Kevin
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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.
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.
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.
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.
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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
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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 ....
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 ....
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.
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.
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.
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?
Right Channel 0.035 vdc
Left Channel 0.033 vdc
Am I ok to hook up some speakers to this amp?
I believe the concern about the power supply capacitors is that they may blow up when you energize them, if they are defective. If you are past the point of turning the amp on, then they have survived that test.
I believe I have determined that the amp does NOT have leaky PS capacitors. For those of you who have a GFA-555 amp and you see stains in and around your PS caps check this 1st. The rectifier bridges and the output transistors. The compound used to lay these components down on my amp heated up and leached around the case some. I have four output transistor boards on my amp and this stain is under each one. Also around the two rectifier bridges which run toward the PS caps. Now the white compound is not running and looks normal but there must be an oil that leached out. I am attaching a few links to pics for those who would like to see it.
Thank you to everyone who chimed in to help this newbie to the game. As I learn more about amplifier components I may replace some of them on this amp. Sounds good now though!
http://www.civilwarmedicalbooks.com/caps/leak1
http://www.civilwarmedicalbooks.com/caps/leak2
http://www.civilwarmedicalbooks.com/caps/leak3
http://www.civilwarmedicalbooks.com/caps/leak4
Thank you to everyone who chimed in to help this newbie to the game. As I learn more about amplifier components I may replace some of them on this amp. Sounds good now though!
http://www.civilwarmedicalbooks.com/caps/leak1
http://www.civilwarmedicalbooks.com/caps/leak2
http://www.civilwarmedicalbooks.com/caps/leak3
http://www.civilwarmedicalbooks.com/caps/leak4
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Sorry to post this if it is in another thread. I searched but didn't find the answer. I see that there is a recommendation to bypass the filter caps in the 555 with something 22-66 uF. Is there a best value for these caps if I'm ordering them? I assume they should be 100v. Also, what would you recommend if I'm going to order them speacially- brand, type, etc
Thanks
Thanks
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