JBL PRX 712 - Help!
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Category: General
Forum Name: Amp Forum
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URL: https://forum.speakerplans.com/forum_posts.asp?TID=101326
Printed Date: 23 April 2024 at 7:11pm
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Topic: JBL PRX 712 - Help!
Posted By: Earplug
Subject: JBL PRX 712 - Help!
Date Posted: 14 February 2018 at 11:18am
I´ve got a prx 712 amp module here that someone has "had a go at" and is missing some components.  Namely:- T501, T505, T508, D500, D503, D505 Anyone have the schematics, or able to identify the missing bits. At least that would help me get started on the thing. The preamp module is still working, so I´m hoping that it is not totally beyond salvation.  ------------- Earplugs Are For Wimps! |
Replies:
Posted By: doctor
Date Posted: 16 February 2018 at 8:19pm
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In the PRX712 powered speaker the S-PRO2 digital power amplifier
is used. |
Posted By: Earplug
Date Posted: 17 February 2018 at 1:09pm
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Ok, thanks for the heads up. I do know how bad they are, but replacement boards are stupidly expensive. A friend bought 12 of these of which 3 blew up fairly quickly. Fortunately the problem was just the the TVS diode (D522) - maybe a bad batch, or design fault? It´s just trying to replace parts that aren´t there is a bit impossible - and getting hold of some schematics would help as well...  Since posting, I have had a closer look at the board and noticed at least one discoloured IC (not sure of the number - 8 pin device between C504 and C506), so - as you recommend, will most probably pass on the repair. ------------- Earplugs Are For Wimps! |
Posted By: doctor
Date Posted: 17 February 2018 at 1:58pm
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Defected D522 (TVS diode) is the simplest defect, which arises
due to external overvoltage. As a rule, a board remains intact. Unfortunately, most boards are damaged due
to internal reasons. A method of fixing a board paying attention to discolored or blackened components is ineffective, especially for complex digital boards. In order to repair such board one need to know how SMPS and digital power amplifiers work. The simple example: discolored IC505 chip is the IRS21867S (MOSFET driver) - very simple chip.You need to read its datasheet and you must understand this so that you can explain its work to someone else. Try. Are you ready? |
Posted By: Earplug
Date Posted: 17 February 2018 at 5:14pm
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Ok, thanks for all the advice, but do you have the schematics? Then let me worry about figuring out how the thing works! ------------- Earplugs Are For Wimps! |
Posted By: doctor
Date Posted: 17 February 2018 at 6:36pm
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Pascal Audio does not disclosure schematics even for authorized laboratories. Their repair policy provides only the replacement of the complete module. I do not have these schematics. I fix such modules without schematics. |
Posted By: Earplug
Date Posted: 18 February 2018 at 12:48pm
Yes - just what I suspected. So much for building a more sustainable world! And why it´s better never buy crappy self-powered cabinets. From what I´ve seen, even the Crown plate amps JBL are now using aren´t that reliable either - especially in the heat we get down here.   ------------- Earplugs Are For Wimps! |
Posted By: Partyson
Date Posted: 04 May 2019 at 10:04pm
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a little bit late, but here is a list of parts that I replaced and everything earned the first time, some replaced by the closest analogues that were in stock
IC505 IRS21867SPBF /INFIN /SO8 T501.5.8 STF21NM60ND/ST/TO-220F IC500 UCC2893D /TI/UTD /SO16 most likely burned out resistor R507 (10 Ohm) I will be grateful for the hint which transistor is installed T511 he is feeding IC500 UCC2893D Thank! |
Posted By: Earplug
Date Posted: 05 May 2019 at 4:17pm
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Ok, yes - been a while. Thanks for the parts ID. ------------- Earplugs Are For Wimps! |
Posted By: doctor
Date Posted: 09 May 2019 at 2:23pm
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T511 is the BC857B. T501,T505, T508 are the STP26NM60.
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Posted By: Partyson
Date Posted: 10 May 2019 at 12:37pm
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thank you so much for the tip! The question on T511 is the transistor of the PNP structure, but on the base it has the same voltage as on the emitter and it is constantly closed, pressing the standby button does not change the situation. There is still some kind of malfunction, and this is not a dual transistor that controls the base t511, please give a part of the circuit of this chain
|
Posted By: huanvojnito
Date Posted: 11 June 2022 at 11:12am
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Hi Doctor! I have an amplifier like this, and I am confused a little bit. Do you can help me please? I am not sure to identify some of the components for change in the motherboard |
Posted By: sk760
Date Posted: 16 October 2023 at 5:08pm
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Hi, D504 what diode is? Is marked SK on body. |
Posted By: VECTORDJ
Date Posted: 17 October 2023 at 1:02am
| If Sound Guys would stop buying D-class than the Resellers would STOP selling it....D-class is non-repairable JUNK.....I have a large pile of Dead D-class Amps and Plate Amps with the local Metal Scrap Yard offering 8 Cents USD a pound....$8.00 per 100 Pounds Weight.... |
Posted By: Earplug
Date Posted: 17 October 2023 at 7:18am
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Haha, yes - you'd need a truck load of Class D blown amp modules to get anything from a scrap yard. They're far too light to be worth bothering... A few weeks ago, a friend replaced a blown amp in one cab he had with one of these:- https://es.aliexpress.com/item/1005006078974938.html?spm=a2g0o.order_detail.order_detail_item.3.571539d3QKBlYn&gatewayAdapt=glo2esp" rel="nofollow - https://es.aliexpress.com/item/1005006078974938.html?spm=a2g0o.order_detail.order_detail_item.3.571539d3QKBlYn&gatewayAdapt=glo2esp He was initially really chuffed at finding such a cheap replacement - and told me that it seemed to be great and sounded fine. It lasted about 2 gigs, then blew up.  The last powered cab I had here for repair was a Thomann thing. Amp module completely fooked. They wanted 200€ for a new module. The owner agreed with me - just stick in a passive xover & use and external amp. It is still working fine several months in. The only powered cabs I have are a couple of old JBL EON15 G2's. Maybe 20 years old and still going strong. I don't see any of the modern stuff doing that. And definitely nothing as simple to repair as the EONs. ------------- Earplugs Are For Wimps! |
Posted By: kedwardsleisure
Date Posted: 17 October 2023 at 8:28am
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Still got one here, I haven't heard from the client recently, he went very quiet when I told him the price of the replacement module and I hope he's alright.. https://forum.speakerplans.com/amp-internals-2_topic44897_post1069395.html#1069395" rel="nofollow - amp internals ------------- Kevin North Staffordshire |
Posted By: Earplug
Date Posted: 17 October 2023 at 8:52am
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Offer him one of those Alibaba things!  ------------- Earplugs Are For Wimps! |
Posted By: kedwardsleisure
Date Posted: 17 October 2023 at 5:06pm
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Not sure he'd be impressed. An icepower unit would be more suitable I suppose. ------------- Kevin North Staffordshire |
Posted By: Earplug
Date Posted: 18 October 2023 at 6:39am
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Yes, but those can be pretty pricey as well. No easy way out of the problem - other than turning the cab passive! ------------- Earplugs Are For Wimps! |
Posted By: sk760
Date Posted: 24 October 2023 at 2:20pm
Can help me someone ? Thanks.
|
sk760 wrote: