- Capacitor Venting - 12 Updates
- Headphone socket on laptop? - 4 Updates
- what is the difference btn -48volts and 48volts power supply? - 1 Update
| Cursitor Doom <curd@notformail.com>: Jan 22 09:03PM On Fri, 22 Jan 2016 06:45:32 -0600, Mark Zacharias wrote: > increases, the actual DC output rails out, usually shorting a zener > diode which gives up it's life to save components downstream. > My .02 worth... Thanks for that. Worth more than 2c I'd say. In that case I'll check the duty cycle unloaded by scoping the B/E junction of the chopper transistor. That should be a good indicator of anything having gone low-res on the secondary side from what you say. I'm still curious as to why that power resistor is getting so hot. Even if the tranny is fine something's still amiss somewhere. |
| "Ralph Mowery" <rmowery28146@earthlink.net>: Jan 22 04:18PM -0500 "Cursitor Doom" <curd@notformail.com> wrote in message news:n7u5fn$9kp$1@dont-email.me... > what you say. I'm > still curious as to why that power resistor is getting so hot. Even if > the tranny is fine something's still amiss somewhere. Power resistors often get hot. Can you measure the voltage drop across it and knowing the resistance calculate the wattage it is using. |
| Cursitor Doom <curd@notformail.com>: Jan 22 09:38PM On Fri, 22 Jan 2016 16:18:21 -0500, Ralph Mowery wrote: >> somewhere. > Power resistors often get hot. Can you measure the voltage drop across > it and knowing the resistance calculate the wattage it is using. No visible markings on it at all (typical). In the photo I posted, this is the one near the top right hand corner. You got the two big bulk storage caps, then to the right of those the bridge rectifier, then to the right of that and down a bit is the resistor in question - brown coloured one lying between two black diodes. It reads 20 ohms, but could be in parallel with god knows what, so that's not much help I know. I'll lift one leg and remeasure if you think it'll do any good. |
| Cydrome Leader <presence@MUNGEpanix.com>: Jan 22 10:28PM > You're running a switcher at way out of spec input voltage. The magnetics > making awful noisy or hissing sounds is not unexpected under those > conditions as it fails to startup correctly. No load could also cause weird noises- that board looks really old. If that transformer is burned or arcing it's already trashed- more testing won't make the problem worse, but giving it with no load or with no load and at a weird input voltage won't help troubleshoot anything easier. |
| Cursitor Doom <curd@notformail.com>: Jan 22 10:31PM On Fri, 22 Jan 2016 22:28:23 +0000, Cydrome Leader wrote: > that transformer is burned or arcing it's already trashed- more testing > won't make the problem worse, but giving it with no load or with no load > and at a weird input voltage won't help troubleshoot anything easier. Yes, the world of vintage has its pros and cons. The plus side is everything is big enough to work with - handy if you are half-blind and clumsy like me. But the con is things get very fragile so you have to think thrice before disturbing anything (and there's quite a bit on this board that's been disturbed before due to previous issues.) |
| John Heath <heathjohn2@gmail.com>: Jan 22 03:45PM -0800 On Friday, January 22, 2016 at 5:34:38 PM UTC-5, Cursitor Doom wrote: > clumsy like me. But the con is things get very fragile so you have to > 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. |
| Cursitor Doom <curd@notformail.com>: Jan 23 12:03AM On Fri, 22 Jan 2016 15:45:32 -0800, John Heath wrote: > 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. Yes, a schematic would be extremely useful but I don't have the precise one; just a similar model of scope with a similar ps section. Some parts are correct and in the right place, others aren't. You have to work with what you've got. Hopefully tomorrow I'll discover a few more clues... |
| JC <Chipbee40_SpamNo@yahoo.com>: Jan 22 07:24PM -0500 On 1/22/2016 7:03 PM, Cursitor Doom wrote: > one; just a similar model of scope with a similar ps section. Some parts > are correct and in the right place, others aren't. You have to work with > what you've got. Hopefully tomorrow I'll discover a few more clues... For goodness sake, this is out of the PM3264 right? So what happens when you put it in the scope? I can't find your original posts on this but these are not very complicated supplies and pretty reliable. Main fail is the electrolytic caps, all of them will be useless, Philips blue caps suck, they were never low ESR in the first place and from your photo it looks like you haven't replaced any of them. The hissing is probably the 1.5Kv from the transformer. Its a good scope if you can get it working. Buy the manual. http://www.jetecnet.com/ |
| Cursitor Doom <curd@notformail.com>: Jan 23 12:58AM On Fri, 22 Jan 2016 19:24:31 -0500, JC wrote: > For goodness sake, this is out of the PM3264 right? So what happens when > you put it in the scope? I'm reluctant to do this until I'm sure the psu won't toast it. > is the electrolytic caps, all of them will be useless, Philips blue caps > suck, they were never low ESR in the first place and from your photo it > looks like you haven't replaced any of them. No, because I've tested all of them with one of these: http://www.peakelec.co.uk/acatalog/jz_esr70.html and they all check out totally fine. > The hissing is probably the > 1.5Kv from the transformer. Its a good scope if you can get it working. > Buy the manual. http://www.jetecnet.com/ Thankfully I've now managed to get a circuit for the psu section off the net. That will be a *major* help. I'll be happy to buy the complete manual if I can get the thing at least partly working. |
| "Mark Zacharias" <mark_zacharias@sbcglobal.net>: Jan 22 07:07PM -0600 "Cursitor Doom" <curd@notformail.com> wrote in message news:n7uj7f$9kp$5@dont-email.me... > Thankfully I've now managed to get a circuit for the psu section off the > net. That will be a *major* help. I'll be happy to buy the complete > manual if I can get the thing at least partly working. Do look for a short to (cold) ground on the secondary, and if you can isolate and open up that short (like by removing the shorted zener, if any) then bring it up briefly on a variac and 'scope the dc line(s) for noise. Remember to use an isolation transformer when servicing the primary circuit. Mark Z. |
| Cursitor Doom <curd@notformail.com>: Jan 23 01:18AM On Fri, 22 Jan 2016 19:07:54 -0600, Mark Zacharias wrote: > noise. Remember to use an isolation transformer when servicing the > primary circuit. > Mark Z. Thanks, Mark. I'll try that in the morning along with a few other things as it's getting very late here (1.20am) so I'm going to call it a day for now. |
| Cursitor Doom <curd@notformail.com>: Jan 23 04:13PM On Fri, 22 Jan 2016 16:18:21 -0500, Ralph Mowery wrote: >> somewhere. > Power resistors often get hot. Can you measure the voltage drop across > it and knowing the resistance calculate the wattage it is using. Sorry for the delay. I'm having to do odd bits towards this project in between other chores. OK, it IS a 20 ohm resistor and the voltage across it giving rise to this heating effect is 3.6V and given that this looks like about a 4W resistor, makes no sense at all to me. It shouldn't even be getting warm. The resistor in question is R1814 just to the right of the chopper transistor on the schematic: https://www.flickr.com/photos/128859641@N02/24535280896/in/dateposted- public/ That's all I know right now and I have to dash off again for a couple of hours.... cheers. |
| "Bob F" <bobnospam@gmail.com>: Jan 22 10:09AM -0800 Please learn to properly cross post, rather than multi posting. |
| Look165 <look165@numericable.fr>: Jan 22 09:15PM +0100 I suggest : Laptop off , put another socket inside the plug (a "normal" one). Since the plug is endless, the tip of the other will fall somewhere in the laptop. Then open and pick it up. Kenny a écrit : |
| jurb6006@gmail.com: Jan 22 04:26PM -0800 On Friday, January 22, 2016 at 3:15:26 PM UTC-5, Look165 wrote: > > whole plug would then become lodged in the socket! > > Any ideas anyone? > > Kenny Cargill I dunno, I have seen quite a few with closed backs. But that is a good idea if it is not. And with your method, if it works, it is VERY important to find the end and not have it rolling around in there. Hopefuly the construction of the thing will allow that. If it is closed back, if that can be accessed it might be possible to melt a hole in it and then use a paperclip to push the piece out. In fact I think the paperclip would be used to make the hole as well. I remember people breaking off an RCA plug in their TV and with the open back jacks would just push another plug in it, and it would work. However, once the thing gets moved it can travel and short something out if it didn't right away. Saw a $300 signal board turned into scrap over that. |
| "Kenny" <me@privacy.net>: Jan 23 06:37AM The m/b would have to be completely removed to even see what type of socket it is. Using a pin I was able to slightly move the tip inside the socket and I have sound again from laptop speakers, can't get a grip on it with tweezers to pull it out though. At least I now have sound but can't use headphones or mic. Don't think the idea of pushing another plug in would be advisable since I can't see the upper side of socket and even if it did work the broken bit would be trapped between m/b and casing. Kenny Kenny wrote in message news:7dcd0da0-02f9-4967-a0b7-c830d2e9199b@googlegroups.com... On Friday, January 22, 2016 at 3:15:26 PM UTC-5, Look165 wrote: > > whole plug would then become lodged in the socket! > > Any ideas anyone? > > Kenny Cargill I dunno, I have seen quite a few with closed backs. But that is a good idea if it is not. And with your method, if it works, it is VERY important to find the end and not have it rolling around in there. Hopefuly the construction of the thing will allow that. If it is closed back, if that can be accessed it might be possible to melt a hole in it and then use a paperclip to push the piece out. In fact I think the paperclip would be used to make the hole as well. I remember people breaking off an RCA plug in their TV and with the open back jacks would just push another plug in it, and it would work. However, once the thing gets moved it can travel and short something out if it didn't right away. Saw a $300 signal board turned into scrap over that. |
| Jeff Liebermann <jeffl@cruzio.com>: Jan 22 05:22PM -0800 On Thu, 21 Jan 2016 09:32:53 -0800 (PST), janetnkansah1@gmail.com wrote: >Thanks a lot Jeff you've actually given me a good understanding. >so I can build a normal 48 volts supply and ground the positive >terminal instead. Yes, that will work. However, when specifying a power supply, you also need to deal with over-current limiting, fold back power dissipation, transient response, stability with various loads, line ripple, power line isolation, and EMI/RFI emissions. Any or all of these might be important for running your unspecified device. -- 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 --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
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