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avatar_WacKEDmaN

Jumpy screen with GBS-8200

Started by WacKEDmaN, 05:44, 24 December 22

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WacKEDmaN

this isnt strictly CPC related but i hope someone can help...

it looks like ive run into a strange issue trying to power a GBS-8200 (no mods) and CPC on the same power...

i have just setup a PC PSU with breakout board that breaks out 12v 5v 3.3v.. and fuses!
connected to 12v i have a buck converter at 5v showing current draw...to power the CPC..
i also have 12v connected to the GBS...

this is where problems start.. gbs' onscreen display is perfectly fine..but CPC output seems to jump and distort...its not just screen but it looks like the characters change a little..
i also tried powering the gbs from the a separate 5v rail... but it did the same thing...

...next i powered the gbs via a 12v wall wart..separate from the main PSU...and it works perfectly...
ive tried 3 different psus now..ranging from 160w to 250w and they all do the same..

its like theres some ground loop or something happening..

does anyone have any idea?.. one would think the 12 and 5v rails are separate on a PC PSU

thanks..




Bryce

It's not a ground loop, it sounds like an offset ground, ie: certain mixtures of PSU's are causing the grounds of the different devices to be slightly off from each other.

Bryce.

WacKEDmaN

#2
the thing is bryce...the issue is only showing up with a single power supply and single rail..  it should be all at same ground potential level... its when i seperate the supplies that it works (where ya would think its more possible for the levels to be different!)

mains power comes into my box...
main is split to power LCD, and PSU...

PSU rail putting out 12v@10A.. (through 5A fuse!)
12v to directly to GBS...
same 12v to buck..down to 5v to power CPC  (this is where the screen bounces)...

where is the ground level difference?! can the buck change the ground level?

if i power the GBS separately its fine... (totally separate supply..does the same if i use 5v PSU rail)
ive had this issue for a while trying to power the CPC and GBS off the same supply...doesnt matter if its wall wart or PC PSU..


edit:
it seems to be like looping through the video connector
i do notice something strange...
ok so ive got 12v rail... from that 2 sets of wires.. one goes off to the buck then to the CPC.. one straight to the GBS...
the buck has voltage and current output displays... with CPC switched off and video not plugged in...buck shows 5v and 0mA current...
then i plug in the video connector from the GBS to the CPC...and instantly see the current increase to 100mA...
turn on CPC.. it works fine.. but the screen is bouncy... (again..only CPC output.. GBS onscreen display is stable)
the bounciness changes depending on power supply used.. and even between CPC boards!..i have another one here where the bounce is very mininal..still there but its not as bad as my own board!

it looks like the bounce...is being generated by the CPC...(which cant be good for it!)

maybe i should do away with the buck.. and power the CPC directly from the 5v rail...(and through a 3A fuse!..i only really want the buck for the current display and extra level of current protection)

WacKEDmaN

#3
here a quick layout i drew up to make it a little more clear... black is power ground.. blue is vga's ground..its like theres leakage in this config.. (that 100mA i see on the buck with CPC switched off..if i pull the RGBs connection the amperage drops to zero)

You cannot view this attachment.

WacKEDmaN

#4
ok.. after some more playing around... powering the gbs from its own power..causes the amperage to drop whiles the cpc is running...
eg.. ill pull the video cable from the CPC while its running and the amps going into the CPC increases!...im seeing 680mA...pull it and increase to 1.1a (with usifac)..

should i disconnect the ground to the gbs from the CPC?

so for clarification..
with video cable plugged in..its pulling 100mA with CPC off.. and its pulling 600mA with it on..
pull the video cable and it drops to 0v with CPC off, and increase to 1.1A when CPC is on..

edit: on more playing around...
i pulled the monitor side vga cable while it was running and the voltage increased..
so ..seems like monitor is causing it?! WTF

Audronic

@WacKEDmaN

Try it without the Buck I think the Buck is -ucking it up.

Keep Safe

Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

WacKEDmaN

Quote from: Audronic on 08:09, 25 December 22@WacKEDmaN

Try it without the Buck I think the Buck is -ucking it up.

Keep Safe

Ray
i just powered the cpc from a 5v wall wart.. and gbs from another 12v wall wart

defeats the purpose of running it from the PC PSU...

and cant see if theres any power draw with video connected and cpc off.. :/

Bryce

Quote from: WacKEDmaN on 23:51, 24 December 22PSU rail putting out 12v@10A.. (through 5A fuse!)


PSU's don't "put out" anything. They "offer". In this case the PSU can offer up to 10A, but if the consumers (the devices attached) only pull 3A, then the 5A fuse is fine.

The issue seems to be the PC PSU messing the PSU inside the LCD. The GND in the LCD (which comes from its own internal PSU) is clashing with the GND of the PC PSU and because they are using differing ground references, the voltages are not aligned. By using the wall warts you have everything referenced from the LCD GND.

A possible solution would be to swap the live and neutral of the LCD if it's one of those two pin 240V plugs on the back of the monitor. This might solve the problem. Or does the LCD have an earth connection too?
A better solution (and best practice) is to not connect two separate switched mode supplies (LCD and PC PSU) to a single system.

Bryce.

WacKEDmaN

..thanks Bryce.. merry xams!

...i know a psu offers up to 10A ..it only "pulls" whats needed...

..its strange..ive now powered the LCD from a seperate power board..(still with the wall warts)..
i think the problem still exists to some extent as the usifac seems to be like not getting full power (crashing and not connecting etc)

i will try adding the PSU and buck back into the mix tomorrow (eg power lcd and psu from seperate 240v wall sockets and the cpc and gbs with PSU)

thanks guys.. dont get too drunk (like me) for xmas! :)

eto

could you take a picture or maybe even a video of how that looks like?

WacKEDmaN

#10
Quote from: Bryce on 11:24, 25 December 22A possible solution would be to swap the live and neutral of the LCD if it's one of those two pin 240V plugs on the back of the monitor. This might solve the problem. Or does the LCD have an earth connection too?
A better solution (and best practice) is to not connect two separate switched mode supplies (LCD and PC PSU) to a single system.
they are both 3 wire earthed "jug" cords.. and thats what im not getting...it should ALL be referenced back to mains ground....like both chassis of the PSU and monitor are connected to the same ground...
..'best practice to not connect two seperate switch modes PSUs'..??.... umm well then how the hell do PCs work?! like PSU in PC and PSU in this PC monitor (oh and ive run 2 PSUs in a PC fine!..thermaltake GPU power supply+standard pc PSU)..aslong as the grounds are the same it will be fine..
hmm maybe i should "bond" the 2 chassis to make sure both ground levels are at the same potential? (they already should be - through the ground wire)

im thinking i might just pull the ground connection between the GBS and CPC...might still work...ill give it a go!

today..powering the GBS from 5v rail on the PSU...and CPC through the buck on the 12v rail.. but CPC switched OFF.. theres 200mA current draw going through the CPC...(includes bounce when cpc is switched on!)
powering the GBS from seperate wall wart seems to be ok.. but.. i want it all on 1 power! thats the purpose of doing it all!...

@eto.. its not a pretty setup atm.. im just trying to get it all working right b4 hot glueing it all in place..
BTW: dont get hotglue on ya fingers!... it leaves a nasty burn!.. i found out the hard way on xmas eve!  :picard:

WacKEDmaN

heres a quick vid of the bounce... ..best i could do..my camera is a potato!
..every time it looks like the focus is changing..its bouncing!...


eto

I do have pretty much the exact same set-up, except for that I also have the GBS control mod installed. I'll check when I am back in a few days, if I can see something similar. 

I have seen something similar with some LCD TVs where the image was just not 100% sharp and steady but it was not as bad as this and I am not sure if that is in any way related. 

Bryce

Quote from: WacKEDmaN on 02:16, 26 December 22
Quote from: Bryce on 11:24, 25 December 22A possible solution would be to swap the live and neutral of the LCD if it's one of those two pin 240V plugs on the back of the monitor. This might solve the problem. Or does the LCD have an earth connection too?
A better solution (and best practice) is to not connect two separate switched mode supplies (LCD and PC PSU) to a single system.
it should ALL be referenced back to mains ground....

Most SPMPSU's aren't ground referenced, which is what is most likely causing the issues that I've mentioned.

PC's have a massive amount of filtering. In particular for the type of high frequency noise created by SMPSU's. Retro computers have none of this as they were designed for linear power supplies.

Bryce.

WacKEDmaN

#14
Quote from: Bryce on 10:37, 26 December 22
Quote from: WacKEDmaN on 02:16, 26 December 22
Quote from: Bryce on 11:24, 25 December 22A possible solution would be to swap the live and neutral of the LCD if it's one of those two pin 240V plugs on the back of the monitor. This might solve the problem. Or does the LCD have an earth connection too?
A better solution (and best practice) is to not connect two separate switched mode supplies (LCD and PC PSU) to a single system.
it should ALL be referenced back to mains ground....

Most SPMPSU's aren't ground referenced, which is what is most likely causing the issues that I've mentioned.

PC's have a massive amount of filtering. In particular for the type of high frequency noise created by SMPSU's. Retro computers have none of this as they were designed for linear power supplies.

Bryce.

ok..i get that some psu's dont ref to mains ground..but i was under the impression that all PC/Monitors PSUs are all ref to mains...

and..it all works fine if i just power the GBS seperatly.. (CPC powered from PSU.. LCD off its own PSU..so theres still 2 in the mix and its fine)..its just adding the GBS where the issue shows up..(and only when the GBS is powered)

anyways...
would you suggest i try to tap power off the LCDs power supply to power the CPC and GBS off?
(it would be a nicer solution..just not sure it the LCD PSU can supply the extra current)
edit: actually thats gonna be a PITA..coz the monitor is glued to the box lid! gonna be a pain to get off! LOL

Bryce

You could try that, but remember to add appropriate fusing on the new output and be extremely careful when poking around on the PSU board. There's usually around 400VDC across some of the capacitors that could really ruin your day.

Bryce.

WacKEDmaN

Quote from: Bryce on 15:27, 26 December 22You could try that, but remember to add appropriate fusing on the new output and be extremely careful when poking around on the PSU board. There's usually around 400VDC across some of the capacitors that could really ruin your day.

Bryce.
..thats going to be an issue.. cant get the monitor off the box to take it apart! :P
looks like im just going to have to use 2 seperate supplies for the CPC and GBS n be done with it
...
what a waste of money n time that was... :picard:

Audronic

@WacKEDmaN 

If you want small power supplies have a look here (They are in Australia)

https://www.ebay.com.au/itm/393010083064 

Keep Safe

Happy new Year 

Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

WacKEDmaN

#18
Quote from: Audronic on 22:57, 26 December 22@WacKEDmaN

If you want small power supplies have a look here (They are in Australia)

https://www.ebay.com.au/itm/393010083064

Keep Safe

Happy new Year

Ray

i dont need a new psu... ive got like 20 PC PSUs here.....

and besides...it wont fix the issue at hand....it doesnt matter what power supply i use... i CANNOT power CPC and GBS with same power supply... as it causes the bouncys...aswell as that 100-200mA of current that seem to flow through the CPC and out the video connector while the CPC is switched OFF

Bryce

Quote from: WacKEDmaN on 04:08, 27 December 22
Quote from: Audronic on 22:57, 26 December 22@WacKEDmaN

If you want small power supplies have a look here (They are in Australia)

https://www.ebay.com.au/itm/393010083064

Keep Safe

Happy new Year

Ray

i dont need a new psu... ive got like 20 PC PSUs here.....

and besides...it wont fix the issue at hand....it doesnt matter what power supply i use... i CANNOT power CPC and GBS with same power supply... as it causes the bouncys...aswell as that 100-200mA of current that seem to flow through the CPC and out the video connector while the CPC is switched OFF
Current will definitely flow through the LUM pin if the monitor it's connected to is powered. Not sure about the other monitor pins, but any current on that connector (when the CPC is turned off) is coming from the monitor.

Bryce.

WacKEDmaN

#20
Quote from: Bryce on 11:29, 27 December 22
Quote from: WacKEDmaN on 04:08, 27 December 22
Quote from: Audronic on 22:57, 26 December 22@WacKEDmaN

If you want small power supplies have a look here (They are in Australia)

https://www.ebay.com.au/itm/393010083064

Keep Safe

Happy new Year

Ray

i dont need a new psu... ive got like 20 PC PSUs here.....

and besides...it wont fix the issue at hand....it doesnt matter what power supply i use... i CANNOT power CPC and GBS with same power supply... as it causes the bouncys...aswell as that 100-200mA of current that seem to flow through the CPC and out the video connector while the CPC is switched OFF
Current will definitely flow through the LUM pin if the monitor it's connected to is powered. Not sure about the other monitor pins, but any current on that connector (when the CPC is turned off) is coming from the monitor.

Bryce.

LUM is the only pin NOT connected to the GBS!! (its connected to GND on GBS side..but CPC side was never soldered to anything..its just floating around and not touching anything else)

...and i dont see any current flow when i use a separate supply for the GBS..its only when the GBS is on same power supply as CPC (the monitor doesnt matter at all.. i can try another monitor and there will be same results..and i am using a 4way power strip to power 3 different supplies aswell..so all the same mains ground)
pulling the VGA monitor cable from the GBS does stop the current flow, but it seems like its an internal switch in the GBS itself, nothing to do with the monitors ground..

WacKEDmaN

#21
....sorry Bryce.. you might be right about it being monitor..

today ive been running CPC and GBS powered from seperate wall warts (5v@2A for CPC 12v@2A for GBS)..
i dont have the buck in the mix so i cant see the current draw...
BUT... im getting a slight bit of bounce occasionally... and now.. usifac is playing up again (especially with esp32 connected).. like its not getting current again..and im getting hella crashes on some boots (like sync goes crazy)..and random reboots during gameplay...i guess it needs more current but all i got are 5v@2A max..

so its looking like this issue is bringing the current down on the CPC input some how..(as it does with the buck..)

this is really strange...

but... i have to send this GBS back to its owner today.. im waiting for one to arrive from china, but its looking like a 2 month wait :(
hopefully its just this version of the GBS and the new one acts better...i dont think i had these issues with my old GBS ..but i killed it by ripping off the clock pin while doing the CBS-C mod

ill hook up direct VGA to one of my PC monitors later and see if theres any current draw through the CPC with it off...

edit: so mate is lending me the GBS some more till i get mine...
well i pulled it all down.. and then reconnected everything...
now..PC PSU is powering CPC through the buck.. and GBS is powered by 12v wall wart...
there is no bounce... and NO current flow with CPC off....(if i use 5v or 12v rails from PC PSU to power GBS the bounces and current flow are back)

...this current setup WAS causing current draw before....

i also just notice this board is label "HD9600" ..so maybe slightly different to the GBS8200..altho they are being sold as the same thing...

TLDR; ..im going to just use this 12v wall wart to power the GBS..and use a PC PSU to power CPC and other things... (ESP32 could do with its an external supply..and i wanna put RGB LED strips in my box! eventually to be controlled from the CPC!)

WacKEDmaN

#22
so it seems im not the only one with this issue....
mate has the same bouncy screen with his other HD9800...he is also powering both from a the same supply..that has isolated outputs..

you can see here in this video clip...

https://youtube.com/clip/UgkxcPZgvmHbz_9v37zRzVvl2FXQrpyAFP5B

00WReX

I have a GBS-8200 that I have been using for over 10 years. I use a 5v 4A double insulated wall plug type power supply, powering both the CPC and GBS.
The LCD has the 'kettle' type 240v power cord. So it's all nice and simple.
I don't have any issues.
The CPC in Australia...
Awa - CPCWiki

WacKEDmaN

Quote from: 00WReX on 03:46, 30 December 22I have a GBS-8200 that I have been using for over 10 years. I use a 5v 4A double insulated wall plug type power supply, powering both the CPC and GBS.
The LCD has the 'kettle' type 240v power cord. So it's all nice and simple.
I don't have any issues.
Quote from: WacKEDmaN on 05:44, 24 December 22this isnt strictly CPC related but i hope someone can help...

it looks like ive run into a strange issue trying to power a GBS-8200 (no mods) and CPC on the same power...

i have just setup a PC PSU with breakout board that breaks out 12v 5v 3.3v.. and fuses!
connected to 12v i have a buck converter at 5v showing current draw...to power the CPC..
i also have 12v connected to the GBS...

this is where problems start.. gbs' onscreen display is perfectly fine..but CPC output seems to jump and distort...its not just screen but it looks like the characters change a little..
i also tried powering the gbs from the a separate 5v rail... but it did the same thing...

...next i powered the gbs via a 12v wall wart..separate from the main PSU...and it works perfectly...
ive tried 3 different psus now..ranging from 160w to 250w and they all do the same..

its like theres some ground loop or something happening..

does anyone have any idea?.. one would think the 12 and 5v rails are separate on a PC PSU

thanks..





i dont think my GBS8200 had this issue either...this HD9800 version seems to be bad for it....
...we'll find out when i get my new GBS8200 i guess!

for the time being powering it from its own wall wart seems to be doing the trick...

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