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| XFX RX 580 5V line problem https://vlab.su/viewtopic.php?f=48&t=106219 |
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| Micchaleq [ 24 авг 2020, 20:08 ] | |
| Заголовок сообщения: | XFX RX 580 5V line problem |
Hi all, I have problem with line voltage stabilizator. It is BM1117-ADJ. Im not sure what is wrong but I know that there schould be 5V on the output. When I connect 5V directly the card starts. I have resistors around adj pin and output pin. I have stressed them on the picture. The numbers means ohms (on the card). I didn't desolder them. Someone has that card and can check this two resistors? Is there any other components which adjust the regulator and I should check? |
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| galkinvv [ 25 авг 2020, 14:50 ] | |
| Заголовок сообщения: | Re: XFX RX 580 5V line problem |
On a very similar card (but completely dead) the resistors are 190Ohms, 490Ohms (instead of yours 157, 207). However, really only there ratio is important. What voltage is generated on your card instaed of 5V? From datasheet Цитата: The BM1117 series develops a 1.25V reference voltage between the output and the adjust terminal. If the card works with external 5V - to check if resistors are correct you should measure voltage between BM1117 OUT and ADJ while external 5V is connected. It should be 1.25V. If it isn't - either BM1117 is burned (so it affects resistance itself) or the resistors are incorrect. The other way to check if BM1117 is fine itself - to measure the same voltage withput external 5V. Power on card, measure voltage between OUT and ADJ. If it is 1.25V - BM1117 is fine (and resistors are not). |
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| Micchaleq [ 25 авг 2020, 15:53 ] | |
| Заголовок сообщения: | Re: XFX RX 580 5V line problem |
Between output and ADJ is 0.7V, output is 3,1 V (to ground) and ADJ is 2,4 (to ground). I have tried to add resistance regulator and when I have R1 about 100ohms it works. But i didnt measure the voltages between output and adjs. I will change this BM1117 and then I check it. Is there any simillar stabilizator which can be used insted BM1117? |
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| galkinvv [ 25 авг 2020, 17:00 ] | |
| Заголовок сообщения: | Re: XFX RX 580 5V line problem |
The resistors dividing coefficient looks fine. Resistors are ok. Either BM1117-ADJ isn't or the load take too much amps. Can you measure the current while card is working on external 5v supply? BM1117 datasheet says that 1A is the limit. I think that BM1117-ADJ can be replaced by any other vendor simlar *1117* ADJ IC that have same:
Generally such *1117* ADJ can be taken from other dead cards that are known to have non-5V related problem. |
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| Micchaleq [ 25 авг 2020, 18:25 ] | |
| Заголовок сообщения: | Re: XFX RX 580 5V line problem |
I have one more question. How do you count it? In the datashet od BM1117 I can see that Vout = Vref (1 + R2/R1) +Iadj R2. Where Vref = 1.25, R2 = 207, R1 = 157, Iadj*R2 doesn't matter (because it is low). So Vout (in my case) should be: Vout = 1.25 ( 1 + 207/157), Vout = 1.25 * 2.32 = 2.89. I have to be wrong, so how to calculate it? |
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| galkinvv [ 26 авг 2020, 03:40 ] | |
| Заголовок сообщения: | Re: XFX RX 580 5V line problem |
Resistors can't be exactly&reliably measured while being soldered on the board (in-though-experiment:if we remove them we'll get a quite small resistance of several KOhms from the components utilizing 5V). So measuring them is useful only to verify that they are, say, not 100x greater or 100x smaller than expected. Those numbers shouldn't be used in calculations, compared with datasheets or compared with desoldered resistors. But their exact ratio still can be found without desoldering: you write Micchaleq писал(а): Between output and ADJ is 0.7V, output is 3,1 V (to ground) and ADJ is 2,4 (to ground). Assuming that BM1117 is not burned-too-much and its resistance of ADJ pin to other pins is kept huge enough: (R1+R2)/R1 = 3,1V/0.7V ~= 4.4 Vref = 1.25. So for working BM1117 with same resistors we'll get Vout = Vref * 4.4 ~= 5.5. This is not exact 5v, but the original number of "0.7" was not very exact, so the result looks "precise enough". I think that with the exact ration known, and inexact measurment results we can calculate the exact values by applying standard basic physic laws about resistance in the complex resister network and some math. However, in practice this is rarely needed. (I'm a mathematician, so perform some calculations is simpler then desoldering for me))) ) |
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| Kim_555 [ 08 окт 2020, 11:26 ] | |
| Заголовок сообщения: | Re: XFX RX 580 5V line problem |
Я установил 1117S ADJ без доработок, работает. Фото прилагаю |
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| leonvn [ 15 окт 2020, 15:05 ] | |
| Заголовок сообщения: | Re: XFX RX 580 5V line problem |
За последние месяцы три штуки именно таких карт и именно с такой неисправностью отремонтировал. Карты 2017 года, т.е. отработали около 3 лет в непрерывном режиме. Вместо 5В 1117 выдаёт около 4,3В. Если его подогреть, то может некоторое время выдавать нормальные 5В и карта будет работать, но недолго. Только замена на такой же исправный стабилизатор решает проблему. |
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| Crimfell [ 16 окт 2020, 10:29 ] | |
| Заголовок сообщения: | Re: XFX RX 580 5V line problem |
Kim_555 писал(а): установил 1117S ADJ А я установил 1117a на xfx rx 580, из за делителя напряжения, распаянного на плате, стабилизатор выдал 8.5 вольт. Сгрели три даблера, основной шим и пару drmos. Хорошо что есть донор, получилось восстановить. Так что будьте предельно внимательными. |
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