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jaugustine@verizon.net: Jan 20 12:23PM -0500 Hi,   I have used a Fluke DMM with a Max/Min capture feature to measure the ringing voltage, not only red to green, but also red to ground (and green to ground).   To my surprise, the red wire to ground ringing voltage (some telephone equipment on line) was 93.2 VAC !! The green wire to ground ringing voltage was 36.4VAC. Note: Telephones are ringing.   Is this normal?   Thank You in advance, John

"pfjw@aol.com" <peterwieck33@gmail.com>: Jan 20 09:34AM -0800 https://www.sandman.com/knowledgebase/ring-voltage-tech-bulletin   The internet is your friend.   Peter Wieck Melrose Park, PA

Fox's Mercantile <jdangus@att.net>: Jan 20 12:15PM -0600 > The internet is your friend.   > Peter Wieck > Melrose Park, PA   Wonderful explanation.   -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com

jaugustine@verizon.net: Jan 21 07:25AM -0500 On Mon, 20 Jan 2020 09:34:17 -0800 (PST), "pfjw@aol.com"   >The internet is your friend.   >Peter Wieck >Melrose Park, PA   Hi, I saw that "sandman", and other places on the web, but it did NOT say anything about the ringing voltages from red to ground or green to ground.   That is why I made this post.   John

"pfjw@aol.com" <peterwieck33@gmail.com>: Jan 21 05:03AM -0800 On Tuesday, January 21, 2020 at 7:26:22 AM UTC-5, jaugu...@verizon.net   > Hi, I saw that "sandman", and other places on the web, but it did NOT say > anything about the ringing voltages from red to ground or green to ground.   > That is why I made this post.   a) Most POTS phones are two-wire these days. b) In most cases, the ground (separate) does not leave the demarc. c) Both the the "red" and the "green" are not at ground potential, *and* also not at the same potential to each other.   Therefore the 'ring voltage' will be different from each to ground than between the POTS conductors. Which was covered in the article linked, but not with these same words. Read carefully the section on measuring AC over DC, and that should help you understand.   Peter Wieck Melrose Park, PA

"jfeng@my-deja.com" <jfeng@my-deja.com>: Jan 21 06:35AM -0800 Try putting a 1K resistor in parallel with the meter. I predict that you will get something close to zero for both wires to your earth ground for both ac and dc measurements.

Cursitor Doom <curd@notformail.com>: Jan 19 01:26AM On Sat, 18 Jan 2020 14:12:19 -0800, John Robertson <spam@flippers.com> wrote:   >damage (moisture working in via the leads) is one primary cause of >failure. If the leads look good then chances are fairly good the device >will work.   No sign of corrosion at all on the leads.   >I use lots of 30 to 40+ year old components all the time for servicing >our classic arcade games. Most are perfectly good. Other than >electrolytic capacitors.   So do I. The question wasn't about NOS components, but components that have been in service for decades.     --   No deal? No problem! :-D

Cursitor Doom <curd@notformail.com>: Jan 19 01:23AM >> but I can't be certain. Are they known to fail?   >> thanks.   >The problem components from that era are lytics of course and glob-top transistors.   OK, I have to know.. "Glob-top"?? --   No deal? No problem! :-D

Trevor Wilson <trevor@rageaudio.com.au>: Jan 19 12:32PM +1100 On 19/01/2020 8:11 am, Cursitor Doom wrote: > and have typically 8 leads in the TO5-8 package. I'm unable to provide > a part number as these don't have one as such. Could be a 741 perhaps > but I can't be certain. Are they known to fail?   **No. Provided supply Voltages remain within the limits set by the manufacturer, metal can OP amps, transistors, etc are phenomenally reliable. For a long time, all MIL-spec semiconductors were metal can only. They might still be, but I doubt it. In the early days of plastic encapsulation, some problems were notable. Mostly with power devices. Things have improved markedly over the years, but you will likely never approach the reliability of a metal can device by using plastic.     -- Trevor Wilson www.rageaudio.com.au

amdx <nojunk@knology.net>: Jan 20 08:23PM -0600 On 1/19/2020 9:01 AM, amdx wrote:   >  and the adafruit pcb.   >> https://www.adafruit.com/product/1918?gclid=Cj0KCQiAmZDxBRDIARIsABnkbYTW4uwwxg5rvIcjY6z2MlUDvmN4QcL5PgAGeBvgHixbOqSlqbiXfFMaAn90EALw_wcB   No one has responded to my post. Is there anything fundamentally wrong other than the cost of filters is high and the sensor has it weakest response in the UVC wavelength. I don't mind the idea getting shot down, I'd learn something.   Mikek

John Robertson <spam@flippers.com>: Jan 20 07:29PM -0800 On 2020/01/20 6:23 p.m., amdx wrote: > response in the UVC wavelength. >  I don't mind the idea getting shot down, I'd learn something.   >                                        Mikek   Hi Mikek,   While your information may be valid, it is of little use to the OP to try to use a UV bulb to sterilize the room. It would be dangerous to his eyes and or skin, and it would be ineffective as the UV only would effect microbes that are on a surface the UV light would strike, plus the UV light has to be near (under 1 foot typically) to have a high enough concentration and it needs to light up the organisms for up to five minutes to be sure of killing them. Thus you have to hold the UV lamp for five minutes over every square inch of the room and you won't get any of the crevasses at all!   So totally impractical.   On the other hand if you made a separate posting under the topic of tools to measure UV bandwidth (or similar) you might get more bites!   John :-#)#

edu.gimeno.0@gmail.com: Jan 20 01:04PM -0800 Ok here some measurements on TLC driver chip: Vcc is ok: 3.3v BLANK is LOW Xerr is pulsing LO-HI BUT this is also happening at the working board, at the same rate if is flashing red to indicate "CAN bus not detected". So this is not indicating a failure Iref is 1.2v while working. Resistor measured to 3.3K, same as marking on chip Voltage measured at outputs (OUT0-OUT15) varies from 0v to 3.2, 3.5v, pulses, etc... Mainly same on working and failing board, but like half of the LED outputs in failing board have like 0.3-0.5v less than their corresponding in the working board.   I would check the LED but I have no way to tell what model it is and whether it is driven color by color (R1-R2 / G1-G2 / B1-B2), or with a common anode and 3 cathodes, or with serial data... I can't find any marking. So I can't tell what's the supplied anode voltage   Any other suggestion for further tests will be appreciated Thanks again

edu.gimeno.0@gmail.com: Jan 20 01:55PM -0800 I also measured SIN and SOUT on both IC's, both boards, giving same pattern (digital tiny flicker around 3.1v).   I checked the LEDS to determine their internal wiring. Found that 3 corner leads are common anode and 3 remaining are cathodes for R / G / B. When I apply low voltage with multimeter in Diode test mode, on good board I get full R / G / B light on each pin, but same test on bad board, I barely get any light (very dim) and sometimes it seems colors get mixed even when Im carefully with leads.   Could be a bad diode, but also the shortcircuit could be in the feeding driver IC (TLC)   At this point Im stuck between bad diodes or bad driver. I guess I should remove one LED and test it isolated, but Im afraid Im going to fry the board as I don't have any good and thin solder tip neither any special tool to desolder 6 pins at a time   Any other hint on how to diagnose?   Thanks!

Jeff Liebermann <jeffl@cruzio.com>: Jan 20 03:55PM -0800 On Mon, 20 Jan 2020 13:04:37 -0800 (PST), edu.gimeno.0@gmail.com wrote:   >pulses, etc... Mainly same on working and failing board, but like >half of the LED outputs in failing board have like 0.3-0.5v less than >their corresponding in the working board.   I think you just found the problem. The LED's on the working board are drawing current from the TLC5943 chips and therefore will show a lower voltage. The LED's on the failed board are not drawing current and will therefore show a higher voltage. What this tells me is that NONE of the LED's are connected to a common bus that goes to either 3.3V, 5.0V, or ground. This is why I suggested that you remove the black plastic insulator from the LED board. Find this common bus that goes to all the LED's and check if it is connected to one of these bus lines. Compare the bus DC voltage and waveforms with the working board to be sure. My guess(tm) is that this common bus goes nowhere. Maybe a blown trace, blown fuse, blown series protection resistor acting as a fuse, or failed connection.   >or with a common anode and 3 cathodes, or with serial data... >I can't find any marking. So I can't tell what's the supplied >anode voltage   You didn't mention that there were different color LED's. The hard way to do this is to trace out part of the PCB and produce a schematic. A better way is to assume that whatever has failed, has simultaneously affected all the LED's, irrespective of color. My guess(tm) is still that it's the common bus that connects all the LED's.   >Any other suggestion for further tests will be appreciated   Yes. I should have suggested this earlier. Remove the LED board and shine a bright flashlight from behind the PCB. Any broken or fused trace will be instantly visible, unless the broken trace happens to be under a component. This will also sometimes show bad solder connections. Try shining the light from both sides of the PC board.     -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

John-Del <ohger1s@gmail.com>: Jan 20 03:13PM -0800 On Monday, January 20, 2020 at 4:59:07 AM UTC-5, Cursitor Doom wrote: > myself on that one. The issue was *not* about the image > shrinking/growing during intensity adjustment!! > --   But it's not uncommon for a low High Voltage circuit to cause what we call "blooming" when the brightness is advanced. If your example was also doing that and you didn't initially notice it, you would say "hey, mine is doing that!!! Thanks!!".   Look, it's still likely a weak CRT (depleted cathode), but it could be many other things as well. I remember 1980s era NEC projection TVs used a DC supply for the filaments, and a lazy bypass electro dropped the filament to about 4 volts. The three tubes looked like they were shot, but it would be unusual for all three to go that weak at once. New cap, filament back to 6.3, TV looked like new.

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