GFA-555 II Thermal

bboptulsa · 21st June 2011, 10:42 PM

I have a GFA-555 II that the thermal overload light stays on even after no speakers are attached any clue when it will go off?

WithTarragon · 22nd June 2011, 12:25 AM

Do not hook up any speakers until this is resolved.
Get a voltmeter and measure DC voltage at each output. What are your readings?

bboptulsa · 22nd June 2011, 12:57 AM

I have it in Bridged mode and the reading is .080 vdc but in reverse polarity. 0 on a/c volts

bboptulsa · 22nd June 2011, 01:09 AM

Now its at .011vdc this is after I unplugged the input channels cable. There is an issue with ground on the wall outlet and after pushing two(2) 18" subs @4ohm load for 30 minutes this problem availed itself. Now I have nothing but the new power source with ground connected and I have the reading that I describe in this post.

WithTarragon · 01:49 AM

Okay, there does not seem to be any DC at the output. That is good news and eliminates a couple of things.

However, you have said some things that are confusing.

What exactly is the problem? when did it start, does it happen all the time, does it happen with all speakers (or a power resistor as a load), odose it happen when the source is turned off, does it happen in both channels?

bboptulsa · 22nd June 2011, 02:01 AM

Well I have had the amp on a circuit that did not have a ground, I thought that this might have had an impact on the internal circuitry so I mentioned it. Now it is on a grounded outlet and no speakers hooked to it nor the input either, after I turn it on the Thermal Protect is still lite and will not go out. I had mentioned that I previously have been pushing 18" speakers and not enough air to the heat sink, this is when the light came on and has not went out.

bboptulsa · 22nd June 2011, 05:07 PM

I'm sorry WithTarragon, I switched back to stereo and I do have 1.4 volts dc at both sides. I had a band last night and was in a hurry to set them up. what are your thoughts to this scenario?

WithTarragon · 22nd June 2011, 07:33 PM

According to the Adcom owner manual, the distortion lights should also light when there is that much DC at the output. Are your distortion LEDs on also?

I am not expert on amps and I do not have a service manual / schematic with me. Others will be more experienced.

My uneducated guess is that the output devices and associated "ballast" resistors are now bad. Possibly some other things also. This could have been due to a short at the outputs, but there are other possibilities also.

First thing is to get a service manual. There are some free ones on the web, and you can get them from eBay also. This is going to take some work, so you will need someone more expert than me.

bboptulsa · 22nd June 2011, 08:01 PM

You have actually been a great help for I went ahead and dove in knowing that people are willing to help. I am confident that this issue has happened to others and already I have found a loose connection and I am in the process of troubleshooting and why it could have become open. I know this to be the result of the light, so finding out if it was over heating or dc'ing at 1.5 ohms is my next step. again thanks for your timely response it inspires confidence in my fellow Audiophiles.

bboptulsa · 23rd June 2011, 12:55 AM

So I see there's a 555 manual, But I need the 555 II manual how do I go about finding that?

21st June 2011, 10:42 PM	#1
bboptulsa diyAudio Member Join Date: Jun 2011	GFA-555 II Thermal I have a GFA-555 II that the thermal overload light stays on even after no speakers are attached any clue when it will go off?

22nd June 2011, 01:48 AM	#5
WithTarragon diyAudio Member Join Date: Jun 2007	Okay, there does not seem to be any DC at the output. That is good news and eliminates a couple of things. However, you have said some things that are confusing. What exactly is the problem? when did it start, does it happen all the time, does it happen with all speakers (or a power resistor as a load), odose it happen when the source is turned off, does it happen in both channels? Last edited by WithTarragon; 22nd June 2011 at 01:49 AM. Reason: ...

22nd June 2011, 02:01 AM	#6
bboptulsa diyAudio Member Join Date: Jun 2011	thermal Well I have had the amp on a circuit that did not have a ground, I thought that this might have had an impact on the internal circuitry so I mentioned it. Now it is on a grounded outlet and no speakers hooked to it nor the input either, after I turn it on the Thermal Protect is still lite and will not go out. I had mentioned that I previously have been pushing 18" speakers and not enough air to the heat sink, this is when the light came on and has not went out.

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22nd June 2011, 12:25 AM	#2
WithTarragon diyAudio Member Join Date: Jun 2007	Do not hook up any speakers until this is resolved. Get a voltmeter and measure DC voltage at each output. What are your readings?

22nd June 2011, 12:57 AM	#3
bboptulsa diyAudio Member Join Date: Jun 2011	I have it in Bridged mode and the reading is .080 vdc but in reverse polarity. 0 on a/c volts

22nd June 2011, 01:09 AM	#4
bboptulsa diyAudio Member Join Date: Jun 2011	Now its at .011vdc this is after I unplugged the input channels cable. There is an issue with ground on the wall outlet and after pushing two(2) 18" subs @4ohm load for 30 minutes this problem availed itself. Now I have nothing but the new power source with ground connected and I have the reading that I describe in this post.

22nd June 2011, 05:07 PM	#7
bboptulsa diyAudio Member Join Date: Jun 2011	I'm sorry WithTarragon, I switched back to stereo and I do have 1.4 volts dc at both sides. I had a band last night and was in a hurry to set them up. what are your thoughts to this scenario?

22nd June 2011, 07:33 PM	#8
WithTarragon diyAudio Member Join Date: Jun 2007	According to the Adcom owner manual, the distortion lights should also light when there is that much DC at the output. Are your distortion LEDs on also? I am not expert on amps and I do not have a service manual / schematic with me. Others will be more experienced. My uneducated guess is that the output devices and associated "ballast" resistors are now bad. Possibly some other things also. This could have been due to a short at the outputs, but there are other possibilities also. First thing is to get a service manual. There are some free ones on the web, and you can get them from eBay also. This is going to take some work, so you will need someone more expert than me.

22nd June 2011, 08:01 PM	#9
bboptulsa diyAudio Member Join Date: Jun 2011	You have actually been a great help for I went ahead and dove in knowing that people are willing to help. I am confident that this issue has happened to others and already I have found a loose connection and I am in the process of troubleshooting and why it could have become open. I know this to be the result of the light, so finding out if it was over heating or dc'ing at 1.5 ohms is my next step. again thanks for your timely response it inspires confidence in my fellow Audiophiles.

23rd June 2011, 12:55 AM	#10
bboptulsa diyAudio Member Join Date: Jun 2011	So I see there's a 555 manual, But I need the 555 II manual how do I go about finding that?

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