MTX Thunder 1501D

[snowman123]

Trying to repair one of these monsters. Battling to find the exact resistor replacement value for R247 which is a 4.75 ohm 1/10w smd resistor in South Africa. Will a 4.7 ohm 1/10w do the job or this a critical component? Any help will be appreciated.

 

[Hexhclass]

R247 on the pre-amp board? I see 39.2 ohms there from a pic.

I have one in the shop,I will confirm it for you tomorrow.

 

[Perry Babin]

Please post a photo showing the location of the resistor in the amp.

 

[snowman123]

Thanks for the reply. Sorry about this I should have been more specific. R247 is located next to FET 247 on the power supply section. FET 247 had failed on this amplifier and I had replaced all of the FETS as a result. Never powered up the amp as yet. Just worried now about the value of R247. Hoping the value is not critical. Thanks for your help!

 

[Perry Babin]

I think the 4.7 ohm would be OK but I would replace all 4 gate resistors for the parallel FETs.

 

[snowman123]

Thanks Perry. I will give this a try. Should I replace all of the 8 gate resistors with 4.7 ohm value? I have ordered about 20 of these so replacing all of them wont be an issue. Main concern is the performance and long term stability.

 

[Perry Babin]

The other 4 are 39.2 ohms in the photos I have. Are all of yours 4.75 ohms?

 

[snowman123]

I stand under correction Perry. You are correct. There are only 4 of these resistors which are 4.75 ohms which are R245, R246, R247 & R249. I had imported the FETS & resistors from overseas as these weren't available in my country. The resistors came in a bag labelled with a part number: CRCW06034R75FKEA which is confusing me because this part number is a 4.75 ohm resistor. If I look at the actual marking on the resistor, it is marked 4R7. Tried looking up the data sheet for the resistor part number which shows a generic coding structure & does not prove useful. Measuring with a multimeter also wont give accurate results.This is why I am sending this post just to work on the worse case scenario of the resistor values being 4.7 ohm because the marking in no way looks similar to the marking of the original resistor marked 4R75.

 

[Perry Babin]

That looks like a 0603 size part. That's may be why the value is truncated. The originals were likely 0805.

 

[snowman123]

Thanks Perry. I am just going to import the originals seeing that these are the wrong type and wattage. Not worth the risk to damage the mosfets or possibly other components because of silly low cost resistors.