|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
207.134.250.139
In Reply to: RE: Mike, Steve, Fender Lover posted by Michael Samra on April 09, 2014 at 11:26:09
Thanks Mike.
I'll try the plugs tonight.
Hope it's not a cap. Then I'll have to review all the cap shootouts! Sigh... I thought I was getting passed this... :)
Appreciate the tip on the bias pots!
Sincerely,
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
Follow Ups:
No, you don't have to review all cap shootouts because 90% of them are bull shit.In your amp,I would use Vitaman Q or K40y paper in oil caps..ARC products tend to lead a bit on the sterile side so putting paper in oil caps on the output tubes helps them a lot because it gives the amp a more spacious sound with more body.The other caps I would use the white solen film and tin foil.They are a bit pricier but only because you can't buy them on Ebay or the surplus markets like you can the Russian k40s or even the Russian Teflons..Lets see what shorting the input does first.
Honest amplification is better than excessive 2nd order distortion anytime.
bias on all output tubes still unsteady.
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
...because things now become more complicated. I went back and read your original posts of a week or so ago and what you describe sounds like a low freq instability has developed when the overall feedback loop is closed. Taking out front end tubes opens the loop and promotes stability under otherwise marginal conditions. Based on your descriptions I'd be suspicious of power suppy/stage decoupling caps. They're usually electrolytics and have a finite life. Do you know if any of them have been replaced or are they original? I don't have a schematic so I can't be any more specific but maybe Mike has one handy.
I'll go through all my paperwork and check what's been replaced.
I know I have a schematic of either the amp or preamp somewhere. Maybe I'll be lucky and it'll be the amp.
"I know just enough to get into trouble. But not enough to get out of it."
When you put the shorting plugs in,are you hearing any noise hum or static when you put your ear up to your loudspeakers?
Honest amplification is better than excessive 2nd order distortion anytime.
No noise hum crackling.
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
I want you to desolder the 1uf coupling caps C9 and C10 on the side that goes to the output tubes control grid and the 1k resistor..There are four of these caps and I only see C9 and C10 in the schematic as they are showing one channel..Anyway,the side that you lift up on each,plug the amp back in and measure the DC voltage on the desoldered side of each cap to ground..If it reads more than a half volt,change the cap as its leaky.
Honest amplification is better than excessive 2nd order distortion anytime.
Are the two resistors per channel just before the 6550 tube sockets, look like position R37 and R40?
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
Well, I can't find any resistors 4 or 5 color banded that equal 1k in my amp. Schematic is MKII. Mine is MKI. I don't know if that makes a difference.
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
Don't worry so much about that,just do the caps that go to pin 5 of the output tubes...Drop me an email with your phone number.
Honest amplification is better than excessive 2nd order distortion anytime.
Contact info emailed.
Pin 5 it will be!
"I know just enough to get into trouble. But not enough to get out of it."
To try this. Argh. Patience.
Cant wait to get home.
Thanks Mike!
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
That's why I love being a college instructor..You have summers off along with weekends from Thur thru Sun in my case and now I'm off on spring break.You have a fair share of meetings but that goes with the territory.
Honest amplification is better than excessive 2nd order distortion anytime.
I had a small business with one employee. Flex hours and freedom was great for about 10 years. Business went in the deep end. Back in the workforce now almost 2 years.
What happens happens. No regrets.
I'm sure you're a good instructor.
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: