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| "Mr Sandman" <fzczc@ntlworrld.com>: Jul 23 08:18AM +0100 Hi all, I have an aircon unit that failed. Fault code 'PU' says the capacitor charging circuit failed, this is confirmed by checking the voltage at the three large electrolytic caps which show 43vdc, but oddly 85v ac. The expected voltage at the capacitors should be 180-380vac. I am a low level electronics experience chap, so need some advice on how these caps would typically be charged. They are used, as i understand it, to smooth the supply to the variable speed fan and compressor in the aircon unit. Looking at the other test points on main pcb, everything else checks out ok. Here is a link to the (large) manual for the aircon unit if any one fancies helping me out. http://www.manualslib.com/download/896742/Sinclair-Ash-18aie.html Id apreciate any help/guidance, Many thanks, Steve |
| Rheilly Phoull <rheilly@bigslong.com>: Jul 23 03:56PM +0800 On 23/07/2016 3:18 PM, Mr Sandman wrote: > Id apreciate any help/guidance, > Many thanks, > Steve You have worked through the logic of the trouble shooting guide for the charge failure ?? |
| Phil Allison <pallison49@gmail.com>: Jul 23 02:11AM -0700 Mr Sandman wrote: > charging circuit failed, this is confirmed by checking the voltage at the > three large electrolytic caps which show 43vdc, but oddly 85v ac. The > expected voltage at the capacitors should be 180-380vac. ** Gobbledgook. Large electros acquire *DC voltage* after being charged. What sort of multimeter / voltmeter are you using ?? An old moving coil one by any chance - many of the latter read double voltage on the AC ranges compared to the DC ranges if mistakenly used for DC. Reverse the probes and the reading drops to zero. .... Phil |
| "Mr Sandman" <fzczc@ntlworrld.com>: Jul 23 03:18PM +0100 "Rheilly Phoull" wrote in message news:d7GdnaRHmZ7dvg7KnZ2dnUU7-L3NnZ2d@westnet.com.au... On 23/07/2016 3:18 PM, Mr Sandman wrote: > Id apreciate any help/guidance, > Many thanks, > Steve You have worked through the logic of the trouble shooting guide for the charge failure ?? yes i have, i went through the tests for main board, the only test that was wrong was test three, giving readings i mentioned. There is no further troubleshooting that would identify the component that is faulty as i could see in the manual. cheers steve |
| "Mr Sandman" <fzczc@ntlworrld.com>: Jul 23 03:27PM +0100 "Phil Allison" wrote in message news:f3fd34de-e385-4ca6-bb90-aedc4018f777@googlegroups.com... Mr Sandman wrote: > charging circuit failed, this is confirmed by checking the voltage at the > three large electrolytic caps which show 43vdc, but oddly 85v ac. The > expected voltage at the capacitors should be 180-380vac. ** Gobbledgook. Large electros acquire *DC voltage* after being charged. What sort of multimeter / voltmeter are you using ?? An old moving coil one by any chance - many of the latter read double voltage on the AC ranges compared to the DC ranges if mistakenly used for DC. Reverse the probes and the reading drops to zero. --------- I am using a digital multimeter, a fairly decent one. Probing the caps directly i get the voltages i mentioned. is this showing ripple indication a bad capacitor rather than a bad charging component? the caps show no signs of leakage or expansion externally. thanks for the help, sorry im a newbie, and dyslexic so may sound muddled. cheers steve |
| "Gareth Magennis" <soundserviceleeds@outlook.com>: Jul 22 07:19PM +0100 "N_Cook" wrote in message news:nmsslu$fp3$1@dont-email.me... > Thanks for the schematic links, > Gareth. I wonder if it was a multi-layer cap in there with metal migration growth leading to short. Any other similar caps on there? Not my photo, but this is a new PCB: http://i852.photobucket.com/albums/ab83/audiosteve1/IMG_8676.jpg My blown cap is the one in the middle of the bottom of the PCB, below the 3 parallel sense resistors and between FET TR200 and Tx T200. Gareth. |
| "Gareth Magennis" <soundserviceleeds@outlook.com>: Jul 22 07:36PM +0100 "Gareth Magennis" wrote in message news:0ttkz.867178$rI.825966@fx37.am4... "N_Cook" wrote in message news:nmsslu$fp3$1@dont-email.me... > Thanks for the schematic links, > Gareth. I wonder if it was a multi-layer cap in there with metal migration growth leading to short. Any other similar caps on there? Not my photo, but this is a new PCB: http://i852.photobucket.com/albums/ab83/audiosteve1/IMG_8676.jpg My blown cap is the one in the middle of the bottom of the PCB, below the 3 parallel sense resistors and between FET TR200 and Tx T200. Gareth. This small SMD cap is carrying rectified 240v mains voltage. Is that wise? Gareth. |
| N_Cook <diverse@tcp.co.uk>: Jul 23 10:48AM +0100 On 22/07/2016 19:19, Gareth Magennis wrote: > Gareth. I suppose a 400V MLCC can suffer from metal migration as the numerous 50V notorious MLCC failures. I've not looked for any manufacturers of 400V rated devils, I assume they exist, should anyone be foolhardy to use them |
| Phil Allison <pallison49@gmail.com>: Jul 22 08:38PM -0700 JC wrote: > I'm not really sure how much use this meter will be anyway without a > calibration tape. Using the output signal and recording on a machine of > unknown quality then replaying the tape is just compounding errors. ** W&F test tapes simply have a pure tone recorded at 3 or 3.15 kHz. In the real world, people normally record and play back on the SAME machine - so it makes sense to test a recorder that way using a sine wave generator as the 3kHz source. There will be a higher reading on the W&F meter than given in the maker's specs when frequency deviations add in the same direction during playback. If the machine allows simultaneous record and play, that makes the process all much easier. FYI: I regularly do repairs on Roland tape echoes ( models 201,301 & 555 ) which all have a pretty high quality transport with ball race tape guides and a direct drive capstan motor with large pinch roller. Testing is normally done with a square wave input at 500Hz, a single playback head selected and the output monitored on a scope. If the generator is linked to the scope's external sync input, any serious W&F is pretty obvious on the screen. Using a square wave quickly reveals if the high frequency response is good and consistent for all playback heads, so checking the head alignment. Servicing these machines involves a lot of cleaning and polishing of the tape path and heads plus resurfacing the pinch roller when it has become hard and glazed. The tape's back tension is a critical adjustment as it affects both amplitude and W&F in the playback. Sometimes the main ball race in the capstan motor has to be replaced - when there is severe W&F or a steady tape speed cannot be maintained. Lotsa fun. ..... Phil |
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