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| Hilda Winkler <hildawinkler77@gmail.com>: Nov 22 09:27AM -0800 On Thursday, November 19, 2020 at 11:07:18 AM UTC-5, Chuck wrote: > >after reheating the BGA chip, i checked the power supply board. and I'm getting zero volts going to the main board on all pins. looks like a short, checked all connections. maybe i could have melted the solder under the chip when reheating and created a short??? > Very possible. That is what happened when I reflowed a bga chip on my > son's X-Box. I did look for shorts, didn't find any. i do get 5v stanby. I get 5v on fuse one on main board nothing on fuse two, and no voltage on ce2 and ce2 caps, these are two of the five bulging caps that i replaced... i get 5v on voltage regulator main board |
| "ohg...@gmail.com" <ohger1s@gmail.com>: Nov 23 04:50AM -0800 > > >after reheating the BGA chip, i checked the power supply board. and I'm getting zero volts going to the main board on all pins. looks like a short, checked all connections. maybe i could have melted the solder under the chip when reheating and created a short??? x. > I did look for shorts, didn't find any. i do get 5v stanby. I get 5v on fuse one on main board nothing on fuse two, and no voltage on ce2 and ce2 caps, these are two of the five bulging caps that i replaced... i get 5v on voltage regulator main board Did you check for the ps on command from the main back to the power supply? These things "ping pong". The power supply sends the standby voltage to the main when AC is applied. The main (on command) then sends a logic high back to the power supply to turn on the rest of the supply. The power supply goes into full run and provides the rest of the voltages, including the 12V or 24V back to the main to allow full operation. All we know right now is that you have the first step: the standby voltage. Push the power button and see if there's any change on the command line back to the power supply. If not, best odds is that the BGA got torched during the reflow. |
| John Robertson <spam@flippers.com>: Nov 22 09:29AM -0800 On 2020/11/21 10:39 p.m., Phil Allison wrote: > Problem solved by the damn Ruskies !!! > =============================== > ...... Phil So, what do I win? There must be a prize... John ;-#)# PS, the Ruskies can do some things just fine it seems, even improving designs from time to time. Some interesting electronic devices come from there. |
| guijarrosoy <fuertelindo@gmail.com>: Nov 22 09:52AM -0800 El domingo, 22 de noviembre de 2020 a las 14:29:17 UTC-3, John Robertson escribió: > PS, the Ruskies can do some things just fine it seems, even improving > designs from time to time. Some interesting electronic devices come from > there. Hi there... 1. Did the 58.55 Hz hum disappeared after swaping tubes? 2. What was the voltage at SPEAKER LEADS or output connector when the hum was present? 3. What was the voltage at SPEAKER LEADS or output connector when the standby switch cut the hum out? 4. Did you have all volume/gain controls counter clockwise (Zero level)? 5. Have you checked the amplifier specifications for residual hum and noises , for expected Signal to noise ratio? Please let us know. Thanks and regards. Al. |
| Phil Allison <pallison49@gmail.com>: Nov 22 03:42PM -0800 guijarrosoy wrote: ------------------- > Hi there... > 1. Did the 58.55 Hz hum disappeared after swaping tubes? ** Absolutely. > 2. What was the voltage at SPEAKER LEADS or output connector when the hum was present? ** About 1V rms. The problem was exactly as I stated - must be you have never seen a microphonic output tube. Or a guitar amp, where most tubes end up that way over time. ..... Phil |
| Chuck <chuck445@yahoonospam.com>: Nov 22 11:49AM -0500 On 11/16/20 1:50 PM, Chuck wrote: > probably then some. Needless to say, the only way I'll be using any > more of these is with an in line fuse as well. Of course, the dimmer > doesn't have one inside. That's it, no more Chinese dimmers! I just can't trust them. This week, I managed to pick up a linear variable voltage and current Astron 12 amp power supply. It won't be as efficient as switching units, but Astron is apparently a winner with amateur radio folks and reviews tout its reliability. I looked at the schematic and it seems that all of their units use the same general design, just different transformers and components of course as size increases. I like the fact that the schematics are readily available unlike this Chinese stuff where it is next to impossible to find one! I have even been able to peek at several internally online of course, but apparently people often tweak and modify them and post images and such online. Nice to see the innards. |
| Ralph Mowery <rmowery28146@earthlink.net>: Nov 22 12:17PM -0500 In article <rpe4qj$42v$1@dont-email.me>, chuck445@yahoonospam.com says... > next to impossible to find one! I have even been able to peek at > several internally online of course, but apparently people often tweak > and modify them and post images and such online. Nice to see the innards. Astron has been using the same basic design for many years for their linear supplies. There is almost no difference in any of them, just more pass transistors and bigger transformers. That same circit has been used in many other power supplies with minor variations. All designed around the 723 voltage regulator. It is almost like a cockroach and the circuit will not die as it is very reliable. I have a 50 amp one that has been on 24/7 for around 30 years. Only cut off when I moved and to rearange the equiipment. They do have two weakness in that if you push their ratings the transistor socket pins get loose and do not make good contact. If the power is cut off and right back on say as can hapen during a storm the over voltage protection will trip and you have to cut it off,count to about 10 slow and then turn it back on. I have another supply of no name that uses the same basic circuit and it has been on over 40 years. |
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