I blew the 3 of the 4 speaker out fuses on my amp with my Polk SDA speakers when hooking it up blindly. I realized my mistake, but wanted to finish my listening session. So I stuck 2 15a, and a 20a fuse in. Fixed the speaker wiring. Turned it on, and poof. I looked for damage, and found none. So I busted out my mm found power on the soft start board. Unplugged it. Started testing resistors. The big 20watt 4.7ohm was open. Took a hammer to it. Found the burnt spot. I am scared to just replace the resistor( I have 2 10ohm 10watt resistors). I don't want to blow anything else. What caused the resistor to blow after installing the speaker fuses?
Should I raplace the rail fuses, The 20watt resistor, and give it a go with 5ampers instead of 10ampers?
Thanks Ben
Should I raplace the rail fuses, The 20watt resistor, and give it a go with 5ampers instead of 10ampers?
Thanks Ben
amp
Saw your other thread.
1. The soft start resistors blew? I would not blame this on the Polk's cause I know you were not cranking the amp during the soft start cycle, were you????
Typically AC or DC power is shunted through soft start resistors which have a much lower power rating than required. Cause the time is short you usually get away with it. See Elliot Project #39. Do the math and see. Perhaps they just wore out and you need to replace them?
2. No need to start a new thread, people here get what you are talking about.
3. I owned an Adcom 555 II and drove Martin Logan Sequel II's (2 ohm) in bridge mode, never had a problem...heat sinks got really hot. Great amp, might want to bring yours in for a tune-up.
Saw your other thread.
1. The soft start resistors blew? I would not blame this on the Polk's cause I know you were not cranking the amp during the soft start cycle, were you????
Typically AC or DC power is shunted through soft start resistors which have a much lower power rating than required. Cause the time is short you usually get away with it. See Elliot Project #39. Do the math and see. Perhaps they just wore out and you need to replace them?
2. No need to start a new thread, people here get what you are talking about.
3. I owned an Adcom 555 II and drove Martin Logan Sequel II's (2 ohm) in bridge mode, never had a problem...heat sinks got really hot. Great amp, might want to bring yours in for a tune-up.
Thanks for your reply. I blew the Amps output fuses when I shorted the speaker connector. Then I replaced the fuses after blowing them with ones I had on hand. When I fired it up with no input the resistor burnt. I don't want to fry my amp, and I can't afford to get it serviced. Also I don't trust any of the service shops in this area(Ft Lauderdale) with a complicated amp like mine.
Ben
Ben
ben62670 said:
Hi Ben,
You most likely toasted your output transistors when the original fuses blew. Unfortunately the fuses are pretty slow and don't blow cleanly, so when they do blow allot of times it's after the damage has been done.
When you turned it on with the 20 amp fuse, the fuse was to big and allowed whatever is shorted to take out the 4.7 ohm, which is in series with the power.
Unfortunately it sounds like a trip to shop is required. If Adcom is still around (I don't follow these things anymore) A call to their service department might give you an idea as to what to expect cost wise. Local service can be a roll of the dice if they don't specialize in audio gear and do a fair number of these and similar amps on a regular basis.
Regards Mike.
yes. at a minimum, the one channel is blown. About $100-125 for the repair. The big issue is the matched output transistors....or..potentially..any OTHER parts you blew up when you put the 20 amp fuse in there.
It needs to go to a experienced technician who is well versed in Adcom repair,and has matched sets of output transistors ready to go. Otherwise, the matching process can be quite expensive, as many have to be bought to match up the nessessary sets. Thus endeth my personal experience with that particular model of adcom.
It needs to go to a experienced technician who is well versed in Adcom repair,and has matched sets of output transistors ready to go. Otherwise, the matching process can be quite expensive, as many have to be bought to match up the nessessary sets. Thus endeth my personal experience with that particular model of adcom.
Hi Ben,
Mike is correct. Adcom still exists but was bought and moved. They are not really familiar with the older product. Find an old (good) Adcom warranty shop.
You will require two sets of 5 matched outputs for that channel plus driver transistors and some resistors. You can not use five of each type without matching. ECG and NTE parts can not be used either.
That channel will require to be stripped down and cleaned. New grease and insulators and it should be at least as good as new.
Hi Ken,
So Ben, the most important thing will be to get your amp into the hands of a really good technician. It's the least expensive route for repair.
-Chris
Mike is correct. Adcom still exists but was bought and moved. They are not really familiar with the older product. Find an old (good) Adcom warranty shop.
You will require two sets of 5 matched outputs for that channel plus driver transistors and some resistors. You can not use five of each type without matching. ECG and NTE parts can not be used either.
That channel will require to be stripped down and cleaned. New grease and insulators and it should be at least as good as new.
Hi Ken,
You know it. Also, the repair will be more than $150 USD I'm afraid. You got a smoking deal.
So Ben, the most important thing will be to get your amp into the hands of a really good technician. It's the least expensive route for repair.
-Chris
Hi Ben,
In that case, I'd urge you to learn.
How basic do you need to start from Ben? What areas would you prefer to concentrate on?
Did you ever take an electronics course in high school? If so, did they cover vacuum tubes or was it solid state?
Lastly, what test equipment do you have right now?
For this topic, start a new thread. Keep this thread for your amp. I have repaired a number of these over the years. It's amazing how many guys with their shingle out do not understand what they are doing.
-Chris
In that case, I'd urge you to learn.
How basic do you need to start from Ben? What areas would you prefer to concentrate on?
Did you ever take an electronics course in high school? If so, did they cover vacuum tubes or was it solid state?
Lastly, what test equipment do you have right now?
There is that! I completely agree with you there!
Same here. You have to spend your money wisely.
For this topic, start a new thread. Keep this thread for your amp. I have repaired a number of these over the years. It's amazing how many guys with their shingle out do not understand what they are doing.
-Chris
Ben,
Sorry for that rermark about the Polk's and your $$. I was really just impressed that you had a nice system.
Good luck with this, Anatech knows what he is talking about so listen to him.
tip......I would first ask how to test the output transistors with a DMM to see if they are still good...
Sorry for that rermark about the Polk's and your $$. I was really just impressed that you had a nice system.
Good luck with this, Anatech knows what he is talking about so listen to him.
tip......I would first ask how to test the output transistors with a DMM to see if they are still good...
I have very basic knowledge. I don't know if you remember me from when I was having a DC offset problem. I fixed that, and now I screwed up my wonderful amp by shorting it
I have very good logic skills. I can figure out a lot. I just need to learn about testing different components mostly. I really want to learn more about electronics. Strictly analog solid state, and tube. I like to upgrade any thing I have.
Thanks Ben
I have very good logic skills. I can figure out a lot. I just need to learn about testing different components mostly. I really want to learn more about electronics. Strictly analog solid state, and tube. I like to upgrade any thing I have. Thanks Ben
Hi Ben,
I have problems with short term memory, so my life is a "current" affair.
Any Fluke meters in that collection?
Okay, the most important thing to learn then is that all components follow the laws of physics at all times. No magic parts exist. Always consider an "improved" component in it's contest in your circuit. Silver leads instead of copper is pointless in 99.99999% of the circuits out there. Compared to the circuit impedance and resistance of copper traces. Same for caps. There are better component materials that also depend on how they are used in a circuit. So one good part may not work as well as a standard "bad" part. Always consider these things when "upgrading".
So, right now. Measure for continuity from each supply wire on each output assembly to the speaker output (bar between sections). If you have a variac, you could run the amp at low voltage with the resistor position shorted. Measure bias currents to see where your trouble lies. Remember, one bad output means an entire set + drivers.
-Chris
I have problems with short term memory, so my life is a "current" affair.
You're a dangerous lad then!
Any Fluke meters in that collection?
Okay, the most important thing to learn then is that all components follow the laws of physics at all times. No magic parts exist. Always consider an "improved" component in it's contest in your circuit. Silver leads instead of copper is pointless in 99.99999% of the circuits out there. Compared to the circuit impedance and resistance of copper traces. Same for caps. There are better component materials that also depend on how they are used in a circuit. So one good part may not work as well as a standard "bad" part. Always consider these things when "upgrading".
So, right now. Measure for continuity from each supply wire on each output assembly to the speaker output (bar between sections). If you have a variac, you could run the amp at low voltage with the resistor position shorted. Measure bias currents to see where your trouble lies. Remember, one bad output means an entire set + drivers.
-Chris
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