- Capacitor Venting - 2 Updates
- HP DV9000 no video, part 2. [Resolved] - 1 Update
- EVOX 142 Phone - 1 Update
| John Heath <heathjohn2@gmail.com>: Jan 24 02:29PM -0800 On Sunday, January 24, 2016 at 10:46:03 AM UTC-5, John-Del wrote: > > Clearly major stability issues here. :( > At the risk of raising the ire of some contributors, I've found over my 45 plus years in the trenches that electrolytic capacitors can pass an in circuit ESR test and still be bad. It is an extraordinarily low percentage to be sure (although in Mitsu DM boards it's typical), but it's still a probability. > If I had that supply on the bench, I'd pull every cap and test for ESR, value, leakage, and dielectric absorption. Good thing this is a hobby project and not a repair with the customer breathing down your neck. Your hot 20 ohms resister goes through a diode then the collector of the main switching transistor. That transistor has a emitter resister that is of interest. Can not make out its part number or value from the schematic. I believe it is responsible for over current feed back to the controller IC for auto shot down protection. I will venture a guess it is in the 1 to 5 ohms range. Knowing it is okay would be a plus. It is tricky to find a ground with the whole controller IC and main switch transistor connected to the bridge rectifiers directly from the AC plug. One false move and there will be more than a hot 20 ohms resister to worry about. However the secondary side of the switching power supply is nice and isolated for easy measurements. I see at least 6 or 7 DC outputs there ranging from 5 to 60 volts. None of these voltages will be correct however by comparing then a general idea of what percentage of their target. If +60 volts is measuring +20 volts then all the rest of the DC outputs should be 33 percent of their target output voltages. By going through the other 6 or so DC outputs you can see if they are reasonable or possible have a problem. I do not think this will pan out but at least you can say you made the measurements. Another last minute desperate grabbing at a straw , try unplugging the 14 K Volt cup off the CRT just in case it is gassy loading down the power supply. Unlikely as you would have seem in glowing but hey you never know. |
| legg <legg@nospam.magma.ca>: Jan 24 11:00PM -0500 On Fri, 22 Jan 2016 15:45:32 -0800 (PST), John Heath >> think thrice before disturbing anything (and there's quite a bit on this >> board that's been disturbed before due to previous issues.) >Interesting problem. Many great suggestions have been put on the table from different members so there is not much to add. The resister that is running too hot is telling us something. Why is that resister not a happy camper? What is it connected to. There is a hiss or possibly plasma arcing and a resister that is not happy. looking at a diagram to see what the unhappy resistor does in the power supply could provide a clue. It will run hot whenever operation is abnormal. Just doing its job. RL |
| "David Farber" <farberbear.unspam@aol.com>: Jan 24 01:57PM -0800 Genesys wrote: > controller. In other cases, they just weren't in the condition listed > (typically listed as new, when "used", "seller refurbished", or in > one case "as-is/for parts or repair" were more appropriate). I didn't realize that motherboard sellers took such liberties were their product descriptions. I suppose they have product to move and do what's necessary. It is also *very* difficult to get any support from eBay or PayPal when trying or to prove an item isn't "as described." I won my PayPal dispute because I saved the tracking numbers for all of the returned boards and argued that the seller didn't have any plans for sending me another replacement. Thanks for your reply. -- David Farber Los Osos, CA |
| Matt-NJ <mm@taco.com>: Jan 24 10:35AM -0800 My daughter's apartment building uses an EVOX 142 series 2-wire intercom system. She would like to have in her apartment an old style "retro" bell system phone. (A few others in the building apparently have old looking phones connected.) The system apparently is designed to use an EVOX 8877 type phone (2-wire connection) for use in the apartments - definitely not Ma Bell! Any ideas on what can be done to use a standard, old fashion phone with this? Matt - mm@taco.com |
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