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Beeblebrox

130XE brought back from the dead - Advice re glitching display

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Ok, so one of the XE's I had it my attic was just the lower case and the board from a 130XE. Sometime in the mid 90's I have clearly labelled this as a none working 130XE board and it went in a spares pile.

 

Alongside all my other A8 hardware tinkering over the course of this year I've been revisiting this board on and off to try and get it to at least show signs of life.

 

Basically here is the timeline.

 

April - found board in attic. Standard 130XE rev 4 C070067 board which had the following already socketed:

CPU, ANTI, GTIA, PIA

 

Power clearly going in and monitor registers a signal is coming out of it but black screen.

 

Over course of 2021 I remove those chips directly soldered to the board and socketed each chip with the exception of the 16 x MT brand RAM chips. (In hindsight from what I've learnt since I should have gone to the RAM chips first - more on that later)

 

Each time I socketed a chip I try and see if it makes any difference.

 

I also try another alternative chips from those that already came installed in the board, using known working chips I have. Again - excluding the RAM chips at this stage.

 

So I end up socketing (and in the case of some of the existing sockets replacing them) the following:

 

FREDDIE, POKEY, MMU, OS, 4050, 74LS08 (replacing it with 74F08).

 

Again I also tried testing one chip at a time with alternative known to work chips for:

 

CPU, ANTI, GTIA, PIA, FREDDIE, POKEY, MMU, OS, 4050, 74LS08 (again replacing it with 74F08).

 

Nothing made any difference. Black screen.

 

At the weekend after 16pin sockets I'd ordered arrived, I undertook the teadious task of removing all 16 x MT RAM chips from the board, cleaning it up, installing the sockets, and then today I installed checked and working reliable Samsung brand chips. Once installed I flipped the switch....

 

At last it powered up!:music::D

 

However - we have a problem:

image.thumb.png.265647feffad1c27daad8d97deed9488.png

 

FYI the cable is fine - it's the same DIN to S-video cable as I use with all my other A8s on S-video

 

So aside it being in greyscale and vertical lines, etc - what's more after around 15 seconds on the screen starts to glitch and warp, jump around and dark horizontal lines start to appear on the left moving up the display.

See screen examples below.

 

If I power it off, leave it for 30 seconds or so, and power it back on, the above display appears again and once left on repeats the same behaviour.

 

image.thumb.png.03ca918b2df31904c060c9e0d9f2f8c9.pngimage.thumb.png.68a7f8d769d22f654b51975571d18784.pngimage.thumb.png.5262dff598df3df7b0645ffc27ab7637.pngimage.png.401956664fc704efa2c31ab143aa40b4.png       

 

image.thumb.png.c7d41d1020c5c3886daf16017f6704fe.png

 

This to me indicates a chip or component is warming up and glitching further.

 

I checked the chips whilst the 130XE is on by touching them and the only two getting warmish (but not hot), are the CPU and GTIA.

So just in case I tried 2 x other alternative CPU and GTIA chips from working A8s and the same thing happens. I thought it might be the 4050 chip but again known to work alternative chips swapped out made no difference.

 

This is the board as it looks at the moment:

 

image.thumb.png.b430addbc48e8d5aaeb44c68de650767.png

 

The new 16 x Samsung KM4164B-12 120ns ram chips are sound. I used a dram tester on each before putting them in place and they all checked out. I don't think this is a ram issue.

 

So in my limited understanding it appears as though perhaps another of the remaining unsocketed smaller chips may be causing this? None of the capacitors are hot or bloated. 

 

The chips/components I've not looked at are:

 

The crystal bottom left near Freddie, the C016801 PAL clock, the C025953 (EMMU?), the M74LS74AP, the BASIC chip, UA555TC, SN74LS138N, and the two TC4051BP chips.  

 

I can't imagine it would be the EMMU or the BASIC chip

 

I've gone though and checked my own socket solder work using my multimeter and it all checked out ok.

I've also checked out the previously existing sockets. I also checked for any shorting, and also that chip legs were making contact with the sockets and in turn the sockets with the board.

I have a donor 130XE board which I also used for cross referencing. I've traced many connections and they all show continuity.

 

Given the graphics glitch would anyone have any suggestions? Could it be the C016801 PAL clock?  Has anyone seen this behavious before and fixed it?

 

Thanks in advance.

 

 

 

 

 

 

 

Edited by Beeblebrox

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Maybe chroma/luma are swapped?  Otherwise... Suggest closely examining the passives, especially in the video circuits.  Have you tried testing a UAV in it?

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7 minutes ago, Sugarland said:

Maybe chroma/luma are swapped?  Otherwise... Suggest closely examining the passives, especially in the video circuits.  Have you tried testing a UAV in it?

Thanks @Sugarland Q: would a crossed luma and chroma connection on the PCB cause the screen to start to glitch and jump around?   I'd imagine the screen would be ok. I guess it could be crossed chroma luma coupled with another issue. Also I am unsure how they could have crossed as the machine doesn't have any post factory work in that respect.

 

Also just to confirm the S-video cable itself is fine as I mention - use it all the time with all of my XL and XE A8s and get no issues with colour.

 

Passives. Never heard of the terms so Googled it and see it refers to the Capacitors and resisters. (I am learning stuff all the time with all this tinkering) 

 

I have a UAV in my 800XL I could transplant but I'd rather see if I can fix it as stock before I go ahead and extract it from my driver 800XL A8. 

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As good old Google tells you passive components are resistors, capacitors, inductors, essentially anything that's not a semi-conductor.

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Incidentally when using Sys Check 2.2 with the 130XE this is what I see in diagnostic mode:

 

(Diagnostic mode being: 

image.thumb.png.d971035b58e3417dee36f15c28f9a56b.png)

 

 

image.thumb.png.41283d3cad72e07f3ede83330c242cb6.png       image.thumb.png.9813c5158a3ebaaae8c5082b1f2d5f87.png

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If you have a socketed spare machine, try the GTIA and ANTIC from this machine into a known-good, working machine. If they test out as good in another machine, check the sockets on this one for bad connections at the chip legs, cold solder joints to the PCB, solder flakes, etc.

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16 minutes ago, DrVenkman said:

If you have a socketed spare machine, try the GTIA and ANTIC from this machine into a known-good, working machine. If they test out as good in another machine, check the sockets on this one for bad connections at the chip legs, cold solder joints to the PCB, solder flakes, etc.

@DrVenkman yup, did that already. The GTIA and ANTIC from this 130XE work when I put them into my stock 65XE. I am going to replace the GTIA socket with precision round one initially and then possibly do the same for the ANTIC. So you don't think initially it could be any one of the following causing any issues?

 

The crystal bottom left near Freddie, the C016801 PAL clock, the C025953 (EMMU?), the M74LS74AP, the BASIC chip, UA555TC, SN74LS138N, and the two TC4051BP chips.  

 

I think it could be the GTIA socket.

 

thanks for your suggestions.

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Ok in the last hour I removed the old GTIA socket, checked the board any obvious issues underneath the chip area/on the underside. (eg for broken traces, etc). Nothing, everything looked good. Cleaned it up and installed the precision round socket. Checked the solder points and continuity. Popped the GTIA in and powered up. Same issue, no change. Tried another GTIA chip. Same issue.

 

Incidentally what I forgot to mention is that the keyboard hasn't responded at all during all this time. It has a new mylar and the keyboard works with my other 65XE.  

 

I do get audio though (well at the boot up basic screen prompt you hear the initial "ripple" sound just before the ready prompt text appears). 

 

I also re-tried just popping known working CPU, PIA, POKEY and OS chips from my 65XE into this 130XE and putting the removed chips back in the 65XE. Same as before, the chips work in the 65XE, but no change with this 130XE. So I don;t think the GTIA is the main issue.

 

So next I'll replace the socket for the ANITC and test it. If no difference I'll try and do the same for the CPU.

 

Does the issue with the keyboard not responding give any further clues I wonder? (Could be multiple issues but just throwing it out there should it be connected with the graphics issue). 

Edited by Beeblebrox

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4 hours ago, Beeblebrox said:

Ok, so one of the XE's I had it my attic was just the lower case and the board from a 130XE. Sometime in the mid 90's I have clearly labelled this as a none working 130XE board and it went in a spares pile.

 

Alongside all my other A8 hardware tinkering over the course of this year I've been revisiting this board on and off to try and get it to at least show signs of life.

 

Basically here is the timeline.

 

April - found board in attic. Standard 130XE rev 4 C070067 board which had the following already socketed:

CPU, ANTI, GTIA, PIA

 

Power clearly going in and monitor registers a signal is coming out of it but black screen.

 

Over course of 2021 I remove those chips directly soldered to the board and socketed each chip with the exception of the 16 x MT brand RAM chips. (In hindsight from what I've learnt since I should have gone to the RAM chips first - more on that later)

 

Each time I socketed a chip I try and see if it makes any difference.

 

I also try another alternative chips from those that already came installed in the board, using known working chips I have. Again - excluding the RAM chips at this stage.

 

So I end up socketing (and in the case of some of the existing sockets replacing them) the following:

 

FREDDIE, POKEY, MMU, OS, 4050, 74LS08 (replacing it with 74F08).

 

Again I also tried testing one chip at a time with alternative known to work chips for:

 

CPU, ANTI, GTIA, PIA, FREDDIE, POKEY, MMU, OS, 4050, 74LS08 (again replacing it with 74F08).

 

Nothing made any difference. Black screen.

 

At the weekend after 16pin sockets I'd ordered arrived, I undertook the teadious task of removing all 16 x MT RAM chips from the board, cleaning it up, installing the sockets, and then today I installed checked and working reliable Samsung brand chips. Once installed I flipped the switch....

 

At last it powered up!:music::D

 

However - we have a problem:

image.thumb.png.265647feffad1c27daad8d97deed9488.png

 

FYI the cable is fine - it's the same DIN to S-video cable as I use with all my other A8s on S-video

 

So aside it being in greyscale and vertical lines, etc - what's more after around 15 seconds on the screen starts to glitch and warp, jump around and dark horizontal lines start to appear on the left moving up the display.

See screen examples below.

 

If I power it off, leave it for 30 seconds or so, and power it back on, the above display appears again and once left on repeats the same behaviour.

 

image.thumb.png.03ca918b2df31904c060c9e0d9f2f8c9.pngimage.thumb.png.68a7f8d769d22f654b51975571d18784.pngimage.thumb.png.5262dff598df3df7b0645ffc27ab7637.pngimage.png.401956664fc704efa2c31ab143aa40b4.png       

 

image.thumb.png.c7d41d1020c5c3886daf16017f6704fe.png

 

This to me indicates a chip or component is warming up and glitching further.

 

I checked the chips whilst the 130XE is on by touching them and the only two getting warmish (but not hot), are the CPU and GTIA.

So just in case I tried 2 x other alternative CPU and GTIA chips from working A8s and the same thing happens. I thought it might be the 4050 chip but again known to work alternative chips swapped out made no difference.

 

This is the board as it looks at the moment:

 

image.thumb.png.b430addbc48e8d5aaeb44c68de650767.png

 

The new 16 x Samsung KM4164B-12 120ns ram chips are sound. I used a dram tester on each before putting them in place and they all checked out. I don't think this is a ram issue.

 

So in my limited understanding it appears as though perhaps another of the remaining unsocketed smaller chips may be causing this? None of the capacitors are hot or bloated. 

 

The chips/components I've not looked at are:

 

The crystal bottom left near Freddie, the C016801 PAL clock, the C025953 (EMMU?), the M74LS74AP, the BASIC chip, UA555TC, SN74LS138N, and the two TC4051BP chips.  

 

I can't imagine it would be the EMMU or the BASIC chip

 

I've gone though and checked my own socket solder work using my multimeter and it all checked out ok.

I've also checked out the previously existing sockets. I also checked for any shorting, and also that chip legs were making contact with the sockets and in turn the sockets with the board.

I have a donor 130XE board which I also used for cross referencing. I've traced many connections and they all show continuity.

 

Given the graphics glitch would anyone have any suggestions? Could it be the C016801 PAL clock?  Has anyone seen this behavious before and fixed it?

 

Thanks in advance.

 

 

 

 

 

 

 

Not to hijack but where u get the 16 x Samsung KM4164B-12 120ns ram and sockets? I need 8 badly

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Measure your voltages from power up until the screen warp.  Also, try cooling the chips, then passives with compressed cool air to see if it stabilizes. 

nothing works on the keyboard? Reset or option key on boot? The led light up?

 

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same power supply used on good and bad system?

check video color pot voltage doubler circuit...

then check delay line

check 4050

check pokey

check two keyboard decoder chips...

Edited by _The Doctor__

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3 hours ago, _The Doctor__ said:

same power supply used on good and bad system?

check video color pot voltage doubler circuit...

then check delay line

check 4050

check pokey

check two keyboard decoder chips...

@_The Doctor__

Yes, same power supply (usb new style) used on all my a8s. I just leave it plugged in when alternating between them. 

I have used 2 other known to work pokey chips and also put this pokey chip in my 65XE and it works in that. I will have another looks at the pokey socket though later. 

4050 socket and chip is OK. 

 

I'll have a look at the following as you suggest later:

 

Delay line - Excuse my naivety but I can't seem to locate this chip on the board looking for one labelled CO60472.  From descriptions I am looking for a smaller raised chip which looks like it has pins removed. I've seen these on XL models but can't find one on this XE board.

Two decoder chips  (these are presumably chips U24 and U25 lower right side of the board?)

 

Firstly I will re socket Antic and test... then CPU and test, with precision round sockets. Then I'll re-check the Pokey socket although this is already a precision round socket.

 

Thanks 

 

Edited by Beeblebrox

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4 hours ago, kheller2 said:

Measure your voltages from power up until the screen warp.  Also, try cooling the chips, then passives with compressed cool air to see if it stabilizes. 

nothing works on the keyboard? Reset or option key on boot? The led light up?

 

@kheller2

Yup keyboard red led light is on, nothing responds from the known working keyboard Inc function keys. 

Thanks for voltage testing suggestions, etc re the passives. 

Edited by Beeblebrox

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@oo7 Not to hijack but where u get the 16 x Samsung KM4164B-12 120ns ram and sockets? I need 8 badly

No worries. :) I got mine on Ebay in the UK. You just have to search around. I'd probably get 8x of any one of these alternatives which I found out about here on AA courtesy of Level42's post (with the exception of the notorious Micron (MT) brand of course):

 

4164 RAM equivalents:

 

HM4864(A) (Hitachi)

µPD4164 (NEC)

M5K4164 (Mitsubishi)

MK4564 (Mostek)

MSM3764 (OKI)

MN4164 (Matsushita)

KM4164B-15 (Samsung)

HYB4164 (Siemens)

LH2164 (Sharp)

TMM4164(A) (Toshiba)

TMS4164 (Texas Instruments)

MB8264(A) (Fujitsu)

MT4264 (Micron) (DO NOT BUY)

MHB4164 (TESLA)

KR565RU5 (Russian)

 

Edited by Beeblebrox

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Ok, Eureka moment - We are getting somewhere.:-D

 

Firstly the keyboard - turned out it was several weak solder points on the keyboard connector so I fixed that. Keyboard is working.:music:

 

Most importantly I found the main issue regarding the display glitching!:) It's not 100% there but definitely major progress.

 

So this is what I found.

 

Earlier today I removed the old ANTIC socket. It was a clean extract (ie I'd not pulled up any traces or vai's).

 

After cleaning up the board I immediately noticed the via on the pin 2 socket hole didn't look right from the underside of the PCB, (it didn't look complete). It looked fine on top but there are no traces connected topside, only bottom.

I checked the old socket pin 2 to ensure the metal from the via hadn't come off during the extract. It was clean.  So this wasn't something new. Encouraging!:ponder:

 

Sure enough the connection point with the trace here at the pin 2 hole wasn't connecting with the point the trace leads to 2cm away when I tested with the multimeter:

 

Underside of PCB:

image.png.a4d25b8ebb8d750b0d52f448533ee321.png    

 

Topside:

image.thumb.png.46a5094798cc36818a1ad9fcd277d3e6.png

 

Before the socket removal I'd not noticed it in previous checks because of the solder in place. I am sure I'd checked ALL the ANTIC pin connections before but perhaps it was connecting but intermittant, hence the glitching. This might explain the warm up period that was occuring with the glitch screen jumping, distortion, etc..

 

So I installed the new precision round socket, then jumped pin 2 with a wire on the underside of the PCB to connect it to the point it originally connected to:

 

image.thumb.png.55e4451b2b320c70bab0071e4b81d7b8.png

 

 

I cleaned it up some more to remove debris, etc...

...and popped in ANTIC chip in the new socket:

 

image.png.771a8e655a8e831749445442d8c04d3b.png

 

Tentatively I powered up the machine!  

 

Progress at last...I have a working non glitching display. No more vertical lines or distortion.:music::-D:thumbsup:

The only issue is it still appears to be in black and white.

 

On S-video:

image.thumb.png.e1b5e2afbf236f58839a4ac842c997c5.pngimage.thumb.png.0b41acd4fcd3e25c20940ca4a5a89d5a.png   image.thumb.png.9cf496b0134d1dbbac163cd324e3675a.png

image.thumb.png.8202790b35b7560fdc6947329a1bd904.png

 

I am using the S-video cable here and that same cable gives me colour on my stock 65XE as well as my 320K Stereo 65XE. The important thing to note it that my stock 65XE has have the Simple video enhancement which just clears up the output for S-video, and my 320K Stereo 65XE has had no mods for video. So they both display colour on this same S-video cable.

 

I've also adjusted the colour pot just in case. Still black and white.

 

I decided to try hooking it up to composite using another known working Din to composite/audio cable.

I still get black and white:

 

On composite

image.thumb.png.6cddec113006e896472e0f6c345db478.png

 

*****

 

So - fantastic it isn't glitching anymore and I have a workin 130XE (after RAM replacement and ANTIC socket/PCB fix/Keyboard connector fix). However I'll need to figure out why the Chroma and luma for the S-video and also for Composite isn't coming through and why I am only getting black and white displayed. Again I've tried tweaking the colour pot.

 

I'll need to research AA threads me thinks to check the Chroma and Luma lines/components.

 

Any tips still greatly appreciated but thanks again to all who suggested things to date. :thumbsup:

 

 

 

 

 

 

 

Edited by Beeblebrox
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Check/replace 74LS74; measure PAL colourburst oscillator output and clock inputs to GTIA. 74LS74 can be bad, and if you're extremely unlucky, the secondary crystal is dead. Transistors can blow as well.

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7 minutes ago, flashjazzcat said:

Check/replace 74LS74; measure PAL colourburst oscillator output and clock inputs to GTIA. 74LS74 can be bad, and if you're extremely unlucky, the secondary crystal is dead. Transistors can blow as well.

@flashjazzcat  Thanks! :) I have a spare 74LS74 and also the same crystal so I can always swap them out. I'll check the passives too (getting used to this newly learned terminology).:thumbsup:

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5 hours ago, Beeblebrox said:

@oo7 Not to hijack but where u get the 16 x Samsung KM4164B-12 120ns ram and sockets? I need 8 badly

No worries. :) I got mine on Ebay in the UK. You just have to search around. I'd probably get 8x of any one of these alternatives which I found out about here on AA courtesy of Level42's post (with the exception of the notorious Micron (MT) brand of course):

 

4164 RAM equivalents:

 

HM4864(A) (Hitachi)

µPD4164 (NEC)

M5K4164 (Mitsubishi)

MK4564 (Mostek)

MSM3764 (OKI)

MN4164 (Matsushita)

KM4164B-15 (Samsung)

HYB4164 (Siemens)

LH2164 (Sharp)

TMM4164(A) (Toshiba)

TMS4164 (Texas Instruments)

MB8264(A) (Fujitsu)

MT4264 (Micron) (DO NOT BUY)

MHB4164 (TESLA)

KR565RU5 (Russian)

 

Ok thank you, Microns(dead) are the reason Im looking lol. Will go this route.

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2 hours ago, flashjazzcat said:

Check/replace 74LS74; measure PAL colourburst oscillator output and clock inputs to GTIA. 74LS74 can be bad, and if you're extremely unlucky, the secondary crystal is dead. Transistors can blow as well.

ok I replaced 3 x components on the 130XE from my donor board, testing after installing each one in turn:

 

74LS74

clock C016801

Crystal

 

Made no difference in each case - still the same black and white display.

 

Of course here I am replacing the components from a donor board and as such I can't guarantee they don't have issues. As such I've ordered a new 74LS74 chip.  I've also ordered a new trim colour pop (just in case).

 

At this stage I can't order the C016801 or the crystal as don't know where to source them from in the UK, (had a look online earlier although granted these are the Atari specific part numbers if I am correct so I may need to look further).

 

I don't own an oscilloscope unfortuately - (can't really justify the cost just looking online) - and also I'll need to research how I can test the passives (transistors and others) and mainly which passives in which area I need to focus on.

 

I may also resort to doing what was suggested earlier and temporarily transplanting the UAV board I have in my Driver 800XL machine into this 130XE just to see. However I really don't want to do this if I can avoid it as just want to get the stock video/colour fixed on this 130XE first.

 

Incidentally last month whilst tinkering and doing some general research I found a very useful online tool for inputting resistor colour bands to see what Ohm rating they are: https://resistor.cherryjourney.pt/

 

It's come in handy a few times for some of the S-video mods I've done on my other A8s, among other things.

 

Still, very pleased the 130XE is back from the dead given it had been in a spares box and written off all those years ago. Just gonna take a while longer but I am sure I'll get to the bottom of it. :thumbsup::-D

 

 

 

Edited by Beeblebrox

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@Beeblebrox

The pads and traces look as if the iron is being pushed against the pcb and pad causing them to deform and pull. If you are using flux and touch up solder, make sure to use old lead based solder, newer solders and many silver bearing solders require too much heat for the XE's traces...

You are correct, I was thinking XL earlier not XE...

You definitely want to verify each connection to the sockets and components at this point as other pad / trace unions look dodgy in the picture.

so check GTIA and socket then...

check the color pot by turning it and measuring it's voltage as you do, it should be smooth, if there are dropouts or the voltages are out of range, I'd replace it.

Generally transistor do not go bad or fail as much more video problems would being evident in display, you can pull it and test it (most dmm's have this capability these days) or just replace it.

Other outside chances are a mix up with non PAL chip stranger things happen verify proper CO number for PAL

 

as to resistors, you will never need calculators if you remember this or similar phrases.... as a memory aid.

 

Bad  Boys  Race  Our  Young  Girls  But  Violet  Generally  Wins  Gold   Silver

lack  rown  ed    range  ellow  reen  lue  iolet     rey           hite   1st.1  second.01

                                                                                                place  place

resistor-color-chart.png?la=en-US&ts=4db

Single Black line with nothing else is a jumper or zero ohm resistor

you can have a sixth band for temperature coefficient ppm/k    failure and fire rating and the body of the resistor is normally blue for them

Brown  100 ppm/ºC (K)

Red        50 ppm/ºC (K)

Orange  15 ppm/ºC (K)

Yellow    25 ppm/ºC (K)

Blue       10 ppm/ºC (K)

Violet      5 ppm/ºC (K)

these last bits are sometimes used in Atari power supplies etc.

this is also why you might find charred remains in an 800 but there were no flames or the color is distorted making the band appear off in color or the body is blueish brown from heat.

 

 

 

Edited by _The Doctor__

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Now that you have the ANTIC issue straightened out, and you've already swapped the 4050 without result, the remaining color problems indicate an issue with either GTIA itself or its socket (the colorburst signal inputs or its LUM signal outputs) or the color trim pot as the next things to investigate.

 

If you have at least a multimeter, with the trimpot turned all the way to one direction, measure the input and output voltages. Then turn it about half-way and measure again. Then turn it all the way and measure a third time. Those values will confirm that (a), the pot is getting the correct input voltage and (b), that it's generally working correctly, or not.

 

If it appears that the color pot is working, and you are confident there are no issues with the GTIA socket, then you're down to the discrete components in the video circuitry, which can be a pain to diagnose. I'm not familiar with the PAL output circuitry, but if there are transistors involved, it seems to me that - being active components - are much more likely to fail than are resistors and ceramic caps. 

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18 minutes ago, DrVenkman said:

Now that you have the ANTIC issue straightened out, and you've already swapped the 4050 without result, the remaining color problems indicate an issue with either GTIA itself or its socket (the colorburst signal inputs or its LUM signal outputs) or the color trim pot as the next things to investigate.

 

If you have at least a multimeter, with the trimpot turned all the way to one direction, measure the input and output voltages. Then turn it about half-way and measure again. Then turn it all the way and measure a third time. Those values will confirm that (a), the pot is getting the correct input voltage and (b), that it's generally working correctly, or not.

 

If it appears that the color pot is working, and you are confident there are no issues with the GTIA socket, then you're down to the discrete components in the video circuitry, which can be a pain to diagnose. I'm not familiar with the PAL output circuitry, but if there are transistors involved, it seems to me that - being active components - are much more likely to fail than are resistors and ceramic caps. 

@DrVenkman  thanks. 

 

So to confirm:

 

I am happy the GTIA hip and socket itself is ok having replaced it yesterday with the precision round socket type, checking at the time when removing the old/install the new socket:

 

image.thumb.png.d87353eeb47a362037591a5defc737bd.png   image.thumb.png.e234a39939315921ff3e2f646c327bbd.png

I am also happy the GTIA chip is sound as it was transplanted into my 65XE and there are no probs. I also tried another GTIA chip (known to work) and that is ok.

 

I've swapped out the 4050 with 2 x other known working ones and it makes no difference.

 

I will test the trim pot as you suggest. (I've another on order alongside the 74SL74 replacement).

 

In the meantime:

 

Yup I was gonna focus on the transistors - just need to research how to test them, which ones to test and what I am looking for.

I also want to research the signal input lines for colourburst and LUM going into the GTIA so I know what and where to check.

 

 

 

 

Edited by Beeblebrox

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@Beeblebrox

2 responses as I typed my long winded end detailed post, you may want to re read it now that I am done with it.

try to measure from a further away pad with it's trace going to the dodgy pad.

I have seen people say it's good measuring from pad to chip pin.. but the break is at the union... so measure from the bus to the chip leg not the pad...

Edited by _The Doctor__
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