O/S Mobile Authority 116ZX amplifier

[Madjimms]

Ok guys, I need some help finding out what output transistors I need to fix this amplifier. I can't find a schematic ANYWHERE on the web for these 1990-1993 amplifiers. I have found a bad transistor (shown in pic) So what the heck should I do? replace that specific transistor (which I can't find anywhere) or replace the whole set?

[Perry Babin]

The 1065s aren't output transistors. They're being used in the power supply.

Did you remove it from the board to check it? If not, all four of the 1065s should read as shorted in the board.

These older components are the types commonly counterfeited so you should be aware that any you buy may be counterfeit and not up to spec.

Did you check the rest of the transistors?

[Madjimms]

No, I did a visual inspection & the one circled in the picture has a burn mark, I read in another thread that they should be replaced in sets so that's what I plan to do. I don't know much about amp circuitry so I'm somewhat lost. I did a test in my vehicle & it powers on for like 2-3 seconds & you hear faint music & then the fuse blows & you hear a high pitched noise. Hope this helps.

[Perry Babin]

You need to use a multimeter to check the transistors to see which ones are defective.

[Madjimms]

Well I tested them while connected to the PCB, should I de-solder them & what exactly should I be testing for?

[Perry Babin]

Did you read the entire basic repair page (including the parts that you didn't think were relevant)?

You test to see if any are shorted as an initial test.

[Madjimms]

I searched for "basic repair" but couldn't find anything relevant, can you give me the link?.

[EDIT] I found the links on your profile :-D thanks.

[Madjimms]

ok I checked the transistors D1065, D1061 & the other small ones & they keep giving strange results. Sometimes they read shorted & then when I test the next one & come back they read fine. I'm not sure what to make of these. :-(

[Perry Babin]

If they're shorted, they will always read shorted. What's likely happening is that there is a parallel cap (those across the B+ and ground) that are charging and discharging making the meter read as though there is a short.

[Madjimms]

How do I fix it though?