- Terrible tube amp noise - 3 Updates
- 3 phase motor and VFD questions - 7 Updates
- Induction Cooking Table : IGBT keeping to short ! - 1 Update
| etpm@whidbey.com: Dec 29 11:29AM -0800 A little over a year ago, or was it two, I bought a Nobsound tube amp. The amp is a type A and operates in the ultra linear mode. It uses 1 5U4C Russian rectifier tube, two Chinese 6N9P tubes and two EL34B tubes. I don't kinow if they are Russian or Chinese. When I first powered it up everything went smoothly but after maybe an hour or so it made this loud static like noise. I promptly turned it off. Deciphering the directions I realized the amp was made to operate on 110 volts, not the 125 typical in my house. Oops. So I wired up a transformer in buck configuration to get 110 volts and tried the amp again. And it has operated fine since. Until a few days ago. Once again the loud static noise. Changing the volume changed nothing and I shut the amp off. After it cooled I pulled each tube out and then re-inserted it thinking that maybe a bad connection may have been the problem. After again powering the amp up it is once again performing flawlessly. So what gives? I have read about red plating, how it damages tubes pretty fast, and am thinking that maybe I damaged the tubes running them at the too high voltage for a while. But why does the amp sound great after it has a chance to cool off? Since the latest incident I have run the amp for about 4 hours straight so I don't think the problem is heat related. I mean just because the amp is hot it doesn't necessarily mean it is going to act up. Both times the amp made this noise it was getting its input from a built in bluetooth reciever. I thought this might be the problem but since the noise is volume control insensitive it seems to me that the problem is probably unrelated to the input. The noise is LOUD too. I mean hurt your ears loud. I never turn the volume up as loud as the static noise was. When I say static I mean scratchy crackling noises, not white noise. Kinda like if someone was dragging one wire across another. Unfortunately I could not tell if the noise was coming from both speakers. I just ran over and turned it off the first time it happened. The second time I tried turning down the volume and then turned it off. Should I be shopping for tubes? And could it be any of the tubes? There are no tube testers local to me. The closest I know of is an hour and a half drive away. Thanks, Eric |
| "pfjw@aol.com" <peterwieck33@gmail.com>: Dec 30 05:01AM -0800 Chinese amp with Chinese transformers. So: a) Obtain a dental-tool, one of those devices with a sharp, pointy hook on either end. With this tool, check _EVERY_ connection inside the amp. Look for cold-solders, no-solders, cracked solders and so forth. b) https://www.stereo.net.au/forums/topic/246417-exposure-of-fake-chinese-tube-amplifier-nobsound-ms-10d-mkii/ With that in mind, it is unlikely that the tubes within that beast have much to do with your issues, so now go to the boards and look for any faulty connections, over heating components (freeze-spray is your friend), raised traces and so forth. c) Once done with the physical examination, do obtain a metered variable auto-transformer and determine two things: i) At what voltage does B+ kick in? Given a 5U4, should be about 80 V+/- ii) And there should be a definite hard rise in current at that onset. NOTE: You should be drawing within 20% of +/- 50 watts or so, quiescent. If you are drawing substantially less than that, the tubes are eyewash, not functional. Good luck with it - you will likely need it. Peter Wieck Melrose Park, PA |
| "jfeng@my-deja.com" <jfeng@my-deja.com>: Dec 30 06:52AM -0800 Is it a mono or stereo amp? If stereo, is the noise identical in both channels? Can you hear suspicious noises coming directly from the electronics (like crackling from the transformers)? In the absence of any diagnostic linformation, my knee-jerk reflex is to suspect the coupling condensers, followed by the cathode bypass and power supply filters. When you have the noise, try freezing one component at a time using freon spray. If you have an oscilloscope, does the noise show up on the power supply b+? These things do not have very many components, and you ought to be able to divide and conquer. |
| etpm@whidbey.com: Dec 29 12:14PM -0800 I scrapped my GE washing machine. Actually, it scrapped itself when the drum spider broke making repair too expensive to consider. But now I have what appears to be a nice 3 phase motor. The specs are ambiguous. The voltage is listed as variable. The frequencey is listed as variable. The amperage is listed as 2.5 amps. So at least there's that. It is quite heavy. Since I removed all the electronics and the wiring harness I am going to try to get the motor to run on the bench and then measure the voltages at different speeds. I have a pretty nice DVM but I don't know how well it will measure AC voltage at frequencies much above 60 Hz. The meter will measure AC frequency. But I'm guessing that the output from the washing machine VFD is probably pretty far from a good sine wave. The VFD is a pretty simple bare bones unit. Anybody know? I do have a VFD that takes 120 volt single phase input and outputs 230 volts at up to 400 Hz. I would like to run the motor from it if I can but what if the voltage is too high? Can the motor be run at too high voltage for a while without damage? Will too high voltage just cause overheating? Since the motor is VFD rated the insulation must be pretty good so I'm thinking too high voltage is probably OK for at least a few minutes. If I can suss out what the original GE VFD expects for signals from the washing machine control and am able to copy them I will do that. But If I can't then I will want to try another VFD that I know how to control. There are at least two reasons I want to re-use this motor. One is that I hate to throw out good stuff. It pisses me off to waste stuff. Another reason to re-use the motor is that it is a high quality motor. The way it was used in the washer to drive the drum required high quality bearings and general high quality robust construction. The drive belt tension was extremely high so this put a very high side load on the front motor bearing and a high side load on the rear bearing. The motor bearings still feel great and will probably last forever. I'm thinking that with the proper reduction the motor would make a great motor for a small lathe and my son has a 9 inch South Bend that would be much easier to use if it had infinite speed control. Thanks, Eric |
| Michael Terrell <terrell.michael.a@gmail.com>: Dec 29 01:17PM -0800 > would be much easier to use if it had infinite speed control. > Thanks, > Eric Did the washer run on 120 or 240? You should have saved the motor control board and the necessary parts of the harness. The voltage and frequency aren't ambiguous, since the drive voltage has to change with the frequency. |
| Fox's Mercantile <jdangus@att.net>: Dec 29 03:49PM -0600 On 12/29/19 3:17 PM, Michael Terrell wrote: >> going to try to get the motor to run on the bench and then measure the >> voltages at different speeds. > Did the washer run on 120 or 240? You should have saved the motor control > board and the necessary parts of the harness. Do you even read what you reply to? -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
| Michael Terrell <terrell.michael.a@gmail.com>: Dec 29 02:35PM -0800 On Sunday, December 29, 2019 at 4:49:46 PM UTC-5, Fox's Mercantile wrote: > >> voltages at different speeds. > Did the washer run on 120 or 240? You should have saved the motor control > > board and the necessary parts of the harness. > Do you even read what you reply to? Do you ever have a day without PMS? He said his VFD. He gave no information on the one that came with the motor, or if it was in good condition. His statement of 'trying to get it working' is rather vague. It may or may not operate like the stand alone VFD. I was hoping to get more information out of him, but all you do is bitch. If he can get it to run from the existing drive, yes he can measure the frequency and voltage. From there, he can determine if his 120V VFD can be programmed for his needs. VFDs aren't that complicated, but a lot of idiots can mess them up. I had to repair a pipe bender at a local Art Canopy factory. They had just moved, and hired a contractor to wire up their machinery. The idiot wired the 208/240 Volt machine to a single 120V circuit. You could stop the thing with your finger. I made the idiot install the right breaker, then I added a boost transformer to run it off 240 to 245 volts. It ran twice as fast as it had, on 208V. Aren't you supposed to be working on your latest plans to catch that #$%Z^7 Road Runner? :) |
| Fox's Mercantile <jdangus@att.net>: Dec 29 05:05PM -0600 On 12/29/19 4:35 PM, Michael Terrell wrote: > I was hoping to get more information out of him, but all > you do is bitch. And all you do, as usual, is act like an asshole, then make the posting about you and how clever you are and how stupid everyone else is. -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
| Jeff Liebermann <jeffl@cruzio.com>: Dec 29 05:34PM -0800 >I scrapped my GE washing machine. (...) But now >I have what appears to be a nice 3 phase motor. (...) >I do have a VFD that takes 120 volt single phase input and outputs >230 volts at up to 400 Hz. Most VFD's can be jumpered for either 120 or 240VAC. Maker and model number would be helpful here. >I would like to run the motor from it if I >can but what if the voltage is too high? If the voltage is too high, you'll burn up either the VFD, motor, or both. >Can the motor be run at too >high voltage for a while without damage? No. You'll burn up the motor or burn up the VFD from too much current. >Will too high voltage just >cause overheating? Yes. You will rapidly begin sweating profusely as the motor begins performing a rapid self-disassembly. >I'm thinking that with the proper reduction the motor would make a >great motor for a small lathe and my son has a 9 inch South Bend that >would be much easier to use if it had infinite speed control. Washing machine motors are usually 1/2 or 3/4 horsepower. The South Bend 9" light duty (10K) lathe will suffice with a 3/4 hp motor. The 9" heavy duty flavor (10L) lathe might need a 1 hp motor. Bigger is always better: <http://www.chaski.org/homemachinist/viewtopic.php?t=83521> I'm not sure about the RPM but you should be able to extract it from the existing motor's nameplate. More: <https://www.practicalmachinist.com/vb/south-bend-lathes/what-correct-9a-motor-size-238473/> <https://groups.google.com/forum/#!topic/rec.crafts.metalworking/uHEsa0IHoxI> etc. Lots more on SB lathe motors, etc found with Google. You'll probably also need a spindle speed tachometer. Something like this: <https://www.ebay.com/itm/332908532113> -- 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 |
| "pfjw@aol.com" <peterwieck33@gmail.com>: Dec 30 05:08AM -0800 3-phase motor on a washing machine? Must be an industrial device, not hardly an over-the-counter consumer device. With that in mind, you will need a simple 3-phase VFD, as a single device. They may be had with little fuss and at a reasonable cost. Such as: https://www.automationdirect.com/adc/shopping/catalog/drives_-a-_soft_starters/ac_variable_frequency_drives_(vfd)/micro/drive_units/gs2-21p0?gclid=CjwKCAiA3abwBRBqEiwAKwICA90933xWXOub4tqOEwtiM2NTBIQOIMPluf5Adgkwgq4LVLq26XmkxxoCZ6kQAvD_BwE Only one of many options. Do check that the motor is well-and-truly 3-phase, however. Peter Wieck Melrose Park, PA |
| dmmadushankadisanayaka@gmail.com: Dec 30 12:12AM -0800 On Tuesday, November 20, 2012 at 12:20:17 AM UTC+5:30, cLx wrote: > And a little picture of the board : > http://clx.shacknet.nu/random/IMG_5803.JPG > Thanks ! There are couple of transistors for drive the IGBT. replace those transistors and your problem will be solved. Thanks |
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