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Vectrex (newer version - no buzz) - Troubleshooting Sound but no Video

The other possibility is that the through hole plating was damaged when you removed the capacitor legs, and only one side of the joint (solder side) was soldered. If the plating goes through the hole to the component side of the PCB and then on to further components, this may have compromised the PCB. This type of fault is easy to check (and repair) with an axial capacitor, but not so with a radial capacitor.
Done that myself before :-( I had to replace a capacitor on a multi-layer PCB and it was a pig to get out, Yep i damaged the through hole plating and confirmed it with my DMM, With the new capacitor in place I used Kynar wire, removed the insulation and several small lengths down and around the VIA ( just enough to protude above the solder pad ), Fluxed and soldered and it was fixed, Made a nice tidy job, I was dreading using patch wires if it didn't work.
I agree with you Dave. It was quite difficult to reach to the points with the iron yesterday without de- installing the board. And I guess because of missing the hole plating the solder would not flow through hence the blobs.
I actually underestimated this fault root cause. But apart from the time to spend it’s a kind of easy troubleshooting to measure continuity on all solder joints I have made. Some capacitors I have to pull out a bit to be able to solder on both sides.
Hi Dave, do you repair Vectrex? Am in the UK and have one that is working but needs some CRT realignment and buzz fixing. Thanks in advance!
As this is your first post - welcome to VCFED.

I am a bit rushed this morning (dental check-up); but I will send you a DM when I get back.

Update. I have now checked whether all capacitors I have replaced got continuity on both ends. I have checked by following the traces vs. the schematic. On the analog board they look all good.

Now I have this odd condition that the Vectrex only shows a dot on the screen and there is no game sound at all. AC and DC voltages are ok, just the -13V on the power supply to the digital board is missing (measured 0,8V). IC401 gets +9V and -9V.

Looks like the computer is not booting and thus there are no vectors. Very frustrating 😳 I have to figure out why the system does not start anymore…
Success! 😊

Today I found some time to take care about my poor Vectrex. After switching on and unplug/plug in the VDC connector to the digital board multiple times I never got the -13V available at the connector pins. It helped in the past but not anymore.

I measured +5VD and -5VDC on the major Chips without a problem though. I have checked with my scope whether there is life on the address and data Bus and yes there is! But no game sound. And no proper X,Y and Z signal.

So, I focused on the missing -13 VDC on the analog board. Input AC voltage is still good. Found AC voltage across C120. Good. Expecting some DC voltage across C121 (behind the diodes D106 and D107) but just some DC mV there. Strange. Found 2,1 VAC across D122 which is suspicious.
I turned off the unit and looked for shorts. And sure enough, capacitor C120 is shorted! De-soldered C120 and checked that cap on the bench. No short! Interesting. There is still a short across the pin holes of C120. Ok. So I de- soldered D107 and checked that one. Short! This Diode lets the voltage through in both directions.

And you know what, after replacing D107 I now get stable -13V. And the
Vectrex is working fine. Came right on.

I wonder whether D107 was only working marginally after it finally gave up the ghost. Is that possible? For some reason that short prevented the video game to boot.

I am still in doubt whether that’s all. Its too simple, isn’t it? I will see in the next days whether my Vectrex is now always booting up.

For the moment I am happy 😃


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Briefly update. I call this repair now successful. My Vectrex always turns on, also after many days stored in the cold storage room. Sometimes it takes 30 seconds or so until the unit turns on for a cold start. When stored in the warm apartment it comes right on. I also took the Vectrex to a party and the kids were playing for >6 hours without interruption.

Thanks again to Dave for his great help 👍😊


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>>> Thanks again to Dave for his great help

No problem. Glad you are happy...

Yes, an insignificant diode can just go open circuit or short circuit. It could have been stressed when it was installed many, many years ago and just fail for no apparent reason.

That is what makes vintage computer restoration 'fun'!

Most of the faults can be easily diagnosed, but it is the obscure faults that sort the men/women out from the boys/girls!

Some good diagnostic skills though to sort that out yourself. You learn quickly and are able to apply the knowledge you have learnt. Well done.