Bad Bob 5 board

[cigarbpedalmaker]

Hello,

I am trying to get into this and I am assembling the DSO 068 kit that I got for Christmas. I am to the part that all of the bob boards are installed and I am doing the first power up test (usb only). It passed the first part of the test, but after I close Jp4 and press sw12, the light does not blink. I took some voltage readings and it appears that I do not have any negative voltage at all. Bob 5 has +5 volts going into it just fine, but there is no -5 volts going out of it. Is it safe to assume that the board is bad, or are there other possibilities?

[jye1]

How was the voltage at +5V power rail? If it drops after BOB5 is mounted please remove BOB5 for the time being and proceed to test the rest. BOB5 generates negative voltage for the analog circuits. The digital circuits can work without BOB5.

[cigarbpedalmaker]

How was the voltage at +5V power rail? If it drops after BOB5 is mounted please remove BOB5 for the time being and proceed to test the rest. BOB5 generates negative voltage for the analog circuits. The digital circuits can work without BOB5.

The +5v rail was fine. Sorry about the late reply, but I am a college student and just have time to get back to this. My multimeter is not autoranging, so I didn't notice that not only is the -5v rail not producing -5v, it is actually producing -22.6 volts. I missed this before because of my lack of autoranging (trying to improve my lab.) Have you ever seen this before? I might have time tonight to remove Bob5 and see if all other voltages are correct.

[jye1]

I haven't seen such large negative voltage on this circuit but it is not impossible if something goes wrong. The output voltage is supposed to be regulated. If you see that voltage at out the regulator must be not working or damaged. Can you post a photo of the board?

[cigarbpedalmaker]

I haven't seen such large negative voltage on this circuit but it is not impossible if something goes wrong. The output voltage is supposed to be regulated. If you see that voltage at out the regulator must be not working or damaged. Can you post a photo of the board?

Here are some pictures showing the +5 voltage being just fine going into the Bob5 and the -22.4 volts going out. Also, I took pictures of the entire board. I'm not above hearing that I put something in the wrong place, but I have gone over the first section of instructions so many times that I am sure that I have it right. Also, using the temperature probe on my meter, with an ambient room temperature of around 20 degrees Celsius, the bob 5 board measures 40 degrees celsius. Everything else on the board measures around 30 degrees celsius.

[cigarbpedalmaker]

It seems that Bob 5 is not my problem. I removed it (which was actually pretty difficult with just solder braid) and the LED is still not flashing when I press sw12.

[cigarbpedalmaker]

I finally got GIMP to trim this picture down enough to upload it here.

[jye1]

If possible please try replace the crystal with any that has similar frequency (this is just for verifying so not necessary being accurate). The small cylinder crystal is easy to get damaged by heat.

[cigarbpedalmaker]

I do not have one on hand to replace it with. When the parts come in, I will try it. I have seen online that other people have had the same problem and that has fixed it.