recapping amps

[izeek]

here i go again.
i bought an adcom gfa 5500.
its lacking ass-end. someone here provided information that it is out of spec to due cap age.
a few questions, maybe.
1. i spent 500 on it. it will cost 245 for a recap kit. then ill be in for almost 800 not counting my time. going price is 500-700. id assume a good few have the same problem.
is it worth it.
2. its been a looong time since i was a practicing electronic tech though ive done a decent job soldering on some cables and switches i replaced.
i have good hand skills from my current job as a pedorthist.
not a cakewalk but i should be able to do it. can i do it?

i sorta thinking about doing it for the experience. but then id have another piece of equipment, one i might not use.
comments please.
if you have nothing positive to add please keep it moving.

 

[pseudoid]

#1] here i go again.
#2]is it worth it.
#3] its been a looong time
#4] not a cakewalk but i should be able to do it. can i do it?
#5] i sorta thinking about doing it for the experience. but then id have another piece of equipment, one i might not use.
comments please.
if you have nothing positive to add please keep it moving.

Yeah! Mine is certainly negative but I am not moving: All those above snippets from your post look negative.
Like "I am thinking to think"!
We all know the answer to [#2], so I can only encourage you to simply ignore that question, and start w/a schedule, so if you DO start, you can't stop.

 

[solderdude]

The real question is if all the relevant caps all indeed have lost capacitance in such a way that bass will be lacking.
I am not convinced.

Perhaps use a capacitor checker and just measure one of the big capacitors and check capacitance and ESR.

To check I would get out the scope and look at the power supply ripple and see how big that gets under continuous load or burst load.

If you don't have an ESR meter or scope than perhaps simply recapping will do nothing but emptying your wallet.
Trying to fix that what is not broken will not bring much improvement.

 

[DanielT]

Good luck!

I'm not experienced in recap but I guess if you want answers on whether it's worth it:

it will cost 245 for a recap kit

So it probably makes sense if you tell what is included in that kit and if it is sensible quality of the capacitors and so on. That so those with experience can help you.

Edit:
Now saw that solderdude wrote before me. He is good and knowledgeable. I'm following your thread now. I'm pretty inexperienced so I will not write more in it.

 

[izeek]

The real question is if all the relevant caps all indeed have lost capacitance in such a way that bass will be lacking.
I am not convinced.

Perhaps use a capacitor checker and just measure one of the big capacitors and check capacitance and ESR.

To check I would get out the scope and look at the power supply ripple and see how big that gets under continuous load or burst load.

mmm. i dont as yet have that equipment but i know now.

 

[izeek]

Good luck!

I'm not experienced in recap but I guess if you want answers on whether it's worth it:

it will cost 245 for a recap kit

So it probably makes sense if you tell what is included in that kit and if it is sensible quality of the capacitors and so on. That so those with experience can help you.

lemme track it down.
https://www.ebay.com/itm/Adcom-GFA-...2349624.m46890.l49286&mkrid=711-127632-2357-0

 

[izeek]

Yeah! Mine is certainly negative but I am not moving: All those above snippets from your post look negative.
Like "I am thinking to think"!
We all know the answer to [#2], so I can only encourage you to simply ignore that question, and start w/a schedule, so if you DO start, you can't stop.

figures. guess you forgot that unwatch button.

 

[solderdude]

It is clear what's in the kit. The PS caps and a few coupling caps for the input.
The schematic is easily found.

Before ordering the kit you need to know if the caps NEED replacement (which they might not).

 

[izeek]

It is clear what's in the kit. The PS caps and a few coupling caps for the input.
The schematic is easily found.

Before ordering the kit you need to know if the caps NEED replacement (which they might not).

definitely

 

[sergeauckland]

I read a lot about recapping amplifiers, even as young as 10 years old. I find his fairly ludicrous as capacitors unless they actually fail, have very long lives.
A capacitor is rated for a certain number of hours, at a rated temperature and voltage. Unless the caps have been poorly chosen, or located right next to a source of heat then the main degradation comes from internal heat. A capacitor is rated at say 5000 hours at 85degrees. Life doubles for every 10 degrees of temperature reduction below their rating, so at a temperature of, say 45 degrees inside the capacitor, that's 80000 hours, or 10 years left on 24/7, but sensible usage of 2 hours a day, that's 109 years of use, 2 hours a day, every day.

There are other mechanisms that degrade capacitors, not just temperature, but that's the main one, so provided the caps are sensibly rated for ripple, which affects internal temperature and voltage, they'll last a very long time.

I have 50+ year old equipment working to spec with original caps, so I leave well enough alone unless there's a reason to change them.

S

 

[MRC01]

The caps might need replacing, but it's not a 100% given.

My Adcom 5800 is 29 years old with daily use over all that time. It still produces measured flat frequency response down to 20 Hz up to its rated power. And distortion too low for me to measure. DC offsets measure < 5 mV on each channel. Still performing like new to original specs. The only part I've had to replace is the power switch.

You say this old GFA 5500 "lacks ass-end". I assume you mean bass response. Can you measure and quantify that? Perhaps use your DIY skills to measure it and see what it really needs.

 

[Timcognito]

Does one have to desolder the Caps to test them. I have 20+yo ARC CA-50 that I plan to hand over to my son who loves it when he hits 30. Plan to replace the tubes also. It still sounds good if little shy in bass control but with all the good subs ou there this easily fixed these days. ARC never went for the tube warmth in their tube stuff. ARC CA50 is not in use currently.

 

[MakeMineVinyl]

Does one have to desolder the Caps to test them.

Generally, yes, power supply capacitors cannot have any other circuitry connected to them to get an accurate reading of capacitance. A coupling capacitor between audio stages might be able to be measured, but I'd check a schematic or trace the circuit to be sure nothing is in parallel with it.

 

[izeek]

The caps might need replacing, but it's not a 100% given.

My Adcom 5800 is 29 years old with daily use over all that time. It still produces measured flat frequency response down to 20 Hz up to its rated power. And distortion too low for me to measure. DC offsets measure < 5 mV on each channel. Still performing like new to original specs. The only part I've had to replace is the power switch.

You say this old GFA 5500 "lacks ass-end". I assume you mean bass response. Can you measure and quantify that? Perhaps use your DIY skills to measure it and see what it really needs.

yes. it seems wanting in bass response.
ill measure it this weekend hopefully and have that answer.
im glad to know yours is still cooking.

 

[escksu]

USD245 for recap is very expensive!! OK, from my personal experience + readups from other forums, those power reservoir caps are most likely the culprits. If possible, check them first (then you don't need to desolder every cap).

You can also check the manufacturing dates on those caps (maybe previous owner have replaced it).

 

[escksu]

I read a lot about recapping amplifiers, even as young as 10 years old. I find his fairly ludicrous as capacitors unless they actually fail, have very long lives.
A capacitor is rated for a certain number of hours, at a rated temperature and voltage. Unless the caps have been poorly chosen, or located right next to a source of heat then the main degradation comes from internal heat. A capacitor is rated at say 5000 hours at 85degrees. Life doubles for every 10 degrees of temperature reduction below their rating, so at a temperature of, say 45 degrees inside the capacitor, that's 80000 hours, or 10 years left on 24/7, but sensible usage of 2 hours a day, that's 109 years of use, 2 hours a day, every day.

There are other mechanisms that degrade capacitors, not just temperature, but that's the main one, so provided the caps are sensibly rated for ripple, which affects internal temperature and voltage, they'll last a very long time.

I have 50+ year old equipment working to spec with original caps, so I leave well enough alone unless there's a reason to change them.

S

Thats not how the lifespan of electrolytic caps work. Apart from operational-lifespan, they also have shelf-life. The main reason is that the electrolytes degrade over time. They also evaporate over time (the rubber gasket is not 100% deal).

Btw, electrolytics degradation is pretty gradual. They still function beyond their operation life-span, just that its out of specs (its not sudden complete failure). Of course, some do blow up but thats not really common.

 

[MRC01]

Generally speaking, temperature is a contributing factor to shortening lifespan of electronic components.
I wonder whether one reason my 5800 has lasted so long is because it has temperature controlled variable speed cooling fans. When you first turn on the amp, it takes about 10 minutes for the fans to turn on, spinning slowly and quietly. If you crank it up to high power the fans speed up.

 

[gene_stl]

I am resetting up my late seventies system and have been taking all the pieces to a young man who has assembled an excellent test bench.
Since I was there last he got an audio precision unit.
All my late seventies gear really acquitted itself amazingly well. Much better than I expected. Before you spend $250 on a recap kit you should look into who specified the kit and what is actually in it.
I take a very dim view of all this recapping that is going on. If it ain't broke don't fix it.

 

[DanielT]

18 000 uF, 100 V. As in my Fostex 600 that my friend did a recap on. That plus a number of capacitors. No $ 245. Incidentally, the electrolytes look very similar. You have twice as many, but if I had had it, it would still have been less than $ 245.
Okay, he ordered quite a lot from Mauser (also for other projects), plus some offer or whatever it was so it may not be possible to compare with your kit. Price that is. . I did not investigate how he got the gadgets at such a good price.

Could not help but write.

Edit:
Can I hear any difference? Well, hum. Seriously I do not know. How do I know if I now feel I hear any difference, if it is imagination or wishful thinking? Nevermind. He checked with an occiloscope. It looked good. DC offset (I think he checked, I assume). A bit of the usual service and checking. It was good that he did it anyway.

 

[escksu]

Generally speaking, temperature is a contributing factor to shortening lifespan of electronic components.
I wonder whether one reason my 5800 has lasted so long is because it has temperature controlled variable speed cooling fans. When you first turn on the amp, it takes about 10 minutes for the fans to turn on, spinning slowly and quietly. If you crank it up to high power the fans speed up.

Yes, temperature is one reason. However, electrolytic capacitors do not usually fail after its rated life-span. It mostly just degrade beyond specs but still entirely functional. Thats why they still work after 20yrs.

And then, caps degradation in amps are not necessarily audible. Eg. for power reservoir caps, you may not even notice anything unless you crank the amp to very high volume.