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Old 30th January 2012, 08:53 PM   #1981
agdr is offline agdr  United States
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Quote:
Originally Posted by sonja View Post
I need a power adapter for the objective2, which is capable of 230V environment. It was a link to an ebay site some time ago, but I don`t remember where I saw it. I think it was on the ebay UK. Anybody knows?
Maybe this one NEW AC-AC TRANSFORMER MAINS ADAPTOR 240V TO 16V 700 ma | eBay
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Old 30th January 2012, 09:59 PM   #1982
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Originally Posted by agdr View Post
Unfortunately solder bridges wouldn't show up well in a photo. Best thing to do is use a magnifying glass and take a look at them directly. Especially the solder joints on U6 - it is very hard to see a bridge between those pins without the magnifier.

You should get -24.9V or so to ground (metal shell of the gain switch) at the non-banded side of D4, going into the regulator.
I'm a bit suspicious of the PCB at the moment. I have a spare one here. I thought I'd check out the traces.

It seems that the topmost pin (relative to the jack) of the U6 pinholes is shorted to both the top of pin of C7 and the ground of the jack. I first noticed that the top pin of U6 shorts to the middle pins of the battery area (which are ground yes?)

Looking at the PDF of the circuit, that doesn't seem right to me.

The center pin for U6 does NOT short to the ground where the batteries are. But it does for U5. Fishy?

EDIT: Tried to edit and failed. I realise now that the central pin of U6 is not ground (thanks to the trace diagram). I have ~106 Ohms from the bottom pin of U6 (furthest from power plug) to ground. That must be going over R1/R2 in parallel? (1/220+1/220)^(-1) ~ 100

Last edited by SEdwards; 30th January 2012 at 10:26 PM. Reason: i was wrong
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Old 30th January 2012, 10:00 PM   #1983
sonja is offline sonja  Norway
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Thank you very much! That was the one I was thinking about.
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Old 30th January 2012, 10:55 PM   #1984
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I've found a short from the non-banded side of D6 (and R2) to ground. Now I need to work out how it got there.
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Old 30th January 2012, 11:13 PM   #1985
agdr is offline agdr  United States
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Quote:
Originally Posted by SEdwards View Post
I've found a short from the non-banded side of D6 (and R2) to ground. Now I need to work out how it got there.
Good work! Yes, with the batteries out and the power switch off that D6-R2 junction shouldn't have a (shorted) path to ground. Keep in mind that one leg of the power switch also connects to that junction. Maybe you have a solder bridge to ground on one of the power switch terminals. Would be easy to do - those are very small solder joints.

You are right, the top pin of U6 is ground, the middle is the voltage input and the bottom is the voltage output. The pinout of U6 is different from U5. I just did a resistance measurement (not the diode check function) from from the ground pin to the output on a LM7915 and I get about 18K either way. With a 1N5818 diode I get about 2K in one direction and 250K in the other. So 106 ohms to ground on the output pin of U6 is way to low.

If it were me I would start unsoldering things. Unsolder the unbanded end of D6 and see if the short goes away. If not do the same for the end of R2 that goes to the same junction. If not, then the unbanded end of D5, etc. until you find out what part or trace has the short.
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Old 31st January 2012, 01:22 AM   #1986
nezbleu is offline nezbleu  Canada
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Quote:
Originally Posted by SEdwards View Post
I'm a bit suspicious of the PCB at the moment... The center pin for U6 does NOT short to the ground where the batteries are. But it does for U5. Fishy?
Why would you find that fishy? Have you looked at data sheets or pin-outs for the 2 IC's? Why would you suspect the PCB? While anything is possible, the PCB's are identical and work perfectly for virtually all builders. If it isn't working for you then in all likelihood you have made an error. Perhaps you inserted a part incorrectly, perhaps you made a bad solder joint.

The symptoms you describe (0V on voltage regulator output, hot regulator) indicate exactly one thing: a short to ground from the regulator output. It is not the circuit board or a mysterious defective component, it is a construction error. Find it and fix it, that's what DIY means. All you need is a multi-meter and patience.

I am not trying to be a jerk, but I get frustrated when people keep trying to blame everything but their workmanship despite all contrary evidence. The PCB is fine, the circuit works as advertised, you made a short somewhere.
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Old 31st January 2012, 01:27 AM   #1987
nezbleu is offline nezbleu  Canada
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Quote:
Originally Posted by Willakan View Post
How hot is too hot to touch? It is a voltage regulator: there's going to be some heat generated. What power supply are you using?
Well, yes and no. With no batteries and no load, those regulators pass a few tens of milliamps. They do not get hot, they barely get warm (a couple degrees above ambient). A newborn could hold that regulator all day without discomfort.

If the regulator is actually hot, or even noticeably warm, something is wrong, either a dead short or a downstream component shorted or damaged.
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Old 31st January 2012, 01:30 AM   #1988
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Default The Objective (O2) Headphone Amp

This volume-controlled and high fidelity headphone amp (O2) can be used to exemplify a specific facet of the management of Gain Structure per the teaching of the article by DIYer Pano which is entitled: What is Gain Structure? Given that this headphone amp is driven by a pristine line level signal from a high quality CD player, then its output can be fed directly to the input of a power amp via a 1/4 inch headphone to RCA stereo conversion plug (sold at Radio Shack). The input impedance of common power amps is normally high; for example greater than 20 Kilo Ohm. Thus, the operational status of this headphone amp is an ideal quiescence. It is doing minimal work in this high impedance load. It is conceptually akin to that of STASIS (R) of Threshold Corporation; inventor Nelson Pass. A fall back to (O2) maybe the volume-controlled headphone amp which may happen to be internal to the CD player at hand. This amp of unknown fidelity relative to (O2) also operates in an ideal quiescent state driving the same power amp of high input impedance.
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Old 31st January 2012, 02:57 AM   #1989
MrSlim is offline MrSlim  Canada
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Quote:
Originally Posted by Antoinel View Post
This volume-controlled and high fidelity headphone amp (O2) can be used to exemplify a specific facet of the management of Gain Structure per the teaching of the article by DIYer Pano which is entitled: What is Gain Structure? Given that this headphone amp is driven by a pristine line level signal from a high quality CD player, then its output can be fed directly to the input of a power amp via a 1/4 inch headphone to RCA stereo conversion plug (sold at Radio Shack). The input impedance of common power amps is normally high; for example greater than 20 Kilo Ohm. Thus, the operational status of this headphone amp is an ideal quiescence. It is doing minimal work in this high impedance load. It is conceptually akin to that of STASIS (R) of Threshold Corporation; inventor Nelson Pass. A fall back to (O2) maybe the volume-controlled headphone amp which may happen to be internal to the CD player at hand. This amp of unknown fidelity relative to (O2) also operates in an ideal quiescent state driving the same power amp of high input impedance.
Um... OK?
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Old 31st January 2012, 03:19 AM   #1990
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