Hi Nigel,
Yes they do, but if you run into the ones that are orange and sealed on the bottom, they are often as good, or even better than the new ones. I test them anyway just to be safe, but the number of bad ones I have found is a very small number.
Just look for a shiny, black seal over the rubber with the legs coming out as normal.
-Chris
Yes they do, but if you run into the ones that are orange and sealed on the bottom, they are often as good, or even better than the new ones. I test them anyway just to be safe, but the number of bad ones I have found is a very small number.
Just look for a shiny, black seal over the rubber with the legs coming out as normal.
-Chris
Hi maty,
Most of what was done was not going to contribute to the sound quality at all. It looks like a collection of what you read on the internet, but doesn't address improving the sound quality at all.
The lead dress in the original photo makes the amp possible to service without disconnecting everything. Very often, the original power supply capacitors are fine. You check them using an oscilloscope and looking at what shape the ripple waveform is. I didn't see anything about checking the output transistors or matching the input transistors, and those are critically important for improved sound quality.
-Chris
Most of what was done was not going to contribute to the sound quality at all. It looks like a collection of what you read on the internet, but doesn't address improving the sound quality at all.
The lead dress in the original photo makes the amp possible to service without disconnecting everything. Very often, the original power supply capacitors are fine. You check them using an oscilloscope and looking at what shape the ripple waveform is. I didn't see anything about checking the output transistors or matching the input transistors, and those are critically important for improved sound quality.
-Chris
I have never listened to an Adcom and I believe there are not many in Europe, much less in Spain.
As regards the electrolytic capacitors, this graph is illustrative about useful life.
As regards the electrolytic capacitors, this graph is illustrative about useful life.
Hi maty,
That graph is a good rule of thumb for filter caps. However, it does not hold for modified capacitors (sealed for example) or across different types.
I've tested capacitors in every single audio product I have ever touched, that is a lot. There are some where capacitors are in better shape than the new ones. I don't replace those as it is not in the best interest for the customer. I have had defective new capacitors, so I check each one before it goes in too.
What is the graph showing? Some labeling appears to be missing. Failure rate? I see temperature vs run time. What are they attempting to show? Also, be aware that this would be valid for that manufacturer's parts and not necessarily anyone Else's parts.
That graph is a good rule of thumb for filter caps. However, it does not hold for modified capacitors (sealed for example) or across different types.
I've tested capacitors in every single audio product I have ever touched, that is a lot. There are some where capacitors are in better shape than the new ones. I don't replace those as it is not in the best interest for the customer. I have had defective new capacitors, so I check each one before it goes in too.
What is the graph showing? Some labeling appears to be missing. Failure rate? I see temperature vs run time. What are they attempting to show? Also, be aware that this would be valid for that manufacturer's parts and not necessarily anyone Else's parts.
Hi maty,
One type of capacitor people like to yank are those wet slug tantalum capacitors. Those are almost always in excellent condition, and cost $30 + USD to replace with like. They are extremely good and have reduced package size. Replacement capacitors tend to be far too large to fit, but people still put them in. One unit had 6 missing that an "internet techy" had "improved". A set of new, very expensive capacitors returned the unit to its former, excellent performance. The "upgrade" cost the owner north of $200 at cost pricing for the return of the original capacitor types. So unnecessary and stupid.
I guess everyone is an expert if they have an internet connection.
-Chris
Not as good in that case. This is not a strange finding. However, I am not saying that old product is better than new products. Those capacitors were special back then, and if I were to compare against new ones the same I might see some degradation.
One type of capacitor people like to yank are those wet slug tantalum capacitors. Those are almost always in excellent condition, and cost $30 + USD to replace with like. They are extremely good and have reduced package size. Replacement capacitors tend to be far too large to fit, but people still put them in. One unit had 6 missing that an "internet techy" had "improved". A set of new, very expensive capacitors returned the unit to its former, excellent performance. The "upgrade" cost the owner north of $200 at cost pricing for the return of the original capacitor types. So unnecessary and stupid.
I guess everyone is an expert if they have an internet connection.
-Chris
Adcom GFA-555 MKII [Updates]
Striking: he do not change these capacitors.
http://www.adpslab.com/en/audio/upgrades/10-adcom-gfa-555-mkii
Striking: he do not change these capacitors.
http://www.adpslab.com/en/audio/upgrades/10-adcom-gfa-555-mkii
Yes, I don't change the power supply caps unless the customer wants them. They're usually fine and cost about $130 in parts alone. Also, should they fail, the consequence is not catastrophic. Since the new ones are so much smaller, and I have to install new capacitor brackets anyway, I line them up side-to-side, and mount the bridges to the chassis instead of up on top of the caps. This means new buss-bars, so I go a little nuts and use 4ga solid copper wire.
I'll admit a lot of this is cosmetic, but it matters to me. The amp is still easy enough to service. The only additional difficulty is that one must remove two screws from the back panel in order to get at the new terminal block to change AC input voltage.
And I do match the input transistors.
My primary concern when I restore these amps is reliability. Every component and every solder connection is checked. I make no outlandish claims about improved sound quality, and I am very cautious about second-guessing the designer.
I'll admit a lot of this is cosmetic, but it matters to me. The amp is still easy enough to service. The only additional difficulty is that one must remove two screws from the back panel in order to get at the new terminal block to change AC input voltage.
And I do match the input transistors.
My primary concern when I restore these amps is reliability. Every component and every solder connection is checked. I make no outlandish claims about improved sound quality, and I am very cautious about second-guessing the designer.
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