Swapping Op-Amps... you have checked to see it's stable haven't you ? - Page 10 - diyAudio
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Old 23rd June 2012, 12:41 AM   #91
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HI there!

Sorry, but I am not a native english speaker and sometimes I don't understand figurative language. What did you mean?

Quote:
Originally Posted by wrenchone View Post
You're lucky you got any probes at all... The ones that came with my orig. Hitachi Scope (new!) were nothing to write home about.
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Old 25th June 2012, 07:16 AM   #92
RCruz is offline RCruz  Switzerland
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Quote:
Originally Posted by Audio Maniac View Post
HI there!

Sorry, but I am not a native english speaker and sometimes I don't understand figurative language. What did you mean?
Quote:
Originally Posted by wrenchone View Post
You're lucky you got any probes at all... The ones that came with my orig. Hitachi Scope (new!) were nothing to write home about.
Traducao: Mesmo assim tens sorte de ter "Probes".. As que vieram com o meu osciloscopio Hitachi (novo), nao eram nada de especial.

Maybe he means you are lucky that your rig came with probes.... it could be worst and you could have none at all.
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Last edited by RCruz; 25th June 2012 at 07:18 AM.
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Old 25th June 2012, 10:16 AM   #93
AndrewT is offline AndrewT  Scotland
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Buy fast probes.
There's no point in buying cheap 10MHz nor 20MHz probes and then find they are not much use when you upgrade to 60MHz or 100MHz scope.
A switchable probe is nice, but a fixed 1X and a fixed 10X are likely to be just as useful. Maybe even a 100x, for very special HV use.
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Old 25th June 2012, 03:37 PM   #94
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Thanks for the translation! He he he!

Quote:
Originally Posted by RCruz View Post
Traducao: Mesmo assim tens sorte de ter "Probes".. As que vieram com o meu osciloscopio Hitachi (novo), nao eram nada de especial.

Maybe he means you are lucky that your rig came with probes.... it could be worst and you could have none at all.
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Old 26th June 2012, 03:25 AM   #95
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For a rough understanding of what I meant (a common English (at least, American English) saying), think - WOW! these probes are so fantastic I must write my parents and tell them all about them! Now consider the opposite of that. The translators got the basic meaning, I'm just providing the context. A pair of 60-100 MHz 10X probes are cheap these days, if you don't mind that they come from China. I just bought some Chinese 100X probes (nice for tube voltages) that were very reasonable. Most of the time your scope will be used for "indication" rather than ultra-precise measurements, so cheap probes are still useful.

Last edited by wrenchone; 26th June 2012 at 03:32 AM.
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Old 26th June 2012, 05:22 AM   #96
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Hi! Thank you for being pacient!
And yes, I agree with you. There's no need of ultra precision, I just need an osciloscope to detect oscilation on my audio modifications.

Quote:
Originally Posted by wrenchone View Post
For a rough understanding of what I meant (a common English (at least, American English) saying), think - WOW! these probes are so fantastic I must write my parents and tell them all about them! Now consider the opposite of that. The translators got the basic meaning, I'm just providing the context. A pair of 60-100 MHz 10X probes are cheap these days, if you don't mind that they come from China. I just bought some Chinese 100X probes (nice for tube voltages) that were very reasonable. Most of the time your scope will be used for "indication" rather than ultra-precise measurements, so cheap probes are still useful.
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Old 17th February 2013, 01:06 PM   #97
JMFahey is offline JMFahey  Argentina
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This post should be a sticky.
It explains how to avoid a "very" common problem, and doubly so at DIY, because a natural temptation is "always use the best/newest/fanciest" which per se is fine, but may bring unseen problems.
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Old 20th March 2013, 07:48 PM   #98
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Hi all,

Question perhaps related -- I have the EE Minimax and have placed (through brown dog adapters and yes they are correctly oriented) dual LME49990 and single LME49990 in U1 and U2, and U6 and U7 respectively...

Here is my question:
1) U1 and U6 (well I assume they are U1 and U6 -- they are closest to the back of the unit when facing it from the front) - U1 and U6 (again opamps closest to back) run hotter than U2 and U7 in both tube and SS mode. Why the difference? U1 runs about 130F and U6 runs about 105F, U2 and U7 run "cool" in the 80'sF

Last edited by dmccoach; 20th March 2013 at 08:11 PM.
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Old 20th March 2013, 08:20 PM   #99
Mooly is offline Mooly  United Kingdom
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That is impossible to answer without looking at both the circuit and the unit with the replaced IC's. It may be normal and just due to different loading on the IC's or different rail voltages to different opamps. Or instability ! Have you put a scope on the opamps to check ?
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Old 20th March 2013, 09:54 PM   #100
qusp is offline qusp  Australia
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the 49990 does run pretty hot, like worryingly hot and thats normal and every condition ive tried it, but without the schematic and pics I cant tell you if that mismatch between them is what you should expect, you may be asking too much of them, or 2 may indeed be oscillating.
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