RGB out from my turbografx express

hi ,

following my previous post on this handheld iam working on right now, I have some doubts about its RGB out ..
looking at the picture, there seems to be more breaking/ segmentation in the lines,
second which is a new issue, after little time of usage, the screen fades out like this , there appears to be a problem somewhere..


I noticed that some caps voltage is just 2.2 v (cc 703) instead of 4.7 approximately on some others, 1 has 3.5 (cc205) , another zero almost which is cc505.

iam taking all 5v from a single leg of cap cc700.

any ideas?

note : earphones jack replaced and audio working on internal speaker as I have mentioned in a thread that i had an issue there

 

one funny stuff is just an and off brings colors to normal, then another few minutes and back to fade

 

any help will be appreciated..
funny stuff more
now I only get full colors on high crazy voltage of this psu i have, it is supplying some 16v !! this is only where i get color for some minutes, fades again , restart system its ok !! any help please ? thnx

 

still seeking some help

it only works when I supply crazy voltage !! and of course Q502 gets very hooooooot ..

and still some caps gets lower voltage (2.5v & 3.2v if I remember correctly)

so any useful information or advise?

thnx

 

Recap the unit. Random problem disappearing for a while with an higher voltage could be related to defective/aging caps.

 

thanks for your reply, it was already recapped when I got it from ebay .. I wonder if I should do s re-recapping as advised by some people..

 

Onestly I am not able to follow you. Can you post an hi-res image of your motherboard? RGB moddding for your unit works much better with an amplifier for RGB lines. RGB fading out can be a symptom of some issues between your monitor and the rgb modded unit that can be solved with an amplifier. Overvolting the power supply will do nothing good and can lead to fry some component. The segmentation should be normal when you connect a low resolution console to a gigantic lcd screen but I do not have a Pc Engine.

 

thank you for your reply, thanks for the advice about segmentation, but auto fading is unknown, iam using an amplifier, picture is great at first , fades out later .. anyways I will c , thanks

 

You should never, ever jack up the voltage. That is a complete amateur move and you are lucky you have not killed it.

It's never a solution to fixing or diagnosing a console.

If voltages are low, most likely a short to ground somewhere.

 

you might find my answer strange, but I do realize that raising voltage is absolutely funny thing to do intentionally, but how it all started was by an old Chinese variable voltage psu, it was there since my childhood and really funny that I never doubted its output until very recent when I found out that it was outputting extremely high voltage at what supposed to be the voltage I seek, for instance you put on 6v and it gives some 14v !!

so by the time I found out this, the console had already worked for loooong time with the high voltage, so I started Lowering the voltage to get a near required number, so when I say give high voltage I was doing nothing other than returning back to high voltage it was working at.

not very smart I know, just testing purpose of what was tested accidentally.

thanks for your valuable advice

 

I suspect you are talking about an unregulated power supply.

With no load (no device attached) you will get a much higher voltage if you measure with a meter.

Soon as there's any sort of load, it will be near the rated voltage.

So I don't think you are fully understanding what's going on.

Try measuring the voltage when a device is attached and I suspect you will see its near its proper voltage rating.

Also read: https://www.sparkfun.com/tutorials/103

 

well there is absolutely no shame in having lack of information and asking for help to learn, but what you said is absolutely not applicable here.

on 6v i measured from turbografx it reads 8.5
on 7.5v it reads 12.7 volts

using this power supply and due to its over voltage it causes q502 medium power transistor to cook.

so your assumption is wrong.

ok any helpful reply please? thanks

 

Voltage supplied depends on current being drawn. (ohms law)

If its a heavy type of PSU (that has a transformer in it) - its unregulated, which I suspect it is given the age.

Also:

"6v and it gives some 14v !!"
"on 6v i measured from turbografx it reads 8.5"

Sounds exactly like an unregulated PSU and what I am describing.

Read the link I provided

 

The assumption in right. The power supply is unregulated OR defective. You should read 6v to the PC Engine plug with the pc engine powered and working (assuming it needs 6v). If you have a decent multimeter (el cheapo china is not decent) do not matter what is the reading you haveon your power supply. What it counts is the reading on the PCE. But, to simplify the setup, why don't youput some batteries inside?

Then, if you want more help, post some images of your device.

 

well , it is not heavy

 

posted plenty of them in my previous posts so i thought no need to duplicate , thnx anyway