| Author | Message | ||
     Mike H |
My amp was noisy, had a bad humm/hiss when pushed, and there was about a 20mv difference in bias. So, I decided to replace all the electrolytic caps, the driver transistors, and op amps. I used spraague atom caps except for the big 100uf/450v caps. For those, I used Xicon. I used LM1458N driver transistors rather than JE1692, based on a thread I read somewhere on this site. And, I used LM1458N RCA for the op amps. I put it all togethor, and I screwed something up. I have no sound from neither the high nor low input. However, I get sound from the 3V line input. Nothing from the 100mv input. The amp powers up and the tubes both have the same bias current (I set it at 25mv). So, in my excitement to finish, I think I put an op amp(or two or three...)in backwards. I currently have the notch on all the op amps toward the rear of the amp/chassis. Anyone know if this is correct? Any advice is greatly appreciated. | ||
| Mike H |
Just checked all the op amps, the notch on the IC matches the base on all the op amps, so I believe that they are all in correctly. I'm checking the caps I installed now. Got great voltage on the tubes - 750ish and 450ish - very even on each tube. So, the reason I replaced the caps etc. is addressed. Now I have to sort out this preamp issue that I apparently caused. Any ideas, let me know. Thanks | ||
| Mike H. |
Never mind, bad solder joint on one of the new 20uf caps breaking the circuit in the preamp. Back together, sounds great. | ||
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