Memphis 16-mc3004 pops fuses

[StillLearning]

Ok, so pops fuses every 10 secs of being hooked up. Yall have stated the output transistors are shorted. Last time I hooked it up I seen the resistors smoking when I had the cover off, so I am replacing them too. Only thing is, The color code looks black, green, silver, gold. Ive been all over the net looking at color charts and there is no silver stripe other than the last one that would be 10% tolerance. Maybe what i think is silver is either white or grey?

An externally hosted image should be here but it was not working when we last tested it.

The resistors still in the amp.

An externally hosted image should be here but it was not working when we last tested it.

 

[1moreamp]

This might help some

 

[StillLearning]

Nice, the ones I found didn't have silver as a choice on the 3rd stripe, lol.

 

[StillLearning]

So my resistor is .05 ohm with +/- 5% tolerance? If so, digikey dont have it..bah

 

[1moreamp]

0.5 ohm is more likely the correct value.

 

[StillLearning]

Before I start getting parts ordered, would this one work? Or do I need higher wattage ones.

LVR01R0500FE12 Vishay/Dale Current Sense Resistors

 

[1moreamp]

The one you have in hand appears to be a 2 watt version, 3 watt would work also. The spec of the one listed is 1 watt...

 

[Perry Babin]

71-LVR2-0.05

I think 0.05 ohms is correct. THIS is an example of a 0.02 ohm.

 

[StillLearning]

How do you tell the watt rating of a resistor?

 

[Perry Babin]

It's generally determined by the physical size but that's not 100% reliable because some resistors are made of high-temp materials and can dissipate more power than other resistors their size. I don't think that's the case here. These appear to be run-of-the-mill wirewound resistors. Using replacements the same size should be sufficient.

I doubt that your resistors are defective. Wirewound resistors can take a lot of abuse.

 

[StillLearning]

Figured I would replace them, but ill check them with a DMM to make sure they still hold the same ohm value. If they do Ill toss them back in. Just seems right to replace parts that smoke up. I'm a mechanic and work on h-60b helos for the navy, so its natural for me to replace parts that look damaged or worn, lol.

 

[Perry Babin]

A bit different type of repair. An amp isn't going to drop out of the air from 10,000ft.

 

[StillLearning]

Hmm, good point.

Ok, replacing the transistors so heres a pic of it.

An externally hosted image should be here but it was not working when we last tested it.

Thinking one of these-
Digi-Key - IRF540ZPBF-ND (Manufacturer - IRF540ZPBF)
or
Digi-Key - IRF540PBF-ND (Manufacturer - IRF540PBF)

 

[Perry Babin]

I'd recommend the non-Z version. It's best to use the original part number unless there is a known reason not to do so.

 

[StillLearning]

sounds good. I know I am full of questions, but what difference does the "Z" make? I like to understand the parts i replace, mechanic or electric.

 

[Perry Babin]

It's just a different version of the same basic part. In general it performs the same but sometimes minor differences make a big difference (i.e. IRF540N in place of the IRF540 in Rockford amps).

 

[StillLearning]

Oah, and is there anything else I should check before ordering the parts for this amp and the JL?

 

[StillLearning]

Replaced the transistors and shes working on bench, so tomorrow I will hook her up and see if theres any problems on putting power through it.