GBS-8220, 23DB Connectors and Leads

[tomse]

sorry, got sidetracked here (I started playing Tropico... and then the hours disappeared)

I've tried the C= adapter again as mentioned earlier, both in PAL and dblPAL
and that doesn't work.. getting no signal or sometimes I get either a green or a gray screen on the GBS.

I take it that the C= adapter gives RGBHV out (I haven't checked for that though)

hope that's useful for you.

[Johan1973]

The C= made one gives RGBHV out, yes. And as I suspected, it does not conform to what the GBS boards want to display an image, and we have to resort to composite sync.

[Solo761]

Originally Posted by Johan1973

Cable is about 15 cm in all, and it really is luck of the draw. Some do not have a problem with the GBS 8220, and some have. Even between the two remaining good ones I have, there is differences that makes it not so easy to find a good solution that applies to all to solve the white dot issue.

Load IK+ check the screen when the logo are up with small characters fighting around it. And try State of the Art demo, look when there is much going on in the screen, on the black areas, if you see white dots.

Tried it and haven't noticed anything. I took some pictures to check but again, nothing strange (I resized them a bit)



Only anomaly is bar at the bottom.

[Johan1973]

Very interesting. And I see you have the same monitor as I do, though I have not hooked the amiga up to that one yet. I will test that. Just to exclude that part of the equation..

[Solo761]

This Dell (U2311H) has one other interesting feature. You can connect Amiga directly to it, it accepts 15kHz .

[Johan1973]

Ah, its the U2311H, mistook the model. I have the S2740L (it does not accept 15khz).

Found that part of the problem is the caps on the GBS 8220, they are cheap chinese caps, specifically those for the voltage regulator, are not up to printed specs. Need to get some 470uF good ones and recap the board.

[Higgy]

Are you talking about the two caps near the power connections?:



It would be really great to finally get the white specks gone. I did turn down one of the RGB pots and got some to go, but I could still see them elsewhere.

I have mounted my GBS onto some board, then attached the board to the VESA holes on the back of my monitor. This way it is all hidden and you can't see a circuit board with loads of wires going in/out !!!

[Johan1973]

Those are indeed the caps I am talking about. And nice idea about the mounting. You can easily see if the caps you have are by the manufacturer "Cheng". I have run across these caps quite a bit in the last three years, and they inevitably fail, sometimes after just a short time, and sometimes after a long time. Since the GBS 8220 are very sensitive to bad voltage, having bad filter caps is not ideal.

[Johan1973]

Jackpot. Replaced 470 uFs and the 22 uF beside them, reduced noise by another 5%. I need to get more caps to recap the whole board. But I am now certain that the white dot issue stems from bad caps on the boards. It went from full screen snowing to a few occasional white dots.
The buffer circuit I have made should be used so that the GBS 8220 do not risk causing the amiga to crash or not boot. But beyond that, it is only recapping the boards that help. Get some quality caps and remove the bad cheng caps (check what brand your caps are first).

[Johan1973]

You need;
2 x 470 uF Electrolyte caps 16V
3 x 22 uF Electrolyte caps 16V
5 x 100 uF Electrolyte caps 16V

Especially around the 22uF ones, beware that the holes are very tight together, so make sure your soldering is good, with clean smooth solder joints. Anything less can result in a short.

[Higgy]

I am looking at my GBS (V3.0) now. I have LSHC, Chang & JACKCON caps.

i.e. cheap cheap quality ones I guess.

I have decent make replacements here, so hopefully will have a go at replacing them later.

I noticed one difference between GBS's. Mine has a 'hynix' chip (memory?) in the middle. I have seen V4.0 pictures showing a 'samsung' chip.

[Higgy]

Right, I have recapped the board.

Been running State of the Art & then Jesus on E's as there is lots of black backgrounds, and it seems good. I have not been watching all the time as doing other things, but when I have looked speckles are not there!

As I am typing this I am trying other games and again it all seems good. Walker is a good game to test as there are lots of blacks.

I have not tried fiddling with the RGB pots yet, as that seemed to do something before (but now my colours look good, so no need to fiddle!).

Thanks for the 'heads up' on the recap. Fingers crossed speckles are a thing of the past now.

[Higgy]

UPDATE - on the opening sequence of 'Wing Commander CD32' there are some occasional speckles, but nothing to really worry about.

I again just loaded up 'Jesus on E's' and there are no speckles in the black areas.

[Stedy]

Hi,

What are the values of the capacitors around IC5?
This is a AME1117 Low dropout regulator that needs some care in it's design, notably:
The Equivalent Series Resistance (ESR) of the output capacitor must be less than 0.5 ohms. The suggested value is 10uF tantalum or 50uF electrolytic.

I don't own a GBS-8200, have studied some pictures of the PCB on the internet. I can see a ceramic capacitor connected to the tab of IC5, value unknown. This could cause issues as the very low ESR of a ceramic can make LDO regulators unstable.

Food for thought.

Ian

[Johan1973]

They are 470 uF, 22 uF and 100 uF
One 470uF is in series with IC 5

[Johan1973]

I got the Scart to HDMI adapter today. Running tests on it now.
Initial impressions; Dont bother with GBS 8220.

Good: Easy to setup. Picture quality is pretty good. Sharp image for an upscaled picture.
Bad: No aspect ratio control. So make sure your display can do that part, or your image will be scaled to 16:9 aspect ratio, no matter what. With 50 Hz input, and the converter set to 50Hz, you get some interlace flickering. If you mismatch it to run 50hz input at 60hz output, that disappears. Dont know yet if that will cause any other artifacts.

[amigappc]

I have two VGA monitors at home, no HDMI.
I seriously thought about GBS-8220, as solution. Can someone reccomend me best and affordable converter which can handle amiga screenmodes, without having to sell kidney for it?

For workbench and gaming.

[Jope]

Originally Posted by amigappc

I have two VGA monitors at home, no HDMI.
I seriously thought about GBS-8220, as solution. Can someone reccomend me best and affordable converter which can handle amiga screenmodes, without having to sell kidney for it?

For workbench and gaming.

How about just getting a small flat panel TV with a SCART connector from the second hand market? Cheap and cheerful.

[Hewitson]

Lol @ "Upgrade Interface - Don't Demolition"

[Johan1973]

If you can live with the faults, and change the caps, and have an extremely stable power source for the GBA8220, it can be a cheap alternative. But in my opinion it is money better spent on buying a small tv with SCART connection.