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Hi, i was wondering if i could get some help working out whats gone wrong with my master system?

I plug the unit up to the mains and my TV as per normal, power on but over RF and AV out i get nothing but a black screen (even over RF, a signal is being seen by my the TV), No sound, nothing

opening the unit nothing seems to have catastrophic failure (No bad caps and 7805 is still visably intact and no blown fuses)

the only thing i notice that seems off is IC6 and IC3 get painfuilly hot to he touch when powered on for more than a minute

inspecting the solder joints i see no bridges (except at JP1) or cold joints on the underside of the mainboard

im not super technically minded and only have a fairly basic knowledge on the subject so im stumped as to whats failed on it

any help solving this mystery i will be greatly thankful for

A visual inspection won't tell you a lot unfortunately. If you have a multimeter you can check the voltage regulator, the reset line and clock signals as a start.

Quote

the only thing i notice that seems off is IC6 and IC3 get painfuilly hot to he touch when powered on for more than a minute

That definitely isn't right. IC3 and IC6 (and IC7) are DRAM Chips. That don't get that hot, and not that quickly. That could be the fault.

If you can't fix it don't bin it. I'm sure the UK members wouldn't mind having a dead console for spare parts.

Quote

If you can't fix it don't bin it. I'm sure the UK members wouldn't mind having a dead console for spare parts.

For me not really an option as the console has substantial emotional value to me, if it was my model 2 system that had the issues i would have no quams about letting someone else in the community have it for spares but this one is a bit of a special case

Nobody's mentioned dodgy capacitors yet, it's often a thing to replace (electrolytic capacitors dry out and go out of spec after 30 years). If you can replace them it might help.

Maxim wrote

Nobody's mentioned dodgy capacitors yet, If you can replace them it might help.

i guess, but you think that would cause the overheating ram modules?, i mean is it possible for dodgy caps to cause a 0 resistance dead short bridge?

I always thought a dead capacitor usually cuts the current as a safety mech to protect the remainder of the PCB?

Aged caps generally loose capacitance and tend to become resistive as they dry out. They can also leak which makes a mess of things if they do. They can short internally too although some types are worse than others for that.

wasup wrote

They can short internally too although some types are worse than others for that.

hmmm... ill have to try and re-cap the board and see if that makes any improvement, would it be worth replacing the current caps with Rubycon ones? i hear the make some of the best on the market

This is most definitely caused by the dead VRAM chips, replace those (and the capacitors) and the machine should come back to life.

I almost don't believe it, but you still buy new 4168 DRAM chips.

I'm thinking of buying a few myself to keep as spares.

Author	Message
neocoyo Joined: 05 May 2018 Posts: 4 Location: United Kingdom	Black screen video issues on a SMS Power base (PAL) VA3 Posted: Sat May 05, 2018 4:17 am
	Hi, i was wondering if i could get some help working out whats gone wrong with my master system? I plug the unit up to the mains and my TV as per normal, power on but over RF and AV out i get nothing but a black screen (even over RF, a signal is being seen by my the TV), No sound, nothing opening the unit nothing seems to have catastrophic failure (No bad caps and 7805 is still visably intact and no blown fuses) the only thing i notice that seems off is IC6 and IC3 get painfuilly hot to he touch when powered on for more than a minute inspecting the solder joints i see no bridges (except at JP1) or cold joints on the underside of the mainboard im not super technically minded and only have a fairly basic knowledge on the subject so im stumped as to whats failed on it any help solving this mystery i will be greatly thankful for

asynchronous Joined: 14 Aug 2000 Posts: 742 Location: Adelaide, Australia	Black screen video issues on a SMS Power base (PAL) VA3 Posted: Mon May 07, 2018 3:11 am
	A visual inspection won't tell you a lot unfortunately. If you have a multimeter you can check the voltage regulator, the reset line and clock signals as a start. Quote the only thing i notice that seems off is IC6 and IC3 get painfuilly hot to he touch when powered on for more than a minute That definitely isn't right. IC3 and IC6 (and IC7) are DRAM Chips. That don't get that hot, and not that quickly. That could be the fault. If you can't fix it don't bin it. I'm sure the UK members wouldn't mind having a dead console for spare parts.

neocoyo Joined: 05 May 2018 Posts: 4 Location: United Kingdom	Posted: Mon May 07, 2018 5:17 pm
	Quote If you can't fix it don't bin it. I'm sure the UK members wouldn't mind having a dead console for spare parts. For me not really an option as the console has substantial emotional value to me, if it was my model 2 system that had the issues i would have no quams about letting someone else in the community have it for spares but this one is a bit of a special case

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14740 Location: London	Posted: Mon May 07, 2018 9:34 pm
	Nobody's mentioned dodgy capacitors yet, it's often a thing to replace (electrolytic capacitors dry out and go out of spec after 30 years). If you can replace them it might help.

neocoyo Joined: 05 May 2018 Posts: 4 Location: United Kingdom	Posted: Tue May 08, 2018 1:54 am
	Maxim wrote Nobody's mentioned dodgy capacitors yet, If you can replace them it might help. i guess, but you think that would cause the overheating ram modules?, i mean is it possible for dodgy caps to cause a 0 resistance dead short bridge? I always thought a dead capacitor usually cuts the current as a safety mech to protect the remainder of the PCB?

wasup Joined: 05 Nov 2014 Posts: 435 Location: Auckland - NZ	Posted: Tue May 08, 2018 3:29 am
	Aged caps generally loose capacitance and tend to become resistive as they dry out. They can also leak which makes a mess of things if they do. They can short internally too although some types are worse than others for that.

neocoyo Joined: 05 May 2018 Posts: 4 Location: United Kingdom	Posted: Wed May 09, 2018 8:43 pm
	wasup wrote They can short internally too although some types are worse than others for that. hmmm... ill have to try and re-cap the board and see if that makes any improvement, would it be worth replacing the current caps with Rubycon ones? i hear the make some of the best on the market

TmEE Joined: 31 Oct 2007 Posts: 853 Location: Estonia, Rapla city	Posted: Thu May 10, 2018 3:33 am
	This is most definitely caused by the dead VRAM chips, replace those (and the capacitors) and the machine should come back to life.

asynchronous Joined: 14 Aug 2000 Posts: 742 Location: Adelaide, Australia	Black screen video issues on a SMS Power base (PAL) VA3 Posted: Fri May 11, 2018 10:05 am
	I almost don't believe it, but you still buy new 4168 DRAM chips. I'm thinking of buying a few myself to keep as spares.

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