I picked up a 5300 intending to use it as the foundation to my system. Was using an NAD 2150, and while it sounded fine it just didn't have the beef to drive my inefficient speakers (Infinity Reference 5). It's plugged in and working fine. Sounds good, driving the speakers very easily, lots of dynamic. I'm happy with the sound.
However, there are two noise issues I need help on. I've had a lot of guitar and stereo gear pass through my ownership, but power amp building and troubleshooting are new for me. That being said, hopefully these problems are an easy enough intro to this kind of work. Issue 1: When turned on, the amp makes a loud "PUP" sound. Issue 2: with preamp on/up/down/unplugged/different pre/whatever, the 5300 makes a slight "ZZZZZZZ" noise in both tweeters.
So my question is this: What might be the problems here, and how do I test them? I'm ordering an auto-ranging multimeter (my first) tonight
Just assembled an op-amp preamp, so I'm feeling hopeful. Help make me one of you, DIY'ers!
However, there are two noise issues I need help on. I've had a lot of guitar and stereo gear pass through my ownership, but power amp building and troubleshooting are new for me. That being said, hopefully these problems are an easy enough intro to this kind of work. Issue 1: When turned on, the amp makes a loud "PUP" sound. Issue 2: with preamp on/up/down/unplugged/different pre/whatever, the 5300 makes a slight "ZZZZZZZ" noise in both tweeters.
So my question is this: What might be the problems here, and how do I test them? I'm ordering an auto-ranging multimeter (my first) tonight
Just assembled an op-amp preamp, so I'm feeling hopeful. Help make me one of you, DIY'ers!
Go to the Hifiengine website, register and download the service manual and rev.1 schematic for free:
Adcom GFA-5300 Manual - Stereo Power Amplifier - HiFi Engine
Browse through and check off the locations of various large objects and get a feel for what is what. Jon could also be referring to the main, 10,000 uF smoothing caps -C202,203 and C206,207 but all caps. associated with the power supply ( there are several examples of paralled caps in there too) could be considered suspects for poor connections.
Adcom GFA-5300 Manual - Stereo Power Amplifier - HiFi Engine
Browse through and check off the locations of various large objects and get a feel for what is what. Jon could also be referring to the main, 10,000 uF smoothing caps -C202,203 and C206,207 but all caps. associated with the power supply ( there are several examples of paralled caps in there too) could be considered suspects for poor connections.
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(Also sorry to double up, but I don't see an "edit" option)
I got a visual on those big Nichicon caps, and they don't appear to be leaking. If I'm soldering one of those leads, is there a chance that the solder iron will form a ground circuit and discharge the cap? Should I be aware of this before I work on things?
I got a visual on those big Nichicon caps, and they don't appear to be leaking. If I'm soldering one of those leads, is there a chance that the solder iron will form a ground circuit and discharge the cap? Should I be aware of this before I work on things?
'Had forgotten your post and thought we had lost you, sorry. You were checking the integrity of solder joints, according to the posts, though I doubt there will be any issues here that aren't obvious as either dirty looking joints or some may even have faint "stretch marks" which are characteristic of so-called dry joints. Reflow those and as long as your amplifier is not connected to anything else, you won't have issues with discharging caps or other non-problems.
The problem will more likely be with failed caps and these take more than a DMM to test, which is why many people just routinely replace them according to what life is expected from them and some caps branded Adcom didn't last all that long. If you have one cap to try that has at least the minimum voltage rating required, You can temporarily place this in parallel with the existing caps, on at a time and see if it helps but it should be at least half the required, marked capacitance value to make a clear difference.
The problem will more likely be with failed caps and these take more than a DMM to test, which is why many people just routinely replace them according to what life is expected from them and some caps branded Adcom didn't last all that long. If you have one cap to try that has at least the minimum voltage rating required, You can temporarily place this in parallel with the existing caps, on at a time and see if it helps but it should be at least half the required, marked capacitance value to make a clear difference.
Just replaced the power caps. Popped a fuse while adjusting the bias on one channel (oops hehe)
Checked the DC voltage and it was safe, so plugged in the one channel that didn't have a blown fuse. No buzz! Also the pop when I turned the amp on was minimal.
Haven't played any music through it because the wife was sleepy, but after a new fuse I should be in business.
Checked the DC voltage and it was safe, so plugged in the one channel that didn't have a blown fuse. No buzz! Also the pop when I turned the amp on was minimal.
Haven't played any music through it because the wife was sleepy, but after a new fuse I should be in business.
The noise improvement after the smoothing cap change was huge. I think I'm gonna go ahead and redo the electrolytics on each channel board too (there are only 4 caps in each channel). Even if this doesn't change the quality as strikingly, it would still be nice to know I've done a full, thorough recap on an amp I intend to keep.
As you don't mention any signs of previous damage and it was actually working, I would assume you've done something like reversed a cap, bridged a couple a tracks or perhaps gotten one of those connector leads refitted wrongly. Check your work over carefully against the schematic - its not a simple task but it needs to be done if a cap suddenly burns like that.
Following another line of reasoning that when you adjusted the bias and the fuse blew, more damage may have occurred than you think. Fuses don't blow unless the current drawn exceeds that required for maximum power output by a considerable margin. This won't be simple to troubleshoot but lets check the other possibilities first.
As C101 is a 47uF/63V bypass cap from the + rail to ground, I'd measure the power rails as quickly as I could without causing more damage (clips for the meter leads are good idea for safety in a hurry). You should have +/- 45-50V wrt ground on the power rails (as you can find at fuses M101,103 for the left channel). Odd that voltages are not shown on the schematic but there it is.
I can't find an R101 in either the schematic or parts list so that may be an earlier or later
inclusion for what I can't tell.
Following another line of reasoning that when you adjusted the bias and the fuse blew, more damage may have occurred than you think. Fuses don't blow unless the current drawn exceeds that required for maximum power output by a considerable margin. This won't be simple to troubleshoot but lets check the other possibilities first.
As C101 is a 47uF/63V bypass cap from the + rail to ground, I'd measure the power rails as quickly as I could without causing more damage (clips for the meter leads are good idea for safety in a hurry). You should have +/- 45-50V wrt ground on the power rails (as you can find at fuses M101,103 for the left channel). Odd that voltages are not shown on the schematic but there it is.
I can't find an R101 in either the schematic or parts list so that may be an earlier or later
inclusion for what I can't tell.
bulb limiter/tester
Its also time to use a bulb limiter to prevent further damage while you check this stuff out. Here's an example of how to construct one, though in your situation I'd use a ~60W bulb (Halogen or conventional filament) and a dual socket of insulating plastic mounted on a board, one socket wired normally and the other incorporating the bulb in circuit (and clearly marked so). Keep any kids or folks with no appreciation of electrical safety well away from this gear.
https://robrobinette.com/5e3_Modifications.htm#Light_Bulb_Current_Limiter
The idea is that no more than the bulb's bright current (about 0.5A for 115V supplies) can flow to the amp. and this protects against shorts and wiring mistakes causing heavy damage. You can even adapt a table lamp to this duty, wired in series with the line voltage active lead. Note this means working with circuits connected directly to the mains and personal safety and that of others who come in contact with the gear, is literally in your hands. Take great care with wiring, suitable insulating materials and safe practice.
Its also time to use a bulb limiter to prevent further damage while you check this stuff out. Here's an example of how to construct one, though in your situation I'd use a ~60W bulb (Halogen or conventional filament) and a dual socket of insulating plastic mounted on a board, one socket wired normally and the other incorporating the bulb in circuit (and clearly marked so). Keep any kids or folks with no appreciation of electrical safety well away from this gear.
https://robrobinette.com/5e3_Modifications.htm#Light_Bulb_Current_Limiter
The idea is that no more than the bulb's bright current (about 0.5A for 115V supplies) can flow to the amp. and this protects against shorts and wiring mistakes causing heavy damage. You can even adapt a table lamp to this duty, wired in series with the line voltage active lead. Note this means working with circuits connected directly to the mains and personal safety and that of others who come in contact with the gear, is literally in your hands. Take great care with wiring, suitable insulating materials and safe practice.
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Ian, you're becoming something of a sensei to me.
I will rig up the bulb contraption, and I will be extra careful. Thanks for the tip.
I only replaced the four smoothing caps on the 3/4xx board. I paid careful attention to make sure that the negative strips were facing the correct way, and a doublecheck of this confirms that they are oriented correctly. Besides this, I only I clipped the wires in the sides of the board. These are also reattached properly.
Before reporting with my new fuse, I set the bias trimpots to center so as not to flood it current. Is there a chance that the new power smoothing caps are providing the correct amount of power, but C101 was worn out and couldn't handle the load? Is this something that happens?
I know that the new 10,000uf caps are powering much better because even the LED on the power switch is noticeably brighter. So in my beginner's suspicion, I'm thinking the cap may have just been old and worn out
I will rig up the bulb contraption, and I will be extra careful. Thanks for the tip.
I only replaced the four smoothing caps on the 3/4xx board. I paid careful attention to make sure that the negative strips were facing the correct way, and a doublecheck of this confirms that they are oriented correctly. Besides this, I only I clipped the wires in the sides of the board. These are also reattached properly.
Before reporting with my new fuse, I set the bias trimpots to center so as not to flood it current. Is there a chance that the new power smoothing caps are providing the correct amount of power, but C101 was worn out and couldn't handle the load? Is this something that happens?
I know that the new 10,000uf caps are powering much better because even the LED on the power switch is noticeably brighter. So in my beginner's suspicion, I'm thinking the cap may have just been old and worn out
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Stopped in to see my favorite group of audio salesmen today and talked about my burned cap. They confirmed my theory that the smaller caps on my driver boards are worn out. I'll order replacements later today and finish a full recap. I suppose the lesson is that recaps mean ALL electrolytics. I'm kind of enjoying this process of discovery. It's very empowering to be have my hands on my own gear
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