I tried running my diecimila with an external power source (either 12v wallwart or 9v battery) - both don't work. - The power regulator (7805) gets VERY hot and the power-led is only dimly lit.
I thought the regulator might be broken and replaced it with a (slightly bigger) L7805CV TO220. Now the power led doesn't even light up anymore and the regulator gets too hot to touch after only 5-10 sec. Powering via USB or supplying 5V to the unregulated power pins does work !
Do you have the official Arduino diecimila made in Italy?
If you have a digital multimeter try to measure what your external power source is putting out and what voltage is getting to the voltage regulator and what voltage the voltage regulator is putting out.
Also as kg4wsv suggested, check for shorts and other problems.
Make sure that the voltage regulator you used has the correct pin configuration for your board.
Make sure that the voltage regulator you used has the correct pin configuration for your board.
In particular, the MC33269D regulator specified in the Diecimila schematic does NOT have the same pinout as a 7805 type regulator in the same package! (Something about the circuitry of LDO regulators causes the heatsink tab (and center pin) to usually be tied to Vout instead of GND.
At least one of the freeduino designs was modified back to use the 7805, on the theory that supporting higher input voltages (12V wallwart possibly at 16+V) was useful that supporting lower input voltages (less than 7.5V...) It's pretty much a toss-up, though.
@kg4wsv: I have nothing attached to the Arduino. - The polarity is - on the outside, + on the inside of the connector.
@gnu_linux: Yes, I have the one made in Italy.
@westfw, gnu_linux: Not sure about the polarity. - The 7805 has Vin, GND, Vout from left to right. It seems the MC33269D has Gnd, Vout, Vin - correct ? So the Vout of the original regulator is not connected to the board ? - Hmmm I don't really get it...
At least now I know that the regulator I used has wrong (incompatible) pinouts. I'm gonna try mounting it correctly but I'm not sure how it's gonna work with just GND and Vin connected...
Also: Am I the first person to fry a regulator ? I couldn't find any related posts to my problem with the dim power-led when running on the ext-power...
I suppose you could use a breadboard and jumper wires to route the voltage regulator pins to the correct pads on the board temporarily until you can get the correct voltage regulator for the board
You could also use an external regulated power supply
So the Vout of the original regulator is not connected to the board ?
The center pin (that isn't actually there) and the "body" of those smt regulators (soldered to a relatively large copper "heat-sink" area on the arduino board) are internally connected, so the Vout that you're worried about is handled via that "body" connection.
As westfw said, the center pin ( pin 2 ) which is cut off and is not connected to anything on the board itself, it is actually connected to the heatsink surface on the back of the regulator which is treated as pin 4 according to the datasheet
I connected the Arduino to a 8.4V battery and used wires to connect the 7805 (on a breadboard) to the solder-points on the board. - Nothing. Absolutely nothing. - Not even a dim light from the power led. When measured at the solder points on the board, the voltage seems right: 8.4V @Vin, 5.0V @Vout. The powerpins show 8.4V@Vin and 0 @5V, 0@3V.
Connected the 9V to the 7805, connected the GND and +5V to the powerpins on the board: works.
So it seems something else is broken ? Any tipps ?
The soldering iron is a good one - with temperature regulator , etc. - The thing is that I didn't know how to remove the 'broken' MC33269D - so I chipped and cut it with tools. But I don't think that this did any damage to other components. - Besides: How DO I remove the remaining piece of the old voltage regulator ?
Luckily I took two pics with my cellphone while I was doing the tests... You can see them here: http://www.rancho-relaxo.de/?p=75
If needed, I can take better pics today. Maybe I can test/measure something ?
I notice that you have the jumpers positioned to select the power from the USB port and not the external regulator. Move the jumper over, it's the one next to the USB socket.
How DO I remove the remaining piece of the old voltage regulator
You need a hot air gun with a fine nozzle, even then you run the risk of damaging the plastic components close by.
I notice that you have the jumpers positioned to select the power from the USB port and not the external regulator. Move the jumper over, it's the one next to the USB socket.
You may be able to desolder the regulator pieces and then solder a new MC33269D to the board
Don't put too much heat on because you may toast your PCB
Put a blob of solder on your solder tip then hit the big pad with that, it should melt the solder holding the regulator pieces to the board and let you pull the pieces off
Might be a little overkill for this task - I'd rather get a new Arduino (if needed). But tell me - Is this used only for de-soldering or what else are the capabilities of that thing ?
It's a hot air rework station you can use it for a variety of tasks including soldering and desoldering SMDs, such as SOIC, CHIP, QFP, PLCC, BGA etc. ( this is from their product description )
It can take a lot of practice to get good at it and the tips can cost a lot more than the unit itself
A kit of 33 SMT Hot Air Nozzles can cost about $600.00
I bought one of their units but haven't used it much and haven't gotten very good at it
If you're very lucky and very careful you may be able to desolder it with a good soldering iron and big blob of solder as suggested in my previous post
Well - putting the jumper in the right position really helped.
The Arduino now runs with the external regulator, connected to the 8.4V battery.
Now another problem: where do I get the MC33269D ? It seems that this is a rather exotic part - at least in Germany. All the shops I've tried don't have those. Is there another model that's pin-compatible and easier to get ?
Trying to desolder the old MC33269D now...
But I don't think that this did any damage to other components. - Besides: How DO I remove the remaining piece of the old voltage regulator ?
