I have an Arcam AVR100 receiver needing repair. There is an audible 60hz hum from the speakers (all speakers, including center and surrounds) that is volume independent. I've tried different outlets, enabled and disabled the ground loop, and have disconnected every input, and the hum is still present. All this lead me to the conclusion that I likely have a power supply filter cap or 2 failing (or failed), so I opened up the unit, and did a visual inspection, and as far as I can tell, all the filter caps (there are many on different boards in the unit) appear to be in good shape. Unfortunately, in order to test capacitance, I have to remove lots of boards and connectors and other things. Through that disassembly process, and continued testing, I noticed that the power transformer is giving off the same hum that I hear through the speakers. It's not tremendously loud, but I can hear it from 2-3 feet away.
Can anyone provide some guidance on what may be the problem, what steps I should take next, etc.?
Thanks in advance for your help!
Can anyone provide some guidance on what may be the problem, what steps I should take next, etc.?
Thanks in advance for your help!
60HZ is mains hum, not smoothing (that will be twice the frequency due to the effect of a bridge rectifier).
Poor internal ground connection?
RCA/Phono connectors no grounded properly?
Almost anything.
Poor internal ground connection?
RCA/Phono connectors no grounded properly?
Almost anything.
hi
i have worked on similar model with same fault. i think you are on the right track.
look around the regulators and filter capacitors ajacent, remove the bottom pcb yes its the last one, and hard to get at. check for dry joints at the hot spots (beneth regulators) and any caps around that area as they get cooked
and replace with 105 deg types if suspicious.
i have worked on similar model with same fault. i think you are on the right track.
look around the regulators and filter capacitors ajacent, remove the bottom pcb yes its the last one, and hard to get at. check for dry joints at the hot spots (beneth regulators) and any caps around that area as they get cooked
and replace with 105 deg types if suspicious.
Rgb,
measure the hum
Remove the speakers.
Short the input. Use an RCA plug with the Hot to Barrel soldered together.
Set your DMM to read 200Vac and read the output AC voltage.
Adjust the DMM down through the ranges, 20Vac, 2Vac, 200mVac until you get a sensible reading.
You are looking for less than 1mVac on the 199.9mVac scale and preferably <0.2mVac.
If you have >3mVac you have a serious problem.
Now reset your DMM to 200Vdc and measure the output offset. Again reset down through the range to 199.9mVdc. Expect <50mVdc. <10mVdc is excellent.
Come back with some measurements.
measure the hum
Remove the speakers.
Short the input. Use an RCA plug with the Hot to Barrel soldered together.
Set your DMM to read 200Vac and read the output AC voltage.
Adjust the DMM down through the ranges, 20Vac, 2Vac, 200mVac until you get a sensible reading.
You are looking for less than 1mVac on the 199.9mVac scale and preferably <0.2mVac.
If you have >3mVac you have a serious problem.
Now reset your DMM to 200Vdc and measure the output offset. Again reset down through the range to 199.9mVdc. Expect <50mVdc. <10mVdc is excellent.
Come back with some measurements.
Thanks for the guidance and feedback!
I will try these ideas when I get home form the office tonight.
I will try these ideas when I get home form the office tonight.
Making progress...
So, I further disassembled the unit, removing all the boards to get to the main board, which has several regulators and smoothing capacitors that could be the problem. I found several capacitors that were slightly out of spec - off by 10-20%. Nothing major, and certainly no smoking gun, but I replaced them anyways since I was in there already. As expected, this didn't fix the hum problem.
I did further diagnostics, and this is what I found:
- hum present on CD, tape, dvd, sat, aux, and video inputs
- hum not present on external 5.1 input (dead silent)
Tracing the schematic, I found that all the inputs that have the hum go through the AC3/DSP board, while the multi-channel input board does not. I did further testing and found:
- Dolby Pro Logic and Hall modes result in a very loud hum across all 5 channels
- Stereo mode results in a much softer hum only on the front L/R channels - surrounds and center are dead quiet
All of this led me to believe that the problem was on the AC3/DSP board, which has it's own regulators. So, I removed that board and removed the smoothing capacitors, both of which were slightly out of spec (>10%), so I replaced them, again because I already had the board out of the unit. As expected, the hum is still present, as described above.
I am convinced that the problem is on this board, but not sure what to check next or what to look for.
So, I further disassembled the unit, removing all the boards to get to the main board, which has several regulators and smoothing capacitors that could be the problem. I found several capacitors that were slightly out of spec - off by 10-20%. Nothing major, and certainly no smoking gun, but I replaced them anyways since I was in there already. As expected, this didn't fix the hum problem.
I did further diagnostics, and this is what I found:
- hum present on CD, tape, dvd, sat, aux, and video inputs
- hum not present on external 5.1 input (dead silent)
Tracing the schematic, I found that all the inputs that have the hum go through the AC3/DSP board, while the multi-channel input board does not. I did further testing and found:
- Dolby Pro Logic and Hall modes result in a very loud hum across all 5 channels
- Stereo mode results in a much softer hum only on the front L/R channels - surrounds and center are dead quiet
All of this led me to believe that the problem was on the AC3/DSP board, which has it's own regulators. So, I removed that board and removed the smoothing capacitors, both of which were slightly out of spec (>10%), so I replaced them, again because I already had the board out of the unit. As expected, the hum is still present, as described above.
I am convinced that the problem is on this board, but not sure what to check next or what to look for.
You have the CLASSIC symptoms of the DSP circuits "failure".
Actually, in 95% of cases, the DSP PCB is still perfectly fine - the DSP circuits simply fail to perform correctly, because the PSU circuits have FAILED, and cannot supply super-stable current to the DSP. Therefore the DSP "fails".
Contact CondorAudio in Jerusalem for overhaul kits.
The kit restores ALL the PSU circuits to super stable operation, and by magic, the DSP circuits return to full function, without ever having had to "repair" them.
If you're looking for a quick repair with minimum work or parts, this is NOT for you.
Buy this kit only if you are a perfectionist, and committed to doing nothing less than the best.
I'm afraid you're totally wrong. The OP was talking about an AVR100 not an AVR300. They are 2 different beasts.
No, I'm not wrong.
The AVR100/200 has similar PSU problems, as the AVR250/280/300/350, even though the motherboards are different.
The PSU failures create secondary symptoms, such as the DSP circuits "failing", even though they haven't actually "failed".
It's just a visible Wow symptom for the owner to convince himself that the problem is in the Digital Processing area.
I have documentation of over 700 of these Arcam machines, which I've serviced over the years.
I know very well what's going on with them.
The AVR100/200 has similar PSU problems, as the AVR250/280/300/350, even though the motherboards are different.
The PSU failures create secondary symptoms, such as the DSP circuits "failing", even though they haven't actually "failed".
It's just a visible Wow symptom for the owner to convince himself that the problem is in the Digital Processing area.
I have documentation of over 700 of these Arcam machines, which I've serviced over the years.
I know very well what's going on with them.
No the AVR100 doesn't have similar PSU problems as the AVR300. You're talking nonsense. Stop misleading people just to try to sell your services. The DSP boards are totally different too.
Look Kram, unless you have my level of experience and can back up your claims with proof, you don't any right to talk to me like that.
In fact you don't have any right to talk to anyone like that, I don't care who you are, where you come from, or what is the color of your skin.
You are in no position to judge "nonsense" or otherwise, whether you presume to like my services or not, and I have never had any customer remotely resembling a kram or a tweeter, who can speak from personal experience with me.
So F.. what if the PCB's are different?
Thousands of power supplies in hundreds of machines all have the same problems.
Get a life.
If you want to show us all that you actually know something, then say something which has actual technical significance.
You're digging yourself into a hole you won't be able to crawl out of.
Any more replies from you will not be dignified with an answer.
Flame over.
In fact you don't have any right to talk to anyone like that, I don't care who you are, where you come from, or what is the color of your skin.
You are in no position to judge "nonsense" or otherwise, whether you presume to like my services or not, and I have never had any customer remotely resembling a kram or a tweeter, who can speak from personal experience with me.
So F.. what if the PCB's are different?
Thousands of power supplies in hundreds of machines all have the same problems.
Get a life.
If you want to show us all that you actually know something, then say something which has actual technical significance.
You're digging yourself into a hole you won't be able to crawl out of.
Any more replies from you will not be dignified with an answer.
Flame over.
It behooves both of you to read the RULES and understand the forum culture. Personal attacks are NOT allowed on this forum.Keep it factual, not personal. Support your arguments with facts, not personal attacks. Failure to do so will find you quickly in mute mode.
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