18 replies to this topic

[brokenchip]

Hey guys,

I've been building my sammich kit over the last few days and it's been smooth sailing up to the part where the LCD screen failed.
At first it was dim and the contrast was horrible (I could just make out the word "Ready"). I tripple checked the Jumper settings and joined boards once again.

After turning the power back on I saw the backlight get very bright and then a small pop and the light went out. This was accompanied with the smell of something getting burnt out. Not to sure where the source of smoke came from but I could smell it stronger around T1, P1 and the resistors behind it.

I turn it off, unplugged it and went looking for any possible signs of damage but couldn't see any.

PSU that I'm using is the regulated 12V DC Powertech, switchmode from Jaycar. Cat No: MP3242.
LCD screen was the one supplied by Wilba. One thing that has puzzled me is the LCD has written on it 5V.

I'm going to be using 6581's and the Jumper configs are as follows: Jumper on 12v for backlight with jumper on JR4, SID jumper on for 6581 and both jumpers on JBP.

I made all voltage checks and all were correct, but I was getting a 12.1V reading on the 12V points which I didn't think was enough to cause an issue.

Also the Trimpot P1 was set at the 12 o'clock position when the LCD screen went out.

Would appreciate any suggestions.

EDIT: From my understanding the supplied LCD is a 5V and I positioned the jumpers to supply 12V. So I've given it 7V too much and cooked it.

Cheers,
Marty.

[Melted Hugo]

I also had almost the same problem, but I switched everything off quickly enough... My problem was the shunt in JR4. After removing it everything runs fine but the display is quite dark...
Can you let me know when you fixed everything so I can look at mine again and find out why my backlight is so dark? =)

[Gilesjuk]

I have both the 12v jumper and the high current jumper on my Sammich. It has the negative yellow LCD and that does say 5v on the backlight.

[brokenchip]

Giles, your screen came with the kit?

This has now really stumped me as to whats going on.

And Hugo, as I can make any sense of what's up I'll get back to you - but it may not be the same issue.

[Gilesjuk]

Yeah, I bought a kit from someone who hadn't built it.

But I have 8580s.

[brokenchip]

Anyone else got any suggestions?

[nILS]

After turning the power back on I saw the backlight get very bright and then a small pop and the light went out.

That was the backlight LED, which sank too much current.

If you don't need/want/care for backlight you should still be able to use the display, if not you want a new one.

[brokenchip]

Thanks nILS.

I'll replace the screen.

What should the jumper settings have been with the the supplied green screen? It's got me confused. Also, where can I pick up an identical LCD screen?

[nILS]

That LCD is pretty much an industry standard, so you should find matching ones @ mouser, reichelt, rs, digikey, ...

As per jumper settings: I don't know exactly which one you have (Wilba ships different ones with the different batches), your best bet is to write to him directly (PM or eMail), he typically has some spares, too ;)

[Gilesjuk]

Green screen as in green backlight and black text? or the inverse green text on black background?

[brokenchip]

My screen is meant to be the inverse green text on black background display. I've not had it working properly so I can't totally be sure.

Looks like I need a new screen due to excessive current destroying the backlight . I've sent Wilba an email to this thread so hopefully he'll shed some light.

Are there proper circuit schematics for both boards?

[Wilba]

The LCDs I supply are high-current, they can take up to 250mA but look good at around 100mA (brightness pot at half-way).
Since 100mA is a lot of extra current to go through the 5V regulator, the JBL header allows sourcing this current from the unregulated input power, i.e. around 12V.
But for some reason, a lot of builders have trouble with this - either the BC337 burns out, or the backlight. I'm not exactly sure why, as I've not had this problem myself.

I may have to change my recommendation, perhaps JBL should be set to 5V and let the 5V regulator run a bit hotter, and lessen the chance of burning out the BC337 or the backlight.

If you are having LCD issues, please email me directly and I will send you whatever replacement parts you need to get it working.

[brokenchip]

Thanks Wilba.

So in future you may recommend going through the 5V regulator with a shunt placed on JR4 to get the additional current (to get the 100mA)?

Otherwise I should just have the shunt set to 12V and no shunt placed JR4.

[Gilesjuk]

Perhaps people don't turn down the pot before first switch on? meaning it could be set really high on first test.

[brokenchip]

^ that could be part of the problem. Maybe the brightness pot should be set at the 8 or 9 o'clock position and then adjustments can be made up to and not beyond the 12 o'clock point.
When I powered up the LCD mine was set on 12.

Anyway, Wilba has kindly posted off a new LCD and I try a few things first with JBL at 5V. In Wilba's words "I would probably suggest leaving JBL at 5V until you know everything is working and switch to 12V if you're confident you have a stable and low enough voltage at the 12V rail (i.e. it's less than 12V not more). Or just leave it at 5V and keep the brightness down to less than half way."

Apart from this my sammichSID is working properly and sounds absolutely amazing!!! Thanks guys for the help

[brokenchip]

Wilba sent me a new LCD display and a 337 transistor. I've put them in and everything works well

[Gilesjuk]

Cool. Glad you got it going.

An OLED display is next on my list, although it may go in the MB6582 first. I put one in my PreenFM and they are seriously impressive.

Edited by Gilesjuk, 20 April 2012 - 12:15.

[brokenchip]

So pleased with the sound!!!

Giles, I'm interested in the OLED display.
Would you be able to post a link to the type you're looking at using? Any images of it up and running?

Edited by brokenchip, 24 April 2012 - 01:26.

[Andromeus]

Anyway, Wilba has kindly posted off a new LCD and I try a few things first with JBL at 5V. In Wilba's words "I would probably suggest leaving JBL at 5V until you know everything is working and switch to 12V if you're confident you have a stable and low enough voltage at the 12V rail (i.e. it's less than 12V not more). Or just leave it at 5V and keep the brightness down to less than half way."

Wilba sent me a new LCD display and a 337 transistor. I've put them in and everything works well

Which combination of settings do you use now and is acceptable for you? I'm also afraid about burning my inverse LCD which is labelled with 5V. Now I'm using 5V jumper with low current (no jumper) and it seems not enough bright even turning contrast whole up. I'm thinking about 12V from my power supply OR high-current jumper at JR4, but don't know about suitable power supply in the first case or maximum allowed heat of 7805 in the second case. Thanks for any recommendation.

Edited by Andromeus, 08 May 2012 - 23:07.