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Search: Posts Made By: redwire
Forum: Equipment Usage, Soldering, Techniques, and Reviews Today, 03:37 PM
Replies: 138
Views: 18,247
Posted By redwire
Re: New tool to find short capacitors on motherboards : shorty with display

A one or two transistor constant-current source is not difficult, and possible to voltage-limit it. On laptops, GPU etc. I could see a need to keep it under 2V max.
Forum: General Capacitor Questions & Issues Today, 03:31 PM
Replies: 7
Views: 123
Posted By redwire
Re: 3300F 450V caps...

In the repair shop one tech would charge caps to 400VDC in the Heathkit and toss them at you yelling "catch!". I let them fall on the ground but a few people got nailed.
Forum: General Electronics Technical Discussion Today, 03:29 PM
Replies: 30
Views: 240
Posted By redwire
Re: flourescent ballast resistance

I know two-wire tubes are cold-cathode. If you have a HV AC source, like a car ignition coil+555, you can put the HV wire anywhere near the tube and it will ionize and light. BBQ lighter not sure....
Forum: General Electronics Technical Discussion Yesterday, 01:32 PM
Replies: 30
Views: 240
Posted By redwire
Re: flourescent ballast resistance

Pic shows two wires to the tube and the Osram datasheet (https://www.osram.com/appsj/pdc/pdf.do?cid=GPS01_1027844&vid=PP_EUROPE_Europe_eCat&lid=EN&mpid=ZMP_58994) showed two and said DULUX S is CFL....
Forum: General Capacitor Questions & Issues Yesterday, 12:19 PM
Replies: 7
Views: 123
Posted By redwire
Re: 3300F 450V caps...

You can do the math but the energy to lift up a person a foot off the ground, is stored in one cap. How far a commie would launch... they're full of so much hot air lol.

I don't short...
Forum: General Electronics Technical Discussion Yesterday, 11:15 AM
Replies: 30
Views: 240
Posted By redwire
Re: flourescent ballast resistance

Oh it's cold cathode? Then it's just a matter of the starter/ballast making a kV pulse. Sometimes holding the tube or having it next to grounded sheet metal helps it ionize at lower voltages.
There...
Forum: General Electronics Technical Discussion 06-28-2022, 03:28 PM
Replies: 30
Views: 240
Posted By redwire
Re: flourescent ballast resistance

That seems reasonable. You can check if there is a ground fault, winding shorted to case.
If the overall startup current is too low I think the starter will just sit there trying to get the...
Forum: General Electronics Technical Discussion 06-28-2022, 02:10 PM
Replies: 30
Views: 240
Posted By redwire
Re: flourescent ballast resistance

I would measure its inductance. F14T5 is 14W 0.265A lamp current, need around 900ohms impedance, so 148R from the coil and maybe ~2.5H is needed. Using 240VAC and 40V tube drop for rough math.
Does...
Forum: Troubleshooting Game Consoles & Other Weird Devices 06-28-2022, 10:46 AM
Replies: 17
Views: 260
Posted By redwire
Re: Graco ST MAX II 495 PC PRO , paint spray machine help

I understand the conformal coating can make the repair extra hell. I use needle probes to poke through for readings, and hot air gun to heat/soften the coating and scrape it off.
TBH the board is a...
Forum: General Electronics Technical Discussion 06-28-2022, 10:42 AM
Replies: 18
Views: 231
Posted By redwire
Re: Reading input and output of bridge rectifier on the same scope?

OP it's always good to have a fuse/1A circuit breaker because transformers can put out much more current into a short circuit.
Check the scope's internal ground did not melt open, I have seen that....
Forum: Equipment Usage, Soldering, Techniques, and Reviews 06-27-2022, 11:11 PM
Replies: 10
Views: 343
Posted By redwire
Re: Short finder

All that is missing is a PCB layout? It's not that complicated, it's just people wanting changes and complaining etc. that takes away all the fun....
Forum: General Electronics Technical Discussion 06-27-2022, 05:56 PM
Replies: 4
Views: 124
Posted By redwire
Re: Microwave advise please

Last to check is for open filament wiring at the connector/feed-through capacitors or for a bad connection there, or inside the can at the EMI chokes. Magnetron filament is low voltage, high current...
Forum: General Electronics Technical Discussion 06-27-2022, 04:06 AM
Replies: 52
Views: 2,697
Posted By redwire
Re: Fixing a multimeter based on VC9805 schematic

Display shows 1___ with those readings?
Pin 40 COM voltage is too low, it needs to be at least 1V above V-. On the schematic it would be QC4,QC3 to check- that would short COM below 1V. On your...
Forum: General Electronics Technical Discussion 06-26-2022, 11:20 AM
Replies: 18
Views: 231
Posted By redwire
Re: Reading input and output of bridge rectifier on the same scope?

Fixed: just as well oscilloscopes are sold in packs of 10 on aliexpress! :D
Forum: Equipment Usage, Soldering, Techniques, and Reviews 06-26-2022, 11:17 AM
Replies: 9
Views: 189
Posted By redwire
Re: Buy a Agilent U1242A or Fluke 179 DMM?

I'm repairing three old American-made multimeters, but I might have maxxed out at having 10 lol I've got no Flukes, just HP, Beckman, Wavetek.
I hate Taiwan-built multimeters, either they blow up...
Forum: General Electronics Technical Discussion 06-25-2022, 02:11 PM
Replies: 11
Views: 188
Posted By redwire
Re: Conversion of Anolog Voltmeter into Ammeter

"the meter still needs to be touched to work".
Find the bad connection, then worry about the design issues.
Forum: General Electronics Technical Discussion 06-25-2022, 10:29 AM
Replies: 11
Views: 188
Posted By redwire
Re: Conversion of Anolog Voltmeter into Ammeter

Your test setup looks good, I think there is a poor connection or maybe a switch is inside the meter so you must press it down to take a reading.
Usually panel meter specs are two things - the coil...
Forum: General Electronics Technical Discussion 06-24-2022, 09:54 PM
Replies: 52
Views: 2,697
Posted By redwire
Re: Fixing a multimeter based on VC9805 schematic

Post #28 I said to use a multimeter and measure some voltages "On DCV 20V range, measure the A/D voltages: IN HI, IN LO, REF HI+, REF LO-, COM wrt V-"
That is 5 readings to take.
Forum: Troubleshooting Game Consoles & Other Weird Devices 06-24-2022, 09:51 PM
Replies: 7
Views: 142
Posted By redwire
Re: Turbo Start QPET 16V/25A racing charger repair

It looks like a typical battery charger using phase control. The SCR's gate is driven by the H11 opto-couplers U4, U5. There's a current-transformer so it must do CV/CC control.
The only scenario...
Forum: General Electronics Technical Discussion 06-24-2022, 12:41 PM
Replies: 18
Views: 813
Posted By redwire
Re: Using car key fob as generic remote control

Check the RXB6 pinout, it has an enable pin 6 which floats high to enable data, not power save.
Some of those 433MHz RX modules have extremely weak data output 10uA (!) so a low value pullup or LED...
Forum: Troubleshooting Game Consoles & Other Weird Devices 06-24-2022, 12:26 PM
Replies: 17
Views: 260
Posted By redwire
Re: Graco ST MAX II 495 PC PRO , paint spray machine help

D16 is usually a SOT-23 diode like BAV99, BAS16, MMBD4148 etc. I think BAT54 (https://www.vishay.com/docs/85508/bat54.pdf) at 30V is too low. Around 10R looks reasonable for the resistor. C20 must be...
Forum: Troubleshooting Game Consoles & Other Weird Devices 06-23-2022, 07:17 PM
Replies: 17
Views: 260
Posted By redwire
Re: Graco ST MAX II 495 PC PRO , paint spray machine help

C20 looking preggo, D16 pin not soldered, was a gorilla inside trying to fix this?
Forum: Equipment Usage, Soldering, Techniques, and Reviews 06-18-2022, 10:39 PM
Replies: 10
Views: 343
Posted By redwire
Re: Short finder

I think you'd need the compliance voltage-limited to say 0.2V to not damage anything. That pretty much rules out the LM317, have to use an op-amp and power transistor.
I also do well with a good...
Forum: General Electronics Technical Discussion 06-18-2022, 10:34 PM
Replies: 4
Views: 166
Posted By redwire
Re: SMD marking 2290?

Looking at the board, my guess is an RF Amplifier MMIC or LNA IC.
Forum: General Electronics Technical Discussion 06-17-2022, 04:51 PM
Replies: 52
Views: 2,697
Posted By redwire
Re: Fixing a multimeter based on VC9805 schematic

Ok, that transistor matches the schematic for Tp2, controlling battery power to the multimeter, for the auto-power off.
If it was shorted, the multimeter would stay powered on, it would not...
Showing results 1 to 25 of 500

 
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