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OHM FL Series amp

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JOLD View Drop Down
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Joined: 21 April 2021
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JOLD Quote  Post ReplyReply Direct Link To This Post Topic: OHM FL Series amp
    Posted: 21 April 2021 at 9:24am
Hi guys, I have a question about one of my FL series amps , at the rear by the incoming power there is  a small riser board attached and the incoming mains is then sent to the rocker at the front

look like thermistors they have 10SP AND UEI 050 one is loose and not soldered are they acting as soft start etc , the big Jamicon caps look fairly new but not tested just yet.

Also looks like one or more of thermistors may have blown are they soft start as such?  

Probably the next question is what can i replace these with been searching but no luck yet. 

Maybe https://uk.farnell.com/amphenol-advanced-sensors/cl-140/ntc-inrush-current-limiter-50/dp/1707220    ???

So now found out its NTC 50 OHM 2 AMP now on the hunt for couple of transistors      

        


Edited by JOLD - 22 April 2021 at 3:45pm
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hmaudio View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote hmaudio Quote  Post ReplyReply Direct Link To This Post Posted: 23 June 2021 at 7:55am
There was a few different version of the Ohm fl series amplifier. some were built by Andy Hunt Matrix amplification and i am not sure who built the others.

The Ntc thermistors are used to slow the inrush current on power up, then a relay on the pcb will close bypassing them.

If they keep blowing check the relay is operating properly, you can replace the thermisistors with the same value and does not have to be the exact same make. I cannot remember the value for these but it looks like they have been changed before in your picture.

The jamicon capacitors tend to be crap in these amplifiers and tend to leak after a while. The best thing to do is measure them. If you need some capacitors i have four F&T 125v 6200uf some left over from when i did mine years ago do not know the condition of them at the minute.


If this is a Matrix version the best person to speak to is Andy Hunt he gave me alot of advice with these amplifiers years ago when i fully rebuilt one and changed everything on the pcb and used hitachi fets for the outputs instead of the Buz901p/ 906p fets.

Jamie





Edited by hmaudio - 23 June 2021 at 8:03am
Nottingham based cab builder. https://www.facebook.com/HMAudio-154352667920145/?ref=bookmarks
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kedwardsleisure View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kedwardsleisure Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2021 at 2:33pm
you'll probably find most matrix amps dont have an inrush bypass relay, the NTC's are left in circuit.
They can fail just through old age
Kevin

North Staffordshire

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