DCP going south??

62vauxhall

62vauxhall

Veteran and General Yakker
#141
Joined
May 14, 2014
Messages
2,324
Location
Southwest Kootenays BC
Tagline
No such things as bad days, just bad moments
#141
A few months ago, I was installing new components in a Toshiba preamp that had an op amp in the phono stage. Several were suggested including OPA2134. Being the obsessive compulsive sort that I am, I read to death opinions about op amps. Somewhere I came across something that said because an OPA2134 was JFET, they could oscillate in some circuits in some gear. Although I bought a couple, I never tried them. I stuck in an NE5532 and since it worked and seemed to sound better than what it replaced, I left it alone.
 
roccus

roccus

Chief Journeyman
#142
Joined
Jul 4, 2016
Messages
1,112
Location
Maine
Tagline
You'll blow your ears out kid
#142
WOPL Sniffer said:
It's a big learning curve doing these amps. I learned some hard lessons. Iffn it weren't for the crazy goombahs here that helped me through my mistakes, Id still be employed... Crap, that didn't come out right.. LOL
Click to expand...
lol... yea I'm learning to my background was mostly old simple 50's tube amp type stuff and the crazies here can't make me crazy I already am but damn this is driving me crazy :banghead::banghead:
 
roccus

roccus

Chief Journeyman
#143
Joined
Jul 4, 2016
Messages
1,112
Location
Maine
Tagline
You'll blow your ears out kid
#143
62vauxhall said:
A few months ago, I was installing new components in a Toshiba preamp that had an op amp in the phono stage. Several were suggested including OPA2134. Being the obsessive compulsive sort that I am, I read to death opinions about op amps. Somewhere I came across something that said because an OPA2134 was JFET, they could oscillate in some circuits in some gear. Although I bought a couple, I never tried them. I stuck in an NE5532 and since it worked and seemed to sound better than what it replaced, I left it alone.
Click to expand...
In this application the 2134 has been used very successfully after I did the mod with them and saw things go boom I posted on the carver site where the info from on this mod someone posted there may be a chance the supplier I got the 2134's from may have a bad batch..... guess you could say I most likely confirmed that 3 of the 6 2134's I bought were faulty... think when I get the c-1 back if it is all working good I will weld the covers on it to keep my fingers out of it lol
 
roccus

roccus

Chief Journeyman
#144
Joined
Jul 4, 2016
Messages
1,112
Location
Maine
Tagline
You'll blow your ears out kid
#144
See I set my meter to mv and I get mv reading in this case (point) .548 mv dc

 
roccus

roccus

Chief Journeyman
#145
Joined
Jul 4, 2016
Messages
1,112
Location
Maine
Tagline
You'll blow your ears out kid
#145
laatsch55 said:
Except bias, ya don't want just a third of a millivolt for bias....
Click to expand...
My mistake that is volt not mv I am resetting bias now
I now have .3501 V dc on the right channel and left channel is now .3503 V dc
 
WOPL Sniffer

WOPL Sniffer

Veteran and General Yakker
#146
Joined
Aug 10, 2015
Messages
11,522
Location
Minnie-Soda
Tagline
Screw it
#146
roccus said:
Here is offset with DCP removed
Right .585 mv dc ( this went up from when DCP was in and is pretty jumpy compared to left)
Left .038 mv dc

Looks to me like something may be going on in that right channel??
Click to expand...
So, there is no issue with your offset. It's less than 1 millivolt.
 
WOPL Sniffer

WOPL Sniffer

Veteran and General Yakker
#147
Joined
Aug 10, 2015
Messages
11,522
Location
Minnie-Soda
Tagline
Screw it
#147
roccus said:
Want to record my readings here before I disconnect DCP next I will take the DCP out of the loop and and see what offset is

Offset
Right .125 mv dc
Left .065 mv dc

Bias
Right .3447 mv dc
Left . 3486 mv dc (the bias seems to have dropped just a tad since break in)

Rail volts
84.02 vdc

DCP pins
J1-1 .082 mv dc
J1-2 not used
J1-3 .001 mv dc, 0.27 ohms

J2-1 .296 mv dc
J2-2 not used
J3-3 .006 mv dc, .31 ohms

J3-1 83.46 v dv
J3-2 .0002 v dc, .51 ohms
J3-3 61.50 v ac
Click to expand...

Your bias was recorded WRONG. You said now it's .344 VOLTS which is near perfect
 
WOPL Sniffer

WOPL Sniffer

Veteran and General Yakker
#149
Joined
Aug 10, 2015
Messages
11,522
Location
Minnie-Soda
Tagline
Screw it
#149
Maybe you should have Lee test it. Since the readings are fine, it needs to be run up and monitored without your speakers. By applying a signal and monitoring the output with a scope, we can tell what's up. Or, with the DCP out, crank it.... (don't do that)
 
laatsch55

laatsch55

Administrator,
Staff member
#151
Joined
Jan 14, 2011
Messages
74,946
Location
Gillette, Wyo.
Tagline
Halfbiass...Electron Herder and Backass Woof
#151
Yep, drive it with no load while hooked up to check for ac, see where it clips, then switch meter to DC AFTER bringing it BELOW clip, see what ya got then....
 
roccus

roccus

Chief Journeyman
#152
Joined
Jul 4, 2016
Messages
1,112
Location
Maine
Tagline
You'll blow your ears out kid
#152
laatsch55 said:
Yep, drive it with no load while hooked up to check for ac, see where it clips, then switch meter to DC AFTER bringing it BELOW clip, see what ya got then....
Click to expand...
Hi Lee when you say drive it no load does that mean connect preamp for input but no speakers?
 
roccus

roccus

Chief Journeyman
#154
Joined
Jul 4, 2016
Messages
1,112
Location
Maine
Tagline
You'll blow your ears out kid
#154
laatsch55 said:
Well, I was hoping you had a signal generator....
Click to expand...
All I have is a DMM, an oscope and an app to send signals from my laptop but it wont put any voltage out... anyone here have a signal generator they will part with??
 
laatsch55

laatsch55

Administrator,
Staff member
#155
Joined
Jan 14, 2011
Messages
74,946
Location
Gillette, Wyo.
Tagline
Halfbiass...Electron Herder and Backass Woof
#155
OK, well, best thing to do now is wait until the 1237 shows up, get it swapped in and hook the DCP back up. Then see if it keeps tripping. IF that happens, search for a signal generator program you can burn a steady state signal to a CD,. then burn a CD and pop it in your CD player. IIRC, there are some burnable signal sources that will have different frequencies for a pre-determined period of time.
I haven't used one but when I was sniffing out signal sources i stumbled across one somewhere. I don't remember which one it was....
 
roccus

roccus

Chief Journeyman
#156
Joined
Jul 4, 2016
Messages
1,112
Location
Maine
Tagline
You'll blow your ears out kid
#156
laatsch55 said:
OK, well, best thing to do now is wait until the 1237 shows up, get it swapped in and hook the DCP back up. Then see if it keeps tripping. IF that happens, search for a signal generator program you can burn a steady state signal to a CD,. then burn a CD and pop it in your CD player. IIRC, there are some burnable signal sources that will have different frequencies for a pre-determined period of time.
I haven't used one but when I was sniffing out signal sources i stumbled across one somewhere. I don't remember which one it was....
Click to expand...
I need a signal generator not an audio generator correct?
 
You must log in or register to reply here.
Top