Oh right. The only 2 data sheets for that part that I can find are Fairchild Rev 1.0.5 dated 2005 (that I linked to), or an earlier Rev 1.0.4. Both say absolute.
Can you upload or link to the datasheet you have for comparison?
Cheers.
Radio Fox
Badcaps Veteran
Last Activity: 01-29-2025, 01:18 PM
Joined: 01-01-2010
Location: East London
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Thanks for reply.
Yeah, I hadn't read further down the data sheet to read how the OVP works. I can see now that an 18v zener can't be used on that pin.
However, the data sheet still clearly states that the absolute maximum voltage for Vcc pin is 20v. There's nothing in the table to say that it's the absolute maximum voltage that trips the OVP. That's why it's confusing. That Vcc pin must have a maximum voltage that would break it, so what is it? All we can tell is that it must be greater than 22v, as that's the value of the zener.
It's obviously correct anyway,...Leave a comment:
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Acer AL1916 monitor PSU repair (DM0565R blown)
I'm repairing an Acer AL1916 monitor PSU at the moment. The 400v high voltage smoothing capacitor C114 is measuring completely O/C. The case of U101 has blown apart. Fuse F101 has blown. ZD121 reads 6 Ohms in both directions & ZD120 reads 99 Ohms in both directions. While looking at the data sheet of U101 (DM0565R), I noticed that the absolute maximum voltage for Vcc is 20v. However, the zener diode across the Vcc pin to GND is a 1N4748A (22v).
Now, whether that zener is used to constantly regulate the voltage, or whether its's used to protect the Vcc voltage from rising too high,... -
Re: Folder Is empty
When you copied the Data folder from the HP to the Toshiba disk, did the files show up then, before you put the disk back into the laptop?
I have had problems in the past when copying a folder with thousands of small files. I ended up having to copy them in batches, a few hundred at a time.Leave a comment:
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Re: LED light flashing trying to fix LED driver board
The readings you get on the diode check setting of your meter doesn't make sense to me. If the diode reads 0.5v when it is removed, then you should get that same reading (or perhaps slightly less) when it's in circuit. Reading 1.3v across the same 2 points on the PCB when the diode is in and out of circuit cannot be right, as you say it reads 0.5v out of circuit.
Are you sure that you are keeping the polarity of the probes the same way round when taking all measurements (common [black] lead to banded end of diode)?...Last edited by Radio Fox; 09-16-2021, 07:33 AM.Leave a comment:
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Re: September equipment offer (u.k.)
If you click on the link in your first post & scroll down, it's shown in the associated products. Order code SD02162.
[url]https://cpc.farnell.com/duratool/d00672-spares/spares-kit-for-d00672/dp/SD02162?MER=sy-me-pd-mi-acce[/url]Re: September equipment offer (u.k.).../duratool/d006...Leave a comment:
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Re: SMD Ceramic Componet Identification and Voltage question.
Capacitors can be used anywhere in a circuit. They are not only used for decoupling or smoothing (in which case one side would normally be grounded), but for timing, coupling etc.
Take a look at a random circuit diagram & you will find many capacitors not connected to ground.
Even polarised capacitors don't need one end connected to ground. As long as the +ve end is connected to a voltage higher than that on the -ve end, then it will operate correctly.Leave a comment:
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Re: September equipment offer (u.k.)
Pretty fast delivery too. Arrived within a few days.
I ordered the spares kit with mine. Only cost £2.40, so thought it was worth getting at the same time to save on postage.
Havent used it yet, but I've got plenty of components awaiting removal.Leave a comment:
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Re: September equipment offer (u.k.)
Thanks for the link.
I've been looking around for a desoldering station, so this has come at just the right time. I see that the previous price was £84 (inc VAT). Still cheaper than Ebay & Amazon.
It gets good reviews too, so I'll be ordering one....Leave a comment:
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Re: "overvolting" transmitters for more power
I agree about the 50 Ohm load instead of the antenna, but 40v P-P is the correct voltage for 4W.
40v P-P = 20v peak = 14.14v RMS. 14.14²/50 = 4W....Last edited by Radio Fox; 09-03-2018, 12:24 PM.Leave a comment:
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Re: "overvolting" transmitters for more power
The maths involved in explaining how you can generate a peak to peak voltage greater than the supply voltage can be quite complicated if you want to go right back to basics.
When I built my transmitters I just accepted the fact. I didn't bother to delve too deeply into the maths behind it. Very basically it's like the back emf effect of an inductor. The rapid collapse of the magnetic field when the supply is removed produces a far greater voltage than the supply voltage. Slap in a suitable...Leave a comment:
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Re: "overvolting" transmitters for more power
In my Medium Wave pirate days, I used the same method to check the output of my transmitters.
Using a 50W dummy load, I would tap the voltage across it using my Tektronix 2445B scope & use P=V²/R, where V is the RMS voltage.
For 4W you should see around 40V P-P....Leave a comment:
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Re: Help for Newbie on measuring capacitance
...and an expensive Fluke meter reads them even higher....Leave a comment:
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Re: Help for Newbie on measuring capacitance
[I]All [/I]ESR meters give a reading in Ohms (Equivalent Series Resistance). Some also give a capacitance reading.Re: Help for Newbie on measuring capacitance
[I]All [/I]ESR meters give a reading in Ohms (Equivalent Series Resistance). Some also give a capacitance reading.Re: Help for Newbie on measuring capacitance
[I]All [/I]ESR meters give a reading in Ohms (Equivalent Series Resistance). Some also give a capacitance reading....Leave a comment:
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Re: Ebay seller
He's back.
[url]https://www.ebay.co.uk/sch/h.m.comp/m.html?_nkw=&_armrs=1&_ipg=&_from=[/url]Re: Ebay seller<br /> <br /> He's ...=&_from=[/url]Leave a comment:
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Re: Ebay seller
I have used h.m.comp many times in the past. Always super fast dispatching the parts. Along with semtech1, these were the 2 sellers I would order my Panasonic low ESR caps from.
Hope it's only a temporary glitch.Last edited by Radio Fox; 05-15-2018, 04:13 AM.Leave a comment:
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Re: My basic project - needs simplified - Digital TTL circuit maybe
We tend to forget about old fashioned disrete components these days. If we want to latch a bulb, then why not use a latching component (SCR) to do so!
It will only work for incandescent bulbs though, as it relies on the short circuit of the incandescent bulb to supply the contestants circuits, and thereafter (once a button has been pressed), to remove the gate supply to the other SCRs by halving the main voltage.
Nice, simple, modular design though....Leave a comment:
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Re: My basic project - needs simplified - Digital TTL circuit maybe
Couldn't stand those silly button symbols any longer.
Used DipTrace's component editor to design some better looking ones....Leave a comment:
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Re: My basic project - needs simplified - Digital TTL circuit maybe
My original idea to reset the circuit was to simply have a momentary push to break switch in the 5v supply (Quiz_buttons2.pdf), but that always seems like a bit of a bodge for some reason.
Putting the momentary switch between pin 11 (LE) & the anodes of D1-D6 (Quiz_buttons3.pdf) should release the latch, & take all the output pins high again, ready for the next "fastest finger"....Last edited by Radio Fox; 04-19-2018, 04:50 PM.Leave a comment:
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Re: My basic project - needs simplified - Digital TTL circuit maybe
Sounds like an ideal use of an octal latch like the 74LS373.
Input pins D0-D5 are held high by R1-R6 which is reflected on output pins 0-5 keeping LEDs D7-D12 off.
Suppose, for example, S4 is momentarily pressed. This will pull pin 8 (D3) low. The corresponding output pin 9 (O3) will also go low, lighting LED D10. At the same time Latch Enable (LE) pin 11 is pulled low through diode D4, latching the output pins to their current state. Any further button presses of S1-S6 will have no effect...Last edited by Radio Fox; 04-19-2018, 08:38 AM.Leave a comment:
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