- Ansmann Energy 16 PSU - 5 Updates
- Telefunken PAL Color sync problem (chassis 714) - 1 Update
- can I mount a stereo amplifier vertically - 1 Update
| Robert Roland <fake@ddress.no>: Jul 30 12:04PM +0200 >if you test individually: 0.6v one way only Unless the output is shorted. -- RoRo |
| Robert Roland <fake@ddress.no>: Jul 30 12:21PM +0200 >Would you think one of those component testers would be able to >identify the PWM reg, at least with a go/no-go result? I do not know which component tester you are talking about, but I would be very impressed if it could. -- RoRo |
| T i m <news@spaced.me.uk>: Jul 30 11:54AM +0100 On Sun, 30 Jul 2017 12:21:53 +0200, Robert Roland <fake@ddress.no> wrote: >>identify the PWM reg, at least with a go/no-go result? >I do not know which component tester you are talking about, but I >would be very impressed if it could. Well, whilst I think they are 'quite clever' I agree that it probably couldn't test the TOP223Y's. http://www.eetimes.com/author.asp?section_id=30&doc_id=1329331 I bought one (ironically) for measuring the ESR on SMPS caps (Topfield STB) but have used it (mostly successfully) for many other things since. ;-) On that ... do you think it might be worth testing (or even just replacing) the two main caps in case they are getting weak? I note they have an extra heat shrink 'skin', probably because they are pressed up against the tiny heatsink on the TOP223Y's? Cheers, T i m |
| Robert Roland <fake@ddress.no>: Jul 30 05:18PM +0200 >Well, whilst I think they are 'quite clever' I agree that it probably >couldn't test the TOP223Y's. >http://www.eetimes.com/author.asp?section_id=30&doc_id=1329331 I have one similar. Yes, they are impressively clever for the money. By they do not do ICs, only generic components. The only component that I found will fool it, was a germanium power transistor. The low Vbe, combined with the low DC gain probably threw it off. >On that ... do you think it might be worth testing (or even just >replacing) the two main caps in case they are getting weak? Hard to say. There are so many factors that affect the aging of caps. It does not take many seconds to take them out and test them, though. >I note >they have an extra heat shrink 'skin', probably because they are >pressed up against the tiny heatsink on the TOP223Y's? Yes, I noticed that, too. Hopefully, the TOP does not get all that hot. -- RoRo |
| T i m <news@spaced.me.uk>: Jul 30 05:30PM +0100 On Sun, 30 Jul 2017 17:18:11 +0200, Robert Roland <fake@ddress.no> wrote: >>couldn't test the TOP223Y's. >>http://www.eetimes.com/author.asp?section_id=30&doc_id=1329331 >I have one similar. Yes, they are impressively clever for the money. Aren't they. ;-) >By they do not do ICs, only generic components. My only thought was that whist the TOP is actually a 'clever' 3 pin device, there may be some basic logic that it could respond to that might make the tester think it was a working FET or Triac or some such? eg. You might be able to use it as a go / no-go test, *if* it detected something positive (however misdirected) in comparison to a good one? >The only component >that I found will fool it, was a germanium power transistor. The low >Vbe, combined with the low DC gain probably threw it off. Ok ... and that's not even a 'clever' component at such. eh. ;-) >>replacing) the two main caps in case they are getting weak? >Hard to say. There are so many factors that affect the aging of caps. >It does not take many seconds to take them out and test them, though. True, as whatever 'glue' they used to hold stuff down seems to have gone off a bit in any case. Maybe I'll replace the diodes first and if the unit then works, treat it to a fair of quality (low ESR?) caps at that point. >>pressed up against the tiny heatsink on the TOP223Y's? >Yes, I noticed that, too. Hopefully, the TOP does not get all that >hot. I doubt it would (for that heatsink) as it's got next to no radiative qualities (being partially masked by the cap) and only a small thermal mass. It might just be there to rest the cap on. ;-) Cheers, T i m |
| Jeroni Paul <JERONI.PAUL@terra.es>: Jul 30 06:31AM -0700 Last week I was playing my favourite vintage games in my vintage television when the picture began to slightly shake horizontally with a tendency to shift to the left and back to its correct position quickly. I shut down the set, take the cover off and try tapping some boards, that did not change anything. It got progressively worse, shifting more and more to the left, until it stabilized to its new position: https://imgur.com/a/nNu7b Now the picture is stable but misplaced. Depending on the picture content the color is decoded or not and darker horizontal bands appear when bright objects are displayed in the hidden part of the picture. Also when tuning the signal from my DTV decoder the horizontal shift is the same but the vertical hold is very weak, it requires precise fine tuning and even so the picture rolls randomly. This is a 26" Telefunken PAL Color from around 1980 of unknown model/chassis as the identifier label fell off many years ago however the relevant video/sync circuits are identical to chassis 714: http://www.eserviceinfo.com/downloadsm/62140/Telefunken_Chassis%20714.html It uses a TBA950 IC horizontal oscillator and phase sync, apparently the most likely culprit. I also have my scope in need of repair, so for now only DVM and ESR meter. I have checked U3 12V supply, all capacitors and resistors in the board with special attention to C531 and R531 composite sync pass through and the video buffer in the CHROMA IA board T201, R200, R201, R202 and R203. Given the picture brightness/color did not change I believe the composite video output on pin 201/4 from CHROMA IA should be fine. That leaves the TBA950 itself or some associated component that escaped my checks. Capacitor C538 is tantalum, checks 15 ohm on ESR meter and 10K on resistance check, that could be effect of the IC. Any thought before I try to source a replacement TBA950? (I couldn't find any in my pile of junk old boards). |
| T i m <news@spaced.me.uk>: Jul 30 10:49AM +0100 On Sat, 29 Jul 2017 19:26:36 -0700 (PDT), Tim R <timothy42b@aol.com> wrote: >I run the headphone jack of the PC we use for internet into a Yamaha AV amplifier and a set of stereo speakers. It's not an audiophile system but it's much better than PC speakers. >It would be really convenient to stand the amp vertically to save desk space. But it has vents top and bottom, none on the front back or sides. >Can you run these vertically? or do they need the airflow from the bottom to stay cool enough? If you consider how it cools itself normally, it probably draws a small amount of air in though the bottom and passes it out the top, plus random air movement of air from the top of the board out though the top grille. So, depending on where the vents were (all along or just specific locations) you might find it could be made to cool better when on it's edge because you could get a greater 'chimney' affect. On my home server I blocked all the external holes in the case except the air intake under the front panel and the PSU exhaust. I then created air dams from polycarbonate sheet that ensured all the incoming air went over the 3 hard drives and another over the motherboard that ensured the air then went over the RAM and LSI heatsinks, before being drawn out an over the PSU by the only fan in there (in the PSU). By sealing the case like that, ensured the air had to move *though* the case, and not just round and round inside it and because of it's height and general openness to airflow, convection would possibly keep it cool even if the fan failed (in fact now the PSU only contains a 120mm slow speed fan as the PSU is an external 'brick'). So, say your amp had vents all the way along the top and the bottom but a main board that covered most of the area of the inside of the case. If you blocked off the middle section of the top and bottom of the case and stood it on it's edge, convection would then cause air to be sucked in at the (new) bottom of the case (on both sides), up inside (behind the blocked off bits) and back out of the top? The remaining open grill at each end only needs to roughly equal the cross sectional area of space that is available inside the case. In fact that's exactly what I have here with a TP-Link 16 port Gb switch where there are only vent holes at the two ends and back and nothing anywhere else (and no fan etc). I use it on it's end and just added some extra feet to (what is now) the bottom to lift the end off the work surface. It's also sitting beside a PC to I also added bigger (stick-on rubber) feet to the bottom (now the side) so that it ensures an airgap between the switch and the PC so that heat can radiate out of the switch case and then air convect up the gap). With some cardboard and tape you can experiment with your amp and see if it feels hotter in use. ;-) Cheers, T i m |
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