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Amp Internals 2 |
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jbl_man 
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Joined: 12 January 2005 Location: London. Status: Offline Points: 11308 |
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 Posted: 19 July 2023 at 6:33pm |
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Fusible resistors? No Sir, we use fusible semi-conductors and IC's. You just have to replace all the burnt, or on-fire components.
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Be seeing you.
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ceharden
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Joined: 05 June 2005 Location: Southampton Status: Offline Points: 11851 |
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Posted: 19 July 2023 at 7:26pm |
Have you managed to get hold of the service info for these or have you just had to reverse engineer them? If you're replacing the uC then you must need to blow firmware onto them? |
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kedwardsleisure
Old Croc 
Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 5157 |
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Posted: 19 July 2023 at 11:58pm |
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No I haven't got the code for the micro, it's an Allegro something or other, not even sure if my programmer can do it. (I have a feeling I checked last time and it wouldn't) Either way it's likely to be read-protected so I have not gone to the trouble of removing a perfectly good SMD micro to find out.
Very poor when an IGBT failure can track right back to the micro. I thought the QSC PLX was bad with its fusible housekeeping transformer! Luckily the LA8 is pricey enough to warrant a set of new boards, however the repair will be a 4-figure sum. Although Camco (this is basically a Q10 with a posh DSP/Network adapter) refuse to supply parts, L'Acoustic will. |
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Kevin
North Staffordshire |
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ceharden
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Posted: 20 July 2023 at 10:01am |
I very much prefer SMPS with gate drive transformers. Solid state high side drivers are no doubt the cheaper and more manufacturing friendly option but you can't beat galvanic isolation for preventing an IGBT failure from taking out the rest of the SMPS drive circuitry. |
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kedwardsleisure
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Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 5157 |
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Posted: 25 July 2023 at 3:12pm |
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JBL PRX712. Looks like JBL have given up fitting crown-badged amps to their 'made in china' active speakers and are having them made in Mexico instead. Pascal amp module.
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Kevin
North Staffordshire |
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kedwardsleisure
Old Croc
Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 5157 |
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Posted: 25 July 2023 at 3:18pm |
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Very on-trend HK Audio 'Polar 12' bass bins with sticks coming out of the top.
A close-up of the amp module betrays it as a Soundking Artos-1000.  
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Kevin
North Staffordshire |
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kedwardsleisure
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Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 5157 |
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Posted: 25 July 2023 at 3:24pm |
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HK panel
 and the soundking 
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Kevin
North Staffordshire |
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kedwardsleisure
Old Croc
Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 5157 |
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Posted: 02 August 2023 at 10:05am |
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C-Audio TR850.
Never liked these particularly the over-protective protect circuit and the endless bodge wires and components soldered in at jaunty angles. An array of random fault lights on this example, no response to the switches, same old...  
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Kevin
North Staffordshire |
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EmPro
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Joined: 26 June 2020 Status: Offline Points: 992 |
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Posted: 02 August 2023 at 10:29am |
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That C Audio will be a waste of time....same as RA series....good for spare parts only...
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EmPro Audio
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simonp1100
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Joined: 01 September 2008 Location: Bristol Status: Offline Points: 1150 |
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Posted: 02 August 2023 at 10:40am |
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The RA series was fine, easy to repair and do sound sweet but they do run hot. The TR850 is a lovely sounding amplifier (RA driver stage and output drivers are 2SJ50 & 2SK135 then running into a load of MJ15025's) & i had a few running some bass bins, but from a engineering point of view are a pain in the ass due to the mass amount of mods and updates.
Edited by simonp1100 - 02 August 2023 at 10:48am |
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EmPro
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Posted: 02 August 2023 at 10:54am |
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well yeah....but i like an amp that doesn't breake all the time like those RA series
 ,running hot,lack of proper bass as the hitachi's goes into thermal limit due to the high temperatures...poor design of cooling,and the rest of the eternal problems they had with this series...the SR series on the other hand....even the Avitec Pro Beta Series were 100 light years better,based on the same desing the Beta series but with proper cooling design and protection.
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EmPro Audio
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simonp1100
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Joined: 01 September 2008 Location: Bristol Status: Offline Points: 1150 |
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Posted: 02 August 2023 at 11:24am |
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I agree. All of the RA series i had, i put a NTC on the soft start circuit & sprayed conformal coating around the PCB near the fan, never had any more problems with mine breaking after that, but again they run hot and poor design of the cooling.
The beta Series were better due to the 3U design, which allowed a bigger fan at the back but allows a lot more crap / dust going into the amplifier. The heatsink arrangement (heatsinks on each FET as well as the base heatsink) are a lot like the SR series & a lot better. The SR series had a few problems but mostly due to the poor design around the soft start PCB board & i had a few to repair with the power supply driving the TLO72 op-amp where the wirewound resistors were getting way to hot and over time affecting the tracking of the PCB board. I re-designed The SR driver PCB board as well as the soft start PCB with all the mod's that C-Audio recommended as well as a few "tweaks" to the pads & tracking etc and have used this to update my stock of SR series The C-Audio IA650 is another amp that also sounds good and has a lot of improvements on the RA series (better heatsinking. better soft start, and just uses an op-amp running a load of FET's), but never seem to take off.
 Edited by simonp1100 - 02 August 2023 at 11:36am |
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kedwardsleisure wrote:
