An absolute beginner?....really? Then why are you poking in and around in an amp? You could easily get electrocuted if you don't know what you're doing.
Let's start from the beginning, what brand of amp is it & what's the model number?...I'll assume it just stopped working for you, under what circumstances did it stop working? Please stop randomly poking around the insides of electrical equipment....ever read the warning that is printed on the back of some stereo gear, "No user serviceable parts inside. Refer servicing to qualified personnel."
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Rick...
Let's start from the beginning, what brand of amp is it & what's the model number?...I'll assume it just stopped working for you, under what circumstances did it stop working? Please stop randomly poking around the insides of electrical equipment....ever read the warning that is printed on the back of some stereo gear, "No user serviceable parts inside. Refer servicing to qualified personnel."
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Rick...
Many ICs are difficult to determine as good/bad by a simple test.
It would help to know more, are you culling parts from dead equipment?
If so, what kind of parts are they, op amps, logic gates, timers, etc?
In amplifiers, often the power transistors and drivers will be bad, rather than the input devices.
But there are not really that many ICs in most amplifiers, just discrete devices.
It would help to know more, are you culling parts from dead equipment?
If so, what kind of parts are they, op amps, logic gates, timers, etc?
In amplifiers, often the power transistors and drivers will be bad, rather than the input devices.
But there are not really that many ICs in most amplifiers, just discrete devices.
You are an absolute beginner. We on this board want to help you. To do that you must help us. the model# and brand of the amp is required. A schematic would also be great, but with that number there are many on this board that will post it for you if they can find one. Also needed is a detailed description of the problem, how it developed, specific symptoms. Did you ever hear it work?
This is the absolute minimum and it's not that much. We love to help and teach, even though some of the feedback may seem rough, its mostly given with good intentions.
Good luck.
This is the absolute minimum and it's not that much. We love to help and teach, even though some of the feedback may seem rough, its mostly given with good intentions.
Good luck.
I am sorry for my previous message, So Ill start again...... I have this amplifier that broke down about 10 years ago and its been in my garage ever since. So I decided I would drag it out and see if I can get it going again. It is a Fender 200 BRX bass amp. It turns on, but no sound.....I changed all the capacitors and the power trasisistors, Still no sound.....So I was checking through the board and thought I would check the IC's. I watched about ten+ videos on you tube. They say how to check them, I gave it a try and I got nothing like the readings I was supposed to get.......(round about 0.710 voltage drop). None of the IC's read anything like that. These are the IC's in the amp......1, MN3007 wich is used for reverb......1, MN3101 witch is a clock generator and 10, TL072CP's witch are J-Fet dual op amps......I am studying electronics by myself , just to keep my self busy. I am retired form work and I am 77 years old. I just thought someone could help me find out if these IC's are working or not...........I cant find the schematic....If it is too much of a problem Ill just forgrt about it............
The Negative probe (Black) is the one that normally goes to the ground or negative.
The Red is normally the one you use to poke around with.
That way it is easier to see what are positive, or negative readings.
Having a meter and good intentions is one thing.
Being able to use and interpret the readings are another.
Unless you have a schematic, or someone that is intimately acquainted with this device,
you may as well be dropped in the middle of china and ask someone how to get to moonie ponds.
Being a 'musical instrument amp', maybe a kind Mod would be good enough to move this thread into the Sub forum dedicated to this.
The Red is normally the one you use to poke around with.
That way it is easier to see what are positive, or negative readings.
Having a meter and good intentions is one thing.
Being able to use and interpret the readings are another.
Unless you have a schematic, or someone that is intimately acquainted with this device,
you may as well be dropped in the middle of china and ask someone how to get to moonie ponds.
Being a 'musical instrument amp', maybe a kind Mod would be good enough to move this thread into the Sub forum dedicated to this.
So you changed the power transistors...i assume you tested them outside and they were bad? You do not change parts unless there is a reason.
If all the power transistors were bad, its likely some drivers are bad too. Before you go measuring ic's, first just make sure the power amp section is up and running. It makes no sense poking around clock generator, while your amp section is still dead.
You know the amp section is working by touching the volume pot input, it will buzz in speaker.
Concentrate on amp first, its likely ic's are fine.
Did you test the speaker(s)? A few of the bass amps I have repaired simply had dead speakers.
A DC resistance check with an ohm meter will tell you if the voice coil is good or open.
Disconnect at least one of the speaker wires first, then measure across the speaker terminals.
A good 4 ohm speaker will measure about 3 ohms and a good 8 ohm will measure about 6 ohms. There will be no reading for a burned, open circuit coil.
If there are two speakers, test them separately.
Troubleshooting is process of elimination.
Yes, the reason you are frustrated is the method being used. Just replacing parts often does not work.
The time honored method of signal tracing is much better. Use a scope, start at the input, and verify
presence or absence of signal at each circuit block. Of course a schematic is necessary.
The time honored method of signal tracing is much better. Use a scope, start at the input, and verify
presence or absence of signal at each circuit block. Of course a schematic is necessary.