Award BG500 amp

telstarventure
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Award BG500 amp

Postby telstarventure » Fri Dec 16, 2016 9:07 pm

Have a Award BG500 Ventures model amp. Looking at the service manual what is the reason for the four no 313 bulbs in the power amp circuit board for?

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Re: Award BG500 amp

Postby Mr. Bill » Fri Dec 16, 2016 11:35 pm

Not sure, but a typical use for small lamps are as ballast resistors for the output transistors. These will limit the current that passes through the output transistors.

I will look up the schematic and try and give you a better answer once I see where they are located in the circuit.

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Re: Award BG500 amp

Postby Mr. Bill » Sat Dec 17, 2016 10:40 am

Looked at the schematic and see that the 4 lamps are being used as variable resistors in the bias circuit for the output transistors. As more current is passed through the lamps, their internal resistance will change and the filaments will begin to glow.

Without doing a circuit analysis, I wonder what happens when one of the bulbs burns out or breaks from vibration.

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Re: Award BG500 amp

Postby panther » Sat Dec 17, 2016 10:57 am

Mr. Bill wrote:Looked at the schematic and see that the 4 lamps are being used as variable resistors in the bias circuit for the output transistors. As more current is passed through the lamps, their internal resistance will change and the filaments will begin to glow.

Without doing a circuit analysis, I wonder what happens when one of the bulbs burns out or breaks from vibration.


My guess it will act like a blown resistor, and the amp with malfunction.
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telstarventure
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Re: Award BG500 amp

Postby telstarventure » Sat Dec 17, 2016 7:33 pm

Thanks for the information. You would think they could of designed some thing a little bit more reliable then that.

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Re: Award BG500 amp

Postby Mr. Bill » Sat Dec 17, 2016 8:29 pm

telstarventure wrote:Thanks for the information. You would think they could of designed some thing a little bit more reliable then that.

If the lamp goes open circuit, the bias may just shut off the corresponding transistor only causing the amp to distort. Worst case would be that the bias turns the transistor full on and blows up the power amp. I would hope that it would be the first situation and not the second.

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Re: Award BG500 amp

Postby Bob Shade » Sun Dec 18, 2016 5:28 am

On my BG 1000 I had the lamps taken out and this section converted over to a more traditional system.

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Re: Award BG500 amp

Postby telstarventure » Sun Dec 18, 2016 9:05 am

Bob Shade wrote:On my BG 1000 I had the lamps taken out and this section converted over to a more traditional system.
Would it costly to have the lamps taken out and converted over to a more traditional system like Bob Shade had done to his BG 1000 amp?

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Re: Award BG500 amp

Postby Mr. Bill » Sun Dec 18, 2016 5:41 pm

Cost would be different depending upon where you are located and which shop you have do the work. The actual work would be to remove the lamps and replace them with resistors.

The hard part would be to figure out what value the resistors would need to be. the cost of the actual resistors would only be a few dollars.


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