I recently had a short in my cigarette lighter and now the Empeg is stuck in AC mode. With the help of my backup unit, I was able to trace the problem to a transistor. It is located below the upper right hand corner screw on the main board. It has a marking "MG A6" on it. Does any one know where I can get a replacement for this part or maybe a similar one? Any info is appreciated. Thanks.

- Tom

Sure it's a transistor? I'm guessing since I can't see inside my empeg right now. Is it a SOT23 package? It could be single or a dual diode which can quite easily look like a transistor

See here:
http://www.semiconductors.philips.com/pip/BAS16W.html
http://www.repairfaq.org/REPAIR/F_SMD_trans.html

Ah...maybe that's the same problem I have... I'm pretty sure mine is not the AC sensor switch. I had a similar short when installing in my wife's car and one time when I put the empeg in it went pop and turned off. Since then, it will only boot in AC mode. PLEASE let me know if that fixes the problem.

If replacement of this transistor solves the problem, please notify me or follow up on this thread. I should like to update the FAQ entry about the AC sensor switch if that's the case.

Please also have a look at this thread:
http://empeg.comms.net/php/showflat.php?Cat=&Board=bigs&Number=151957&page=&view=&sb=&o=&vc=1

Thanks for the info. You're right, it's a diode in a SOT23 package. Looks like a common component. I'm going to see if I can find one in my pile of surplus parts.

http://www.fairchildsemi.com/ds/BA/BAS16.pdf

Fixed! My player is now switching between AC/DC mode. I found an "A6" diode on a Diamond Multimedia Supra Express 56i ISA modem. I'm glad I didn't chuck it when I switched to an all PCI MB. I'm attaching a picture of the component for those that would like to see what it looks like.

I hope this info will help you fix your player.

In DC mode, I was measuring 2.53V on pin 1 of the diode when it should be 0.5V

So does this mean that if the player is stuck in DC mode then it is the buffer ic and if it stuck in AC mode then is the diode? Oh well, I'm just glad that your player and my player is working like it should.

During the course of this little venture, I also decided to upgrade the HD to a Seagate Momentus 40GB. Couldn't have done it without the guidance of your excellent FAQ. Thanks Tony.

Can you edit the thread title to Defective Diode instead of Dead Transistor?

Could you elaborate (and use small words for the EE ignorant) on how to test to see if this is the same issue on my player? I have my player dissected and a VOM handy.

EDIT: Your picture was too large...it didn't attach

I think I've found it...is it between the +3v jumper and the top of the board? Also, how do I test it? Do I just put the red on pin one and the black on the player case and measure the voltage?

I have an Mk2...so I imagine it could be in a slightly different spot on my board.

Low Res: http://www.trung.com/empeg/A6-640x480.JPG
High Res: http://www.trung.com/empeg/A6-1280x960.JPG
Pin 1 and 3: http://www.trung.com/empeg/A6-PIN1AND3.JPG

How to test the diode:

1) See the pictures to help you locate the component.

2) You need to power your empep like if it was in the car before running the test. Don't plug the AC adapter into the power jack. Power the unit through the sled connector and make sure that the 3A fuse on the Yellow line is good. I use a regulated 13.8V power supply but you can use the AC adaptor. If you want to use the AC adaptor then the center is Positive and the outside part is Ground. Connect the Yellow line to the Positive center and the Black wire to the Ground of the AC adaptor. Since you are dealing with power lines please take your time and verify all the connections before applying power.

3) Connect the black lead of the VOM to the chassis of the player.

4) Now find the floppy power connector. It has a Blue, Orange, Black, and Red wire on it. Use the red lead of the VOM to check for power on the Red line. Double check your connections if you are not getting power.

4) Use the red lead of the VOM to measure the voltage at point 1. (see picture) The work area is very tight, so be careful you don't create a short.

5) If the diode is working, then the reading on the VOM should be about 0.5V. My defective diode was reading 2.53V.

Thanks for the great info!

I've been putting off posting back until I can get some pictures.
Unfortunately, my MK2 board does not have that diode (at least in the same place.) Evidently the rearranged some of that stuff between the MK2 and the MK2a.

The only pic I could find that looks like mine is this lower-res image I cribbed from mrmunsell's fuse replacement guide.



I'm going to snap some higher res pics soon and hopefully figure out what could possibly be the issue.

Ideally, if PCA could comment on what would be the likely suspect...

Stay tuned...

I've got my empeg on the test bench, but am not having any luck figuring out what's wrong. (Mostly from lack of knowing what to check.)


The camera I borrowed doesnt seem to be much better than the one above...here's the best shot I could get, even in macro mode.



I'm afraid I'll have to send it off to someone who knows what they are doing.

The component in there is only present in the mk2a, and helps to protect a 74LVX04 (IC33); on a mk2, pin 9 of one of these (the one nearest the unused internal LCD connector) connected directly to the power jack switch.

If AC/DC sense dies on a MK2, and the fault is *not* with the plug itself, then you need to swap out IC33 which is a bit harder than a SOT23 but not too bad. The biggest issue is getting a TSSOP 74LVX04, in fact.

Hugo

[blank stare] Oh. [/blank stare]

/me shuffles off to the back of the support line.

Seems easy enough to get a TSSOP 74LVX04. Quite easy to find and purchase actually. So the diode protects IC33 in a MK2A? And if the diode goes out, apparently the layout is such that IC33 still survives. Replacing TSSOP and SOT is a piece of cake.

Stu

You've got mail via your website.

Which one is IC33? This is a picture of a RIO/MK2a board.

The IC is available at Mouser Electronics
http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=304482&e_categoryid=97&e_pcodeid=51218

The top left one, ie the one closest to the connector labelled LCD

Hugo

I thought that was the one you were talking about but was not quite sure. Thanks for the info.

Tom

Which one is IC33 in an MK2? There are buffer chips on either side of the LCD connector pads.

Stu

Seeing as much of the brain trust is in one location this weekend, I thought I'd bring this thread back from the long dead.

What else can affect the ability to dectect AC or DC power? I had Ian replace the LVX04 chip at the empeg meet in Cincy two years ago. That didn't fix the problem, so Mark replaced the power jack for me a couple weeks ago. Still no dice. Empeg seems to work quite well other than this.

Pretty much you have only the level shifter IC (LVX04) and the GPIO on the Strongarm on an MK2 and the MK2A has a diode. I think maybe there is a voltage divider resistor network with two 12K resistors as well.

Nothing else there.
Stu

Nope. Never did solve it. If I have Hijack Force DC mode, everything seems to work as it should, so I never bothered. I'd be very interested if you find a solution. Hugo? Patrick? Anyone out there?

Hmmm. Usually when the display light goes out and nothing happens it's the 60v PSU trying to start but taking too much current and causing the system to brownout (and cycle). Did you have a look at the 60v supply? This should come on the instant the standby light stops flashing.

Don't think it'd be the power PIC (it's the PIC that turns the display on).

Hugo