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Beginners / Re: Help identify diode!
« Last post by 13hm13 on Today at 12:33:27 am »
The accident: the CD60 tipped off its shelf on one side (left) , and free-fell about 12 inches  to a soft, carpet (which had foam mat underneath).

Some weird issues afterward, including:

The 1541 got very warm. I removed it -- tested it another CDP, it's okay.

Also, laser current adj was off  (CD would not spin up). Not sure how that happened??? Anyway, after adj. of trimmer pot ... it booted and played. Tracks as good as any player.

No PCB or chassis cracks, broken traces. All voltages ok.

Except one nagging issue remains: Some noise (distortion) on music (audio) when recorded level is low (quiet passages, fade-downs, start of fade-ups). When audio level moderate and above, music is clean ( low-level noise is probably still there, but masked by music. It's almost like "dirty dither").

Most of your troubleshooting suggestions are been-there-done-thats: Freeze-sprayed all ICs, etc. No change. Swapped TDA1541A and SAA7220. No change.

It might be the SAA7310 decoder (or something close to it). Or it might be uP chip. Haven't swapped those. But if those LSI multitasking chips were faulty, many other CDP systems (processes) would be affected. Right?

BTW, the eye pattern looks very good:



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Projects, Designs, and Technical Stuff / Re: Snubbing relay contacts
« Last post by JS on Today at 12:29:09 am »
I see a problem with your approach.

Let's take your 1Ω 10A innyour example, you put a big enough cap for all tonwork. You want to limit the current while switching at those 10 amps, the cap presumably is charged with those 10V so you need 1Ω in series with your cap. When you switch off the load, right immediately after thebcontacts loose contact (uhu) you have half the voltage already. If the source is also resistive you are in an even worse situation as you need a higher R in the snubber as the voltage while open is higher than the voltage at the load when connected. With this in mind, the snubber could make things worse that not even being there abusing the contact at switch on times.

JS

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Test Equipment / Re: Lecroy options -=recovery=-
« Last post by darkstar49 on Today at 12:21:48 am »
Quote
Yeah it sucks that Wuerstchenhund was banned as he had a hell of a lot of knowledge to offer this forum about high end scopes and LeCroy in particular.

on the other hand, he probably wouldn't have been too happy with this thread... from what I saw, he was not too keen giving out any information around this 'touchy' subject...
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Thanks Dave,
Yeah ,the actual value is misquoted on the packaging ,in my favour ,but it still comes to 30 euros or so , I could just pay up and be done with it ,but if theres a creative accounting solution I would rather save myself the thirty eurobucks anyday.
Due to a dispute with the dept of social welfare here over biometric recognition , the suplementary payments I was getting on top of what I earn from self employment have been cut off completely for well over a year now ,of course the two things are completely seperate issues , but I loath paying over a red cent to a government who hood winked almost the entire population into being on a biometric database for which there seems to be no legal basis . Data protection comissioner was supposed to issue a report on the legality of this biometric system and the id card that goes along with it over six months ago ,but the release of the report keeps getting bounced down the line ,as far as I can see because it could show that the government were wrong on this.
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Wait - this is a vector display, so no signal to the monitor just gives a dot in the center of the screen.
Don't leave it like this long, it can burn the phosphor.
The main board might be dead, so no signal being made to the screen.
More info and manuals: https://www.arcade-museum.com/game_detail.php?game_id=6939

I'd never come across a vector display before. I thought it was just like an ordinary CRT. Thanks for the lesson. :)
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It sounds like both remotes send exactly the same codes and have the same address - which is why training a receiver with one remote, causes the other to be picked up as well.

Whilst there are custom solutions, many remotes use PT2264 or equivalent encoders.  These have an address that is set by connecting pins high (V+) low (GND) or not connected (High Z).  If you can open up the remotes you might be able to see a row of pins with PCB traces running along side.  Most remotes like this, you can set the address with solder bridges.

Maybe open up one of the transmitters, and take a photo :)
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Beginners / Re: High side current sense using differential opamp
« Last post by Hero999 on Today at 12:09:50 am »
So the output impedance will be a combination of Rdson and R2 depening on how much the tranasistor is turned on. With the transistor off the output impedance is 2k, but it shouldn't go higher than 2.5V so Rdson should be the dominating resistance here.

The large amount of gain and negative feedback makes the output impedance much lower than that, as long as there's still a reasonable amount of current flowing through the pull up or pull down resistor.

I've just measured the output impedance of my simulation with the 8k2 pull up, at 600mV output, supplying +/- 1mA at 1kHz the output impedance was ~0.025 ohm.
That's only when the loop is closed. The output still can't go lower than R8 and R2 would allow. With a single supply, the loop will be broken at output voltages near the supply rail, resulting in a high output impedance.
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Is there a primer on this stuff? I have seen industrial catalog advertizements for things you plug into pld power supplies which monitor them for weird behavior.

I dont know much about how os work and backbones of modern processors but i figure it would be interesting discussion
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Repair / Re: Reball "repair" (the Rossman video and such)
« Last post by LateLesley on Today at 12:01:18 am »
I did a bit of googling into this at the time, and it appears he is right. It's an inherent flaw in flip chip design of a certain time, and what was breaking was not the solder balls under the chip, but the solder balls between the silicon and the package substrate. No amount of reballing would fix that.

http://www.sonoscanchina.cn/us/images/18FCBumpPassivationFailIRPS97.pdf

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