Hi All,
So I have been playing with the idea in Carlosfm's "The OPA627 really sings" of biasing the newly installed OPA627AP op amps in my Rotel RCD 965BX. Zei helped me understand how to measure the voltage to figure out the resistors I need.
I am looking for someplace local to buy the two 1.8K ohm resistors. I have some time to kill so let me understand what he (Carlos) was saying about the desired 5-10ma for this mod. So I take out my trusty DMM and plug in the probes to the Amps connectors, set to milliamps and touch the red to the +Vs and the black to the Ground/common on the screw to the chassis. Big Spark!
Uh oh! What did I just do? I'll bet it isn't good!
Back to the trusty DMM but I an NOT using the ma setting. Back to the DC volts setting! Now on the Sparking op amp, 3.9 volts on the 6 pin (output) and back to the un-sparked pin 6 and got 6 volts!
YIKES! What did I hurt, my op amp or something around it?
The op amp is my first mod and it wasn't easy to get under the PCB due to the disassembly required. I think I gonna CRY now.
HELP! I feel like such an idiot! Thanks!
Regards//Keith
So I have been playing with the idea in Carlosfm's "The OPA627 really sings" of biasing the newly installed OPA627AP op amps in my Rotel RCD 965BX. Zei helped me understand how to measure the voltage to figure out the resistors I need.
I am looking for someplace local to buy the two 1.8K ohm resistors. I have some time to kill so let me understand what he (Carlos) was saying about the desired 5-10ma for this mod. So I take out my trusty DMM and plug in the probes to the Amps connectors, set to milliamps and touch the red to the +Vs and the black to the Ground/common on the screw to the chassis. Big Spark!
Uh oh! What did I just do? I'll bet it isn't good!
Back to the trusty DMM but I an NOT using the ma setting. Back to the DC volts setting! Now on the Sparking op amp, 3.9 volts on the 6 pin (output) and back to the un-sparked pin 6 and got 6 volts!
YIKES! What did I hurt, my op amp or something around it?
The op amp is my first mod and it wasn't easy to get under the PCB due to the disassembly required. I think I gonna CRY now.
HELP! I feel like such an idiot! Thanks!
Regards//Keith
Hi
Lets first hope that you did,nt fry something,,
Then.. i did,nt understand fully how and what you messured.. so is it possible to explain abit more? ( a picture perhaps?
Also,, take a look at this link.. it might give you some more insight in what you are trying to achive..
And last, I schematic of you amp is always helpful in trying to figure out stuff..
Lets works this out
/Zhttp://tangentsoft.net/audio/opamp-bias.html
A meter on current measure is effectively a short circuit (very low impedance.) You have just shorted +Vs to ground and probably destroyed something.
Bad move
I think you are going to need some close hand-holding to sort this out as you apparently do not really understand voltages and currents and how they relate.
Do you have a friend / neighbour who can help you out?
Bad move
I think you are going to need some close hand-holding to sort this out as you apparently do not really understand voltages and currents and how they relate.
Do you have a friend / neighbour who can help you out?
I'm not familiar with your circuit, but the OPA627 uses a +/- supply to obtain a "balanced" output. Normally, if you ground the positive supply pin (which you did through your DMM when set to measure current) of a single supply chip, the chip most likely won't be damaged. However, with a dual-supply chip like the OPA627, you severely unbalanced the internal biasing of the chip. I'm afraid to say that you most likely did damage it. If you need (or want) a data sheet of that chip, you can get it here:
http://www.datasheetcatalog.com/datasheets_pdf/O/P/A/6/OPA627AP.shtml
Good luck with your project.
sherlock
http://www.datasheetcatalog.com/datasheets_pdf/O/P/A/6/OPA627AP.shtml
Good luck with your project.
sherlock
Hi zei and cliff,
zei, I am glad you are still around! My turn for some wine!
cliff, you aren't kidding about a "Bad Move". This is where the learning part for new guys s*^ks! You guys and DIYAudio are my friends and neighbors when it comes to this! I don't even know of a decent local audio/elecrtonics repair guy that is good with mods and creativity!
Here is the hyperlink to the TI specifications pages for the OPA627AP: http://focus.ti.com/lit/ds/symlink/opa627.pdf
Here is a schematic of the op amp PCB area of the Rotel CD Player, the OPA627s replaced the XR5534s:
http://www.diyaudio.com/forums/attachment.php?postid=1256137&stamp=1184457241
The schematic shows all the components around the op amps. I think I fried one or more of the components in the op amp! I have two more if necessary to replace the one. I wasn't sure how I was going to add the resistor to the two pins of the op amps without taking them out and rutting the resistorpin and the leg of the op amp in the same holes and soldering. Now it looks like I have been shown the way! Yikes! Be careful what you ask for!
Hi sherlock, just noticed that you posted as I was writing this! I was afraid it was something like that. I would think that an IC is a self contained PCB with many components inside and at least one of those components got fried on the + side.
So gentlmen, does it look like time for surgery? Thanks for your help and support, now where did I put that Prozac?
Regards//Keith
zei, I am glad you are still around! My turn for some wine!
cliff, you aren't kidding about a "Bad Move". This is where the learning part for new guys s*^ks! You guys and DIYAudio are my friends and neighbors when it comes to this! I don't even know of a decent local audio/elecrtonics repair guy that is good with mods and creativity!
Here is the hyperlink to the TI specifications pages for the OPA627AP: http://focus.ti.com/lit/ds/symlink/opa627.pdf
Here is a schematic of the op amp PCB area of the Rotel CD Player, the OPA627s replaced the XR5534s:
http://www.diyaudio.com/forums/attachment.php?postid=1256137&stamp=1184457241
The schematic shows all the components around the op amps. I think I fried one or more of the components in the op amp! I have two more if necessary to replace the one. I wasn't sure how I was going to add the resistor to the two pins of the op amps without taking them out and rutting the resistorpin and the leg of the op amp in the same holes and soldering. Now it looks like I have been shown the way! Yikes! Be careful what you ask for!
Hi sherlock, just noticed that you posted as I was writing this! I was afraid it was something like that. I would think that an IC is a self contained PCB with many components inside and at least one of those components got fried on the + side.
So gentlmen, does it look like time for surgery? Thanks for your help and support, now where did I put that Prozac?
Regards//Keith
I will remove the op amp either late tonight or tomorrow late morning! Do I measure the DC voltage at the PCB where the +Vs and the -Vs pins would go from one to the other, or one or the other to groung/common? The +Vs to -Vs is 30 volts with the op amps in and the +Vs to common and -Vs to common are both 15 volts with the op amps in. These voltages are the same before my name was changed to "Sparky" and after! The only thing that changed was the output voltage on pin 6 in the one op amp that made a spark! The un sparked op amp remained constant at all values. I will bring the news!
Like Arnold says," I'll be back!"
Regards//Keith
Like Arnold says," I'll be back!"
Regards//Keith
Yeah, sounds like your power supply is probably still okay, but your opamp is probably blown.
The easy way to get a current measurement is to measure the voltage across a resistor in the path and then use ohms law.
To measure current directly with a multimeter you need to disconnect a component, and put the meter in series with your circuit, not in parallel.
Often there's a resistor you can measure to get the same result without all the messing around.
-Nick
The easy way to get a current measurement is to measure the voltage across a resistor in the path and then use ohms law.
To measure current directly with a multimeter you need to disconnect a component, and put the meter in series with your circuit, not in parallel.
Often there's a resistor you can measure to get the same result without all the messing around.
-Nick
Gentlemen,
Thank you for your expertise! I guess this can get ugly sometimes! But there is a power supply Guardian Angel out there somewhere! Nick, now that you mention it, I read that somewhere about using a resistor in line. NOW I won't forget it!
Thank G^d I have two more in the house! Well now I can add the resistor to make it bias to Class A easily by sticking the two ends in the same holes as the proper pins and solder it up!
Thanks to all my teachers on this lesson! (Can't wait to graduate already!)
I owe you all at least a drink! Zei, cliff, sherlock and Nick and The PS Guardian Angel too!
Regards//Keith
Thank you for your expertise! I guess this can get ugly sometimes! But there is a power supply Guardian Angel out there somewhere! Nick, now that you mention it, I read that somewhere about using a resistor in line. NOW I won't forget it!
Thank G^d I have two more in the house! Well now I can add the resistor to make it bias to Class A easily by sticking the two ends in the same holes as the proper pins and solder it up!
Thanks to all my teachers on this lesson! (Can't wait to graduate already!)
I owe you all at least a drink! Zei, cliff, sherlock and Nick and The PS Guardian Angel too!Regards//Keith
yes,
I'll bet he can report that the spark sounded really lifelike.
I hope, now that you know the difference between volts and amps, you can smile again.
Almost as bad as the day I thought I'd help my brother in law to find why his lightbulb in the living room was flickering.
Went upsatirs and litted the access panel to reveal the back of the lighting rose. Applied my analogue multimeter and BANG, my meter is
Oops, set to amps across the mains
Buy a new digital meter (I still have it some 20years later).
Hi Zei,
Like Andrew said, the most memorable impact of this op amp was the sound of Lightning (but a slightly smaller version)!
Andrew, it was for your own good!(Only kidding) The DMM is probably a nice one and you are glad you have it now. But that is not the way any of us want to have to upgrade! Volts, Amps it's all the same as far as wattage is concerned! YIKES! What a lesson!
I can't comment on other op amps because I have no experience with them but I can say that all the positive things said about these are true and I didn't experience any of the negative things posted!
I listened for a short while before moving on to the Biasing mod. Also, at the same time as the new op amps were changed the muting transistors were clipped off so I can't swear to what percentage of the improvement belongs to which mod.
However, the OPA627APs put the missing air back into the equation. The 5534s in this setup were really nice (but not like the 627s) and I can see how some of the people here like them (but like most op amps in the right configuration). Things in the background seemed like they were behind something else, seemed to take on a presence of their own and add to the music rather than kind of blend in, in a muddy sort of way. Many people suggest the AD826 saying it is more bright and the 627 is a little darker. The 627 seems brighter than the 5534 with more timbre from the mids through the highs so I am glad I didn't use the AD826s. The Bass seems to extend just a little lower and is some how more clear. What they call soundstage and imaging is increadible. Bigger, wider, deeper and everyone in the band seems like they are back in their place when it was recorded (artificially or whatever but the effect is nice). The 5534s did a nice job with this too but the 627 is in another league. More reviews after I get through the Lightning strike!
Regards//Keith
Like Andrew said, the most memorable impact of this op amp was the sound of Lightning (but a slightly smaller version)!
Andrew, it was for your own good!(Only kidding) The DMM is probably a nice one and you are glad you have it now. But that is not the way any of us want to have to upgrade! Volts, Amps it's all the same as far as wattage is concerned! YIKES! What a lesson!
I can't comment on other op amps because I have no experience with them but I can say that all the positive things said about these are true and I didn't experience any of the negative things posted!
I listened for a short while before moving on to the Biasing mod. Also, at the same time as the new op amps were changed the muting transistors were clipped off so I can't swear to what percentage of the improvement belongs to which mod.
However, the OPA627APs put the missing air back into the equation. The 5534s in this setup were really nice (but not like the 627s) and I can see how some of the people here like them (but like most op amps in the right configuration). Things in the background seemed like they were behind something else, seemed to take on a presence of their own and add to the music rather than kind of blend in, in a muddy sort of way. Many people suggest the AD826 saying it is more bright and the 627 is a little darker. The 627 seems brighter than the 5534 with more timbre from the mids through the highs so I am glad I didn't use the AD826s. The Bass seems to extend just a little lower and is some how more clear. What they call soundstage and imaging is increadible. Bigger, wider, deeper and everyone in the band seems like they are back in their place when it was recorded (artificially or whatever but the effect is nice). The 5534s did a nice job with this too but the 627 is in another league. More reviews after I get through the Lightning strike!
Regards//Keith
AndrewT said:yes,
I'll bet he can report that the spark sounded really lifelike.
I hope, now that you know the difference between volts and amps, you can smile again.
Almost as bad as the day I thought I'd help my brother in law to find why his lightbulb in the living room was flickering.
Went upsatirs and litted the access panel to reveal the back of the lighting rose. Applied my analogue multimeter and BANG, my meter is
Oops, set to amps across the mains
Buy a new digital meter (I still have it some 20years later).
I doubt if there is an engineer alive who hasn't done that or similar at some stage in their career.
The trick, of course, is to do it with someone else's meter!
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