- Technics SU-Z55 transformer - 11 Updates
- Alternator on DD-3-53 does not charge at idle - 1 Update
- How can I analyze an audio download to see WHERE the distortion is coming from? - 2 Updates
| frank <frank@invalid.net>: Dec 06 09:25PM Hi all, I have on the bench a Technics SU-Z55 with a faulty transformer. First of all, does anyone have a copy of the service manual? I've been able to only find the schematic. The transformer appears to have a fuse or a thermal fuse buried between the primary and the secondary windings. The primary itself is not interrupted, but the buried fuse is interrupted. I plan to disconnect all the connection to the secondaries and try to power the transformer through a light bulb, that should tell me if the transformer primary is shorted or something else happened. A regular fuse just after the power switch is still ok, so I really wonder what caused the transformer internal fuse to burn. Ideas? Should the transformer have the correct voltages, what would you do? Just bypass the open thermal fuse? Thanks Frank IZ8DWF |
| ohger1s@gmail.com: Dec 06 02:11PM -0800 On Tuesday, December 6, 2016 at 4:27:13 PM UTC-5, frank wrote: > Just bypass the open thermal fuse? > Thanks > Frank IZ8DWF It's a thermal fuse. I can tell you that of the several dozens or so of these fuses I've seen fail over the years, not one of them was because the XFR ran too hot, nor did they fail because of any kind of short or inherent XFR problem. They just go for no reason. As to whether or not to jump it, that's another issue. I have an Onkyo receiver that I use for my HT, and it's got a jumped out thermal. If you want to be safe, I guess you can epoxy a thermal fuse to the core or even stuff a small one between the windings and wire it in the primary: http://www.allelectronics.com/item/thsw-75/thermal-circuit-protector-75-c/1.html |
| Phil Allison <pallison49@gmail.com>: Dec 06 04:45PM -0800 frank wrote: > The transformer appears to have a fuse or a thermal fuse buried > between the primary and the secondary windings. The primary itself is > not interrupted, but the buried fuse is interrupted. ** AC supply transformers do not have regular fuses buried inside them. If they have a thermal fuse, then it is invariably wired in series with the primary and fitted in close contact with the winding. > what caused the transformer internal fuse to burn. > Ideas? Should the transformer have the correct voltages, what would you do? > Just bypass the open thermal fuse? ** Seems you have access to the terminals on this "fuse" - which may be a temperature sensor or the like. Do some more testing and see what you find, cos at the moment your story is full on contradictions. .... Phil |
| Phil Allison <pallison49@gmail.com>: Dec 06 05:49PM -0800 > It's a thermal fuse. I can tell you that of the several dozens or > so of these fuses I've seen fail over the years, not one of them was > because the XFR ran too hot, ** I wonder how you know that? A thermal fuse in the primary is specified to open BEFORE damage happens to the windings of the tranny. In case of a "double insulated" device like the Technics, it is the only user protection against electric shock hazard resulting from a damaged insulation between primary and secondary of the supply transformer. > nor did they fail because of any kind of short or inherent XFR problem. ** An internal short or overload on the secondary would blow the AC supply fuse. > They just go for no reason. ** There is always a reason. > As to whether or not to jump it, that's another issue. I have an Onkyo receiver that I use for my HT, and it's got a jumped out thermal. If you want to be safe, I guess you can epoxy a thermal fuse to the core or even stuff a small one between the windings and wire it in the primary: > http://www.allelectronics.com/item/thsw-75/thermal-circuit-protector-75-c/1.html ** The device in the link is a self resetting type with a rather low operating temp of 75C - most thermal fuses used for this job one time only and rated at 115C to 130C. .... Phil |
| ohger1s@gmail.com: Dec 07 04:26AM -0800 On Tuesday, December 6, 2016 at 8:49:28 PM UTC-5, Phil Allison wrote: > > so of these fuses I've seen fail over the years, not one of them was > > because the XFR ran too hot, > ** I wonder how you know that? Because bypassing them at the primary junction board allowed full and normal operation. Every single I ever did this to never had any issue whatsoever, nor did they show any signs of overheating visually. They all ran cool and at full power after bypassing. If the fuses were rated to open that close to the normal operating temp of the XFRs, then they were either badly made and failed over too little hours, or spec'd incorrectly IMO. As to whether other techs experienced situations where the AC XFR was indeed overheating by external loads or shorted turns causing the fuse to open, I certainly couldn't say, nor did I. I only know that none of the ones I encountered were nothing more than nuisance failures. Strangely, the transformers that I have seen overheat and burn in older 60s and 70s vintage electronics (both TV and audio) were *not* equipped with thermal fuses. They just sat there and puked tar. > ** The device in the link is a self resetting type with a rather low operating temp of 75C - most thermal fuses used for this job one time only and rated at 115C to 130C. > .... Phil Perhaps, and while other higher values can be selected, a XFR running at 115C would be hotter than I've ever seen one of these run at. I suppose one could try it and if it kept tripping, another value could be tried. |
| frank <frank@invalid.net>: Dec 07 02:09PM Update: Of course the thermal fuse was buried, but terminals are accessible, otherwise I couldn't tell it was open. It's unlikely that a secondary dead short would take out the thermal fuse before the main AC fuse, so I just bridged the thermal fuse and the amplifier works perfectly. Can someone suggest a failure mode where the thermal fuse would blow before the main AC fuse? This amplifier has a double insulation AC input, so no earth wire. Its chassis has a ground post anyway, so it could be connected to some external equipment that is earthed. Thanks Frank |
| dansabrservices@yahoo.com: Dec 07 06:57AM -0800 I would suspect that like other things (circuit breakers for example), over time with repeated heating and cooling, these either become more sensitive or don't respond at all to conditions. I have replace a few thermal fuses in transformers in the past as well. Replace it with another thermal fuse and move on. Thermal fuses are not expensive. From a liability standpoint, I always replace the fuse rather than just bypassing it. Dan |
| "G. Paul Ziemba" <unp@ziemba.us>: Dec 07 03:47PM >Can someone suggest a failure mode where the thermal fuse would blow before >the main AC fuse? I'm not familiar with thermal fuses used in transformers, but I have worked on a few toaster ovens and coffee makers that have thermal fuses. These fuses are typically attached to the hot plate or heating box. I believe, internally, they are made with a spring and a wax bead. When the wax melts, the spring moves and opens the circuit. Given enough time (not sure if it is operating time or merely age), these fuses trip on their own. I have replaced them with new thermal fuses with the same temperature threshold and the unit works fine for many years (until the fuse gets old again). -- G. Paul Ziemba FreeBSD unix: 7:46AM up 108 days, 11:25, 11 users, load averages: 0.48, 0.62, 0.66 |
| "pfjw@aol.com" <pfjw@aol.com>: Dec 07 08:17AM -0800 On Tuesday, December 6, 2016 at 8:49:28 PM UTC-5, Phil Allison wrote: > ** There is always a reason. Yes, there is _always_ a reason. But any device of this nature is a wearing part, if only over a very long time. Essentially, they get tired and simply fail - especially if run close to the margins. So the reason may be as simple as old age. This is not to suggest that simply replacing the fuse and call it done is the correct approach even though that may work for some while. Any blown fuse not for obvious and/or immediately apparent reasons requires additional diagnostics. Peter Wieck Melrose Park, PA |
| Baron <baron@linuxmaniac.net>: Dec 07 04:24PM G. Paul Ziemba prodded the keyboard with: > these fuses trip on their own. I have replaced them with new thermal > fuses with the same temperature threshold and the unit works fine > for many years (until the fuse gets old again). Some that I have seen are what looks like a blob of solder hung between two wires inside the plastic case. I once tried to repair one by using a soldering iron. It just dissolved into a blob on the iron tip. -- Best Regards: Baron. |
| Baron <baron@linuxmaniac.net>: Dec 07 04:28PM > reasons requires additional diagnostics. > Peter Wieck > Melrose Park, PA Based on my limited experience with these embedded thermal fuses, I would say that the failure mechanism would be like that of a dry solder joint. -- Best Regards: Baron. |
| "Michael A. Terrell" <mike.terrell@earthlink.net>: Dec 06 09:12PM -0500 >> The stupid #$%^&* pulled his gun on me and screamed that he was going >> to kill me, if I moved the car. > You needn't have worried... Deputy Fife only carries one round and he keeps that in his shirt pocket. This was before he shot himself in the foot, and Andy imposed that rule. -- Never piss off an Engineer! They don't get mad. They don't get even. They go for over unity! ;-) |
| Hazuki Nakamura <HazukiNakamura25@zeendo.com>: Dec 06 08:06PM How can I analyze an audio download to see WHERE the distortion is coming from? This is technical qustion in that I'm trying to understand why under one circumstance the sound is fine while on the other circumstance the sound is garbled, as if it's overdriven. So this is a technical debugging question, so saying the app fucked up isn't really a technical debug or to say use another app isn't really a solution to the problem. I can't debug or solve what I don't yet understand, so this is a technical debugging question. 1. On Android, I can listen to a Youtube video using FDroid's youtube lookalike app called "New Pipe" and the sound is fine. 2. I can also download that wbem movie (or just the m4a audio) from within NewPipe and play in VLC on Android. No matter what movie I download, when I play that downloaded movie or audio in VLC, the sound is "overdriven" in that I have to lower the volume just to hear the words more clearly. But I don't have to lower the volume when playing in NewPipe (or in Youtube itself). The volume is the same (as far as I can tell) in terms of decibels, but the sound is garbled. So this has something to do with frequency or distortion. My technical qusetion is how can I analyse the results to see WHERE the audio distortion in the downloaded audio track is coming from? |
| jurb6006@gmail.com: Dec 06 04:19PM -0800 You probably can't. Audiophiles are getting into getting these stand alone DACs for better quality. They pick up the data stream from the USB port and do the converting independently from the soundcard in the PC. Soundcards in PCs vary greatly in quality, and it seems to be a totally independent issue than the quality of the PC. (or MAC for that matter, which is also a PC) I have what used to be my server until the CAT5 cable went bad with an elcheapo Foxconn board in it. It has a pretty good soundcard and feeds my stereo which used to be pretty good. It was until I got that Phase Linear amp and now half the speakers are blown. Then there is my laptop, I bought these because they have a big screen and full keyboard, but found that the sound sucks. It is compressed, lke AM radio compressed, and has been described as such when connected to the amp and speakers. What I found to work to help it is to take the volume control OF THE PLAYER and turn it way down. This is NOT the volume control of Windows in the lower right. Same with youtube. |
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