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Post by sinistar87 on Nov 9, 2021 23:24:24 GMT -5
Hey everyone! Finally got a Vectrex for a deal after wanting one for years. Unfortunately to get said deal, it was broken.
So here's where we're at: As stated, no sound or picture/spot(even with adjusting the brightness) with Minestorm or a cart. However there is a faint hum from the speaker(amplifier still picking up interference?) and the tube's heater glows. I get all the correct voltages from J204: -5v, 5v, and -13v. I do NOT get 8.6vac between EP105 and EP106/104 like the troubleshooting guide calls for, I get about 11vac. There's a little discoloration from what would be below capacitors C411 and C404 on the power board if it's upright but I'm not sure if that's where my problem is from reading the schematics(I'm still a novice at that). None of the capacitors look bulged or leaky from the top.
I've reseated all the socketed IC's and I've reflowed some solder points. I haven't tried using any contact cleaner in the power/volume pot but I will if it sounds like that is the root cause of my issue.
Anyway, I hope I've provided enough info that a Vectrex repair expert can pinpoint my problem or at least guide me to what I need to do next. Thanks!
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Post by SiLic0ne t0aD on Nov 13, 2021 12:58:04 GMT -5
DEFINITELY clean that power switch! 🙂
It's a common problem and could possibly fix it. Some good contact cleaner such as Deoxit D5 should do the trick. After you spray some in from the back, cycle the switch back & forth a couple dozen times minimum. Might not hurt to follow up with some Deoxit Fader F5 after that, or even a bit of dielectric grease. Anyways, try that and let us know how it works out. 👍
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Post by sinistar87 on Nov 13, 2021 22:31:03 GMT -5
So I've been picking at it off and on for the last few days and here's some more info:
-Used contact cleaner in the power/volume pot, no change with the picture and sound however it's not scratchy when I change the volume anymore lol
-As stated I get almost 11vac out of the transformer, but I've also discovered that the 9v dc rail runs at almost 13v and the -9v runs at almost -14v... I can't imagine that's good, but like I originally posted all the voltages going through J204 are correct.
-I tested the diodes out of circuit and they all tested good.
-I also replaced the 2 capacitors that had some green flakey stuff at the bottom.
-I've run continuity tests all up and down the 9v and -9v traces with no obvious breaks.
I'm almost wondering if it's playing completely blind, like the game is running but there's no way for it to get the picture and sound out... It just seems so weird that I can be getting the correct voltages to the logic board but the power board is so messed up. Ngl, this is way above my level of electronics knowledge so i am kind of flying in the dark.
I'm guessing someone might ask so just to be safe, I only have a multimeter at hand. I don't really have access to a scope or high voltage meter.
Appreciate anyone who can help, thanks!
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Post by kokovec on Nov 14, 2021 14:23:34 GMT -5
It's so tough to troubleshoot without having the unit in front of you.
I'm guessing there's a bad chip somewhere.
In this case there's no picture and no sound.
If it's not power related then it might be a bad CPU.
Without an oscilloscope it's almost impossible to trace down problems like these unless you get lucky.
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