19v1000 big issue.

cleverlyj

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allright, so thanks to arcrevival (dave), i got a new transformer. got it wired in, and when i turned it on and tried to adjust the picture, the new transformer started to cook and i could hear a (cooking/popping) noise and it got pretty hot.

shut it off asap, but what would be causing this? need to fix that before i turn it on again.

edit - and also, will the transformer still be good, or does cooking it a bit once fry it permanently?

also, to add, the power wiring is set up to the 125v lug on the voltage selector. haven't adjusted the b+ or anything else yet, happened right when i turned it on.
 
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also, if it makes any difference, the transformer is from a cocktail space invaders chassis, but has the same input/output the other chassis does.
 
Sounds like you have a dead short someplace.

would it be a short in the wiring -> the chassis or a short on the chassis itself? and could it be something else backfeeding into the transformer or would it have to be before the transformer in the circuit?
 
just disconnected the output. i got a brief crackle, but am not getting it now... the transformer gets hot as hell, hot enough i have to remove my hand. is that normal?

one thing i did do was remove the fuses and swap them with the fuses from the chassis dave sent me. the reason i did that was because the fuses in there didn't have the values on them, wanted to be safe. i don't know if that changed anything.

also, i did measure the ac voltages from the output wires with the output disconnected.

100v measured 79 volts, 6v measured about 7v.

any thoughts?
 
i did go through the chassis and board and i'm not seeing any shorted components or broken legs, etc. one thing i did see -

in regards to the big can cap on it, the resistor along the side (1.5k ohm) measures only about 1.3 ohms across it but if i take it out of circuit it measures the proper 1.5. also, i did let the game stay on for a minute to see it come up - the screen has a big wave through it that kinda sits in one place. from what i've read, the big can cap could be bad. could that possibly be what's causing the transformer issue?
 
Let me look in the garage again. I think I have another transformer for that monitor.

edit: I just saw what you said about the hum bar. It probably is being caused by the big cap.
 
i did go through the chassis and board and i'm not seeing any shorted components or broken legs, etc. one thing i did see -

in regards to the big can cap on it, the resistor along the side (1.5k ohm) measures only about 1.3 ohms across it but if i take it out of circuit it measures the proper 1.5. also, i did let the game stay on for a minute to see it come up - the screen has a big wave through it that kinda sits in one place. from what i've read, the big can cap could be bad. could that possibly be what's causing the transformer issue?

That resistor - you said its 1.5K, is it reading 1.5K or 1.5 ohms? If 1.5 ohms there's your short.
 
I'm going to take a shot and say that there's a possiblity that transformer may have already been compromised or just aged to the point of failiure. If it got wet or humid the coils inside may have corroded.

Looking at the schematic (http://www.mikesarcade.com/arcade/monitors.html), it looks like that big can cap which is C101 A,B, and C filters all the major outputs, so it going bad can be bad. It also appears the transformer outputs go right to a bridge, so if one section of that bridge is shorted, its possible it could cook the transformer but I'm surprised the fuses didn't blow first. Make sure all your fuses are the correct values.

I'd next check the bridge, and try desoldering the + side off the bridge. According to the schematic you should have 97volts (maybe slightly higher with no load) there. If that looks good and the transformer isn't a crispy critter, then the next step may be to check Q101 for shorts or the big can.

Ya know -looking at this schematic makes me wonder if that transformer really is practically an iso with a 6v tap. 97v+6v=103v. Could possibly replace with an old game transformer thats an iso and power brick in one. Too bad I just threw one away (Crispy wires).

Yeah the more I think about it - 100v minus .7v times 4 (voltage drop on each diode of the bridge) and you have about 97 volts!
 
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Ya know -looking at this schematic makes me wonder if that transformer really is practically an iso with a 6v tap. 97v+6v=103v. Could possibly replace with an old game transformer thats an iso and power brick in one.

You are correct.

Edward
 
just disconnected the output. i got a brief crackle, but am not getting it now... the transformer gets hot as hell, hot enough i have to remove my hand. is that normal?

That's not normal. With the output disconnected, it still gets hot as hell? Are you still getting good voltage out of it as it heats up? Strange.

Edward
 
i tested the transformer last night. on the 6vac side i'm getting 7vac with no load. more importantly, on the 100vac side, i'm getting 79.5vac with no load applied.

note - i didn't test it without a load before i installed it, so i don't know if it was higher before.
 
yeah. after being on for 5 minutes or so, it gets hot to the touch enough i can only touch it for a few seconds before removing my hand. but, i don't know if it was this way to begin with. when i put it in i turned everything on and the transformer started to cook after a couple minutes that first time, so i don't know if it was working before i hooked it up.
 
Yeah the output being kinda low + getitng hot = no good. The transformer may have been sitting somewhere or got damp and the windings inside may have corroded and shorted.

I have an extra moto chassis but I think I promised it to someone a while ago.
 
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