Adcom GFA-555 Leaky Power Caps?

PreCD · 02:47 AM

Hello All. This is my 1st post here and am happy so see that there seem to be many educated people here. I am just entering into the game of audio and just purchased a Adcom GFA-555 amplifier. I have common sense so when I received the amp the 1st thing I did was crack the lid. Inside I found what seems to be leaking power capacitors. Can someone confirm this from the pics please? If so is this cause to be alarmed and if that is the case what am I looking at to get it fixed? Have not had a chance to power it up yet because the preamp is in the mail. Thank you in advance for any help.

Kevin

jordheis · 29th September 2011, 04:04 AM

Many posts on this issue, will help you know how alarmed or not you can be, some safety concerns with big amps, and specific ways to address the caps.

Read up before powering the 555 up.

djk · 29th September 2011, 08:43 AM

$23.95

Radial Capacitors

ODougbo · 09:39 AM

Looks a little strange, maybe somebody dripped something through the top of unit (beer/soda).

Hard to tell from pic. but the connector on left looks likes it has some corrosion, so that doesn’t make sense.

One good thing about Adcom easy to work on - pull the caps out and inspect them.

Good advise from member, don’t hook up a good pair of speakers to it :-/

Ebay amp? Hit or miss buying amps on there…….. I was out $660 on an Ebay amp deal, I was one of the lucky ones and got it all back, but took a lot of emails, etc.

PreCD · 11:01 AM

Quote:

Originally Posted by djk

$23.95

Radial Capacitors

Looks like this one is rated higher than the caps that are installed now. The caps that are there now are 15,000uF, 100V. Would it hurt to move up 7,000uF? Can I get straps to screw down to the cap so that I could solder? The amp has about a 8 awg wire running across the caps along with the others that are necessary.

Thanks for the response.

Kevin

cliffforrest · 29th September 2011, 12:58 PM

Going in higher VALUE (not rating - that's the voltage max) by up to 50% should make no difference at all, although there will be an increase in switch-on inrush current.

SOLDER TAGS (google it) under the screw heads easily allow you to wire to them. Wire guage is not important here, within reason. Components across the cap terminals are resistors to ensure caps are discharged when powered off.

Looking at the photo, I'm not sure that the stain comes from the cap. Best to take them out and check for bulges, splits etc.

The long term failure mode is drying out of the electrolyte increasing the impedance. This causes extra heat from the ripple current and further degradation.

A 'scope to measure the ripple voltage would be a good thing ....

WithTarragon · 29th September 2011, 12:59 PM

While you are at it, there are other electrolytic caps on the amp that should probably be replaced (simply due to age). Use the same values and pay attention to polarity. It is not expensive.

Again, while you are at it, in the later version of the GFA 555, usually there was a bypass cap on that big PS cap. If you have one, replace it. If you do not have one, then add one (in the range of 22 to 66 uF). There are threads on this mod. It is simple, cheap, and tightens up the bass respsonse. Search the threads.

I think these amps are a great bargain.

ODougbo · 29th September 2011, 02:41 PM

My buddy has 4 565s, he had cap problems, said he got replacements at Radio Shack (hard to believe) btw, his system; a 2 channel stereo, is awesome. The amp are working perfectly now.

WithTarragon · 29th September 2011, 03:50 PM

Quote:

Originally Posted by ODougbo

My buddy has 4 565s, he had cap problems, said he got replacements at Radio Shack (hard to believe) btw, his system; a 2 channel stereo, is awesome. The amp are working perfectly now.

The GFA 555 and 565 are not comparable amps. They are a different design. I like them both.

PreCD · 30th September 2011, 10:58 AM

Ok. I checked the voltage at the speaker outputs with no equipment attached and here is what I got:.

Right Channel 0.035 vdc
Left Channel 0.033 vdc

Am I ok to hook up some speakers to this amp?

29th September 2011, 02:29 AM	#1
PreCD diyAudio Member Join Date: Sep 2011 Location: USA	Adcom GFA-555 Leaky Power Caps? Hello All. This is my 1st post here and am happy so see that there seem to be many educated people here. I am just entering into the game of audio and just purchased a Adcom GFA-555 amplifier. I have common sense so when I received the amp the 1st thing I did was crack the lid. Inside I found what seems to be leaking power capacitors. Can someone confirm this from the pics please? If so is this cause to be alarmed and if that is the case what am I looking at to get it fixed? Have not had a chance to power it up yet because the preamp is in the mail. Thank you in advance for any help. Kevin Last edited by PreCD; 29th September 2011 at 02:47 AM. Reason: No pics attached.

29th September 2011, 04:04 AM	#2
jordheis diyAudio Member Join Date: Jan 2011 Location: Minnesota, USA	Search the forum Many posts on this issue, will help you know how alarmed or not you can be, some safety concerns with big amps, and specific ways to address the caps. Read up before powering the 555 up. __________________ Striving to remove some ignorance every day (always starting with my own)

29th September 2011, 08:43 AM	#3
djk diyAudio Member Join Date: Feb 2001 Location: USA	$23.95 Radial Capacitors __________________ Candidates for the Darwin Award should not read this author.

29th September 2011, 09:34 AM	#4
ODougbo diyAudio Member Join Date: Aug 2011 Location: Maryland USA	Looks a little strange, maybe somebody dripped something through the top of unit (beer/soda). Hard to tell from pic. but the connector on left looks likes it has some corrosion, so that doesn’t make sense. One good thing about Adcom easy to work on - pull the caps out and inspect them. Good advise from member, don’t hook up a good pair of speakers to it :-/ Ebay amp? Hit or miss buying amps on there…….. I was out $660 on an Ebay amp deal, I was one of the lucky ones and got it all back, but took a lot of emails, etc. Last edited by ODougbo; 29th September 2011 at 09:39 AM.

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29th September 2011, 12:58 PM	#6
cliffforrest diyAudio Member Join Date: Sep 2004 Location: UK	Going in higher VALUE (not rating - that's the voltage max) by up to 50% should make no difference at all, although there will be an increase in switch-on inrush current. SOLDER TAGS (google it) under the screw heads easily allow you to wire to them. Wire guage is not important here, within reason. Components across the cap terminals are resistors to ensure caps are discharged when powered off. Looking at the photo, I'm not sure that the stain comes from the cap. Best to take them out and check for bulges, splits etc. The long term failure mode is drying out of the electrolyte increasing the impedance. This causes extra heat from the ripple current and further degradation. A 'scope to measure the ripple voltage would be a good thing ....

29th September 2011, 12:59 PM	#7
WithTarragon diyAudio Member Join Date: Jun 2007	While you are at it, there are other electrolytic caps on the amp that should probably be replaced (simply due to age). Use the same values and pay attention to polarity. It is not expensive. Again, while you are at it, in the later version of the GFA 555, usually there was a bypass cap on that big PS cap. If you have one, replace it. If you do not have one, then add one (in the range of 22 to 66 uF). There are threads on this mod. It is simple, cheap, and tightens up the bass respsonse. Search the threads. I think these amps are a great bargain.

29th September 2011, 02:41 PM	#8
ODougbo diyAudio Member Join Date: Aug 2011 Location: Maryland USA	My buddy has 4 565s, he had cap problems, said he got replacements at Radio Shack (hard to believe) btw, his system; a 2 channel stereo, is awesome. The amp are working perfectly now.

30th September 2011, 10:58 AM	#10
PreCD diyAudio Member Join Date: Sep 2011 Location: USA	Ok. I checked the voltage at the speaker outputs with no equipment attached and here is what I got:. Right Channel 0.035 vdc Left Channel 0.033 vdc Am I ok to hook up some speakers to this amp?

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