
1419 transistor near the clar. circuit to a better location as was
normal in this chassis when they were popular.
i replaced all the 2SC1419's with 2N6487's, as i had a bunch.

then i re-capped the whole radio. just the electrolytics.
replaced c179 tantalum with a 2.2uF elec. again, as was normal back in
the day.

when doing the alignment, the driver bias current adjusts perfectly
normal, but i am seeing between 150-200 mA on the final bias current.

ive never seen this before, (not that ive seen that many radios, LOL)
and im wondering if you guys have run into this problem before.
is it going into self-oscillation? how can i fix it?
the driver and final are the stock 1306, and 1307 repsectively.

thanks for any help,
loosecannon

 

[DTB Radio]

Sounds like you need to trace down the final bias circuit a bit more. I doubt its self-oscillation, or it would how up on the output.

 

[loosecannon]

thanks DTB,

i must say, you are a very helpful guy.

i have the radio here with me today, and will be trying some voltage tests.

i should have known something was off when i couldnt turn the AM power control down past 3.5 watts. doh!

i will post any findings here,
loosecannon

 

[ken white]

Is the beta the same between those two transistor types? If not, then the operating point (class of operation) will be different. Just a thought...

 

[loosecannon]

not sure about the transistor class.

i used the 2N6487 because justin depolis recommended it as a replacement for the 1419 AM power reg. in the MB8719 chassis.

i tried subbing ouit the final with a 2SC1969 i had, and got teh same result.

had to get some solder wick, now i can start testing parts.
loosecannon