Re: zener tester
I built one years ago using a small surplus 60VAC transformer and a 10mA constant current source. Was quite useful to test zener diodes or to use as a simple 10mA current source. I built it to handle a 80V zener that we used that would fail every so often, but it was also useful to test high voltage rectifier diodes that had a 20V or so forward voltage drop. Reverse voltage testing on those was with a 10kV insulation tester, which would show any gross faults, but which was not much use as the equipment in question ran at 30kV on the anode. At least the 10kV allowed...
SeanB
Member
Last Activity: 07-18-2022, 02:35 AM
Joined: 06-14-2013
Location: KZN
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Re: Is instant glue safe for use in electronics?
I use a 2 part epoxy to hold heatsinks to chips. I prefer Pratley quickset steel, but you can use Araldite quickset white epoxy or pretty much any other 2 part epoxy as well. Clean both surfaces, then sand the heatsink and chip top lightly with 220 grit waterpaper and wipe both sides down afterwards with solvent ( acetone, IPA or even methylated spirits, then mix a little eopxy and apply a thin layer to one surface, then clamp the 2 together until cured. I tend to just mix a match head sized bead of each tube on the top of the chip...Leave a comment:
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Re: identify a capacitor?
1uF, 450V rating. Replace with a 630V polyester capacitor with the same pin spacing.Leave a comment:
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Re: bad power
Had the minisub across the road do a dump one night at around 9, loud hum then bang and instant grill, fired by burning GRP housing. Called metro and reported it, and the fire brigade came and put out the fire and cut the jungle so the metro could get to it. They closed the road and brought in a crane during the night to lift the old cooked one off the base and replace it with a spare 100kVA unit. I still have the inside lamp, cooked black from soot, but still working.Leave a comment:
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Re: about capacitance of smd chips
More than me, I made about zero, nada, zilch..... I am busy watching the scammer videos though, have had a few calls this month from a local call centre, really want to find out the centre name and location so that I can complain to other companies that use them.
Senzo from "Microsoft Support" I want you out of a job!Leave a comment:
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Re: Did I do anything wrong?
Tried reflowing those diodes on the secondary side. Some look like they are suspect, which would cause a dropped supply rail. Also on the control board some of the through hole parts at the bottom by the connector look dry jointed.Leave a comment:
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Re: big shadow on LCD screen
It could have been in a room where dirct sunlight hit that part of the screen during the day, which can do that with time. Best bet is keep it, and look out for a broken one of the same model to use as a screen donor. A totally non working one with a dead power supply would probably be best and should be cheap.Leave a comment:
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Re: NTC Temperature probe/sensor
NTC thermistors typically have a resistance of 10k or so at room temperature. They are not polarity sensitive, and if you have ones that are little copper blocks with 2 black leads coming out thet are pretty common spare parts. You are right in the temperature and resistance reading.Leave a comment:
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Re: Anyone tried improving the reliability of Cruddy Samsung Plasmas?
All that would improve reliability, but you know the bean counters did the original to cut costs anyway. If the original is a cheap or free one then go for it.Leave a comment:
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Re: about capacitance of smd chips
If you want to measure ceramic capacitors remember the same physical size capacitor which looks identical can be almost any value from 22uF to 100pF, they can pack a very wide range into a nominally identical looking part. You also have to know the supply voltage, and remember the sad truth that a ceramic capacitor value depends on the applied voltage, so a 22uF capacitor will be that at 0V ( really not ever going to be used at 0v ) and could be down to 100nF at 10V or any value.
You really do need a LCR meter to check the values,...Leave a comment:
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Re: Infrared emitting diodes can also act as infrared detectors
Works for visible light LED's as well ( except white as these have a phosphor coat so they are actually blue or UV leds so only respond to blue or UV light poorly) and you can see how the colour needs to be a shorter wavelength, else you get no output no matter how bright the illumination.Leave a comment:
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Re: The ghetto mod thread
All I did was to add 2 24V 60mm fans salvaged out of an old copier, along with another 2 larger fans (80mm) also salvaged out of the same copier. All run from the 12V rail, and run silent, plus as they are nice ball bearing fans with around 15 years operation on them with no noise they are likely to last a good few years more. The small fans move air along the bottom of the case, and the larger ones move air on the top and there is a 50mm one directed at the HDD bay. Currently sitting at 34C and has been that way for a long time ( highest recorded is 47C)...Leave a comment:
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Re: Using PC PSU to power router?
My router is supplied from the UPS battery, as the UPS i have actually isolates the battery from the incoming mains. Nice in that I save the 5W loss of the original wall wart ( which was written 5V 1A but which gave around 9V open circuit and ran pretty close to 100C internally when in use), and the router power supply anyway uses a SMPS inside to generate the 3V3 and 5v rails it uses anyhow, using a regular SMPS controller pair. this is rated for up to 24V, and runs cooler at 12v than it did with the original wall wart, and the capacitors are 25V...Leave a comment:
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Re: Capacitor cooling - Heatsinks for caps
If the capacitor is getting hot then it will be either something else warming it or it being run way beyond ratings or it is in backwards. Blowing air over it from a small fan will help with the first 2 more than any passive heatsink ever will.Leave a comment:
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Re: You want to do something nice and... (rant)
I think I will have to change my PSU soon, heard a pop today and smelt well toasted electrolytic, so will have to do a look and see what is dead. God thing I have a new in box Huntkey CP350 complete with Jianghou capacitors as a replacement. 51 days of uptime about to be turned off.Leave a comment:
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Re: Capacitor bank on vehicle battery
Hot water dissolves the baking soda better, and you use a stiff brush you no longer like to brush clean the whole top of the battery. Then rinse well with cold water and wipe dry with a clean paper towel.Battery posts clean to bright lead and same with terminals and leads. When attached use a can of battery terminal protector to coat them with a thin coat to keep them from corroding again. If you do not have this then wipe with a thin coat of vaseline over the outside of the terminal, though this will attract dust like magic. While you are there...Leave a comment:
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Re: Risky Ebay purchases
9.5/10 would be my guess for risk, either cooked chips or dead capacitors in nearly impossible to reach locations. Probably the fans got dust in them and the heatsink turned into a fluffball.Leave a comment:
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Re: Who Uses What OS in her/his Box?
It is an OS, ideally should be invisible to the user. Debian is on my computers and laptops, except for the EEpc which is running Puppy. The Win7 install on the laptop has been used twice, first time to make the install DVD's ( 2 copies) and the second time as I did not have a VM installed and needed to use GOTO meeting in a hurry. Now have a copy of XP installed in Virtualbox for those times that Wine will not do.Leave a comment:
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Re: Sonach drinking water heater not working
It will read that, as those are for the internal coil. Likely the relay is faulty, they often fail and are cheap and easy to get as spares. The relay will be either a 12V or a 24V unit, likely a 12V one and the mains transformer will be a 9VAC unit.
Check the heaters and the thermal fuse in the lead to the heater as those are also failure prone. If the heater you need to get a new one from the agents, but the relay and the thermal fuse are common parts.Leave a comment:
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Re: 2Wire psu BT 2700HGV router
I have been using for the last few cases a Pratley product called Wonder bond, a flexible 2 part epoxy. 2 part rsin and hardener available in white and black, which adheres well to almost any plastic after you degrease it with a solvent, and fills gaps well. Use a small spatula ( cut a piece of plastic card to mix and apply it with) to mix it and apply it. Small beads from the tubes and hold the case together with a clamp or some PVC tape while it cures for 24 hours and you have a like new join. Can be opened for rework but does well in filling gaps...Leave a comment:
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