10watt guitar amp <x2> no power

  • Thread starter Thread starter Tremaine
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Tremaine

Tremaine

Chancellor of the EOPA
I got two ten watt amps that dont power up, i know its hardly worth bothering with but right now i got time, and i want to learn something. <as you can see by my other crapy post attempts>

Epiphone studio 10s that i found in the ditch <the speaker works and the tone pots dont feel scratchy.> and

Vibe V-10G that was given to me after a couple kids had it <probably pluged to many pedals into it>

neather of them power up, but both are complete.

i figure its probably the transformers, i was going to try to switch them but they are driffent, the vibe has a built in thermal fuse the epipone does not, the vibe has 2 ins and 2 outs, the epiphone has 2 ins and 3 outs.

i tryed to figure out how to test the transformers with my DMM, but i couldnt find any info that i could completely understand, and thou i tryed a few tests i learned nothing.

so what do you think people of the world? i await your further instrustions.
Peace World
Tremaine
 
Now why would you come to the conclusion that it is the power Transformers ?? Generally Speaking the Power transformer is the Last thing that would go , they are generally protected by Fuses , I would suspect any other Component first before the Power Transformer .....

Testing a Transformer is Simple , Apply Power to the Primary and measure the Voltage on the secondary .......
 
LED unlite

I guess i assumed that because the led light dont light up and its the next thing in the chain
transformer, on/off switch, led.
im just guessing you know, that why im here.

thats a very simple test, sounds like i might be able to do it. thanks for simplifying that.
Peace Duder
Tremaine
 
Actually there are other things between the Transformer and the LED Light like the Bridge rectifier or Rectifier diode which Converts the AC to DC , Most designs will use DC to power the LED even though LED"s can run off AC but it isn"t a very common practice ......

Just set your DMM to AC and Test the secondary of the Power Transformer , that will tell you for sure if the Transformer is the problem .......

I salvage most of my Power Transformers from Old Busted Equipment and i personally haven"t come across an Old piece of busted equipment that had a bad Transformer , even some old Tube amp Transformers that are over 40 years old , but I guess with some newer equipment were the Transformers are Just barely big enough to run the Circuit so are probably more prone to failure ......

Cheers
 
i tryed

i pluged the vox transformer in and put the V/ohm/mA lead onto the out from the transformer and it read 0.8 on both outs, ungrounded, and 4.2 grounded. did i do it right?
Peace World
Tremaine
 
I have no Idea , Doesn"t your DMM have any Settings on it ?? Mine has a seperate setting each for AC , DC , Amps , Resistance , Transistor HFE , Diode , Continuity , Capacitance , To measure the Transformer it needs to be Set to "AC" and the Transformer needs to be Plugged in .....

I have no idea if your Transformer has a single secondary , Dual secondary , Multiple secondary or center Tapped secondary , they type of secondary would determine what wires you test ......

What do you mean By Grounded and Ungrounded ??
 
Ac 200v

i set the dmm on AC 200v, sorry i thought i typed that, i guess i deleted it during my rereading correction.
the transformer has 2 ins and 2 outs and both outs give me the exact same reading. and it has a built in thermal fuse.
Peace World
Tremaine
 
Does your DMM have a Lower Voltage setting ?? There is a chance that the thermal fuze has blown .....
 
200volt AC minimun

im afard not <frown face> its a mastercraft Dmm, only has 200volt and 750volt AC , i dont know what you wood even use 750Volts for. power lines i guess.
any way i can get around it?
another test?
Thanks for your time man
Tremaine

and i know i cant spell worth a crap, i figure language is a man made thing, that holds no real value in the grand skeem of things, like math, so i dont spend to much energy on it, most people can decipher what im trying to type...
 
groundunded

*What do you mean By Grounded and Ungrounded ?? * <i just noticed this.>
grounded the black test lead from the dmm was grounded to the chassis, ungrounded it was just dangling around doing nothing.

the ic is a 4855DD, thought this might help to determine the type of transformer.
Peace World
Tremaine
 
Generally that is not the way you test it , if you have 2 secondary wires you would test the 2 Wires , while the chassis is allways connected to mains Ground that isn"t allways the same as the ground on the secondary of the transformer .....

Unless Im not getting what you are saying .....
 
ok, i see what you mean, the 'mains ground' is the ground of the power cord, running threw my walls and into the dirt underneath my crapy trailor.<right?> so, i should connect the two leads off the dmm to the two outs of the transformer, right?
im making sure this is right before i try it, because my brain is telling me that putting power into both leads of the dmm is a bad idea, and i dont want to die, right now. i mean wont it overload the thing, just a gut feeling. im kinda cautious around electricity, electrisity, E-leck-triss-city, you know.
Peace man, thanks
Tremaine
 
Yup thats the way to do it .... test both leads ....

The mains ground that runs under yer Grubby Trailer (and Under my Not so Grubby trailer ) is there so if there is a Short in the amp any voltage that gets to any exposed metal (like the chassis) will get shunted into the earth and not into you, it isn"t a ground in a sence that it will complete a curcuit , you need both leads of the single secondary transformer to complete a circuit ....


Cheers
 
0

i tryed it, and it read zer0 both ways. but if i only use 1 lead it reads something.
both leads from the transformer are red.
does this mean im getting + and - power? like needed for an op amp <remember i dont know what im talking about>
oh and the ground mains is ground straight to the chassis right from the plug.
Peace
Tremaine
 
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Well then it sounds like the Transformer is fried or the internal fuze is toast .... A Dmm will show a small ammount of Voltage untill it has been put in circuit then it will show the correct Voltage .....

The secondary needs at least 3 wires to get dual Voltages , One wire would be ground also called the center tap, one wire would have a positive Potential to the ground and the other a negitive potential to ground ......

There is a way to get Dual DC voltages from a single secondary Transformer useing a Half wave Voltage doubler but it isn"t suitable for High current applications but works OK for preamps useing opamps ....

Cheers
 
well crap

where do i put the new fuse? <joke> he..ha
so its garbage then, eh?
how close do i need to be for a replacement, the amp says 25watt, could i use 30 watt, or a wall wart? i know im pushing it now,you did says cheers, but im righting this down.
thanks for your paitence and understanding<--i feel like a bag licker saying this nice stuff all the time, but on the other hand i wouldnt want your goods deeds to go un..um..appreated, no ungratituded.
Peace Duder
Tremaine
 
Yeah , its probably humped , thats why i hate Transformer with thermal fuzes , can"t really fix them .....

You can use a Transformer that is bigger than the original but make sure the Output Voltage is the same , You can make a Pretty accurate guesstimate of the Voltage needed , the Amp probably uses a Chip amp of some sort so if you can find the chip in the amp (probably attached to a Heatsink) you can look at it"s Datasheet and see what Voltage it runs at , You can also look at the Power supply Capacitors and see there Voltage specs and know that the DC Voltage will not excede that Voltage which will help you extrapolate what AC Voltage Transformer you will need .... Remember that AC Voltage and DC Voltage are different and the Chip and Capacitor specs will be in DC .....

You probably won"t be able to use a Wall mart as they generally won"t supply enough current ......


Cheers
 
Minion are cool

Thanks man, your awsome. I'll try not to bother you for a while.
if i could and i knew how i would give you reps.
Peace man have a good day.
Tremaine
 
Hey , No problem , There is quite a steep learning curve so it can be a lot to take in at once .... If you need any help with stuff you can allways send me a PM , Im no expert by any means but I know enough of the basics to help you with most stuff ......

I also see you are a fellow canuck !!! greetings from the Island !!!


Cheers
 
I'll be back

Cool man, im on the far side of the vast Canadian Wilderness, in NS.

I got that other amp on this thread around here, but i have misplaced the pcb... i'll find it adventually. then i'll be back, or maybe i'll find a transformer in my junk, i'll do some reasearch thou before i bug you with that.

Peace
Tremaine.
 
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