Talent DPC-200 Power Supply Failure

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By tsMKG

Resident (48)

tsMKG's picture

01-02-2018, 00:22

Hello guys, I'm kinda new at repairing 8 bit computers Smile
So last week I got this beautiful Talent DPC-200 MSX as a gift with a two-button Joystick and an untouched Cassete reader (well, not kinda anymore since my bother really wanted to explode these bubbles that we all like exploding Big smile ) along with three game cassettes (PACMAN/GALAGA, PHOENIX and ACTMAN/BRUCE LEE (BRUCE LEE probs not working because my uncle never got it working)). He told me it would be mine if I could repair it.

At first I was like, this is gonna be easy (not forgetting how easy was to fix that famiclone I repaired last year Tongue )

And the first problem came... I didn't know how the heck open a MSX since it had cables in both sides (up and down, unlike the FC, which didn't have cables attached to the case at all) and I didn't want to break any. Fortunately my Dad came up and helped me open the case withouth breaking the cables.

Not only that, that beast had a complex circut board deticated to deal with the power supply (So not an easy replace-the-capacitor fix like the one I did to the FC). First I tried to aislate the Power Supply from the main board and the case. Had to cut two cables because they were soldered directly to the ON/OFF switch and the switch could only be popped to the outside.

Here was located the power supply:

Now that we have aislated the power supply from everything:

(Note: the photos were taken AFTER removing the heatsink, continue reading)

You might have noticed that from the power supply, we have two sets of cables that go to the main board:

I'm not sure what are I and J but I can confrim that EFGH are the ones that power the main board.

Cables I and J

You can see that those go there:

Cables EFGH

Goes here:

So we had everything set up and the first thing we did try was if the fuse has been blown out. Apparently the fuse was fine.
With the heatsink still in place, we tested the power supply's output through EFGH, by connecting the power and testing the out with a multimeter:

-12 gave -1.2 volts
+12 gave +1.2 volts
+5 gave +0.005 volts

Ok, we have the first hint that the problem resides in the power supply.
We went to try the coil (See image below), specifically the coloured cables.

They returned values similar to the required ones at the power supply's output but in AC

Ok we're fine because that's what a coil does

So I assumed it had to do with something internal, so with the power off (we wouldn't ahve powerd it on without the heatsink anyways), we removed the heatsink (filling our hands with silicone grease) and tested the componets that can be tested without power and for the most part, all the resistor and diodes were fine.

So, it's here where I am at now. Looks like I'll have to put the heatsink again to test out the rest of the components, but my dad says that we could first try to replace the voltage regulators (there's also an huge one, the Saiken STR9005).

So... Will anybody give me a hint? :-?
Kinda new repairing this kind of thing honestly ^^'

Also, might help to let you guys know the transistors:

And some photos of the supply board:

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By FiXato

Scribe (1738)

FiXato's picture

01-02-2018, 01:32

Welcome to the forum Smile
Your post wasn't showing up as the first new posts by new members need to be manually approved by a staff member, as a way to prevent spam. Smile This is why you could see it, but why it wasn't showing up in public. I've approved this post now, and deleted the other one where you were asking about it. Smile

By Philip

Champion (380)

Philip's picture

01-02-2018, 09:48

I'm not an hardware expert either, so no guaranties here...
Anyway, you can measure if the power regulator gets power on it's input. According to the datasheet it should be between 6 and 15V, so it's probably should be 12V.
But... you measured 1.2V on the 12V connection, so that's probably what also goes to the power regulator....

By Jipe

Paragon (1559)

Jipe's picture

01-02-2018, 11:56

I do not know this model but the brown red connector resembles a power ban by contacts slot as on the Yamaha CX5

By tsMKG

Resident (48)

tsMKG's picture

01-03-2018, 23:11

Well, I got as far as replacing the two regulators but I still didn't get the correct voltages so I assumed that it was the STR9005.

I bought two STR9005's and I have no idea on how to put the new one after the old one has been removed oO Question

By tsMKG

Resident (48)

tsMKG's picture

01-03-2018, 23:56

As far as it goes, I replaced the STR9005 but still outputs the wrong voltages [-1.2/+1.2/+0.01] (supply alone) oO

By tsMKG

Resident (48)

tsMKG's picture

02-03-2018, 13:29

Hey! Looks like I found the blueprints for the power supply after searching too long on the net!

I'm taking my time to read and understand this :D

In any case, you are free to give me clues of what could be going wrong.}

EDIT: getting 9 volts DC at the end of the bridge but nothing gets to pin four of STR9005 (Input voltage), something must have happened between these two and C1, C4 and R1.

By tsMKG

Resident (48)

tsMKG's picture

02-03-2018, 15:46

tsMKG wrote:

EDIT: getting 9 volts DC at the end of the bridge but nothing gets to pin four of STR9005 (Input voltage), something must have happened between these two and C1, C4 and R1.

Whoops, that was a mistake, I was measuring the unconnected pin 2 :facepalm:

after making a connection between the two pins of the power ban, it outputs the right voltages! Big smile
but after connecting everything else and turning it on, I get some video response in the easyCap but is a black screen Sad
Which means:
1) I fixed the power supply
2) There's another problem
let's see what's next Tongue

(also, no CAPS key lighting Sad this smells the problem is worse than I thought)

By tsMKG

Resident (48)

tsMKG's picture

02-03-2018, 18:53

Good afternoon, guys!

I did a circuit board tour to see if it is of any help Smile

By Wierzbowsky

Guardian (3492)

Wierzbowsky's picture

02-03-2018, 19:43

1. Try any compatible game cartridge
2. Try RAM expansion cartridge
3. Try RAM testing cartridge (with TESTRAM)

By tsMKG

Resident (48)

tsMKG's picture

02-03-2018, 20:27

Don't you think that it should boot straight into MSX-BASIC? Question
If the case were that TESTRAM should boot even without the BIOS, then how can I make myself a TESTRAM cartridge? Question

Also when they gave me this they gave me only cassettes as they only used cassettes for games, so I don't have any cart or expansion here right now.

Also, I've tested the functioning of the z80 at least the power parts and it indicates five volts as it should Smile

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