Re: [B]After updating motherboard capacitors, what to do next (Asrock K7VT2, SOLTEK SL-75FRN2L)[/B]

​Hi, thanks for these replies.



The new alum-polymer caps have been bought at DigiKey (Minnesota, USA). 3300 microF/6.3 V. are made by KYOCERA (AVX series),
a well known japanese company. 1500 microF/16 V. come from Chinsan (Elite brand), a taiwanese company. I have no reason
to believe they are bad or medium quality. Both have an ESR in the 10 milliOhms range, this is the criteria why I choose them.
As a test I installed the caps on...

Hi, I have some 32 bits computer motherboards that need repair, as they fail to
power on.

Here are some examples :

(N.B. "capacitors" indicated here are electrolytic capacitors located in the onboard
switching supply area).
(N.B. #2 : I could not find a 3300 microF aluminum-polymer with a higher voltage
than 6.3 V.)

1 - Motherboard #1 : this is an Asrock K7VT2 (socket A) that still works well. To put it on test
I replaced capacitors with aluminum-polymer.
3300 microF/6.3 V. x 4 replaced by 3300 microF/6.3 V. (KYOCERA...

Hi, this is an update about that [B]Delta Power MAX 500ATX [/B]project.

After searching on internet I realised I could not find the exact schematics needed. Some "seem" to have
the same exact topology and same parts but, looking more attentively, many parts are not identified.
Others are well documented but the topology/circuit itself is not the same.

Then I tought why not remove/unsolder the resistors, capacitors etc. and after that build a new PSU from an
exact schematics that I have found. Anyway I cannot repair the actual Delta Power, what...

Hi, thanks or replying
[USER="478"]PeteS in CA[/USER] : From my initial message:
"On the high voltage rectifier diodes I read +166 and -166 V. "
"On the high voltage heatsink measure is -166 V. "
[USER="414449"]harp[/USER] : With power supply not connected to 120 V.:​
There is no shorts on the 3 power transistors on the high voltage side.
There is no shorts on the LM339 and 7500B ICs

Yesterday while I was doing...

Hi, [USER="414449"]harp[/USER] : With power supply not connected to 120 V., resistance to ground is:
for 12 V. : 230 ohms
for 5 V. : 22 ohms
for 3.3 V. : 15 ohms

Hoping this will help somewhat.harpHi, [USER="414449"]harp[/USER] : With power supply not connected to 120 V., resistance to ground is:
for 12 V. : 230

Hi, @stj: the voltage switch has been removed and a jumper wire soldered on the pcb for the 120 V. selection.

Here are power transistor voltages on the high-voltage heat sink.
In front of these transistors, from left to right:
Q1-Pin 1: -163 V.
Q1-Pin 2: +163 V.
Q1-Pin 3: -163 V.

Q2-Pin 1: 0 V.
Q2-Pin 2: +163 V.
Q2-Pin 3: 0 V. (connected to Q3-Pin 2)

Q3-Pin 1: -163 V.
Q3-Pin 2: 0 V. (connected to Q2-Pin 3)
Q3-Pin 3: -163 V.

Heat sink vltage: -163 V.

@harp: I will test resistance...

Hi, this is for troubleshooting and, hopefully, repairing a Delta Power psu
that is still quite new, as it worked OK for some months until it failed.
At the time I was not into power supply electronics; it was put
aside and a new power supply installed inside the computer. Also at the time
power supplies were half the price of today's.

On the PCB there are a D339 and 7500B chips.

I have found that schematics with these 2 chips (see included file).
Does it represent the actual circuit of the MAX-500ATX, I cannot tell.

Some measurements,...