| Author | Message | ||
     Robert Thomas (fobile_missile) Username: fobile_missile Registered: 10-2007 |
I have hd130 with 12ax7 phase tube. Changed out electrolytics. Got everything working. Both hi and lo circuits had clear signal. next developement was changing op amps to AD843JN in both channels leading to a LM741CN in the combo 3rd stage. Hi power circuit is be-a-utiful. Lo power is overloaded making low freq feedback like pure line in voltage or something. No music signals coming through. Sounds have no chance!! I can not find any wierd voltage readings from my power caps. Op amp circuits dropping correct readings and works fine on high power.Pulled on resistors and caps found no loose fittings. In low power the heaters light up in 2 out of four tubes and the 12AX7. The hi power operation is soo good. A bunch of junk from the lo power setting. The lo setting has no chance - the overload starts as soon as I turn the volumn knob. Thanks to any ideas. | ||
| Robert Thomas (fobile_missile) Username: fobile_missile Registered: 10-2007 |
just noticed the choke/ transformer 3 hy/100ma is in my low power circuit. Anyone have problems with this choke? But I am achieving proper voltage readings at my 20uf and 100uf power caps. Could this choke ground out? | ||
| Robert Thomas (fobile_missile) Username: fobile_missile Registered: 10-2007 |
answer ... not enough current for my new op amps. old LM307h current was 3ma per op amp = 3ma x 5= 15ma current. new AD843 op amps draw up to 13ma max. 13ma x 5= 65ma max. So I reworked the incoming power resistors/ zener diodes to get more amps flowing. Sounds fantastic.. a better write-up soon. |