Strgazr1967
Active Member
I picked up this ST-70 a few weeks ago and have been cleaning it, going over it and deciding on tube choice for when I set it up after Christmas. The wife's decorations require I take my system out for the holidays. I have a few questions.
While going over the amp I noticed that whoever did the mod must have needed glasses as there are 2 caps that are burnt pretty bad. One looks like it may need to be replaced. They are .47uF 425v Wonder Caps Ultima with Danor. What would you guys use to replace these that won't shatter my bank account? The one looks like the casing is burnt through and I do have noise on that channel.
While trying out a matched set of JJ EL34II's in it I set the bias according to the Welborne instructions with it sitting at 1.56 Vdc. The weird thing is when I came back to it 90 minutes later it had dropped to 1.34 Vdc roughly on both sides. I adjusted it again and shut the amp off. I came back to it this morning, turned it on and let it warm up for about 60 minutes. The weird thing is as it powered up the bias ramped up to 1.77 Vdc and then slowly started falling. When I checked it 35 minutes later it was 1.39 Vdc. WTH?? Any thoughts on this? I can post a schematic if needed. B+ is sitting steady at between 432 Vdc and 440 Vdc
Finally, my wife bought me a matched set of EH 6CA7's Fat bottle, A Genalex KU77 GZ34 rectifier and in the pre-amp section a pair of Tung Sol 6U8A's (Matched) and a matched pair of Sovtek 5751's for Christmas. Would the Gold Lion KT-77's be a better choice? Listen mostly to Blues, Jazz and some classic rock (Sabbath, Zep, Floyd etc) Speakers are a pair of Klipsch KG-4's with both the Crites Xovers as well as new Crites diaphragms or a pair of Pioneer CSA-700's with a full recap done.
Thanks for any help and answers! Merry Christmas and Happy Holidays!
Bobby
While going over the amp I noticed that whoever did the mod must have needed glasses as there are 2 caps that are burnt pretty bad. One looks like it may need to be replaced. They are .47uF 425v Wonder Caps Ultima with Danor. What would you guys use to replace these that won't shatter my bank account? The one looks like the casing is burnt through and I do have noise on that channel.
While trying out a matched set of JJ EL34II's in it I set the bias according to the Welborne instructions with it sitting at 1.56 Vdc. The weird thing is when I came back to it 90 minutes later it had dropped to 1.34 Vdc roughly on both sides. I adjusted it again and shut the amp off. I came back to it this morning, turned it on and let it warm up for about 60 minutes. The weird thing is as it powered up the bias ramped up to 1.77 Vdc and then slowly started falling. When I checked it 35 minutes later it was 1.39 Vdc. WTH?? Any thoughts on this? I can post a schematic if needed. B+ is sitting steady at between 432 Vdc and 440 Vdc
Finally, my wife bought me a matched set of EH 6CA7's Fat bottle, A Genalex KU77 GZ34 rectifier and in the pre-amp section a pair of Tung Sol 6U8A's (Matched) and a matched pair of Sovtek 5751's for Christmas. Would the Gold Lion KT-77's be a better choice? Listen mostly to Blues, Jazz and some classic rock (Sabbath, Zep, Floyd etc) Speakers are a pair of Klipsch KG-4's with both the Crites Xovers as well as new Crites diaphragms or a pair of Pioneer CSA-700's with a full recap done.
Thanks for any help and answers! Merry Christmas and Happy Holidays!
Bobby
