Vectrex Question

[Platinum]

In the built in game on the Vectrex (mine storm) is there suppose to be any sound? I have messed with the volume and cannot hear anything. Thanks.

[InsaneDavid]

In the built in game on the Vectrex (mine storm) is there suppose to be any sound? I have messed with the volume and cannot hear anything. Thanks.

Yup, a "do do do, dooo.. do do do doooo..." when the mines are being spread and then explosion and thrust sound effects during game play.

[APE992]

If other games don't put out any sound you likely need to have the mobo recapped. Not difficult by any means just time consuming.

[Platinum]

Well I was told I need to discharge the system before I work on it, how do I do that?

[Squeept]

I generally don't worry about discharging capacitors unless working on a power supply. If you see caps the size of coke cans, treat them like a loaded gun.

[APE992]

I generally don't worry about discharging capacitors unless working on a power supply. If you see caps the size of coke cans, treat them like a loaded gun.

The Vectrex's built in screen could be a potential loaded gun as you put it.

http://www.repairfaq.org/sam/crtfaq.htm#crtsdc - some info here.

To paraphrase: get a high wattage resistor of a few megaohms in value, tap it to the positive of the capacitor and part of the metal chassis of the Vectrex.

Or you could make sure not to touch the capacitors near the CRT. Been shocked plenty of times by 120vac mains power but not by any capacitors inside anything that I know of. Plenty of hot heatsinks connected to voltage regulators too.

I've never seen the inside of a Vectrex myself but I'd like to think that the capacitors powering the screen are on a separate board from those on the main board. Or maybe they're on the main board as well but they should be pretty obvious given the large size and capacitance values of most capacitors for CRT displays.

Personally I'd replace those caps as well if you have the cajones for it. They're all about 30 years old at this point, every cap fails eventually and 30 years is a LONG time for them to still be functional.

Don't hesitate to send me a PM if you want/need more info/advice. I recap things all too regularly.

[Platinum]

Well I sure do appreciate this. The problem is that i cannot get any tools for this around here. is there some sort of method i can use with simpler hardware?

[APE992]

Well I sure do appreciate this. The problem is that i cannot get any tools for this around here. is there some sort of method i can use with simpler hardware?

Screw driver, soldering iron, and desoldering wick/braid or a desoldering pump are the minimum here. Rubber gloves would be a good idea in case of accidentally touching the capacitors.

Just be sure to document the capacitors as you go along.

[Squeept]

I think using a small DC motor (more likely to already have laying around) to discharge works fine, too? My dad used to say fuck it and just short them with a screwdriver.

I got bit by the cap in an old camera flash circuit once. It's a lot less like electrocution, and a lot more like exploding flesh.

[APE992]

Yep a motor would work too, doesn't even really need to actually turn the motor so much as drain the remaining power which it'd do.

You can short them with a screw driver and you'll find that bit of "advice" all over the internet but there is always the chance it'd ruin the capacitor in question. Then again if you're replacing the capacitor you're about to discharge who cares?

[FABombjoy]

If you're only symptom is no sound, I would forget about the capacitors and figure out where the sound is getting lost.

If you don't get any tones (the music), nor do you get a noise/crash sound (when you blow stuff up), then your troubleshooting begins at the volume pot (R326).

If it were mine, I would remove & reseat the brown audio cable connecting the CPU board to the power board. The contacts tend to build resistance over the years and I've fixed many a vectrex problem by just unplugging and plugging the interboard cables back in.

If it's not that, I would scope the input (pin 3) and output (pin 5) on IC103 and see if it's disappearing there. You could even just take an old small speaker, ground one lead, and use the other to probe those two pins. These pins are accessible from the back of the power board, so you won't have disconnect / discharge anything to test them.

[APE992]

The sound is getting lost somewhere between the cartridge and audio output. Why assume it's something more complicated than 30 year old capacitors which surely can't be up to par with their capacitance rating? Especially since it doesn't sound like Platinum has an oscope...

Though reseating that audio cable is a really good idea that is a lot cheaper than recapping the board. Do that first.

[DogP]

I personally wouldn't suspect the caps without doing other troubleshooting first either. Recapping a Vectrex is no easy feat, especially for a newbie without proper tools. The traces are basically waiting for an excuse to come off, so if you're not REALLY careful, it's VERY easy to lift traces. Not to say that the electolytics couldn't use replacing, but they don't generally fail in a way to completely kill the sound.

First of all... do you hear ANYTHING from the speaker? The Vectrex is notorious for a loud buzz or hum while on. If not, you likely have a general audio failure. I'd check the speaker, verify with an ohmmeter that it's approximately 8 ohms, as well as making sure the speaker connector (P103) is making good contact with the header (J103). You could also check for +9V with a voltmeter between pin 6 and pin 4 on IC103, which is the audio amplifier. This voltage should be present, as I believe this is the same voltage used in other parts of the system, and if missing, there'd be other noticable failures.

Assuming you don't have an oscilloscope, you can take some high impedance input, like a cut headphone cable connected to your PC sound card line in, or even simply a high impedance headphone, and connect the outer sheathing to pin 2, and one of the channels to pin 3 of IC103. If you have audio through the PC, then most likely your IC103 is dead (LM386). That part is common enough that Radio Shack even carries it - http://www.radioshack.com/product/in...ductId=2062598 .

If you do have some sound, give us some details... does the volume control have any affect on what comes out... if you listen very closely, do you hear very faint game sounds, etc?

Of course, be careful... and if you're unsure about anything, ask someone that knows what they're doing for help.

DogP

[FABombjoy]

The sound is getting lost somewhere between the cartridge and audio output. Why assume it's something more complicated than 30 year old capacitors which surely can't be up to par with their capacitance rating? Especially since it doesn't sound like Platinum has an oscope...

Sound is produced by a combination of the AY-3-8912 and 4052B, there is no sound at the cartridge.

I say skip the caps because if the Vectrex has booted and is stable, then there are only 2 capacitors of concern in the audio circuit. I realize he probably doesn't have a scope, which is why I suggested the speaker test.

FWIW, I have ran few different sets of original Vectrex caps through an ESR meter and more often than not they aren't out of spec enough to cause major trouble.

[APE992]

I'm well aware that the cartridge itself is little more than a data storage device and that the sound has to be generated somewhere. My point was just that the cartridge can be read but sound isn't coming out the other end which obviously doesn't do much in the way of narrowing down the problem but it was a start.

I also have to admit I'm not experienced with the Vectrex, at least not as much as you two seem to be.

The speaker test is quite labor intensive. I personally replace caps in almost everything that still has their originals for the sake of preventative maintenance. As I'm sure you know those two capacitors are all that are really needed to fail to remove sound though I'd expect something to come out of the speaker even if it was tinny/scratchy and almost dead silent. Got two GameBoy Colors here like that and I'm almost certain its a capacitor issue (could be a bad speaker but on both GBCs from different people?) given they sound just fine through the headphone jack.

EDIT:
Off-topic some more: it was in fact bad capacitors (2 100uF caps specifically) that was causing the sound problems on these GBCs.

[Platinum]

I hear NOTHING, no buzzing, no humming, turning the volume dial does not change anything.

Also, I only have one game and that is mine storm that is built in.

[Squeept]

and still off-topic: You got lucky with the GB Colors. The speakers in those things...I don't know what it is, but they corrode and rust inside and die. I've probably had 50 with no sound, and almost every one was the speaker.

[APE992]

and still off-topic: You got lucky with the GB Colors. The speakers in those things...I don't know what it is, but they corrode and rust inside and die. I've probably had 50 with no sound, and almost every one was the speaker.

Yep, brother's GBC did that too. Judging by how they look I'm not surprised they rust.

On topic: since there is absolutely no sound, there isn't a likely chance it'll be the capacitors.

[DogP]

With absolutely no sound, I'd HIGHLY suspect this section of the circuit:


The even with the volume control, audio IC, etc. not working, you should hear a buzz when the system is on. If the speaker, wire, connector, or amplifier was bad, you wouldn't hear anything.

My number one guess would be a bad amplifier, though the wire, connector, and speaker are the easiest to test, so I'd check them first.

DogP

[Platinum]

Well I'll have to check them out then I guess. Thank you.