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Cmoy Help!

post #1 of 16
Thread Starter 

So I've been working on building the Cmoy here:




However it is not going so great...

When I got everything wired up and plugged in the DC powers the wires went up in flames eek.gif

I think there was problem a short or something and none of the other parts seemed affected so I've been trying to rebuild it.

I resoldered in the DC socket after replacing those wires (those were the ones that were set on fire), cleaned up some joints, and cleaned the whole board with isopropyl alcohol

The only thing is I'm not sure what caused the fire so I'm hesitant to plug it in again before getting the all clear from more experienced builders (you guys)


Here are some pics:






Is there anything that looks super wrong?

The joints that are fused together looked like they were fused together in the instructions and seemed to be linked on the circuit board but I may be wrong.

I also don't have the LEDs in yet because I'm not sure what polarity they should be oriented in. Could somebody tell me what order it should be from the orientation of the first pic from left to right? (eg: pos->neg->pos->neg)

Also, when I rewired the DC socket I made the longer lead the positive wire. I'm not sure if that matters since I couldn't find anything on it online.


Thanks in advance for any help you can give me!

post #2 of 16

Well, this won't be easy.  The photos are blurry, and I can't find a photo or drawing of the bare unsoldered board to look at.  I tried to improve your photo a bit, but there's not much to work with. Your soldering job is...well...a bit lacking.  The joints look sloppy, and there are many possible solder bridges.  I've circled some possible problem areas in the photo, but I really can't see enough detail to know if these are problems or not.  Check to make sure no solder from one pad bridges to any near by trails or pads.  


On the component side, you've melted the right hand connector pretty badly.  Look for a possible internal short. The parts seem installed correctly.  There's always a chance that the IC has blown, if you still have problems try removing it and powering it up.  If you don't toast the wires again, you might try replacing the IC. 


The LEDs are to be inserted according to the (barely visible) flat portions of the circles.  The LEDs have flats on them that should match the flats on the silk-screened location markings.


There's no need to clean the board with isopropyl. 



post #3 of 16
Thread Starter 

Hahah I think you should circle the entire picture in red tongue.gif


As you may have guessed this is my first attempt at soldering which explains why my joints are a little less than beautiful

I may be in over my depth on this one but I'll give everything you said a try, thanks a bunch!

post #4 of 16
In general it looks like too much solder and not enough heat. If you get the parts hot enough solder will just flow cleanly and evenly around them. You just don't want to heat the trails and pads so hot they separate from the board. I usually suggest people get a little experimenters board for radio shack to learn on before they try their real project. There are no doubt quite a few how-to-solder videos on YouTube.
post #5 of 16



...just read the first post...



post #6 of 16
Thread Starter 

Another question:


The amp runs on 2 9V rechargeable batteries. What power source would be suitable for running the amp from DC?

I think it was recommended to use 24V DC power supply. Would an 18V also work?

post #7 of 16

It depends on how many cell are in the 9 volt battery and if you

want to recharge them with it or not.

Rechargeable 9 volt batteries have either 6 or 7 cells.

Some may even have 8, but I don't know of any that do.


Anyway, 6 cell batteries charge at 9 volts.

7 cell batteries charge at 10.5 volts.


The 18 volt supply would be OK if you have 6 cell

batteries. You would need the 24 volt supply if

you had 7 cell batteries.


You need a current and voltage limited charger

for the batteries as well if you want them to

not damage them by charging them too fast

or with too high a voltage.


Of course, you may already have some other

way of charging the batteries, in which case

either 18 volt or 24 volt should both be fine.

post #8 of 16
Thread Starter 

Thanks for the quick reply!

I'm using these batteries: http://www.amazon.com/Tenergy-Centura-Self-Discharge-Rechargeable-Batteries/dp/B003QUNYQI/ref=cm_cr_pr_product_top

Not sure how many cells they have.


I am mainly going to be using this as a desktop unit so I am not too concerned about recharging the batts, just want to power the Cmoy.

What would happen if I were to remove the batteries and just use the 18v DC supply? Would that essentially be the same as the 2 9v batteries?

And what would happen if they were 7 cell batts and I used the 18v supply with the batts connected?

post #9 of 16

From what I can see, those seem to be 8 cell batteries.

They have a nominal voltage of 9.6 volts and take

12 volts @ 200mA to recharge.


The cmoy will work just fine in a desktop environment

with no batteries.


You can always use a switch to pick between batteries or DC supply.

Diodes can be used to much the same effect.

post #10 of 16

I wouldn't use a -24V supply[ if it isnt a split rail]-the JRC 4556 is only rated up to +/-  18V. Don't take my word for this I am sure there is an old post on this website on the same subject. Looking at it it doesn't look like there is a +/- regulator chip on the PCB. If there was it would need 4/5 volts more than the +/-18V its rated at. [to make the regulator function] or is there hidden zenner diodes--not a good thing to use on a audio ic as they are well known noise generators.Bad news in the front end of SS radio receivers.  If on the other hand there is no regulation then those diodes must be used in a simple voltage splitter to give  -/+ voltages. In that case you are reliant on the total voltage of the PU. so 24V would become = +/- 12V and 36V would become =+/- 18V.

Edited by duncan1 - 8/10/13 at 10:59am
post #11 of 16

There is a regulator on the board LM317, it is set for a charging current of 27mA (10% of the 280 mAh batteries), there is a tle2426 to split the voltage into +12/-12 if using the power adapter, or +9/-9 if running off batteries

the diodes are not used as a rail splitter but just to direct the power flow



post #12 of 16

So, with a 24 volt supply and those eight cell batteries, it should work perfectly.

post #13 of 16

Thanks for letting me know-Fred_fred2004. I must need new glasses. Is the LM317 in TO92 form in front of the chip? These are rated at = 100MA.

post #14 of 16

Yes thats the little sucker :-)


I dont use glasses - just a huge magnifying glass it's the only way these days redface.gif

post #15 of 16
Thread Starter 

Thanks for all the help everyone (especially you Fred, words can't describe how awesome you've been)!


So I'm guessing that this charger would almost definitely work: 


It says AC but if you look closely it is actually AC to DC convertor and goes up to 24V. 


Otherwise I'm looking at this guy: 



24V power adaptors are surprisingly hard to find tongue.gif

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