QSC PWM IC

[nickb]

Not possible!

Pin 5 is the output pin of the TOP210.
It should read +16Vdc.

I see no connection to the +rail that could possibly make pin 5 read +341 volts.

I think the PCB may damaged beyond repair.
Place a call to QSC & see what they want for the replacement board.

Edit: $514.00 PLX2 Module Assemblies

Jazz, I think you are confusing pin 4 (5V input) with pin 5 (switching output).

Pin 5 = 341V reasonable, but it should be switching so the exact voltage measured depends on many other factors (which it's best not to go into here).

It sounds like U16 is not working. Check D62 and C138. It's possible, but very unlikely, that T1 secondary is open. If that is OK then I''d be looking for a short on the 16V rail - Jazz suggested shorted caps way back in this thread - check the DC resistance from +16V rail to PriLo. If those are OK then I would get out (or take the plunge for) the isolating transformer and 'scope U16 pin 5 to see if it's trying to start up since you already replaced it.

[lowell]

D62 is fine. C138 is fine. T1:2 is not open. With neg lead on D62 anode and pos lead on PriLO I get 1.6ohms.

There is only 18ohms from +16v supply to PriLO. I removed C139 and 16v still reads 18ohms to ground.

Question: Why do all the +16v supply points on the schematic have a perpendicular line, but most, if not all other voltages are in boxes? I don't see where the +16v supply is created. This is making it hard for me to troubleshoot why the supply is disfunctional.

Thanks again for helping with this guys!

[nickb]

D62 is fine. C138 is fine. T1:2 is not open. With neg lead on D62 anode and pos lead on PriLO I get 1.6ohms.

There is only 18ohms from +16v supply to PriLO. I removed C139 and 16v still reads 18ohms to ground.

Question: Why do all the +16v supply points on the schematic have a perpendicular line, but most, if not all other voltages are in boxes? I don't see where the +16v supply is created. This is making it hard for me to troubleshoot why the supply is disfunctional.

Thanks again for helping with this guys!

The TOP210 creates the 16V supply via T1:1->T1:2 and the following rectifier D62 and reservoir capacitor C138. The string of 1N4148's drop the 18V down to 16V. The 16V is also divided down to 5V to feedback to the TOP210 which then regulates the supply.

Why aren't they in boxes - I don't now and I don't think it matters.

This is about as complex a SMPS as your likely to find. There are plenty of interlocks that will stop it from working.

18 ohms is too low - something is pulling that down.

[Jazz P Bass]

[QUOTE=nickb;407584]Jazz, I think you are confusing pin 4 (5V input) with pin 5 (switching output).

Pin 5 = 341V reasonable, but it should be switching so the exact voltage measured depends on many other factors (which it's best not to go into here).

It sounds like U16 is not working.QUOTE]

Yup.

Confused.

(I just started a third shift job & it is driving me batty!)

[lowell]

Checked U13 and C125 first since they seemed most likely to have shorted. Then U18 and C162. Lifted pin3 of U18 and the 16v supply is no longer shorted to PriLO. Need a new U18 IR2110. D86 is good. I'll try just the IC, and reconnect everything.

[lowell]

Manager of the club that owns this is suddenly pissed and wants it back in 2 days fixed or not fixed and won't pay anything if not fixed. Frustrating. Gotta track down an IR2210!! YAY! Customers are fun sometimes.

[Jazz P Bass]

Gotta track down an IR2210!!

IR2110PBF Stock and Price by Distributor

[lowell]

Thanks for that. Already had ordered it from Mouser but that's a link I'll be using in the future!

[nosaj]

Manager of the club that owns this is suddenly pissed and wants it back in 2 days fixed or not fixed and won't pay anything if not fixed. Frustrating. Gotta track down an IR2210!! YAY! Customers are fun sometimes.

Sounds like I wouldn't do business with him again after this one

[lowell]

Probably right...Sometimes saying "no" is the way to go!

[The Dude]

........A good reason to charge a bench fee/diagnostic charge up front. Aside from that, you have the gear and hold the cards. I would not release it until he pays you something for your time.

[lowell]

The Dude abides. Yes I agree. Now, I also perform regularly at this venue. So, I guess it's somewhat of a conflict of interest and I may need to suck it up on the amp. But who knows, maybe I won't. We'll see if this person acts respectful when discussing payment. I'll kiss a little ass, but won't suck a D#$%.

[Jazz P Bass]

Buy him a new PCB at $514.00

Repair this one at your leisure & sell it back, for the repair costs, as a 'backup'.

[nosaj]

Buy him a new PCB at $514.00

Repair this one at your leisure & sell it back, for the repair costs, as a 'backup'.

Seems like with the ultimatium lowell got I doubt the dude will spend that.

nosaj

[lowell]

Yah I'm pretty sure he'll get more angry if I even suggest that.