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Author Topic: Proel SMT 15MA Powered Monitor  (Read 2335 times)

Micky Asat

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Proel SMT 15MA Powered Monitor
« on: May 12, 2016, 10:49:00 AM »
Hi All,
         Our proel monitor keeps blowing all 4 internal fuses  The fuses are 4a on the high side and 2.5 on the low side. Can,t see anything burnt,so just wondered if anyone has any ideas. Michael.

J M Fahey

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Re: Proel SMT 15MA Powered Monitor
« Reply #1 on: May 12, 2016, 12:17:29 PM »
Visual inspection is first, but not enough.
That's why we use multimeters and other instruments to really "see" what is going on.

You probably have shorted power transistors / supply rectifiers / fikter caps , in order of probability, but to advance we need to get a schematic somewhere, if anything ask it from Proel themselves, stating model and serial number.

That said, they might send you straight bto some authorized service shop.

Are you experienced in reading schematics, troubleshooting in general and replacing parts, plus having the needed equipment?

From what I saw, and comparing to similar high quality Italian PA equipment, they probably use a complex quad rail Class F/G/H power amplifier, not an easy task to repair.


Micky Asat

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Re: Proel SMT 15MA Powered Monitor
« Reply #2 on: May 12, 2016, 03:48:55 PM »
Hi,just wondering if the output trannies are shot and these are causing the fuses to blow. I have asked proel for a schem, but still waiting.
I am pretty good with multimeter reading schems ect.

Enzo

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Re: Proel SMT 15MA Powered Monitor
« Reply #3 on: May 12, 2016, 06:23:23 PM »
So then find the output transistors or the power amp IC, whichever your system ha, and check with an ohm meter to see if it/they is/are shorted.  The power supply circuits should be easy to find, look at the main rectifiers, are any shorted?

Micky Asat

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Re: Proel SMT 15MA Powered Monitor
« Reply #4 on: May 12, 2016, 06:58:03 PM »
Thanks Enzo,
                    I have ordered 4 output transistors. Will try them first. 

Enzo

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Re: Proel SMT 15MA Powered Monitor
« Reply #5 on: May 12, 2016, 11:42:40 PM »
Wait, please don't just replace them and hope, FIND OUT if they are bad.  That is why I suggested using your meter to determine if they are shorted or not.  Replacing a perfectly good output transistor won;t help a shorted main rectifier, and vice versa.

J M Fahey

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Re: Proel SMT 15MA Powered Monitor
« Reply #6 on: May 13, 2016, 09:47:19 AM »
Agree and add:
1) which are those transistors?
Post model numbers so we have an idea as to what do they use (Bipolar/MosFet?)
Also a general view gut shot showing everything and a closeup showing power transistors might help, in any case it never hurts.

2) if bipolar, you must also check their driver transistors, usually packed in a TO220 case ; MosFets might be directly driven without them but not always.

3) build and use a Lamp Bulb Limiter, check the thread here in SSG.
There is nothing more frustrating than plugging an amp in and blowing fresh expensive transistors because there is still some other smaller problem :(

4) for all tests use the amp disconnected from speakers and any other load until proven minimally healthy (not blowing fuses + no DC on output).

5) does it have a conventional iron power supply or an SMPS?

Micky Asat

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Re: Proel SMT 15MA Powered Monitor
« Reply #7 on: May 26, 2016, 10:05:19 AM »
 I have changed the 4 output mosfets and everything now is working OK  Put in correct fuses also. Cost £10 in parts  Have ended up with some spares as well. Thanks everyone for your help. Michael.

 

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