Hi, all I am new and pretty limited to using a multimeter (although I can disk-level edit a partion table in little endian format - like there was another way) and thanks for your patience.
I bought a pair of these black beauties on Ebay a year ago and they have been working fine ever since. They are mated to my Sony STRDG-1000. Until a few days ago I noticed barely any volume coming from the front speakers, but still some. I attempted a DTS calibration using the Sony mic, but received an error that the fronts were absent or the mic was not plugged in correctly.
The amps arrived with a receipt for repair of the DC Offset issue performed by a Setauket, NY firm and I am trying to determine exactly what was done on these serial #'s but believe, according to the website, it was:
"GFA- 565 Monoblock:
These units develop a DC offset problem that leads to a loud turn on thump and eventually will burn out a speaker or lead to major failure of the output transistors. The cause is poor quality electrolytic caps on the driver board that leak onto the board and cause corrosion. We clean off the board, replace all caps and resistors , replace the driver transistors and adjust the bias."
I notice a thump powering on but began wondering if the problem is the line output from the Sony and not the amps at all as I find it odd they would both begin exhibiting problems at exactly the same time. How can I determine the root of this? The Sony was new and bought for the purpose of scting as a 7.1 processor and preamp for the blocs.
Note: The caps appear to be Adcom 35,000 and In think that would meke them the originals (or s bsd replacement.)
Thanks in advance
I bought a pair of these black beauties on Ebay a year ago and they have been working fine ever since. They are mated to my Sony STRDG-1000. Until a few days ago I noticed barely any volume coming from the front speakers, but still some. I attempted a DTS calibration using the Sony mic, but received an error that the fronts were absent or the mic was not plugged in correctly.
The amps arrived with a receipt for repair of the DC Offset issue performed by a Setauket, NY firm and I am trying to determine exactly what was done on these serial #'s but believe, according to the website, it was:
"GFA- 565 Monoblock:
These units develop a DC offset problem that leads to a loud turn on thump and eventually will burn out a speaker or lead to major failure of the output transistors. The cause is poor quality electrolytic caps on the driver board that leak onto the board and cause corrosion. We clean off the board, replace all caps and resistors , replace the driver transistors and adjust the bias."
I notice a thump powering on but began wondering if the problem is the line output from the Sony and not the amps at all as I find it odd they would both begin exhibiting problems at exactly the same time. How can I determine the root of this? The Sony was new and bought for the purpose of scting as a 7.1 processor and preamp for the blocs.
Note: The caps appear to be Adcom 35,000 and In think that would meke them the originals (or s bsd replacement.)
Thanks in advance
have you possibility to inject any other signal ( source , signal cable ) in monoblocks ?
one solution - headphone output ( with pot ) from CD or boombox , with appropriate signal cable
or any other (volume pot equipped) source , for which you have signal cable , possible to connect to monoblocks .
one solution - headphone output ( with pot ) from CD or boombox , with appropriate signal cable
or any other (volume pot equipped) source , for which you have signal cable , possible to connect to monoblocks .
Welcome to the forums Lockport (I'm in Wpg). I think your reasoning is sound--if you lose sound from both amps at the same time maybe it's the preamp. I'm not a pro, but I have some test equipment and could help troubleshooting if need be. Have you tried what Zen Mod suggested? Alternatively, do you have an integrated amp or a receiver with pre-outs and main-ins that you could try connected to the preamp and to the amps?
Steve.
Steve.
Zen Mod said:
I hooked my laptop to one via the audio out (headphone) jack and the volume has to be far too low for them to be outputting anything near the area of 300 watts!
It just seemsodd to me that they would both go at once. The large cans inside, these are the caps that were famous for leaking, right? Mine are branded Adcoms 110v, 35,000 - would these have been replaced with a different brand if the legitimate fix was done, or is irtpossible they are later caps that were corrected?
spind said:
Cool! Same name, too!
Yes, I have an older Denon AVC2000 with pre-outs I just hooked up and ran my laptop to its Aux (everything to the newer amp is HDMI), and, although I have audio, it is not the booming, overwhelming effect of mono-blocs.
I sent an email to the firm that did the work (according to a receipt I have from the seller 18 months ago) to correct the DC offset and validate the inked in serial numbers. I am curious that the caps still are Adcom branded. I hope to hear from them tomorrow, in hopes they have time to look up a work order/invoice from that long ago. The services they do are posted and are $20more than my receipts but is probably just iunflation speaking and that is what was done. Would still like a parts detail from them if I can get it.
So, essentially the symptoms appear to be low volumes = low power output?
Am still moderated so timely lull between posts.
Thanks,
Steve
Lockport said:
dunno what's your laptop ; there is always chance that laptop have crappy output ;
according to explanation given in your first post - these big can caps aren't "caps on driver board" ;
if these big can caps are leaking , you'll probably hear loud hum in speakers ( disturbed PSU filtering , what's their role ) and distorted sound .
culprit is somewhere else , and it's still questionable is it in power amps .
have you any other ,even integrated , amp - to connect it instead of monoblocks , at least to test Sony STRDG ?
Zen Mod said:
Its basically a line out with enough power to drive a headphone. I have heard the blocs with this setup when I first got them and I have no where near the volume.
Zen Mod said:
I thought those were the infamous faulty ones. Inside of the unit, it is very clean. I see no evidence of corrosion or staining by any of the screws, on the top of the boards or anywhere else for that matter. Underneath may be different, however.
Zen Mod said:
I hooked up my Denon to act as preamp to the blocs as per previous post and this yielded the same result, ruling out the Sony as cause. It appears it is in the blocs now.
Lockport said:
Nope. Looks like you have way too much DC offset (too much DC on the outputs). It should be less than 10mV on this amp. Do some searching on this forum---there is lots of info about this problem here. The driver boards will need to be cleaned VERY thoroughly in an ultrasonic cleaner and then have new capacitors installed. Maybe you could send the boards to Georgetown and Anatech (a moderator on these forums---you may want to email him) could help you out?
Steve
spind said:
Steve
I have a receipt from the seller that these were cleaned and had the capacitors replaced on 08/2007, shortly before I bought them. The insides show no visible evidence of staining or corrosion.
I have also exchanged a couple emails with a tech at Adcom advising him the capacitor leakage issue should have been resolved as per the previous service and he said the following:
"The only key issue is to see if there is any DC offset on the output of the amplifier. If you
put a DC voltmeter across the speaker terminals/amplifier output, there should be well under 0.1
VDC output on each channel. Otherwise, the amplifier's power would need to be bench checked.
The capacitors themselves are likely not an issue."
I have seen some posts were Anatech opted in and would like his view on this.
Lockport said:
Well, if you are getting in the range of 1.0 VDC offset, then you are more than 10x higher than the Adcom tech advised. From my reading of the threads the cleaning is a very difficult process and its very hard to get them really clean enough. Repeated cleaning cycles are often needed. You may have a problem with the servo ic, but I'm guessing it's a cleaning issue.
Steve.
I am far from an expert with these amps but I do have a little experience.
First - the caps that leak and cause damage are small electrolytics on the driver board in the back of the amp. The large Adcom caps are not known for leaking. Even after they have leaked, people can only tell if there is still residue by getting the board hot with a soldering iron and smell the electrolyte burning.
From what I have heard the cleaning process of the circuit board is the critical part. If it is done correctly there should be very little offset, the problem is that it is a very tedious job to correctly clean the board and most people don't do it right. Doing it correctly involves removing most of the components and putting it in an ultrasonic cleaner with a solution for some period of time.
Having said all that, I suspect that the offset, while not good, is probably not related to your no output problem. The odds of both amps failing in the same manner at the same time are slim.
First - the caps that leak and cause damage are small electrolytics on the driver board in the back of the amp. The large Adcom caps are not known for leaking. Even after they have leaked, people can only tell if there is still residue by getting the board hot with a soldering iron and smell the electrolyte burning.
From what I have heard the cleaning process of the circuit board is the critical part. If it is done correctly there should be very little offset, the problem is that it is a very tedious job to correctly clean the board and most people don't do it right. Doing it correctly involves removing most of the components and putting it in an ultrasonic cleaner with a solution for some period of time.
Having said all that, I suspect that the offset, while not good, is probably not related to your no output problem. The odds of both amps failing in the same manner at the same time are slim.
Hi Steve,
The first thing you should do is unplug all cables from your amplifiers and measure the DC resistance from the common power ground (or common speaker terminal) to the RCA ground. Let me know what your reading is please.
Also, it is entirely possible that the cleaning job was not completely done. This would not be the first time I've seen that. Your DC offsets are completely out of spec. Normally, your DC offset will settle to a few mV. There is a DC servo to reduce the DC offsets, your offset is beyond the ability for this circuit to correct.
A turn on "pop" is normal for these amplifiers. When the amp is first powered on, the DC servo is not yet active. Your initial DC offset depends on the matching of the input quad of transistors and other factors. Matching these transistors is a long process and involves buying many of each number. I normally do not do this unless it is really needed.
The main filter caps are normally not in need of replacement, but seems to be on the "to do" list of many owners. To determine how good these caps are, you look at the shape of the ripple across them as the amplifier is idling, then as it outputs a sine wave into a dummy load. If the seal has ruptured, they will need to be replaced no matter how they test.
There are other tests and checks a good technician will do when servicing these amps. The technician you want will be probably 40 to 60 years old with close attention to detail. A guy who does the job right. Most of these people have moved on to industrial work and take clients on the side. I don't know how good Advance is, they were good, but the market today does not reward a patient service technician. That's why most of the better guys work from home these days. You do want a technician that used to do warranty service on higher end amplifiers. TV technicians do not have the correct mind set.
Why did the original owner sell these right after servicing? Seems to me that he had minimal service done in order to sell them. Not a good sign, and not surprising you have trouble now.
The current Adcom company are pretty helpful people, but be aware that there are no original employees working there. The company was bought and moved south to a different state. They probably bought the iP and parts, plus whatever other assets that were left. Other than that, they do not have any real direct experience with the older product. The last time I spoke with them, they had one technician who was getting use to these older amplifiers.
When selecting a service person or company, I think you should be checking to make sure they are actually competent. Many people say they know how to do things without the actual knowledge to back up what they say. You, as the consumer, end up paying for everyone else's mistakes. Worse yet are the "super techs" who work very quickly - and poorly. Any damage they cause will cost you to make right, or cause the loss of that amplifier.
-Chris
The first thing you should do is unplug all cables from your amplifiers and measure the DC resistance from the common power ground (or common speaker terminal) to the RCA ground. Let me know what your reading is please.
Also, it is entirely possible that the cleaning job was not completely done. This would not be the first time I've seen that. Your DC offsets are completely out of spec. Normally, your DC offset will settle to a few mV. There is a DC servo to reduce the DC offsets, your offset is beyond the ability for this circuit to correct.
A turn on "pop" is normal for these amplifiers. When the amp is first powered on, the DC servo is not yet active. Your initial DC offset depends on the matching of the input quad of transistors and other factors. Matching these transistors is a long process and involves buying many of each number. I normally do not do this unless it is really needed.
The main filter caps are normally not in need of replacement, but seems to be on the "to do" list of many owners. To determine how good these caps are, you look at the shape of the ripple across them as the amplifier is idling, then as it outputs a sine wave into a dummy load. If the seal has ruptured, they will need to be replaced no matter how they test.
There are other tests and checks a good technician will do when servicing these amps. The technician you want will be probably 40 to 60 years old with close attention to detail. A guy who does the job right. Most of these people have moved on to industrial work and take clients on the side. I don't know how good Advance is, they were good, but the market today does not reward a patient service technician. That's why most of the better guys work from home these days. You do want a technician that used to do warranty service on higher end amplifiers. TV technicians do not have the correct mind set.
Why did the original owner sell these right after servicing? Seems to me that he had minimal service done in order to sell them. Not a good sign, and not surprising you have trouble now.
Not really true! The capacitors were not known to be a poor quality type when they were bought new. The fault turned out to be the same one that caused capacitor failures in computer mother boards, other audio brands including some Nakamichi car cassette decks. So these capacitors where a nightmare for every manufacturer who used the brands who used this defective electrolyte in their capacitors. It certainly was not done knowingly by Adcom. I really hate when people make incomplete statements like this. It shows how little they think about things that they "know".
The current Adcom company are pretty helpful people, but be aware that there are no original employees working there. The company was bought and moved south to a different state. They probably bought the iP and parts, plus whatever other assets that were left. Other than that, they do not have any real direct experience with the older product. The last time I spoke with them, they had one technician who was getting use to these older amplifiers.
When selecting a service person or company, I think you should be checking to make sure they are actually competent. Many people say they know how to do things without the actual knowledge to back up what they say. You, as the consumer, end up paying for everyone else's mistakes. Worse yet are the "super techs" who work very quickly - and poorly. Any damage they cause will cost you to make right, or cause the loss of that amplifier.
-Chris
Thanks for your reply, Chris
One is 21.3 Ohms, the other is 11.3
Actually, they only seem to "pop" when I turn them off.
Good point, a couple months elapsed, indeed.
After much discussion the Adcom rep I was exchanging emails said the following
"As the DC voltages are far out of specification, my best guess is that it seems that the
circuit boards were not thoroughly cleaned. When the repair is made, it is a onetime repair,
and it does not reoccur. When the circuit boards are originally contaminated, the electrolytic
fluid from the capacitors will leak onto the boards, and because the boards are made of a
fibrous paper-like material, they absorb the fluid. The only way to get it out is to soak the
boards-repeatedly.
As I said, I would guess this has not been done initially, hence there is still excessive DC
offset. The amplifiers are still in need of repair, and although the issue will likely not get
worse (as there are no longer leaky capacitors), it is currently not correct and needs to be
remedied.
You may re-approach the service center who originally did the work, but if the repair was
completed over 30-60 days ago, it is unlikely that they will be responsive. I would suggest you
contact and ship your unit to:
Affiliated Electronics
216 Route 206, Ste 15
Hillsborough, NJ 08844
908-874-3799
teve21@datanyc.com
http://www.teve21.com/index.php
Affiliated Electronics in New Jersey maintains the inventory of Adcom legacy parts. Please note
that Affiliated Electronics performs more service on Adcom products than anyone, including
Adcom, and they typically have a fast turn around time."
Of course priority UPOS to them is over $500
But ground is on $150
Steve
anatech said:
One is 21.3 Ohms, the other is 11.3
anatech said:
Actually, they only seem to "pop" when I turn them off.
anatech said:
Good point, a couple months elapsed, indeed.
anatech said:
After much discussion the Adcom rep I was exchanging emails said the following
"As the DC voltages are far out of specification, my best guess is that it seems that the
circuit boards were not thoroughly cleaned. When the repair is made, it is a onetime repair,
and it does not reoccur. When the circuit boards are originally contaminated, the electrolytic
fluid from the capacitors will leak onto the boards, and because the boards are made of a
fibrous paper-like material, they absorb the fluid. The only way to get it out is to soak the
boards-repeatedly.
As I said, I would guess this has not been done initially, hence there is still excessive DC
offset. The amplifiers are still in need of repair, and although the issue will likely not get
worse (as there are no longer leaky capacitors), it is currently not correct and needs to be
remedied.
You may re-approach the service center who originally did the work, but if the repair was
completed over 30-60 days ago, it is unlikely that they will be responsive. I would suggest you
contact and ship your unit to:
Affiliated Electronics
216 Route 206, Ste 15
Hillsborough, NJ 08844
908-874-3799
teve21@datanyc.com
http://www.teve21.com/index.php
Affiliated Electronics in New Jersey maintains the inventory of Adcom legacy parts. Please note
that Affiliated Electronics performs more service on Adcom products than anyone, including
Adcom, and they typically have a fast turn around time."
Of course priority UPOS to them is over $500
But ground is on $150Steve
Ok, maybe 'poor quality capacitors' is a bit harsh. I retract that and replace it with 'good capacitors that have proven to be unreliable over time'
either way those specific capacitors in those amps (and other products) caused a lot of grief. If fact those capactors and others like them probably single-handedly gave good companies like adcom and antec bad names.
either way those specific capacitors in those amps (and other products) caused a lot of grief. If fact those capactors and others like them probably single-handedly gave good companies like adcom and antec bad names.
Hi Steve,
I agree. The fix is a one time event. However, it can get worse if it was not completed properly as it already has been getting worse.
Asking a shop to redo a repair they didn't complete successfully is valid, unless they indicate that they are unwilling. Then you really should not attempt to push them. You are unsure of getting a good job done and that is up to their morals. This you can gage as you talk with them.
Crossing the border for service is not recommended. Too many problems. You should be able to find someone closer to you. I can help you out if it comes to that, but there just has to be a good technician closer to you than I am.
Your turn off "pop" must be this DC offset problem. It's just that a turn on "pop" is not unusual.
-Chris
Edit: I see that this is a dealer. Good brands, but the service shop isn't always as honest as an independent shop. That is my experience in Canada at any rate. I do not know these people, so I can not judge them, just check dealer service shops more carefully.
I agree. The fix is a one time event. However, it can get worse if it was not completed properly as it already has been getting worse.
Asking a shop to redo a repair they didn't complete successfully is valid, unless they indicate that they are unwilling. Then you really should not attempt to push them. You are unsure of getting a good job done and that is up to their morals. This you can gage as you talk with them.
Crossing the border for service is not recommended. Too many problems. You should be able to find someone closer to you. I can help you out if it comes to that, but there just has to be a good technician closer to you than I am.
Your turn off "pop" must be this DC offset problem. It's just that a turn on "pop" is not unusual.
That isn't right either. There are resistors from RCA shield to ground, so these may need to be replaced. The only other thing I can think of is that your meter and / or probes are not reliable and may give varying readings on the resistance function.
-Chris
Edit: I see that this is a dealer. Good brands, but the service shop isn't always as honest as an independent shop. That is my experience in Canada at any rate. I do not know these people, so I can not judge them, just check dealer service shops more carefully.
Hi CBRworm,
I wasn't referring to anything you had posted, not knowingly anyway. The quote was from Steve regarding the original shop's web site. Service professionals really ought to know better, and I expect better from them.
I even know about certain surface mount transistors with very high failure rates. Thankfully, the cases on these parts have a low melting point. Once again, the manufacturer had no idea until some years had past. They even bought the parts through proper channels to the best of their knowledge. The replacements provided are problem free, thank goodness!
There have been defective ICs, transistors,and just about everything else. Then there are the improper component choices and poor designs that cause troubles. So how do you figure out which fault is at work here?
-Chris
I wasn't referring to anything you had posted, not knowingly anyway. The quote was from Steve regarding the original shop's web site. Service professionals really ought to know better, and I expect better from them.
I like that statement. It's factual and addresses the true situation very well. Nicely put sir!
Don't forget the grief they caused warranty service budgets and shops, followed closely by how much consumers have spent over the years. It's a no win situation for everyone.
I even know about certain surface mount transistors with very high failure rates. Thankfully, the cases on these parts have a low melting point. Once again, the manufacturer had no idea until some years had past. They even bought the parts through proper channels to the best of their knowledge. The replacements provided are problem free, thank goodness!
There have been defective ICs, transistors,and just about everything else. Then there are the improper component choices and poor designs that cause troubles. So how do you figure out which fault is at work here?
-Chris
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