JBL LSR4328P

[Ripcord]

I am way out of my knowledge zone on this one but said I would at least look at these non working JBL LSR4328P monitors. Looking at the power amp pcb I saw three caps blown off the board. Attached picture. I replaced them, hooked up my bulb limiter, fired it up, bulb dimmed out. Bypassed the bulb, turned it on and pop, pop, pop. All three. That's all I know. Based off where the caps are, are you thinking TDA7293's are bad? Looks like the blown caps are all on the +VS rail. I'm guessing that the other monitor is the same problem but haven't taken it apart yet.

 

[xrk971]

Caps blow up when reverse biased or over voltage DC. Connect DVM
And let us know what the rail voltages are.

My guess is that it has a problem with PSU delivering more voltage than deigned for.

 

[Ripcord]

More poking around, I found a metal jumper, F1, I guess a fusible link type, that was open. Thanks X. I'm assuming I have to replace the blown caps, put it back together and run it on my bulb tester to check voltages?

 

[xrk971]

Those are smoothing caps so just remove blown ones and measure voltage before proceeding. The voltage will be there with or without them.

 

[r_merola]

Correct Line Voltage

Are you connecting it in an ac line voltage of 220~240Vac with voltage selection set to 110~120vac?
Do you have schematics of this monitor to us have a look and make more suggestions?
I will send you a PM.
Ronaldo

 

[xrk971]

No schematic but manual.

https://www.jblpro.com/ProductAttachments/LSR4328PLSR4326Pmanual[1].pdf

My guess is that it uses a linear PSU and there is a 120vac/220vac slider switch that switches the primaries on trafo. But can’t imagine that OP has it plugged into 220vAC by accident. Not is US anyhow.

 

[Ripcord]

Had to go to work so haven't had a change to test. Will keep you posted.

 

[r_merola]

No schematic but manual.

https://www.jblpro.com/ProductAttachments/LSR4328PLSR4326Pmanual[1].pdf

My guess is that it uses a linear PSU and there is a 120vac/220vac slider switch that switches the primaries on trafo. But can’t imagine that OP has it plugged into 220vAC by accident. Not is US anyhow.

I know US uses 120Vac line as standard, but how can you explain 50V electrolitcs and fuses bowing out?

I supposed there is some basic mistake in the use of this monitor.

Yes it uses toroidal power transformers. Linear PSU. I saw only 120Vac version in Brazil - NO switch to change line voltage.
Also could be a mistake in power transformer secondary connection. Who knows ...

May be Ripcord uses power generator in country side. It is usual as there is less loss in wires when you use 220V in big farms were you have big distances for wires ...
cherrs
Ronaldo

 

[llwhtt]

It looks like it's only blowing the + side of the power supply, a shorted bridge rectifier would feed AC straight to the capacitors and blow them up.

Craig

 

[Ripcord]

Update. I took the other one apart and same thing but this time on the minus rail, along with the two fusible wire fuses.

 

[xrk971]

Yes, but what is the voltage?

 

[Ripcord]

what is the voltage?

Sorry xrk, but I haven't measured it because I'm not sure how. I'm assuming I have to bolt the power IC's back to the heatsink which means when I plug the power transformer, which is bolted to the inside bottom of the box, back in to the pcb it will be face down in the box. And do I need to plug the speakers back in also? Am I overthinking this?

 

[xrk971]

Imagine you had everything ready to go with replacement fusible links and new caps. But leave off the caps and measure the voltage where the two cap pins are. We just need to know if the voltage there exceeds rated voltage printed on cap.