First PL700 Check Out

[wattsabundant]

Those JBLs are hard to kill. There is an urban legend that says a sound man once plugged a JBL cabinet (a pair of 15" woofers) into the 120V wall socket. The 60 Hz sound was so loud, he had to disconnect it. But it played the line voltage and they used it that night at the show!

Although I can't confirm this story, I seem to recall Cerwin Vega used to claim their sub could be plugged into the wall. Assuming an 8 ohm load and 120 volts at the outlet that would calculate to 1800 watts and 15 amps which would not blow a breaker.

 

[J!m]

I think this should be empirically tested...

 

[mlucitt]

I think this should be empirically tested...

Lee will do it, someone send him some JBLs or Cerwin Vegas, he won't smoke test his K-horns (at least not on purpose).

 

[laatsch55]

That's right, he won't...

 

[J!m]

That is some prime YouTube fodder right there.

“watch this! Here, hold my beer...”

 

[Kma4444]

So home for a little bit before I have to head out again tomorrow. The pic is of my progress sheet in comparing the right and left channels. Q5 showed substantially different values across pin1 and 2 as per my numeration process. I removed it and checked it with a transistor tester and it was fine. Pressing on you can see R3, C1 and C6 seem different on the right (trouble channel) than the left. Not sure if that points me in a direction or not. C6 on the left would show a value then go to infinity when checked in one direction then do the same with reverse polarity of the test leads. The right channel just shows infinity in both directions. Tests were done in diode test mode on the DVOM.

 

[kl0neMan]

Very nice set of amplifiers sir.

I am jealous also.

 

[Kma4444]

It's a neat collection for sure just have to get them up and running.

So here's the next 2 pages. You may be able to read my poor notes but C8 and C9 seemed out of place. Thinking I was on to something I removed them and checked with the little LC1 tester. You can see the results next to them. I presume they are fairly close to spec.

There were some others that didn't match the left channel but I'm not sure what I should check next. I'm headed out of town for a couple weeks so it's going to have to sit.

If anyone needs any interpretation of my scribble just let me know. I appreciate your assistance, I really do.

 

[Kma4444]

And it's good practice prior to assembling and installing a White Oak board. Probe slips, components put in wrong , etc, those are all learning experiences better learned on an old expendable board.
I have all components that board requires if you want to shotgun the whole mess.
Follow Don's recommendations and you should get this board up and running.

Maybe I should take you up on shotgunning this. I wish I had made some troubleshooting progress but I haven't. I'm back in town for a couple weeks and will take some time to maybe start removing components and testing them out of circuit. Thanks all again

 

[wattsabundant]

Were all of the readings made with the meter on diode range or resistance?

 

[Kma4444]

They were made on diode range

 

[wattsabundant]

The random order of the data taken, and lack of consistency makes it very difficult to make any determinations. At this point I don't even recall what the issue is.

 

[Kma4444]

Yeah, I can appreciate that, it is kind of random. The problem I had initially was a bad output transistor on the right channel. I replaced it and then when I got to setting bias, the left channel seemed to set fine and the right was 0 volts if I remember correctly. Let me go check back in this thread...... Yes, that was right, .371 on the left and 0 on the right. I suppose I should go back and go through the basics again at this point.

Thanks again