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N_Cook <diverse@tcp.co.uk>: Apr 26 04:40PM +0100 So it is 2 wires per tube and 4 tubes, not 2 , it seems. Tried 2 CFL tubes on the monitored side and both light for 1 second. So I can leave one CFL in there and use the other supply to test each TV tube plugged-in in turn, surely 4 could not have failed at once, for 1 second.

N_Cook <diverse@tcp.co.uk>: Apr 27 12:41PM +0100 Tested each tube and number 4 will not work. Perhaps dodgey connection of one of the other pair, but now the original pair of 2 tubes at the top work for 1 second. Cleaning pcb around HV areas and resoldering HV and monitoring solder points , still 1 second only. What sort of compact load to represent the duff tube? a few neon bulbs in series perhaps. I don't understand the monitoring as connects to midway point of 2 tubes and no meggy resistors around, just 10s of K. One SMD diode marked A2 is used elsewhere in the LV circuitry, as is transtor marked 3FW. 2 perfectly normal pitch spacing SO23 Q marked 7.AJ or 7AJ are not repeated elsewhere but not obviously HV

N_Cook <diverse@tcp.co.uk>: Apr 27 12:43PM +0100 7AJ are 3 pin diodes, D on the overlay

N_Cook <diverse@tcp.co.uk>: Apr 27 02:50PM +0100 On 27/04/2016 12:43, N_Cook wrote: > 7AJ are 3 pin diodes, D on the overlay   not 7AJ but A7J I "replaced" the duff tube with 3 neons in series on the ps, and the display and backlighting and DVD play works fine. So looks like the unmonitored side needed a load also to bring the monitoring into valid envelope. I have to admit its not obvious which area of the screen is lacking light, needs wrapping up properly and a normal viewing position perhaps. Would there be 2 long tubes top and bottom and 2 short along the sides or 2 short each along top and bottom, I've not ventured fully inside. The neons run at 24 deg C over ambient, so perhaps 5 or 6 would be better if more than a temporary fudge. Going the other way would a CFL lamp make a TV/laptop backlight exerciser? 10 ohms between pins 1 and 2 and another 10R between pins 3 and 4 and then the tube across 1&4 or 2&3.

N_Cook <diverse@tcp.co.uk>: Apr 27 04:28PM +0100 Have a small collection of thin tube flourescents from fax/scanner/laptops of unknown states. I know at least one is green but I did not label as such, so made an exerciser for 2 wire tubes , from the CFL board. Tubes between pins 2 and 3. 2x 10R,.5w soon blew , 2x 0.33R,2W in positions 1 to 2 and 3 to 4 , probably too far the other way, but allowed to run each of them for a few seconds to check for colour and non-evenness or strobing.

bitrex <bitrex@de.lete.earthlink.net>: Apr 26 06:42PM -0400 I have a piece of equipment that has a ROM chip in it which I'd like to upgrade to a newer firmware revision.   I don't want to destroy the old EPROM by cutting the pins, but I'm finding it very hard to desolder the 28-pin chip from the board using an iron and solder sucker.   Is there a better way to do this?

jurb6006@gmail.com: Apr 26 04:28PM -0700 Chemwick. Not as good on two sided plated through holes but usually works well enough.   You mean a desoldering bulb ? Those aren't that good. For plated through, something like a Hakko 808 works well. On lead free, you have to turn the heat all the way up. Also, when you see it melt, do not push the vacuum button tight away or else you will have an air pocket in there and solder at the top where you cant get a good thermal connection to it.   In any case, if it is lead free the first thing to do is to add some 83/37 to the connection.

jurb6006@gmail.com: Apr 26 04:31PM -0700 Not tight away, right away.   And of course that is 63/37, not 83/37.   Half blind, can't type.

dansabrservices@yahoo.com: Apr 26 06:25PM -0700 > Not tight away, right away.   > And of course that is 63/37, not 83/37.   > Half blind, can't type.   Whle it is usually used to remove SMD components, Chip-Quik might be helpful here. Remove as much solder using solder-wik as you can, then apply the Chip-Quik. This with a little heat should allow for easy removal.   Dan

Jon Elson <elson@pico-systems.com>: Apr 26 10:39PM -0500 bitrex wrote:   > finding it very hard to desolder the 28-pin chip from the board using an > iron and solder sucker.   > Is there a better way to do this? I have a Pace machine with a vacuum pump in it, and a hollow soldering tip. It does an amazing job of desoldering parts even from multi-layer boards with heavy copper planes. Generally, after using it, the parts just fall free of the board. The trick is you heat the joint for about 6 seconds, then "swirl" the tip around the hole once, and then keep swirling while you hit the vacuum pedal. The vacuum pump can pump for a lot longer than the plunger-type solder sucker. Usually I take 1-2 full seconds of vacuum while swirling the tip, this gets ALL the solder out of the plated through hole.   When you do this, the swirling of the desoldering tip wiggles the end of the component lead, making sure all the solder in the hole is extracted.   This works about 10 X better than the desoldering suckers, or even the hollow-tip irons that have the vacuum plunger built into the iron.   Jon

jeanyves <jeanyves@nowhere.com>: Apr 27 08:53AM +0200 On 2016-04-26 22:42:12 +0000, bitrex said:   > finding it very hard to desolder the 28-pin chip from the board using > an iron and solder sucker.   > Is there a better way to do this?   desoldering stations are great, but expensive... I have one now but I had a soldier sucker before, and managed to desoldier such circuits with quite success. you must first re-soldier the circuit, with fresh leaded soldier then use the soldier sucker, one pin at a time and it will come off (except if it's a multi layer board there you really need a desoldering station)   practice on another board you can destroy if needed. good luck --   Jean-Yves.

N_Cook <diverse@tcp.co.uk>: Apr 27 07:54AM +0100 On 26/04/2016 23:42, bitrex wrote: > finding it very hard to desolder the 28-pin chip from the board using an > iron and solder sucker.   > Is there a better way to do this?   You have to practise the following on a scrap board , before going for it proper. Retouch solder on each pin, mask off surrounding areas with a "frustrum" made of PTFE slabs, tied together and tied to the pcb. Blast the chip with freezer spray and then blast solder side with hot air gun on full blast, ie as short as possible, while pulling the chip from the other side with bent large circlip pliers, holding the board in a vice while doing all this.

Danny DiAmico <dannydiamico@yahoo.com>: Apr 26 04:03PM On Tue, 26 Apr 2016 14:56:42 +0100, MJC wrote:   > The recipe I used (and the only one I've heard of) uses ammonia as a > source of nitrogen, not acid.   I could be remembering it wrong as it was a few decades ago. It was chem lab, so, there was everything available.   We may have used the nitric acid with the cotton balls ...

"pfjw@aol.com" <pfjw@aol.com>: Apr 26 09:59AM -0700 On Tuesday, April 26, 2016 at 12:03:54 PM UTC-4, Danny DiAmico wrote:   > I could be remembering it wrong as it was a few decades ago. > It was chem lab, so, there was everything available.   > We may have used the nitric acid with the cotton balls ...   Nitric acid, but glacial sulphuric acid as well to pull out the water formed as a byproduct. The making of nitrocellulose (gun cotton) is more dangerous than the using of it, for the most part.   Peter Wieck Melrose Park, PA

Jon Elson <jmelson@wustl.edu>: Apr 26 02:56PM -0500 Danny DiAmico wrote:       > The ground straps seem to have good contact, so, I think it's > the MMU or the CCU but I don't know yet what to do next. > http://u33i.imgup.net/groundstraebd1.gif Since the CCU is powered up and communicating with the buttons and indicators, it is likely OK. Since there was a big POP, and the CCU can't communicate with the MCU, which is where all the big power circuitry is, it seems REALLY likely something in the MCU popped. When you get it out, I think you are likely to find visible damage.   Jon

Danny DiAmico <dannydiamico@yahoo.com>: Apr 27 12:47AM On Tue, 26 Apr 2016 14:56:09 -0500, Jon Elson wrote:   > communicate with the MCU, which is where all the big power circuitry is, it > seems REALLY likely something in the MCU popped. When you get it out, I > think you are likely to find visible damage.   Thank you for that advice.   I'm kind of stuck like a deer in the headlights at this point because I have to diagnose if it's the CCU or the MCU (or the power rectifier).   I'm kind of at a loss for diagnostic procedures because the diagnostic test described in the manual didn't kick in.

Jon Elson <elson@pico-systems.com>: Apr 26 10:42PM -0500 Danny DiAmico wrote:   > I have to diagnose if it's the CCU or the MCU (or the power rectifier).   > I'm kind of at a loss for diagnostic procedures because the diagnostic > test described in the manual didn't kick in. Just pull the MCU and examine it closely. If you can't find anything burned, then it gets harder. But, if there was a loud POP, I think you WILL find visible damage. It is possible that there is a fuse on that board, and the failure of the fuse under hard short conditions made the noise. So, Ohm out any fuses you find.   Jon

johnanita1950@gmail.com: Apr 26 11:50AM -0700 On Wednesday, 5 August 2009 17:13:23 UTC-7, Bill Horne wrote:

ok1wire <johnanita1950@gmail.com>: Apr 26 11:57AM -0700 Thanks for the tip. Pulling the control arms solved the mystery. Sharp directions for installation gave no clue for removal.   I found it helpful to remove the stove first. That made it easier to support the microwave for removal.

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