phase linear 400

ABebar

Journeyman
Joined
May 28, 2021
Messages
177
Location
Warrenville, IL
You probably already know my status. I started tearing into the stock chassis on January 22. Had the stock wiring and boards out and the filthy chassis cleaned up on February 6. Started wiring on February 11. Tried to power on for the first time on March 26. Hit a roadblock on April 9 and stalled out. Now with my trip coming up Saturday, I probably won't get it done until early May. It's been on my kitchen counter for the past three months and still no music.
Not to make excuses, but it's tough to devote too much time to it with a stressful 50 hour per week job, two teenage kids with rehearsals and practices who need to be cooked for/cleaned up after/driven everywhere, a needy girlfriend (don't tell her I said that), a basement remodel I started in January and finished in March, and a list of other hobbies that I need to maintain my sanity. I'm averaging about two to four hours per week into this build. I'll get there eventually.
 

ABebar

Journeyman
Joined
May 28, 2021
Messages
177
Location
Warrenville, IL
Hmmm I had bias issues with Tim (700/1 stock back planes and WO board) regarding bias. Ended up being an old back plane capacitor BUT I did notice that bias was wonky (if that’s a technical term) until the mains voltage came up a good bit. Now remember, Im a fookin rookie so ask the experts but if you’re bringing it up that slow that the front end can’t regulate bias, is that the issue? As in, you have NO issue but you’re pussy footing it? I used a 60w bulb and pretty much cranked the variac to 60v I think right off. I believe you said you went 10v. The DCP clicks around 80-90v if I recall. My bias was settling in there. Maybe try a low
Wattage bulb and just bang it 120v? The old “go big or go home”...???
There may be something to that. The first time I brought it up with the driver transistors installed and the control board wired in, I don't remember what voltage I was monitoring on bring up. I could have been looking at rail voltage or offset and then didn't check bias until voltage was higher. It could stand to reason that you need the IC's to fully stabilize before the bias regulates... I also don't want to find out the hard way that there is a maximum bias voltage that the circuit can handle before things start to runaway entirely. Is that at 5v? 10V? I don't know. I haven't seen the bias go above 2v. How much is damaging?
 

Gepetto

Administrator
Staff member
Joined
May 15, 2011
Messages
14,045
Location
Sterling, MA
Tagline
Old 'Arn Enthusiast
You probably already know my status. I started tearing into the stock chassis on January 22. Had the stock wiring and boards out and the filthy chassis cleaned up on February 6. Started wiring on February 11. Tried to power on for the first time on March 26. Hit a roadblock on April 9 and stalled out. Now with my trip coming up Saturday, I probably won't get it done until early May. It's been on my kitchen counter for the past three months and still no music.
Not to make excuses, but it's tough to devote too much time to it with a stressful 50 hour per week job, two teenage kids with rehearsals and practices who need to be cooked for/cleaned up after/driven everywhere, a needy girlfriend (don't tell her I said that), a basement remodel I started in January and finished in March, and a list of other hobbies that I need to maintain my sanity. I'm averaging about two to four hours per week into this build. I'll get there eventually.
Yeah life does get in the way but that is also ‘all good’
 

Gepetto

Administrator
Staff member
Joined
May 15, 2011
Messages
14,045
Location
Sterling, MA
Tagline
Old 'Arn Enthusiast
There may be something to that. The first time I brought it up with the driver transistors installed and the control board wired in, I don't remember what voltage I was monitoring on bring up. I could have been looking at rail voltage or offset and then didn't check bias until voltage was higher. It could stand to reason that you need the IC's to fully stabilize before the bias regulates... I also don't want to find out the hard way that there is a maximum bias voltage that the circuit can handle before things start to runaway entirely. Is that at 5v? 10V? I don't know. I haven't seen the bias go above 2v. How much is damaging?
You know Adam that with full comp backplanes installed that you can debug just about any problem with the control board installed BUT with no output devices of any sort installed. The beauty of the full comp configuration
 

gene french

Veteran and General Yakker
Joined
Mar 6, 2022
Messages
5,564
Location
guayabo de bagaces, guanacaste, costa rica....
Tagline
music...the healer of souls...
eeexxxxcccuuuusssseeee me .... i stand corrected...
WOAD...better???
i dont capitalize much...habit i developed from sco unix days...all lower case....then 20 years of ubuntu...remember dos 2.0???
lol....wow...so many years ago...a long way from pet machines and vic machines....
 
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