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EmPro View Drop Down
Young Croc
Young Croc
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Joined: 26 June 2020
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Points: 766 		Post Options Post Options   Thanks (0) Thanks(0)   Quote EmPro Quote  Post ReplyReply Direct Link To This Post Posted: 21 December 2023 at 8:59am
Originally posted by jbl_man jbl_man wrote:

Well done for repairing that one, are those Alps pots still available new?

 
I'm affraid not....i search for and no results....(unless from China the 20k version i need)thats why i was forced to repair this ones...but jesus christ...this bloody thing running hot as hell,in 2 min from powering on the fan is starting already...that indicates at least 60c on heatsinks Dead

However,is working flawless Big smile but i'm going to touch the Bias little bit Tongue


Edited by EmPro - 21 December 2023 at 9:06am
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Points: 11155 		Post Options Post Options   Thanks (0) Thanks(0)   Quote jbl_man Quote  Post ReplyReply Direct Link To This Post Posted: 21 December 2023 at 8:49am
Well done for repairing that one, are those Alps pots still available new?
Be seeing you.
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Young Croc
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One ch is done,already working as a dream,this is the second ch pott that i restored Big smile also i glued the base on the board,so no presure will be on the solderings and pins again.
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Young Croc
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Joined: 26 June 2020
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Right now i'm rebuilding the pins on ALPS pots to fit them back in my PPX Dead
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Old Croc
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Joined: 16 January 2007
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Points: 2433 		Post Options Post Options   Thanks (0) Thanks(0)   Quote GAZ. Quote  Post ReplyReply Direct Link To This Post Posted: 20 December 2023 at 7:30pm
You might be surprised. The PPX I bought that had been on fire inside still had some usable parts. All but 2 mosfets survived, power supply, alps pots all good. The pcbs were a bit too far gone though.
100% Earth Moving Bass
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Young Croc
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Joined: 16 March 2013
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Originally posted by EmPro EmPro wrote:

Originally posted by jbl_man jbl_man wrote:

^These do run quite hot, even on idle the fan will cut in and out every 10 mins or so. 
Because the manufacturers like to over bias the poor l-fet's to the point of negative coeficient temperature to operate for best sonic experience (at least this is what mr Ben Duncan told me couple of months ago while i asked him why my Rauch amplifier running hot as hell in 2min from turning them on,the bias is fixed in them,so to moddify the bias,parts needs to be changed,also Mr Duncan told that L-Fets are not bothered by high temperatures...however resistors and other parts are!!


My Rauch DVT 250s would run hot too, even with an easy midrange load. I bought a huge fan to blow against the rack instead of swapping them, as they did sound super.
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100% you have the updated version and this one is the older version Smile
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Originally posted by EmPro EmPro wrote:

RSD Studiomaster Mosfet 1000 one ch done,next one will follow the same procedure:

Yup, really weird how my ones have 12 Hitachi, 6 k135, and 6 j50's, and also have the soft-start relays on that bottom board too. Obviously there was a update at some stage, but wonder who has the earlier version. 
Be seeing you.
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Originally posted by shaun1264 shaun1264 wrote:

I know of someone who had a PPX900.  He had is stored in the back of a lorry for a long time on the floor.  Damp too.  I watched him pull it out and switch is straight on even after I recommend him not too!! A very nice firework display out of the grills and then a few flames.   Shame really. 

Yep...bye bye mosfets....bye bye driver boards...good for scrap Dead
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All my L-Fets amplifiers except Rauch ones are lowered in bias and had a normal behavior under normal usage :) i really don't need the negative coeficient to operate :) as they sound cool without 90c on the heatsinks LOL
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Young Croc
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Joined: 26 June 2020
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Points: 766 		Post Options Post Options   Thanks (0) Thanks(0)   Quote EmPro Quote  Post ReplyReply Direct Link To This Post Posted: 19 December 2023 at 5:35pm
Originally posted by jbl_man jbl_man wrote:

^These do run quite hot, even on idle the fan will cut in and out every 10 mins or so. 
Because the manufacturers like to over bias the poor l-fet's to the point of negative coeficient temperature to operate for best sonic experience (at least this is what mr Ben Duncan told me couple of months ago while i asked him why my Rauch amplifier running hot as hell in 2min from turning them on,the bias is fixed in them,so to moddify the bias,parts needs to be changed,also Mr Duncan told that L-Fets are not bothered by high temperatures...however resistors and other parts are!!
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Joined: 26 June 2020
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Points: 766 		Post Options Post Options   Thanks (0) Thanks(0)   Quote EmPro Quote  Post ReplyReply Direct Link To This Post Posted: 19 December 2023 at 5:28pm
RSD Studiomaster Mosfet 1000 one ch done,next one will follow the same procedure:
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