Poorly Vectrex - no sound or picture

[Tickled_Pink]

The Vectrex I bought in '84 stopped working about 3 or 4 years ago. I suspect it was because it was stored in a garage for a while.

 

There's no picture or sound. The bulb at the back of the monitor glows but that's all I get from it. I suspect that it's a problem with the logic board (no power?) but thought I'd ask here first in case someone had a better idea.

[CThiesUGP]

Have you done a cap replacement yet?

 

Sent from my SAMSUNG-SGH-I747 using Tapatalk

[Tickled_Pink]

No. Not yet. The power board looks almost as clean as the day it was assembled. All the caps that I can see look in pretty damned good condition.

 

The logic board is dusty though. There's a bit of oxidisation on the top of some of the caps (I'm assuming it's oxidisation and not leaking. The tops of the caps are flat and not bulging). There's also some oxidisation on the legs of the chips. I've checked that they're seated properly. TBH it would probably take a bit of effort to pull them out.

 

It was working absolutely perfectly until 3-4 years ago. Then one day I took it out to show someone and got nothing.

[vtk]

hi, it would be very helpful to know your level of technical ability, for example are you comfortable using a multimeter and checking for voltages?

 

ps. im in cornwall uk by the way, i'd be happy to look at it with you if by coincidence you are ever down this way (note: im right at the far end of cornwall though... Penzance)

[CRTGAMER]

Since you have the back cover off I am guessing you already did this. Did you adjust the brightness in the back?

[Tickled_Pink]

Yep. Adjusting the brightness was the first thing I did. I know what you're thinking ... No. There is no dot in the middle of the screen.

As for tech ability ... I can solder and use a multimeter. I should have two around here somewhere. I'll have to have a look in one of the sheds today.

I am wary of testing it with the cover open though because of the voltages involved.

[vtk]

hi, unfortunately i would suggest you do need to test it powered on with the back cover removed

 

i would have suggested to check the voltages at the 4 pins of the main plug which is attached to the logic board; the plug labelled J204 -- you will see four wires for the J204 plug, which (in some vectrex models at least) are usually coloured: yellow, green(ground wire), orange, red

 

you should measure the solder joints underneath the pcb where that plug is soldered, to make sure the power is going through the plug ok (because sometimes the pins become corroded, making the electricity struggle to flow through. or sometimes on those 4 pins if you have poor contact, you can bend the pins so that the plug attaches to them much 'tighter/firmer', making better contact). anyway, on the 4 pins you should read with your multimeter +5v, -5v, -13v, and GROUND. this is where i would start.

 

ps. you might get some tips from this video below.. perhaps have a look through that:

Edited December 28, 2015 by vtek

[Tickled_Pink]

Found a multimeter.

 

I'll give it a shot later.

[Tickled_Pink]

Managed to give it a quick test just now. Things aren't looking too good. Now when I turn it on I get a horrible white noise from it and the bulb at the back of the CRT sparks for a while rather than glows like it used to.

 

The voltages look a bit off as well.

 

On the power board side I'm getting +5.1, -4,9 and -12.72

[vtk]

hey sorry to hear that news

i'm not sure what i would suggest next, perhaps you could consider sending it to someone for a good look at/service, but then unfortunately the cost of repairs could add up if it has multiple issues

or perhaps try to sell it (for spares/repairs), there would be interest on ebay i expect

just the vectrex gamepad/controller sells well on ebay, perhaps around £30-£50 depending on condition

then with the funds from selling the faulty vectrex and the controller, this could go towards purchasing a working vectrex on ebay

 

or if you are quite keen to continue to try to get your vectrex working again

perhaps the white noise issue, is a problem with the AY-3-8910 sound chip

you could remove that sound chip from its socket (spray using servisol super 10 spray where the legs meet the socket first though, before trying to remove the chip, as i imagine it's quite stiff in the socket by now), give the socket a clean with servisol super 10 spray (and the legs of the chip itself)

if the sound chip does turn out to be faulty there are replacement AY-3-8910 on ebay for approx. £5 (must buy AY-3-8910 not AY-3-8910A)

 

regarding the crt sparking, im afraid i dont have any suggestions regarding that, as i would consider myself to be quite average regarding repairs/servicing, but not an expert unfortunately

[Rolo]

This is the point where you better print out the Vectrex-schematics and go to your local tv-repair-man, who can check the high voltages of the HV-transfomer (T502).

 

The filament of the CRT is supposed to get constantly something like 5 ... 7 VAC (I don't know the Vectrex-value) for heating the cathode. It is not supposed to sparkle or something, just glow constantly. All CRT-voltages are generated by the same transformer, which is a component, which is quite common to fail in old tv-sets. It is also generating the accelerator high voltage for the electron beam.

Sometimes those transformers desolder themselves, when ageing contacts are getting high impedance.

Or the driving power-oscillator may cause the problem for T502.

 

The CRT socket P501 is clean and in good shape?

 

But this is nothing you do yourself, if you don't exactly know what you do. If the transformer or a compatible type is still available, can be answered by an experienced tv-repair-man. Look for an older one, who really is into CRT-tvs!

Good luck!

Edited December 29, 2015 by Rolo

[Tickled_Pink]

Selling it is an option but I'd rather try and fix it first.

 

I have some NOS sound chips for various systems (I trade in ICs - low scale at the moment but hoping to ramp up in new year). Just checked what I have and I have a few AY-3-8910 (not the A ).

 

So I guess I can try that just to see if I get some audio out of it. I am a little concerned with the voltages I'm getting though. They are stable but whether they're within acceptable tolerances is another matter. I remember that my Veccy display always had a different look to a friend's. We both bought ours at the same time in '84 when they were closing out (paid £40 for it). While his score displays were quite large, mine were always noticeably more compact. Perhaps it's always worked under these voltages, which is maybe what led to the difference in picture?

 

 

Been doing some reading and boy - there is a lot of crap going around about the Vectrex. On one video I watched the other day the guy doing a repair said that there were more than 20,000volts on the CRT. To me, he sounded that he was blustering a bit. The method used to discharge residual voltages from the CRT also didn't make sense. The back of the CRT is grounded.

 

Earlier today I came across a forum post elsewhere from someone who explained where all the voltages are on the Veccy. He seemed to know what he was talking about. There are 7,000volts going through the CRT but because it's grounded it shouldn't cause any harm (I still won't touch it). In effect, by shoving a screwdriver under the suction cup all you're doing is grounding the wire, which is already insulated. The area to be wary of is around the transformer and some of the caps on the power board. Here you have around 175volts. There's a jolt waiting for you if you touch the neck board as well.

[Tickled_Pink]

This is the point where you better print out the Vectrex-schematics and go to your local tv-repair-man, who can check the high voltages of the HV-transfomer (T502).

 

The filament of the CRT is supposed to get constantly something like 5 ... 7 VAC (I don't know the Vectrex-value) for heating the cathode. It is not supposed to sparkle or something, just glow constantly. All CRT-voltages are generated by the same transformer, which is a component, which is quite common to fail in old tv-sets. It is also generating the accelerator high voltage for the electron beam.

Sometimes those transformers desolder themselves, when ageing contacts are getting high impedance.

Or the driving power-oscillator may cause the problem for T502.

 

The CRT socket P501 is clean and in good shape?

 

But this is nothing you do yourself, if you don't exactly know what you do. If the transformer or a compatible type is still available, can be answered by an experienced tv-repair-man. Look for an older one, who really is into CRT-tvs!

Good luck!

 

There is a small local business that's been in existence for about 40 years. Bought our first VHS recorder from them in the early 80s. I think it might be worth giving them a call to see if they can help.

 

Edit: Yeah. When I first took it apart the cathode was glowing. Been a while since I first opened it and the board attached to it had moved, so I gently pushed it back into place.

Edited December 29, 2015 by Tickled_Pink

[Rolo]

That sounds good!

The schematics print the voltages of the CRT. Quote from the service manual: "Turn brightness to minimum and measure the high voltage; it should be 5.8KV+/-150VDC." If you turn brightness up, HV goes up considerably. 7KV could well be the truth. Tv-sets with big CRTs sometimes really are using 20 to 30 KV. But this is just voltage, not current or power.

Pin 1: +170VDC

Pin 2: +50VDC

Pin 3: GND

Pin 4: 12VAC (there it is: filament)

Pin 5: -30VDC

 

CRTs are storing high voltages for quite a long time, due to the vacuum. It's like a big cap. I really would ground it, but not brutally with a screw driver but, via a cable and a big resistor (1MOHM).

[Tickled_Pink]

Did some more reading (I'm good at that ). It may be that the sparking is not be as terminal as it looks. Might be caused by an overvoltage. A monitor repair FAQ says that it's a safety mechanism, a bit like a fuse, to prevent damage to the tube itself.

 

So I am starting to think that all the problems with it are due to voltage issues.

[SiLic0ne t0aD]

If worse comes to worse and you don't feel like messing with it anymore, there are a couple guys on eBay that sell their Vectrex Repair Services.. both very reasonable but the shipping is the bad part.

[sideburn]

Wow I have almost the exact same scenerio. Pulled my vectrex out of garage after storing forever.

Power board looks perfect. But logic board has rusty / corrosion on lots

Of pins. But it could be fixable I think if I keep replacing chips and running the logic probe across it. Unless the ROM Itself is bad. BUT.... I have other problems..

Like yours, nothing happens on power up. But my CRT doesn't even glow. But the power cable to the logic board voltages are good. The transformer is putting out 20v. Each brown lead is 10 vots. Probing around the flyback transformer I get 133v readings. I've re-capped both boards. Still nothing. Trying to find out what makes the crt glow and what voltage readings I should see to rule out if my crt is toast or not before I even move on to figuring out what's wrong with the logic board. I've bought a bunch of replacement parts already but I'm starting to fear my CRT is bad.

Edited January 14, 2016 by sideburn