Re: Digital piano volume control... how hard can it be?
Hello Irene,
It has been a while, but if I remember correctly the potentiometer had one pair of conductive "rails" per channel. For each channel, one of them is a variable resistor, and has one pin connected to each end. The other rail should be connected to just one pin, but there was no continuity. I know Iused conductive paint to retouch the rail, but I can't remember if there was a broken path somewhere I could see.
If are interested in playing the piano and don't care much about cosmetic issues, you...
jarl
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Last Activity: 12-01-2023, 01:34 PM
Joined: 10-25-2009
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Re: Sony HCD-300S problem²
Thank you Longbow,
That's a truckload of good leads
I'll go over the testing later on... I'm catching up with stuff that got behind because of Christmas, so there's not as much time available as I would like...
Last edited by jarl; 12-28-2011, 01:33 PM.Leave a comment:
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Re: Sony HCD-300S problem²
Thank you Scenic, Longbow,
The amplifiers share the same PCB-and are on the same schematic- as the power supply. On the PCB the amplifier section is on the left, and the ICs are IC301, IC331 and IC361. The one that wasn't working originally was IC301, but after the probe "issue" while measuring the pins of IC301 the other channels stopped working as well. It looks like either IC361 or some of the associated components got messed up (nothing looks blown/burned though).
The voltages on each of the pins are shown on...Last edited by jarl; 12-21-2011, 07:02 PM.Leave a comment:
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Re: Sony HCD-300S problem²
Thank you people...
Yep... the link by Lcdman is for an item located in China. I'm aware this IC has been discontinued, and I wouldn't mind buying a used part from a reputable seller, even if on eBay. Even a counterfeit would be an option, as long as the performance was comparable to the original. However I don't have such expectations from sellers who offer discontinued proprietary ICs by the hundreds...
An option would be to buy an old amp at a thrift store and gut it, as long as I knew it had the TA2020-020... but I don't think...Leave a comment:
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Re: Sony HCD-300S problem²
Yuck... buying discontinued ICs from someone in China doesn't sound too reliable...
"Surface was removed with sandpaper and new characters engraved" is one of the feedback left for one of the sellers...Leave a comment:
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Re: Sony HCD-300S - No sound
Update: I was able to solve one part of the riddle...
Turned out the signal causing the "thud" was present in all the channels not related with IC301. The only reason I was able to hear it on the rear-left channel was that a capacitor (6800pf) between that speaker's (+) terminal and ground had failed. It probably has been bad for a while, but that wasn't highlighted until I screwed up with the scope probe.
So... now I have two working and one (apparently) dead TA2020. The protection circuit seems to be triggered,...Leave a comment:
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Sony HCD-300S problem²
Problem squared, that is...
Smart me, I got a home theater from craigslist without thinking too much about it. It's a Sony HCD-S300 (same as the DAV-S300, DVD player + 5.1 amplifier in the same device). Upon testing this thing using the built-in "tone" function, one of the channels (front-right) was dead, so I checked for cold solders at the speaker connectors and redid all of them, with no change in symptoms.
No problem, I thought... got the service manual and my old oscilloscope and started measuring the voltage at the relevant TA2020-020 (there are three:... -
Re: Viewsonic VX510, no backlight
Oh my... exactly one month later I'm back. Isn't it wonderful what replacing a car's engine makes for the forum's continuity?
Anyway...
I tested the transistors in-circuit, and none of them shows a short-circuit. There's something weird with one of them (Q113), though: If you test it after probing Q105, it will make my DVM beep for half a second. It won't happen again until you test Q105 again. Q001 shows a similar behavior.
I measured the resistence of the secondary on PT101 and PT102 (again in-circuit). There seems...Leave a comment:
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Viewsonic VX510, no backlight
Hello again
As soon as I mentioned to my wife I had fixed the 17" Dell monitor of my previous thread, she says "great! I'm needing one for my office"...
So... next in line is this Viewsonic VX510. When I got it last year the backlight wasn't working at all (I think I had posted something, but I can't find it). I opened it up and found some dubious-looking capacitors, so I just replaced them. As far as I remember there were no changes in behavior, so it went back to the stack of "to do".
Well... I put my hands on it yesterday...... -
Dell E176Fpb flashing/blinking -> Solution?
Ok... this is my chance to give a little bit back to the forum, if just a little bit
At the beginning of the garage sale season I picked up a Dell monitor that was being dumped. I spoke briefly with the person throwing it to the garbage, and he said the screen was just flashing the dell logo. I tested it, and in fact the monitor seemed to turn on fine, and after ~10 second or so it started flashing the dell logo. I just put it in the pile of crap (I mean...fine electronic equipment) waiting to be fixed, until today. I connected it again, and I realized the monitor was actually... -
Re: Digital piano volume control... how hard can it be?
Uhm... the problem has been identified, but it doesn't make much sense...
Somehow, the pins connecting to both swipes were "open", meaning there wasn't any electrical connection to the swipe tracks. I don't know if it was due to a manufacturing problem or what, but I have never heard of both swipes on a potentiometer going 100% disconnected without any obvious mechanical damage. The other four terminals (connected to the resistive track) were fine.
In any case, that was the issue. I used...Leave a comment:
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Re: Digital piano volume control... how hard can it be?
More information:
- Connected the keyboard's "line out" to an external amp -> No sound on the external amp
- Connected an MP3 player to the "line in" on the keyboard -> Very loud sound through the keyboard's speakers, no volume control (I'm not sure the main volume control should control this, though)
So... main amplifier seems to be fine, something else is fried?Leave a comment:
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Re: Digital piano volume control... how hard can it be?
What $2000 could get you 25 years ago......Leave a comment:
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Digital piano volume control... how hard can it be?
I have been looking for a digital piano for a while, and last week the opportunity finally showed up on craigslist: a Technics PX7 which "only" had a problem with the volume. The piano produces a very light sound, and doesn't change when moving the volume control. "How hard can it be ?", I thought... Well... Let's say I just remembered how I hated analog electronics back in the day
One of the images shows the guts of this thing. The volume control is on the "control-L" board. Next to the linear pot controlling the volume, there's a M5218L op-amp. When... -
Re: ESD damage to laptop's USB ports
Well... it looks like it as a self-resetting device after all.
I left the laptop disconnected and without a battery for several hours in preparation for "exploratory surgery", and after my last post I decided to open it up. I decided to try the USB port once more, though, to make sure I had the symptoms of the problem straight. Lo and behold, the USB ports have accepted everything I have thrown at them
Just for the record: when the problem first showed up I tried removing the battery but it didn't help. Either...Leave a comment:
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Re: ESD damage to laptop's USB ports
Thank you for the answers, people, but as I stated on the original post the USB ports *are working*. The only problem (albeit a large one) is that there doesn't seem to be enough power to drive non-self-powered devices. Again, I can use external DVD drives, external hard drives, etc, as long as those devices don't draw their power from the USB port.
The USB spec requires 500mA to be available at the ports; the USB-specific current-limiting devices I have seen usually cite 1.5A as the upper limit (check for instance the TI TPS2062)....Leave a comment:
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Re: ESD damage to laptop's USB ports
Hello ratdude,
I can't find anything about failed i855 chipsets. What are the symptoms? When these chipsets "blow" the USB, does it continue working with self-powered devices?
If the USB ports were dead I would just assume it was something major. However, since there is 5V in the power line, and self-powered devices work fine, my guess is that whatever current-limiting device is used to protect these ports was damaged by ESD. Also, do you know if the USB ports on the docking station are driven by the laptop's...Leave a comment:
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Re: ESD damage to laptop's USB ports
Thank you for your answers,
@gretti: do you mean that after a static discharge you had to reflow the southbridge?
The mobo has been out of the case once or twice, but it was a really long time ago, so I tend to believe the problem has nothing to do with a crack or anything like that. I have read about other people who have had similar problems, who are using their peripherics with a powered hub and stuff like that. But I'm moving this laptop all the time and having an extra cord is not an option.
@scenic: I think...Leave a comment:
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ESD damage to laptop's USB ports
Laptop: Inspiron 600m
A couple of days ago, while trying to diagnose another PC (i.e. lots of moving a thumb drive between my laptop and the "patient"), the USB ports on my laptop stopped working. I'm almost sure the problem was due to static electricity.
Symptoms:
Almost any USB-powered device I connect to either port returns a "device not recognized". Self-powered devices work fine (i.e. external DVD burner). Self-powered devices work fine when connected through the docking station. I measured the power line on the USB ports and it's indeed at... -
Re: Vizio VX32L HDTV10A - No backligh
Hello all,
I finally got an inverter board from Ebay, replaced it and the TV seems to be working fine. EXCEPT:
It's evident the 2nd bulb from the top of the screen is not lighting as much as the others. Not a show stopper, but it got me thinking... Can a transformer get damaged by a failing bulb, or is it more plausible the dying transformer may have damaged the bulb somewhat? Is it too hard to replace a bulb?
One interesting thing is that if you turn down the brightness of the screen below a certain point...Leave a comment:
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