K8095 MP3 kit - LCD odd display

Kits Audio Hi Fi Projects
1

Got my MP3 player assembled, and it works beautifully, apart from the LCD screen. The screen lights up when power is on, but there is no display. When I do get a display, it’s all on one line and garbage, like “oo_-ie!/?>//////////////?” that just cycles across and then repeats. I’ve had it come on once or twice and display “Velleman MP3 Player” and got it to display the artist/song and the EQ setting, but that was twice out of about 50 boot cycles. More recently, it’s got no display at all. Not even black boxes on line 1 with the potentiometer set to max. Just backlighting.

I’ve checked resistance across pins 4 and 5 of J8, and they are not shorted. Visually double checked all the solder points around the PIC, the display socket, and ensured all connections are good on the display socket and board, also reseated multiple times. My friend has the same kit, and I’ve also swapped PIC’s just to ensure that it wasn’t the issue. What else should I check, or should I write it off as a bad LCD?

2

It seems that most probably the LCD module is defective.
You can return the whole kit for check/repair.

Alternatively you may do following test:
Swap the LCD module with a known good one to verify the module is defective.
Swap only the LCD module - do not swap the connector board in the header J10.
In this case you can just return the defective LCD module for replacement.

3

Haha, if only my friend had dropped the extra cash for the LCD display… I can return the kit, but it’ll be a while, because I don’t necessarily trust my ship’s postal services to not break it. A few months and I’ll see where I’m at. I think I’m going to read continuity pin to pin from the schematic, just to make sure all my bases are covered, and to be 100% sure that I don’t have any pins shorted to ground or to another pin. Thanks for the help, and I’ll post back if I find something, just to add to the knowledge pool.

4

OK -waiting for your test results.
You may also plug the LCD module to your friend’s K8095 unit.
Use your friend’s LCD adaptor board.
Just remove the “No LCD” jumper from the pin header J8, turn the contrast potentiometer to max and reboot.
If still problems, you can return the LCD display module for replacement.

5

All right, here goes. I tested pretty much every contact connecting to J10. Here’s my results:

J10, P1 to GND : .2Ω
J10, P1 to J10, P5: .2Ω
J10, P2 to D1 : .2Ω
J10, P3 to RV1 P2: .3Ω
J10, P4 to IC3, P24: .4Ω
J10, P5 to GND: .2Ω
J10, P6 to IC3, P8: 491KΩ through the socket, and 262KΩ on solder side. Also, IC3 P8 is a ground on the PCB, and the print layout indicates the same, but the schematic supplied, as well as the one on the website indicates otherwise. Moving on…
J10, P7 to IC3, P25 : .2Ω
J10, P8 to IC3, P26: .2Ω
J10, P9 to IC3, P27: .3Ω
J10, P10 to IC3, P28: .3Ω
J10, P12 to T1 : .1Ω
J10, P12 to LD4 : .2Ω

And lastly, J10, P11 to ground reads 11.75VDC, which should be OK, correct?

Also, the connections between J10/IC3 and J8 are all correct, with none shorting to ground. The only thing I find odd is the connection between J10,P6 and IC3,P8. Also, the fact that P8 on IC3 is a ground, but is not identified as such anywhere in the schematic.

Also, now that I’m looking at the schematic more closely, does LD4 need to be mounted for the LCD to operate? It looks like it might have to, judging by the way it is laid out on the schematic directly inline between VR1 and T1/J10,P11, but I followed the instructions and didn’t use it, since I was going to be using a backlit LCD. I would like to get a positive “yea” or “nay” before I go soldering something on that need not be on there. Also, my friend is dragging his knuckles building his, even though I’ve offered him use of my soldering station and my solder (a commodity while deployed, haha.) If he ever completes it, I’ll try the LCD in his unit, lol.

Looking forward to more expert advice from you guys! Velleman product support is great!

6

Thank you for the test results.
Everything looks OK so far.
You checked the continuity from J10, P6 to IC3, P8.
Actually J10, P6 is connected to IC3, P7 and IC3, P8 is connected to ground.
The circuit diagram you have is not very clear.
Here is the link to download better version of the circuit diagram:
box.com/s/97c50ec26c1f128cbf15

[quote]Also, now that I’m looking at the schematic more closely, does LD4 need to be mounted for the LCD to operate? It looks like it might have to, judging by the way it is laid out on the schematic directly inline between VR1 and T1/J10,P11, but I followed the instructions and didn’t use it, since I was going to be using a backlit LCD. I would like to get a positive “yea” or “nay” before I go soldering something on that need not be on there.[/quote] The board assembly is OK. There is no need to solder LD4 in case the backlit LCD is used.

7

Awesome. I see where I misread the numbers on the schematic. I’ll retest that contact just for the warm fuzzy feeling, but it’s looking more and more like a busted LCD to me. (The handling of packages isn’t very great out here, lol.)

I really appreciate all the help. Believe me, I’ll be using Velleman for all my future DIY projects.

8

[quote]I’ll retest that contact just for the warm fuzzy feeling, but it’s looking more and more like a busted LCD to me. (The handling of packages isn’t very great out here, lol.)[/quote]Indeed, most probably the LCD module is defective.

[quote]Also, my friend is dragging his knuckles building his, even though I’ve offered him use of my soldering station and my solder (a commodity while deployed, haha.) If he ever completes it, I’ll try the LCD in his unit, lol.[/quote]Yes, by doing this test you can verify the suspected fault.