Blown Adcom 555 II

[robertbartsch]

Ok, well this is another reason I'm not found of old electronics.

My Adcom blew and is dumping Dc into the speaker circuits and the fix is $240.

On E-bay a typical version of this amp is worth about $275-300.

What should I do here - toss it inthe trash or take to another repair shop?

[withTarragon]

Ok, well this is another reason I'm not found of old electronics.

My Adcom blew and is dumping Dc into the speaker circuits and the fix is $240.

On E-bay a typical version of this amp is worth about $275-300.

What should I do here - toss it in the trash or take to another repair shop?

It is painful to hear that you might toss it in the trash. They were a great amp in their day.

The safe bet is that the output devices would need to be replaced at the very least. Then you would need to find out why they went bad. So it is understandable why the repair shop wanted to charge you that kind of money.

If you are seriously thinking of getting rid of it, I could use the chassis and transformer. I am a DIYer and have some projects in mind. I live in CT and could pick it up. PM me if you like and suggest a fair price.

On a positive note, you were lucky the DC did not take out any of your drivers.

Thanks,
-Tom

[robertbartsch]

I did not discuss the details of the mortality with the shop but I assume you assume the output transformers are toast.

...I've only had the amp for about 4 months or so. At first I did not like it much because the LF material seemed to be over emphasized.

Since I am now playing the basement system with a different amp, I kinda miss this, however.

Oh well, I'm done buying 20+ year old electronics - been burned to often.

[Russellc]

I did not discuss the details of the mortality with the shop but I assume you assume the output transformers are toast.

...I've only had the amp for about 4 months or so. At first I did not like it much because the LF material seemed to be over emphasized.

Since I am now playing the basement system with a different amp, I kinda miss this, however.

Oh well, I'm done buying 20+ year old electronics - been burned to often.

while I know Mcintosh has output transformers on many of their Solid State units, I wasnt aware that Adcom had output transformers? Perhaps you mean output transistors?

Russellc

[robertbartsch]

....right - output transistors - 16 in all I think!

[hjames]

....right - output transistors - 16 in all I think!

yeah, so post it to ebay as having blown output transistors and see what happens ... Can't hurt and beats just tossing in a dumpster ...
If you're honest about it when you post the ad, that's a reasonable thing to do.

caveat - before you joined I bought a "tested and working" JBL/UREI poweramp that arrived in a box with just a smidge of popcorn - this is a HEAVY pro amp .., it smelled and when I opened it I found evidence it had cooked pretty thoroughly. After 10 weeks and a lot of yelling and fighting with ebay and Paypal, I did get a refund - only because I disputed the charge on my VISA card!! But THAT seller was just SCUM.

See - http://audioheritage.org/vbulletin/showthread.php?t=17362&page=3

[sourceoneaudio]

Ok, well this is another reason I'm not found of old electronics.

My Adcom blew and is dumping Dc into the speaker circuits and the fix is $240.

On E-bay a typical version of this amp is worth about $275-300.

What should I do here - toss it inthe trash or take to another repair shop?

FYI:
Adcom does take trade ins of old broken Adcom gear towards a new amp/purchase. The GFA-5500 would be a great replacement, ($1500.00) last retail. If you are not looking to trade in the GFA-5802 is a highly sought after high end power amp, last retail was $2200.00. The average used mint condition price with box $800.00 to $1200.00. (Nelson Pass Engineered)

http://www.avrev.com/home-theater-po...amplifier.html
Adcom also is now owned by Emerson. Good or bad I don't know, but old Emerson?

[opimax]

that last piece of news is damn scary

Somehow Emerson and Pass in the same breath does not seem natural

Mark

[BMWCCA]

that last piece of news is damn scary

Somehow Emerson and Pass in the same breath does not seem natural

Hey! Emerson Electric used to make a damn good ceiling fan! I think my brother had a summer job with them in St. Louis about fifty-years ago. Do they still make anything here in the USA?

[grumpy]

Emerson Electric
Emerson Radio Corp.

quite different animals as far as I can tell.

So what's going to happen with the blown Adcom?

[BMWCCA]

Emerson Electric
Emerson Radio Corp.

quite different animals as far as I can tell.

You are correct, sir. A look at their product offerings and maybe it is the electric motor company that should be making amps!

[hjames]

Emerson Electric
Emerson Radio Corp.

quite different animals as far as I can tell.

So what's going to happen with the blown Adcom?

Dunno - seems the tales here are going to be legendary ...
Doesn't seem that hard to put it on ebay, mention that it cooked and the seller is not an engineer and doesn't know exactly what that means, but it won't power on now ... and just sell the darned thing!

[Ducatista47]

I labored over an amp for three weeks, ordered all kinds of parts, went through and replaced anything that looked even questionable. I turned it on and it ran for 10 minutes before popping. Really disheartening. I feel once a SS amp takes a dive the cost and trouble of repair is not worth it. There is a lot of energy in there and when things get weak they die in a spectacular manner

As to eventually death, MOS-FET and other thick film outputs are sensitive to static, and can also develop "holes" in the substrate over time. Add to that dirty heat sinks and dry silicone compound on the transistors and it's possible they can just go out. Although we all romance over how things were made better back then, I think quality has greatly improved today when it comes to transistors. Objective sound quality aside, it's a reasonable argument that a modern amp for 300-400 dollars would do just fine and come with a warranty to boot.

I agree, and it is a shame but true that repair prices, complexity and difficulty render most transistor amps Kleenex products - throw away.

MOSFETS can be very reliable when designed and put together with skill. Note the startling failure record of Nelson Pass amps. Startling because some of the designs have never had a failure in the field.

Well I 've owned many tube amps over the years and I would not give two cents for one now.

The new SS amps built today are quite good and reasonably prices; old electronics are just that - old.

And the new SS amps will later become throwaway pieces too. Compare that to replacing a tube. Way down the road, eventually perhaps a few caps, on a tube amp easily accessible with simple tools; usually just removing a cover.

Class A tube amps tend to be very simple circuits. My favorite amp is wired point to point. I have never seen more open and easy access.

The hifi shop I use has a tube tester. I look for 5000 hours for my power tubes and at least 20000 for my preamp tubes.

Notice that where heat is the enemy of transistors, tubes and MOSFETS need to be hot to work best, and their amps are designed to run hot and not be bothered by it. No fans, either. Heat rises so the hot parts or their heat sinks are outside or on top. Heat rises, what a concept! In a Nelson Pass authored amp, the heat sinks are designed to regulate the temperature of the output devices to a range, not to keep them cool.

Clark

[opimax]

I am not an expert or trying to cause trouble, just adding observed info, really

My Perreaux 6000b, (300/c mid 80's vintage, are mosfet and do have fans and run very cool. The smaller 3000b 180/c does not have a fan, not noticeably hot, you can tell it is on, but not hot at all.

I originally ran them with fan disconnected but they got hot when pushed so I reconnected them and in the basement away form the listening room. Heck maybe they should be hot, I thought they are well respected amps.

Mark

[Ducatista47]

maybe they should be hot, I thought they are well respected amps.

Mark

I will go with the flow. Everyone says they sound great and I won't argue.

I am sure they were designed to run at whatever temperature they reach when used as intended. I could have added that hot is relative and applies to the part, not the heat sink.

Nelson feels his First Watt F1 and F2 are most of the way there after a five minute warm up, but better after an hour. Cold, they never make it to where they should be. I notice that when people build them from scratch they sometimes use too much heat sink and they never get hot enough.

Like so many things, while it sounds un-American, more is not better here.

Clark