ashd Posted April 18, 2007 Report Share Posted April 18, 2007 hi, i recently built a core module which does nothing on start up, the voltage seems to be right in all places, the pic was preburned with mios v1.9c, but when i turn the power on all that happens is the backlight switches on, i get nothing over midi and no characters on screen.i'm a newbie when it comes to this stuff, so i'm not really sure what to do, i did notice that apart from the lcd backlight turning on, IC3 (7805?) and the back of the lcd gets very hotany suggestions/help would be appreciated...thanksash Quote Link to comment Share on other sites More sharing options...
stryd_one Posted April 18, 2007 Report Share Posted April 18, 2007 The regulator shouldn't get hot with just the LCD and core.. If you remove the LCD just for now, then you can narrow the problem down to something wrong with the core or PSU. What are you powering it with? Quote Link to comment Share on other sites More sharing options...
ashd Posted April 18, 2007 Author Report Share Posted April 18, 2007 a 'universal ac/dc adaptor' 500mA, i've set it from 6v through to 9v with the same results (voltage regulator becomes boiling) Quote Link to comment Share on other sites More sharing options...
stryd_one Posted April 18, 2007 Report Share Posted April 18, 2007 Sounds like a short circuit mate :( Quote Link to comment Share on other sites More sharing options...
ashd Posted April 18, 2007 Author Report Share Posted April 18, 2007 so are there no components that i could replace to solve it,or should i just start again and build another one?also after buying a new multimeter rather tahn using the one i was (which is quite probably older than me), it seems that the voltage is actually around about 1.7 where it should be 5v... Quote Link to comment Share on other sites More sharing options...
dj3nk Posted April 18, 2007 Report Share Posted April 18, 2007 do you use a 9V PSU?Sounds to me like your 7805 is broken. solder it out and check the incoming voltage. Should be between 7V and 10V. (In the case your using a 9V psu its surely 9V). then solder a new 7805 in your core and measure for shorts. no shorts ==> test againgreetz Quote Link to comment Share on other sites More sharing options...
ashd Posted April 18, 2007 Author Report Share Posted April 18, 2007 the voltage on the psu is adjustable, and is set to about 7.5v, i actually replaced the 7805 with another earlier with no change in behaviour...does the polarity of the 7805 matter? Quote Link to comment Share on other sites More sharing options...
seppoman Posted April 18, 2007 Report Share Posted April 18, 2007 does the polarity of the 7805 matter?YES!!! If you put it in the wrong way, it will heat up and possibly your LCD and your Core will get too high voltages.Seppoman Quote Link to comment Share on other sites More sharing options...
dj3nk Posted April 18, 2007 Report Share Posted April 18, 2007 the voltage on the psu is adjustable, and is set to about 7.5vShould be enough, but with a backlighted lcd 9V is the better choice I think.The polarity matters a lot! Look at the pictures on this site and you see the right direction.greetz Quote Link to comment Share on other sites More sharing options...
ashd Posted April 18, 2007 Author Report Share Posted April 18, 2007 yeah it was as the pictures are, and i have just tried switching it round to the opposite of the pictures, with exactly the same results, (1.6v where there's meant to be 5v...) Quote Link to comment Share on other sites More sharing options...
ashd Posted April 19, 2007 Author Report Share Posted April 19, 2007 ...can you think of any other components that could need replacing? or would you recommend i order a new one from smashtv and start again? Quote Link to comment Share on other sites More sharing options...
dj3nk Posted April 19, 2007 Report Share Posted April 19, 2007 measure the caps. high (endless) resistance ==> finelow (no) resistance ==> shitwhats the input voltage at the regulator ?greetz Quote Link to comment Share on other sites More sharing options...
seppoman Posted April 19, 2007 Report Share Posted April 19, 2007 Should be enough, but with a backlighted lcd 9V is the better choice I think.when the PSU can deliver 7.5V, there´s no reason to use 9V. You´d just get even more heat on the regulator.But you should measure the current that is drawn from the PSU. If your LCD gets hot, I suppose the backlight just draws so much current that the PSU can´t keep up the 7.5 V. There are LCDs where the backlight can draw more than 500mA when adjusted to max. Either the backlight is turned fully up or you´ve got a soldering error around the backlight pot. Is the backlight extremely bright? can you adjust the brightness? You could disconnect just the backlight and find out if the core boots up without it.BTW, broken caps are extremely rare. The chances that exchanging caps or resistors brings any good are perhaps 1%. First again double and tripple check for shorts on the whole module.Seppoman Quote Link to comment Share on other sites More sharing options...
ashd Posted April 19, 2007 Author Report Share Posted April 19, 2007 well i changed a capacitor (c5 2200uF) for a new one and removed the lcd, now there is slightly under 5v (4.6v) where there should be 5, and when powered the module sends out several hundred 1 or 2 byte sysex messages (they seem to all be 00 0F or 00 0F 00), with the occasional clock, stop and active sense message over midi according to midi monitor... Quote Link to comment Share on other sites More sharing options...
seppoman Posted April 19, 2007 Report Share Posted April 19, 2007 4.6V is still too low - this Midi nonsense shows that the PIC is continuously resetting itself. I suppose the regulator still gets hot (even without display)? Again: please measure the current, i.e. disconnect one side of the supply wire coming from the PSU and put your multimeter inbetween in mA mode. another test: Disconnect core, pull out the PIC and the optocoupler, then measure the resistance between Vdd and Vss (e.g. PIC socket pin 31 and 32 or between the legs of the 2200uF capacitor). You´ve most definitely got a short somewhere. Use a magnifying glass and carefully inspect all solder joints.If you´ve got a decent digital camera, perhaps it would be an idea to post hi-res closeup pics of bottom and top of your board.Seppoman Quote Link to comment Share on other sites More sharing options...
ashd Posted April 19, 2007 Author Report Share Posted April 19, 2007 the regulator does not get hot anymore, and after adding solder to some joints i got 4.7 and after changing the psu voltage to '6v' (it sends out 9.6v at this, it sent out 7.5v before when set to an even lower voltage, i think the potentiometer on it must be misaligned) i now get 4.99v across vs/vd, on power i get 8 sysex bytes: F0 00 00 7E 40 00 01 F7 ...which is a good startup unless i'm mistaken, so now should i try reconnecting the lcd? Quote Link to comment Share on other sites More sharing options...
stryd_one Posted April 19, 2007 Report Share Posted April 19, 2007 Cool :) Go for it :) Quote Link to comment Share on other sites More sharing options...
Pablop Posted April 19, 2007 Report Share Posted April 19, 2007 Maybe this helps:I bought a 7.5V 1000mA wall adapter for the MIDIBOX, what´s supposed to be more than OK.It measures 9.5V when not connected to the MIDIBOX, but 6.5V when connected.It makes MIDIBOX run when no LCD connected, but when I connect the LCD nothing shows up in the LCD, and I have no SysEx commands sent.When I measure Voltages in the Core module I see that once the LCD is connected the voltage drops below 4.6V. So, I suppose this Wall adapter does not deliver what it says it does..I´m using the MIDIBOX with another WA without problem. Again: please measure the current, i.e. disconnect one side of the supply wire coming from the PSU and put your multimeter inbetween in mA mode.The current measured is 260 mA. That´s a shitty PSU, isn´t it?. It was supposed to deliver 1A!!! All other things taken into account, could this be your case?CheersPablo Quote Link to comment Share on other sites More sharing options...
doc Posted April 20, 2007 Report Share Posted April 20, 2007 The current measured is 260 mA. That´s a shitty PSU, isn´t it?. It was supposed to deliver 1A!!! All other things taken into account, could this be your case?That's ok. Your powersupply can deliver max. 1A . The 260mA is the amount of current your Midibox "soaks" out of the powersupply. If you soak 1A your PSU will deliver 1A. greetsDoc Quote Link to comment Share on other sites More sharing options...
Pablop Posted April 20, 2007 Report Share Posted April 20, 2007 Maybe I didn´t make myself clear:Shitty wall adapter, rated 7.5V 1A: * Midibox only works without LCD. Good 12V wall adapter: * Midibox works. Regulator gets hot, so I added a heatsink, but nevertheless I´ll buy a 9v one. * When measuring the current drain with this adapter, I see 260mA. (LCD connected)So, I say, the 7.5V 1A PSU isn´t really delivering what´s supposed to. Maybe this is also happenening to ashd? Quote Link to comment Share on other sites More sharing options...
dj3nk Posted April 20, 2007 Report Share Posted April 20, 2007 12V is too much for your regulator.whats "ashd"?greetz Quote Link to comment Share on other sites More sharing options...
ashd Posted April 20, 2007 Author Report Share Posted April 20, 2007 Maybe I didn´t make myself clear:Shitty wall adapter, rated 7.5V 1A: * Midibox only works without LCD. Good 12V wall adapter: * Midibox works. Regulator gets hot, so I added a heatsink, but nevertheless I´ll buy a 9v one. * When measuring the current drain with this adapter, I see 260mA. (LCD connected)So, I say, the 7.5V 1A PSU isn´t really delivering what´s supposed to. Maybe this is also happenening to ashd?It could be, i will try adding the LCD again when I get home tonight and see if it works, if not i'll measure the voltage etc. and try turning the psu up again. I'm getting a little worried about having to resolder that part of the board though, as it is starting to become damaged due to the amount of time the soldering iron has spent near it. I'll post again once i've attatched the LCD with the results. Quote Link to comment Share on other sites More sharing options...
doc Posted April 20, 2007 Report Share Posted April 20, 2007 12V is too much for your regulator.Sorry, but that is wrong.Take a look in the datasheet.The regulator can handle up to 35V of input voltage.12V isn't too much, if you use a heatsink.greetsDoc Quote Link to comment Share on other sites More sharing options...
seppoman Posted April 20, 2007 Report Share Posted April 20, 2007 Sorry, but that is wrong.Take a look in the datasheet.The regulator can handle up to 35V of input voltage.12V isn't too much, if you use a heatsink.I´d say, that´s only half-wrong. Off course you can also use 12 V, but there´s no point in using 12V for a 7805 because you only raise the need for a large heatsink and reduce the PSU efficiency. 7.5 V is really optimal as long as you don´t have other needed voltages from the same source (like in a MBSID).the regulator does not get hot anymore, and after adding solder to some joints i got 4.7 and after changing the psu voltage to '6v' (it sends out 9.6v at this, it sent out 7.5v before when set to an even lower voltage, i think the potentiometer on it must be misaligned) i now get 4.99v across vs/vdCongratulations :) But here we have the reason why it didn´t work with "7.5V". A simple adjustable wall wart PSU always gives higher voltages than selected as long as there´s nothing connected to it. But when you connect the core or even the LCD, this voltage will go down to the official value.This means when you supplied it with "7.5V", the regulator effectively got only 4.5 V (this was the selected value?). That´s not enough. I´d strongly suggest to select the 7.5V position of the PSU, then the voltage will really be around 7.5 V when load is applied (LCD).Seppoman Quote Link to comment Share on other sites More sharing options...
Pablop Posted April 20, 2007 Report Share Posted April 20, 2007 :)I know 12V is not the best, because it´s too much. I´ll buy a 9v adapter.Greets Quote Link to comment Share on other sites More sharing options...
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