Another Parasitic Draw - Fuse 22 - JBL System

[Godzilla2y]

I received a package in the mail over the weekend (Thanks, Turtle!).

This is pretty similar to my old amp but, unfortunately, it's not the same. Notably, this new amp is missing one of the connectors that the old amp had.

I think it's the VBatt and GND cables present in the 96 wiring that is missing from this one:

Can I try plugging this new amp in without plugging in those wires?

Internally, beyond the regular circuitry upgrades that were common at the time (like the update to green silicon boards and traces being visible up top), these amps also look very similar. They also flipped this board in the housing and simplified the assembly process. Country of origin changed from Mexico to China, too.

Please ignore the messy desk. As you can tell from all my posts, I've got a lot going on around here.

Worst comes to worst, I think I can just desolder the components from the new amp and stick them into the old amp.

Do any of you have the radio wiring diagrams for the 2000 MYs? I'd like to know if the pin locations are the same. I would think so, considering it's the same generation, but I wouldn't put it past an OEM.

 

[Turdle]

Make sure to change the larger, heat sink transistors also. Might even swap out all caps you can match.

 

[Godzilla2y]

Got to work on the electronics the past few days. I was able to match the resistors from the new one with the blown resistors in the old one--56 Ohms, according to previous posts on the forum.

Unfortunately, the transistors in the new amp were not the same. After getting it all together (including adding a few jumper wires where needed) and plugging it all in, the amp still doesn't work. No magic smoke escaped during my tests, and I didn't smell that classic "molten electronics" smell, which is probably a good sign. And yet amp no worky.

So. Can anyone help me decode the transistors from the old subwoofer amp? Google has been of little help.

The transistor reads 1101CB PH50 (or maybe P H 5 O ?)

The new ones I put in read 110 1CB M938

These were the closest match I could find to the old ones (both 110 and 1CB matched), but it's possible the PH50/M938 is actually the important part.

Both of these transistors are common on both amps--whereever the PH50 existed on the old, it has been replaced with the M938 on the new. But what's the difference between them? How do I find out?

 

[J_C]

If the new transistors were located in the same part of the circuit on the "new" amp, biasing the output transistors, and given they were both 1101CB, it is probable that the new transistors are compatible enough, even if the gain is different, and that you have some other problem.

The circuit configuration should be that you have the audio signal going into the base pin of the transistor, when audio is playing and IF it is receiving that audio signal, a voltage feed on the collector pin, and the emitter pin output, drives the large output transistor on the heatsink. This means you can measure for signal getting to it, voltage in, voltage out, and similarly measure the large transistor on the heatsink in case it's blown.

 

[Turdle]

Have you verified the amp is getting the 5 v switched power from head unit, , and, is turning on?

 

[Godzilla2y]

If the new transistors were located in the same part of the circuit on the "new" amp, biasing the output transistors, and given they were both 1101CB, it is probable that the new transistors are compatible enough, even if the gain is different, and that you have some other problem.

The circuit configuration should be that you have the audio signal going into the base pin of the transistor, when audio is playing and IF it is receiving that audio signal, a voltage feed on the collector pin, and the emitter pin output, drives the large output transistor on the heatsink. This means you can measure for signal getting to it, voltage in, voltage out, and similarly measure the large transistor on the heatsink in case it's blown.

Is it possible for a transistor to blow without any external indications? Similarly, is it possible that I blew them via too much heat when I tried to desolder or resolder them? My soldering iron isn't ideal

 

[Godzilla2y]

Have you verified the amp is getting the 5 v switched power from head unit, , and, is turning on?

I'd do this by checking voltage from vbatt to ground at the plug for the amp?

 

[J_C]

Is it possible for a transistor to blow without any external indications? Similarly, is it possible that I blew them via too much heat when I tried to desolder or resolder them? My soldering iron isn't ideal

Yes, and yes, but whip out the multimeter and do the measurements.

If power isn't getting to the collector pin, or signal to the base, then it's not the transistor. If power is outputting on the emitter pin (signal out) to the larger transistor, then it's not that smaller transistor. Well, it could still be, if it is failed to a shorted state, but then you'd be getting a terrible high output and the speakers could blow, and this shorted state could be found by measuring output on the emitter without speakers connected or even audio playing.

Power input can be measured any time the amp is live, with the 5V "on" signal from the head unit if that is applicable (IDK, just going by what others stated). Signal in and out requires audio to be playing.