Can you fellow techs explain the why/how of using an AC Voltmeter? I've read a bit about it on a few sites and I don't have a full grasp on it.
Thanks!
Thanks!
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Re: AC Voltmeter?
The second link hides some food for thought for expert boys.
Since the initial writing of this paper, a few ultra-low priced meters have become
available. These are typically made in China and retail for less than ten dollars, and often less than five
dollars. These meters employ a different approach to measuring AC voltage. It was discovered that they
simply eliminate the negative portion of the voltage wave by means of a half-wave rectifier, take the
average of the positive portion, and double it. That is, AC voltage = 2 times the average of the positive half
of the voltage wave. This type of meter can easily be identified because it will not register any AC voltage
if a battery is placed on the test leads with negative polarity, but will show twice the DC value of the battery
voltage if the battery is placed on the test leads with positive polarity.Comment
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Re: AC Voltmeter?
For badcaps.net repair projects we rarely need to measure AC.
Having said that, it is nice to know how a multimeter measures AC. This video might answer some questions?
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Dear Members,
I have an old analog voltmeter that can correctly measure DC voltage between 0v to 3v. The voltmeter is made by Toyokeiki depicted in the photos. It does not need any battery. It works using a coil and a magnet as any other analog voltmeters.
I am going to convert this voltmeter into a DC ammeter that can measure DC current between 0A to 15A.
To do this, I use a 0.2 Ohm resistor for current sensing in the circuit. Then, I use the setup depicted in the photo to measure current.
For example, if the power be 12v and the load be 8 ohms, the voltmeter shows... -
Hi guys
I trust this topic is OK for discussion here
When I am googling for board view files I find a lot are on various pay sites. In particular I find a lot of links to an Indonesia forum but it seems I have to pay (VIP member) to down load them: For example I am currently looking for a boardview for Asrock Z87 Exteme4
I know a lot of folks here kindly share boardview files and schematics for free -and I doubt the sites charging money actually have any sort of intellectual property rights to sell them
Having said that I am not adverse to paying... -
Hey fellow techs. I have a new issue i have been working on for quite some time now while waiting for parts from china to ship.
- Issue started with no power coming into laptop at all. I replaced the DC IN Jack and received 19v.
- Problem then was 19v would only reach to the first power mosfet. Long story short i replaced both the 1st and 2nd power mosfets.
- I currently have the second mosfet off because if i solder it back the charger gets tripped to protect circuit and 19v is not applied.
- I replaced the current sense resistor above this mosfet but no... -
I find myself with my personal laptop, NVME -> USB-C adapter to test/retrieve data on SSDs connected to my laptop
USB DVDRW
odd collection of bootable disks for diagnostics (I know some of you have been raving about a collection of these all-in-one tool DVD/CD's, never looked into those)
USB ethernet adapter (unfortunately requires drivers)
USB Sata adapter
2TB HDD for backing data up
Multi-bit screwdriver
Laptop toolkit with extensive bits, pry tools, etc, etc
USB mouse... -
Has anyone had experience with the foreign sites that charge you for schematics or board-views? I have seen some that you can pay a few dollars and you get access to their files for a day. You can also pay more for longer periods of time.
Has anyone used them? If so, were you satisfied with the schematics, and that they had what they said they had? Let us know your experience with them.
Thanks
Comment