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Replacment mosfets RM Italy KL-503

J

jtrouter

Well-Known Member
Jul 7, 2015
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Hello everyone, I am trying to help a friend repair his RM Italy KL-503 and am having a hard time trying to find out which mosfets to use to repair this amp.
I have been searching all over the web and thru forums and have a list of mosfets that people have listed as what to use for correct replacements.
The problem of course is the the original numbers are removed and it seems that there are no spec sheets out there for the mystery RM3 mosfets. Below are the ones that have been suggested as the correct ones to use.

FQP13N10 IRFZ24N IFR1200 HUF75343P3/subs IRF48NBF/IRL2505PBF/FDA24N40F

If anyone can tell me for sure which one of these to use is correct or if they are all wrong and which to use i would be very in awe and appreciate it.
Thank you very much!
 

I am about to try some Irfz24n fets in an ad-203 that let the smoke out. I think they are a little tougher than the 13n10s but I don't have evidence to back that up
 
Enterprise312ok said:
I am about to try some Irfz24n fets in an ad-203 that let the smoke out. I think they are a little tougher than the 13n10s but I don't have evidence to back that up
Click to expand...
I would be very cautious using the 24N Fets. I had these installed into my Stryker 955v2 and they lasted only about 4 months. I drove extremely conservatively, never putting out more than 50Wpep and never exceeding 10W carrier on AM. Also, they ran VERY hot in my radio which caused me to install a dual fan kit on the heat sink. The Stryker tech told me these transistors are extremely sensitive to SWR and other anomalies. From what I understand, Ranger is also having issues with these in some of their radios.
 
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I think the trouble ranger is having with the 24n fets is they are not being matched where the radios are manufactured. vt and capacitance need to match exactly.
 
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Back to what the o.p. was asking though. What really are those fets in the kl amps? I own a couple of 203's and 503hd and if or when they pop it would be nice to know.

The Ranger rt1 secret didn't hold up long so surely somebody knows the rm secret.
 
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I thought the RM3's were MS1307's.

Member NZ8N posted this stuff:

RM-3 MOSFET TRANSISTOR

ERF9530 is a rebranded TO-3P MOSFET, similar in size to the power regulator on the side wall of a Galaxy or other similar radio. It will probably be too big to fit in place of an RM3 transistor. IRF9530 is a TO-220P (final sized) MOSFET, has lesser heat dissipation then the above. By doing a...
www.worldwidedx.com www.worldwidedx.com
 
Last edited:
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jtrouter said:
Hello everyone, I am trying to help a friend repair his RM Italy KL-503 and am having a hard time trying to find out which mosfets to use to repair this amp.
I have been searching all over the web and thru forums and have a list of mosfets that people have listed as what to use for correct replacements.
The problem of course is the the original numbers are removed and it seems that there are no spec sheets out there for the mystery RM3 mosfets. Below are the ones that have been suggested as the correct ones to use.

FQP13N10 IRFZ24N IFR1200 HUF75343P3/subs IRF48NBF/IRL2505PBF/FDA24N40F

If anyone can tell me for sure which one of these to use is correct or if they are all wrong and which to use i would be very in awe and appreciate it.
Thank you very much!
Click to expand...
88 Radio on the web sells KL503 and they have power transisters for $8 dollars plus shipping
 
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pienari said:
I found that info from KL203 mosfet, bad cover lasering .
Just a look microscope and read original markings.
Click to expand...
Well I just got finished pulling a brand new or is it NOS as i bought it 10 years ago?
Anyways carefully bent one back and used my microscope and all that was there
was diagonal marks thru it, nothing else just that,
 

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