amp is dead!

medicman · 20th January 2009, 11:57 PM

i need some help please. i have a acoustic g100t tube amp, i was playing it and all of a sudden it just quit. the power light on the fron is on but none of the tubes light up. i removed the chasis and eyeballed inside nothing looked or smelled burnt. what could it be? thanks, wendell.

ray_moth · 21st January 2009, 12:27 AM

Fuse?
Transformer primary winding blown?

rdf · 21st January 2009, 01:22 AM

Schematic?

aardvarkash10 · 21st January 2009, 02:08 AM

light is on, ergo there is power to the unit. Tubes are not glowing, ergo there is no heater supply. Thats it. Without a schematic and some voltage readings, there is no more to be said...

Ziggy · 21st January 2009, 04:29 AM

Sounds like a dead power trannie

medicman · 21st January 2009, 06:39 AM

i believe that the heater supply is correct because there is primary voltage. i will post a schematic for it tommorow. thanks everyone.

rdf · 21st January 2009, 06:50 AM

Primary voltage without lit tubes likely means something's sideways in the filament supply. Burnt windings are usually pretty pungent for weeks so luck might still be on your side.

medicman · 21st January 2009, 03:14 PM

here is part of the schematic i found, the power indicator light comes on the front but there are absolutely no lit tubes. i'm really not very good at troubleshooting electronic circuits. i cant smell anything from the transformer here is the link that has the entire schematic i couldn't attach it because it's too big. thanks again for all your help.

http://techpreservation.dyndns.org/b...Schematics.pdf

firechief · 21st January 2009, 05:17 PM

I wonder if this a series filament setup?, in that case it could mearly be a bad tube. A volt meter would be a real help here. I noticed that Antique Electronic Supply has a real digital one (S-Z3220) for $50. This is somthing that will pay for itself many times over as so many problems can be diagnosed with simple voltage/resistance measurnents.

Nihilist · 22nd January 2009, 05:28 AM

Medicman,

Do you own a volt meter or multi meter ?

If so, measure the voltage between the two green leads of the power supply transformer. These are the heater filament leads and should measure 6 volts or so.

If you don't have a meter , you NEED one. Look here for a decent meter on the cheap : http://www.parts-express.com/wizards...n&WebPage_ID=3

Have you checked ALL the fuses ?

.............................Blake

20th January 2009, 11:57 PM	#1
medicman diyAudio Member Join Date: Jan 2009	amp is dead! i need some help please. i have a acoustic g100t tube amp, i was playing it and all of a sudden it just quit. the power light on the fron is on but none of the tubes light up. i removed the chasis and eyeballed inside nothing looked or smelled burnt. what could it be? thanks, wendell.

21st January 2009, 01:22 AM	#3
rdf diyAudio Member Join Date: Jun 2004 Location: big smoke	Schematic? __________________ Ears aren't microphones.

21st January 2009, 02:08 AM	#4
aardvarkash10 diyAudio Member Join Date: Mar 2007 Location: Auckland, NZ	well, heres a start... light is on, ergo there is power to the unit. Tubes are not glowing, ergo there is no heater supply. Thats it. Without a schematic and some voltage readings, there is no more to be said... __________________ Yes, conservatism thrives on low intelligence and poor information. But the liberals in politics... continue to back off, yielding to the supremacy of the stupid. It's turkeys all the way down. - George Monbiot, guardian.co.uk, 6 Feb 2012

21st January 2009, 06:39 AM	#6
medicman diyAudio Member Join Date: Jan 2009	amp is dead i believe that the heater supply is correct because there is primary voltage. i will post a schematic for it tommorow. thanks everyone.

21st January 2009, 06:50 AM	#7
rdf diyAudio Member Join Date: Jun 2004 Location: big smoke	Primary voltage without lit tubes likely means something's sideways in the filament supply. Burnt windings are usually pretty pungent for weeks so luck might still be on your side. __________________ Ears aren't microphones.

21st January 2009, 12:27 AM	#2
ray_moth diyAudio Moderator Emeritus Join Date: Jan 2004 Location: Jakarta	Fuse? Transformer primary winding blown?

21st January 2009, 04:29 AM	#5
Ziggy Account Disabled Join Date: Jul 2004 Location: West Australia	Sounds like a dead power trannie

21st January 2009, 03:14 PM	#8
medicman diyAudio Member Join Date: Jan 2009	g100t schematics here is part of the schematic i found, the power indicator light comes on the front but there are absolutely no lit tubes. i'm really not very good at troubleshooting electronic circuits. i cant smell anything from the transformer here is the link that has the entire schematic i couldn't attach it because it's too big. thanks again for all your help. http://techpreservation.dyndns.org/b...Schematics.pdf

21st January 2009, 05:17 PM	#9
firechief diyAudio Member Join Date: Sep 2008 Location: Near Seattle Wa	I wonder if this a series filament setup?, in that case it could mearly be a bad tube. A volt meter would be a real help here. I noticed that Antique Electronic Supply has a real digital one (S-Z3220) for $50. This is somthing that will pay for itself many times over as so many problems can be diagnosed with simple voltage/resistance measurnents.

22nd January 2009, 05:28 AM	#10
Nihilist diyAudio Member Join Date: Aug 2006	Medicman, Do you own a volt meter or multi meter ? If so, measure the voltage between the two green leads of the power supply transformer. These are the heater filament leads and should measure 6 volts or so. If you don't have a meter , you NEED one. Look here for a decent meter on the cheap : http://www.parts-express.com/wizards...n&WebPage_ID=3 Have you checked ALL the fuses ? .............................Blake __________________ Keep it simple My Page Of SV and DIY Stereo Links

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