Need some help identifying a component

[Jeeptechfred]

component

I’m working on a Helicon VoiceLive2. It doesn’t power up. I have no schematic. It uses a working DC 12v wall wart. I traced power into unit to a surface mounted blown fuse. From the fuse correct flow goes to device Q800. I suspect it is a transistor but markings are not directing me to any part. I added a photo. It appears that from Q800 voltage goes to a LM317 and a circuit that may be a DC to DC converter (can see several coils and a filter cap arrangement that suggests a split supply).
Thanks in advance,
Fred

 

[Binkman]

the IMG doesn't appear? Had to log in to view so I'll post it up.

 

[Jeeptechfred]

Great thanks!

 

[century tek]

Get a meter. That will tell you where the power stops.

 

[Jeeptechfred]

Yeah thanks

 

[Jeeptechfred]

The negative supply seems to be shorted. Smart ass answers don’t help. Positive answers might take me to a new point. I guess when I took the time time to post that was my hope.

 

[century tek]

Not a smart ass answer!

It is 100 percent legitimate that you need a meter and know how to use it before even opening. A meter is the repair persons best friend. You can test diodes, transistors, AC, DC voltages, resistors, transformers, just about anything.

Sorry if I upset you but maybe you should tell us your level of expertise before going any further!

In my 40 some odd years of doing this, a power problem is usually a fairly simple problem needing nothing more than a meter to diagnose.

 

[gslikker]

So basically you are trying to identify the Q800. So it could read as G511 from one side, C11 from the other side and then G5 from one side, or maybe the "11" are actually an 8.
Anyway the Q suggests it will be some transistor indeed, maybe even a dual one. (maybe even an opto device)
I find this SMD number link on the net but I do not see a match, less easy than expected https://smd.yooneed.one/
No idea how old this site is.
I presume you know the dots are supposed to be part of the number...

It can also be a .G58C with the C backwards on purpose, I do not know....
Note pin 1 is at the .G side so starting with ".G5-something" would be way to go.

just trying to help thinking..

 

[Jeeptechfred]

I did some checked online to try to decode it but came up short, went down some of the same thought trails. The 4 pins closest to the “q800” all are possibly all connected together on the board. Very hard to see and on a diode test possibly tests as a shorted transistor but I didn’t attempt to remove it to test out of circuit.
My level of experience is I have been a a Journeyman auto tech for 30 years. I took high school electronics for 3 years way back when. For the last 10 years, as a hobby, I have been repairing and building audio gear learning most from the internet and YouTube. I have been working the past 5 years at the local guitar shop as their head amp repair guy and have been quite successful. I am trying to push myself out of my comfort areas by taking on this project for a friend. The smd Stuff is challenging, especially with out a schematic.
My gut tells me that this transistor is Ok.

 

[Jeeptechfred]

I applied voltage to the unit with my variable power supply starting low and observing how to circuit reacts. I watched volts at the lm317 and at the filter caps of the suspected split supply. As I increase the voltage current draw remains low until I pass about 4v. I can see that voltage at lm317. I see voltage increase on the positive rail but negative rail remains at 0. After about 4 volts the current ramps up rapidly. I suspect that q800 is unlikely causing the negative rail to be pulled down.