Well, where is Holmes ? It's getting late here...I mean it's...ermm...cough...morning. I'm hearing happy birds, chirping before the sunrise ! 🙂
OK heres the update!
1, there was definitely a channel imbalance but only on headphone section! But NOT speaker output. I checked service manual and it just didnt make any sense! At the time only headphone output was tested as the amplifier was in a state of disassembly. The speaker output was same despite different brand opamp.
2, delivery of new opamps arrived. Both were installed and the sound from headphone section became equal. The main output was still good!
3, there was no difference in sound quality as far as I could hear between the opamps using speaker output.
4, the bias resistor mod was done and the DC tested 4-6mv. Slowly rising when warmer. But dropped when speakers were connected. Final measurement after 15 minutes was around 4mv.
Its all working perfectly now, low DC, sounds good. Hopefully it will stay that way lol. Massive thanks for all contributions! I've seen a few of these around, if anyone is in a similar boat then this post will definitely help them too!
Its just amazing how an expert can spare 2 minutes and make someones day and they most of time don't even realise it. Love this forum!
1, there was definitely a channel imbalance but only on headphone section! But NOT speaker output. I checked service manual and it just didnt make any sense! At the time only headphone output was tested as the amplifier was in a state of disassembly. The speaker output was same despite different brand opamp.
2, delivery of new opamps arrived. Both were installed and the sound from headphone section became equal. The main output was still good!
3, there was no difference in sound quality as far as I could hear between the opamps using speaker output.
4, the bias resistor mod was done and the DC tested 4-6mv. Slowly rising when warmer. But dropped when speakers were connected. Final measurement after 15 minutes was around 4mv.
Its all working perfectly now, low DC, sounds good. Hopefully it will stay that way lol. Massive thanks for all contributions! I've seen a few of these around, if anyone is in a similar boat then this post will definitely help them too!
Its just amazing how an expert can spare 2 minutes and make someones day and they most of time don't even realise it. Love this forum!