ADCOM GFA-555 power on but no sound... - diyAudio
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Old 14th February 2006, 01:18 AM   #1
rinsbag is offline rinsbag  Canada
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Default ADCOM GFA-555 power on but no sound...

I am new to electronics repair. A friend gave this to me so Im trying to fix it. I have read very good things about this amp.

I replaced the fuses inside the amp. I do not have a preamp but I do have a dj mixer so I connected my booth out to the 'in' on the amp. then connected one speaker to the right channel. After this I turned it on. At the moment the power light comes on and so does the left channel light. It did make a strange pop sound when first powered on. But then nothing. I tried the other channel still no sound.

I do notice the part ADCOM 72-2206-0-0 on one of the blue things (sorry...if anyone can point me to a site that I can learn some of the basics of electronics please do.) looks fried. I am including a pic of the unit.

Any help or is this dead? I kinda want to do this myself so any links to some sites that I can learn from would be greatly appreciated.
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Old 14th February 2006, 01:40 AM   #2
clem_o is offline clem_o  Philippines
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Are you referring to the part at the lower left of the picture?

The 'Blue thing' is a power supply filter capacitor. On top is a small PCB that looks discolored. I assume under that board (between the board and the blue BIG capacitor) is a resistor. It appears to be used to simply light the lamp at the front panel of the amplifier (orange and black wire)..

Its improbable that this would be the cause of the problem...


Cheers!

Clem
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Old 14th February 2006, 02:02 AM   #3
SY is offline SY  United States
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Those "blue things" can kill you if you don't know what you're doing.

Seriously, repairing a 200 watt amp with high voltages takes some knowledge and test equipment (at a minimum, a DVM, a signal generator, and an oscilloscope). If you don't have these, I would strongly urge you to get some local help.
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Old 14th February 2006, 02:04 AM   #4
anatech is offline anatech  Canada
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Hi rinsbag,
Clem is right. That discolouration is normal and not the cause of any of your problems.

One. Never, ever just replace the fuses and power up unless you have a lot more information. It's a good amp, don't kill it permanently.

Two. It's a big amp. Not exactly a beginners project. You need some test equipment to begin with, and a variac.

Three. I've had customers with mixers that have destroyed perfectly good amps because of the very poor quality of mixer. If yours was not expensive or a really good brand (lost track - too much junk out there), reconsider and pick up a preamp. For sure it'll sound better.

So how much knowledge or training do you have?

-Chris
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Old 14th February 2006, 02:20 AM   #5
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Yes, stay away from those blue things. Note* They can also be white or black. If their big leave them B.

This is kinda like a big red wire in a television set for me. If I get with in a foot of one I get shocked.

Final note* Just sent the Adcom to me.
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Old 14th February 2006, 02:28 AM   #6
clem_o is offline clem_o  Philippines
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Hmm, I keep forgetting to warn people about opening up powerful amps; good thing there are many others on this forum with more foresight...

rinsbag, suggest you put the amp to the side, educate yourself a bit in electronics (i.e. learn to read schematics, discover what each component and its variants look like, acquire some basic service equipment, and do a couple of simple projects FIRST). Then, get back to the amp.

:-)


Cheers!

Clem

ps: Or, send it to Chris - I have no idea how far apart you guys live... hehehe...
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Old 14th February 2006, 02:39 AM   #7
anatech is offline anatech  Canada
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Hi Clem,
You have no idea how close rinsbag is to me. Less than an hour's drive (through some really pretty escarpment country too!). I was going to wait to see where this went before saying anything.

Hey, DIYaudio members are spread evenly across the globe, and that's really cool!

rinsbag,
Hopefully you have some experience and equipment. Let me know if you need my help.

-Chris
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Old 14th February 2006, 02:46 AM   #8
clem_o is offline clem_o  Philippines
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Default OT

Hi Chris,

Sorry for jumping the gun... :-)

That near? Gee! It takes me more time to drive home from work, though Manila's traffic conditions are notorious... 15km takes 40 minutes when 'light', and may shoot up to 1.5 hours when 'bad'...

Cheers!

Clem
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Old 17th February 2006, 10:41 PM   #9
rinsbag is offline rinsbag  Canada
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Default ADCOM 555

I just wanted to say thanks for the info. I did power it up after I changed the fuses. Hopefully its still ok.

In response to CHRIS who lives in Georgetown. How much do you think to repair this? Do you do repairs yourself? Can you hit me back and let me know if you think its worth fixing? If its too expensive I think I'll try to do it myself once I learn how to. Any suggestions on where I could learn more about electronics? What things inside are called or what you think may be the problem.
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Old 17th February 2006, 11:31 PM   #10
anatech is offline anatech  Canada
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Hi rinsbag,
One can never say how much a repair is until you actually see. Not a wise person anyway. Yes, I repair them myself. The amp is worth repairing unless really terrible things have happened. It doesn't sound like that's the case.

What I can do is have you drop by and we'll pop the cover. I can explain what I find and try to estimate it for you. You can decide from there. You may learn a few things just by doing this.

PM me, my e-mail is turned on.

-Chris
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