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Switching PSU advice
Hi !
I'm tryin' to service an IBM Server 325 PSU, suddenly dead. I checked all capacitors, diodes and other stuff for shorts. I put a paper clip connecting the power on pin with gnd. The rectified voltage (generated by a separate board) reaches a primary stage, with discrete components and three ICs TOP200YAI - Three-terminal Off-line PWM Switch LM393P - as usual UC3843AN - Current Mode PWM Controller CQY80NG - Optocoupler and two transformers. Well, from this stage exits nothing, with or w/o the paper clip. My experience on switching PSUs is very limited. The PowerOn signal doesn't reach directly the first stage but a custom made riser card, so the fault could be elsewhere. Any hints on where to begin lookin'? As a last resort, since the output voltages are the same of a standard ATX, only with different connectors, I could swap them and use a "normal" ATX. But I'd give a try, it could be a useful experience... |
Switching PSU advice
John wrote in message ...
Hi ! I'm tryin' to service an IBM Server 325 PSU, suddenly dead. I checked all capacitors, diodes and other stuff for shorts. I put a paper clip connecting the power on pin with gnd. The rectified voltage (generated by a separate board) reaches a primary stage, with discrete components and three ICs TOP200YAI - Three-terminal Off-line PWM Switch LM393P - as usual UC3843AN - Current Mode PWM Controller CQY80NG - Optocoupler and two transformers. Well, from this stage exits nothing, with or w/o the paper clip. My experience on switching PSUs is very limited. The PowerOn signal doesn't reach directly the first stage but a custom made riser card, so the fault could be elsewhere. Any hints on where to begin lookin'? As a last resort, since the output voltages are the same of a standard ATX, only with different connectors, I could swap them and use a "normal" ATX. But I'd give a try, it could be a useful experience... Where does tracing from the opto (control side) lead to? |
Switching PSU advice
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Switching PSU advice
I checked all primary ICs voltages: always 0.
PowerOn signals goes into a custom card, which seems to act as a controller. nearby there's a current sense and other stuff. Then, output signals from this custom card seem to go into the optocoupler, to the primary side. No voltages around the optocoupler... I begin to suspect the custom card. But I can't desolder it. It's in a bad place, I need to desolder other stuff and only with a small desolder pump ... |
Switching PSU advice
John wrote in message ...
I checked all primary ICs voltages: always 0. PowerOn signals goes into a custom card, which seems to act as a controller. nearby there's a current sense and other stuff. Then, output signals from this custom card seem to go into the optocoupler, to the primary side. No voltages around the optocoupler... I begin to suspect the custom card. But I can't desolder it. It's in a bad place, I need to desolder other stuff and only with a small desolder pump ... So what hapens if you cut the control line to the opto and power the opto LED on via a droppered battery for a moment. |
Switching PSU advice
So what hapens if you cut the control line to the opto and power the opto LED on via a droppered battery for a moment. You mean to supply +5V to the control input of the opto, having disconnected that line from the custom card ? |
Switching PSU advice
There's a daughter card, who rectifies the main AC: the voltage across the two
big caps is correct. Across source and drain of the TOP200YAI - Three-terminal Off-line PWM Switch there is the rectified voltage. The control input is 0. On the control line of the opto is not 0, but 0.34V. It seems that the PSU lacks the "start signal". |
Switching PSU advice
N_Cook wrote:
John wrote in message ... I checked all primary ICs voltages: always 0. PowerOn signals goes into a custom card, which seems to act as a controller. nearby there's a current sense and other stuff. Then, output signals from this custom card seem to go into the optocoupler, to the primary side. No voltages around the optocoupler... I begin to suspect the custom card. But I can't desolder it. It's in a bad place, I need to desolder other stuff and only with a small desolder pump ... So what hapens if you cut the control line to the opto and power the opto LED on via a droppered battery for a moment. I see comment about 0 volts all over it.. My question would be, is there any AC coming in and rectified DC ? Switches, etc... Kind of reminds of the IBM service desk trying to help some one with their new computer. The screen is dark. After numerous steps given to the customer to resolve issues, it was then ask if the customer could look in the back to make sure everything was plugged in. When the customer indicated he needed to get a flash light to do so, he then commented about losing power to the house. Of course, most here know the rest of that story, but it is a simple matter of starting at the fuel pump and working your way to the tail pipe. :) Jamie |
Switching PSU advice
John wrote: Hi ! I'm tryin' to service an IBM Server 325 PSU, suddenly dead. I checked all capacitors, diodes and other stuff for shorts. I put a paper clip connecting the power on pin with gnd. The rectified voltage (generated by a separate board) reaches a primary stage, with discrete components and three ICs TOP200YAI - Three-terminal Off-line PWM Switch LM393P - as usual UC3843AN - Current Mode PWM Controller CQY80NG - Optocoupler and two transformers. Well, from this stage exits nothing, with or w/o the paper clip. My experience on switching PSUs is very limited. The PowerOn signal doesn't reach directly the first stage but a custom made riser card, so the fault could be elsewhere. Any hints on where to begin lookin'? As a last resort, since the output voltages are the same of a standard ATX, only with different connectors, I could swap them and use a "normal" ATX. But I'd give a try, it could be a useful experience... How did you test the capacitors? |
Switching PSU advice
John wrote:
There's a daughter card, who rectifies the main AC: the voltage across the two big caps is correct. Across source and drain of the TOP200YAI - Three-terminal Off-line PWM Switch there is the rectified voltage. The control input is 0. On the control line of the opto is not 0, but 0.34V. It seems that the PSU lacks the "start signal". You have a power good wire "PG" and a start wire "GREEN" which as to be pulled to common.. ALso, depending the vintage, you may not have a "GREEN" wire.. I don't remember the color code for the PG line, I think it was Orange but don't quote me on that one. It'll be in the main bundle to the PC board, not any of the hardware power connectors. Jamie |
Switching PSU advice
Jamie wrote: John wrote: There's a daughter card, who rectifies the main AC: the voltage across the two big caps is correct. Across source and drain of the TOP200YAI - Three-terminal Off-line PWM Switch there is the rectified voltage. The control input is 0. On the control line of the opto is not 0, but 0.34V. It seems that the PSU lacks the "start signal". You have a power good wire "PG" and a start wire "GREEN" which as to be pulled to common.. ALso, depending the vintage, you may not have a "GREEN" wire.. I don't remember the color code for the PG line, I think it was Orange but don't quote me on that one. It'll be in the main bundle to the PC board, not any of the hardware power connectors. Jamie Real servers aren't typical desktop computers, and a lot don't use the ATX connectors so wire color can be very misleading. I have several servers with plug in, hot swappable power supplies. Those go to a interface board, then to the motherboard & drives. The OP didn't state whether it was rack mount or desktop, or what connectors are used. http://download.boulder.ibm.com/ibmdl/pub/systems/support/system_x_pdf/90p3053.pdf is a manual on one 325 series server. It is a single power supply, and the manual is dated 2003 |
Switching PSU advice
Digital multimeter and ESR meter ...
I checked cabling against IBM manual. |
Switching PSU advice
John wrote: Digital multimeter and ESR meter ... I checked cabling against IBM manual. How about posting a link to that manual? '325' is a series of servers, like 360 was a series of mainframes. |
Switching PSU advice
On 2012-09-05 17:17:05 +0200, John said:
Digital multimeter and ESR meter ... I checked cabling against IBM manual. often with these 3842 controlers, I change the small cap (often 10uF) around this chip between v+ and v- it has very often solved the problem... and it checks good on esr meter ... but if you have no voltage around the chips it must not be that... -- ---------- Kripton the ESR Repository @ http://kripton2035.free.fr/esr-repository.html the Geiger Repository @ http://kripton2035.free.fr/geiger-repositor.html |
Switching PSU advice
How about posting a link to that manual? '325' is a series of servers, like 360 was a series of mainframes. http://download.boulder.ibm.com/ibmd...x/mt6016us.pdf I followed wiring diagram and trasplanted connectors to a standard ATX (285W vs 240W of the original). The faulty PSU has all the connector shown, but MB lacks two of them, one for the 3.3V and for P12. I found the corresponding wire on the ATX standard connector, except for the +5V standby, present on the ATX, absent on the IBM PSU. I tried the modified PSU and the server started. But ... when I pressed again the power switch, it shuts off partially. The fans spin in spurts, and leds flash, as the PowerOn signal (green wire on the ATX, violet on the IBM PSU) doesn't reset completely. I checked again my rewire and it's correct. May be a different signal handling ... but it's not a real trouble, by now. As soon as I power down, I disconnect it from the main AC, I don't need a standby behaviour, by now ... |
Switching PSU advice
On Wed, 5 Sep 2012 10:52:48 +0000 (UTC), John
wrote: Hi ! I'm tryin' to service an IBM Server 325 PSU, suddenly dead. I checked all capacitors, diodes and other stuff for shorts. I put a paper clip connecting the power on pin with gnd. The rectified voltage (generated by a separate board) reaches a primary stage, with discrete components and three ICs TOP200YAI - Three-terminal Off-line PWM Switch LM393P - as usual UC3843AN - Current Mode PWM Controller CQY80NG - Optocoupler and two transformers. Well, from this stage exits nothing, with or w/o the paper clip. My experience on switching PSUs is very limited. The PowerOn signal doesn't reach directly the first stage but a custom made riser card, so the fault could be elsewhere. Any hints on where to begin lookin'? As a last resort, since the output voltages are the same of a standard ATX, only with different connectors, I could swap them and use a "normal" ATX. But I'd give a try, it could be a useful experience... Usually the AC input is filtered, then goes to a bridge rectifier. The output of the bridge is filtered by one or more caps - typical values start at 100uF, voltages often run up to 400 volts. If it isn't obvious, that can pack quite a wallop. Remember, this is a live ground - voltage is present on all points relative to earth ground. The first step is to check the output voltage of the bridge - it should be 1.4 x your nominal AC voltage. Since that is present, make sure it is correct, then check the three ICs. Using the negative terminal of the bridge for the negative lead of the dmm, check the voltages on each pin of them. One of them MUST have a voltage to start the whole process working. With the components you list, odds are the TOP200YAI is the controller for the standby supply, while the UC3843AN is the controller for the main supply. But it's not impossible the roles are reversed. A common design uses a high value resistor to drop the AC input voltage down to the 20 volts or so the UC3843AN can tolerate on pin 7. One suggestion - datasheets and application notes are available for both. Study the schematics they contain and compare them to what you see. PlainBill |
Switching PSU advice
On Wed, 5 Sep 2012 10:52:48 +0000 (UTC), John
wrote: Hi ! I'm tryin' to service an IBM Server 325 PSU, suddenly dead. I checked all capacitors, diodes and other stuff for shorts. I put a paper clip connecting the power on pin with gnd. The rectified voltage (generated by a separate board) reaches a primary stage, with discrete components and three ICs TOP200YAI - Three-terminal Off-line PWM Switch LM393P - as usual UC3843AN - Current Mode PWM Controller CQY80NG - Optocoupler and two transformers. Well, from this stage exits nothing, with or w/o the paper clip. My experience on switching PSUs is very limited. The PowerOn signal doesn't reach directly the first stage but a custom made riser card, so the fault could be elsewhere. Any hints on where to begin lookin'? As a last resort, since the output voltages are the same of a standard ATX, only with different connectors, I could swap them and use a "normal" ATX. But I'd give a try, it could be a useful experience... You'll need to get the small housekeeping power supply running, with it's output voltage present, before the main one can be troubleshot. The TOP200 integrated controller/switch will be responsible for this. Look for rectifier/zener failures on output and around the small transformer primary. It should be regulating the voltage on it's own control pin 1. RL |
Switching PSU advice
En el artículo , Kripton ?@?.?
escribió: but if you have no voltage around the chips it must not be that... Voltage to the 3842 is fed from the rectified mains via a high value dropper resistor and clipped by a zener diode. I've had several cases of that resistor going o/c or the zener going s/c. -- (\_/) (='.'=) (")_(") |
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