Rock wood amplifier

[Sandre]

The fets were blown and I replaced them now the rectifier diodes pin broke and I want to replace them Perry what do you recommend this is one of the amplifier I used buz11 as substitute they are still ok, just the rectifier diodes pin broke, I can clean them up and add pins to them but I'd prefer to replace them

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

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

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[Perry Babin]

Asking for help from a specific person may prevent others from answering your question.

I'd use the MUR1620CT and MUR1620CTR.

You need to clean up the board before and after replacing any components. Acetone(preferred) or alcohol (91%) and cotton swabs/paper towels or a toothbrush will work. It makes the job look much better. One example below.

 

[Sandre]

Thanks for the advice


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[Sandre]

How would I know what rating fuse this amp needs there is no markings on the amp, and I can't find the manual


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[Perry Babin]

I would start with a 20 amp (25 max). If the owner blows that, they are likely driving the amp into hard clipping.

 

[Sandre]

The fuse didn't blow, fets are ok too the relegation rectifier legs broke I used solder to make legs for the time being until it get those rectifiers


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[Sandre]

Going to take a better picture of the board, there is this resistor that is connected to r+ speaker terminal that has no reading, buts it brother l+ has a reading of 2ohm


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[Perry Babin]

Tin the entire length of the leg and solder a wire (solid, slightly larger than a 1/4w resistor leg) onto the leg. That will work better than solder.

 

[Sandre]

Ok. The resistor however doesn't affect out put, maybe until I bridge it


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[Sandre]

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

resistor wr203 reads open circuit check out of circuit same outcome what is the purpose of that resistor going to clean up the board now


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[Perry Babin]

It's part of the Zobel network (RC network across the output of the amp that helps stabilize the amp (prevents it from oscillating with highly reactive loads).

https://www.google.com/search?q=Zobel+network&ie=utf-8&oe=utf-8

 

[Sandre]

I can't seem to find the resistor in any junk parts, can it substituted?


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[Perry Babin]

Many amps use a 4.7 ohm there. If you order the rectifiers, order the correct value resistor.

 

[Sandre]

Ok. But I can use 4.7ohm for the time being


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[Sandre]

It uses a 2.8


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[Perry Babin]

4.7 ohm is closer to 2.7 ohms (red, purple, gold?) than an open resistor. What are you planning on doing with the amp between now and the time when you order the parts for it?

 

[Sandre]

4.7 ohm is closer to 2.7 ohms (red, purple, gold?) than an open resistor. What are you planning on doing with the amp between now and the time when you order the parts for it?

It's going to used to play mid range


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[Perry Babin]

I guess I should have been more clear. Why the hurry to reinstall it? Why not wait until you get the right parts?

 

[Sandre]

The amp is for a friend he has bad luck, this and another amplifier failed due to battery problems low voltage, but he's saying he can't have music for more than a week or 2 as well as the channel that has the resistor blown isn't being used, I just want him to have music until I can order the parts


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[Perry Babin]

Use the 4.7. It's better than nothing. Check the capacitor in series with it to confirm that it's not shorted.

As a side note, when those resistors are burned, it's a sign that the amp has been driven into hard clipping for long periods of time.