X-Force 6 pill getting hot

[Kruser]

I had a guy bring in an X Force 6 pill that had quit and was blowing fuses. All but one of the four rectifiers had blown so I replaced then all. Amp came on fine, no fuse blowing but things are heating up in the signal input section, mainly the 10 ohm 20 watt resistors of which there are three. The hottest parts are the Shottsky diodes. There is an imbalance of power that could be one of transistors. (Haven't had time to get to it yes to test), but my main question is, What are Shottsky diodes doing running to ground in a bias circuit anyway. Am I missing something here? I have a lot of electronics training (I don't claim to know everything) but I'm stumped here. There are three capacitors in parallel with the diodes. With the diodes passing current at .55 volts would that not sink all the input signal to ground?
As far as the amount of input signal, the radio dead keys 2 watts and modulates to 22 watts peak. No driver or anything.
Maybe I was sick the day this was discussed in class.
Thanks and all help appreciated.
Kruser

 

[543_Dallas]

The first thing is you have an imbalance in a couple of 2 pill sections. Look again at those 20 watt resistors...I think you are mistaken. That's all I'm saying because I think an amp repair man should understand amplifiers. You need to hit the books before you start taking on amp repairs. You don't know enough at this point to know when someone online is full of BS and will pass the BS on to your customer. If you understand how transistor amps work the bias thing makes alot more sense.

 

[Crusher]

LOL, first off that's a very poor biasing design. Those 10ohm 20w are there to drop a little voltage and limit current. I would start checking pills and see if they are all good. Then check and make sure each set of pills is getting right voltage. Since that amp has rectifiers, that means it's an unregulated supply. Could be 19-21v floating. Those resistors are working overtime. Lots to look at in that circuit

 

[222DBFL]

Listen to the 2 above posters they know what they speak!!

 

[9C1Driver]

Is this a mobile or base X-Force and is it the standard class C or is it their B biased amp?

 

[psycho]

Is this a mobile or base X-Force and is it the standard class C or is it their B biased amp?

Base amp due to the rectifiers mentioned.

 

[BBB]

X-Force sells a real class B (6) pill amp?

 

[543_Dallas]

X-Force sells a real class B (6) pill amp?

Texas Star has been calling their stuff class AB for years so why not.

 

[BBB]

That's right ...They're only telling you half the story

 

[222DBFL]

Isn't the bias circuit used by xforce just about the same if not the same as the TS amps? Or did someone blow smoke up my poop shoot??

 

[543_Dallas]

The few I've saw draw less idle current than the Tejas Star but pretty similar circuitry. I have never understood the guys that will tell you not to buy the biased xforce trash but recommend a Texas Star with a computer fan strapped to the heatsink.

 

[Crusher]

Lol, it's class AB/ B at idle. But watch the voltage drop once you key and start pulling current.

 

[Kruser]

The first thing is you have an imbalance in a couple of 2 pill sections. Look again at those 20 watt resistors...I think you are mistaken. That's all I'm saying because I think an amp repair man should understand amplifiers. You need to hit the books before you start taking on amp repairs. You don't know enough at this point to know when someone online is full of BS and will pass the BS on to your customer. If you understand how transistor amps work the bias thing makes alot more sense.

Mr. Dallas, You know, I have never been on a single forum where there wasn't at least one guy blowing a lot of hot air about nothing because he knows nothing. Please refrain from helping me in any manner.

 

[Kruser]

Listen to the 2 above posters they know what they speak!!

Not from where I'm sitting!

 

[543_Dallas]

Mr. Dallas, You know, I have never been on a single forum where there wasn't at least one guy blowing a lot of hot air about nothing because he knows nothing. Please refrain from helping me in any manner.

I don't like crooks taking people's money by making half assed repairs equipment they know little about...BBI and his youtube videos being a prime example. The only right way for you to do this is learn how an amplifier works. I was hoping you'd ask about some books or learning aids but you want a quick answer to put fast money in your pocket. If you were trying to get your personal amplifier fixed so you can enjoy the hobby I'd love to help you, might even give you parts, but that's obviously not the case here.