Hello,
Got a problem with my AVR1909. Problem began with unit going into protection mode after ~5-10 min. Checked power supply voltages and found that -15V is pretty low (~ -14), drops to ~ -13 and and around that moment protection mode kicks in.
Changed regulator (KIA7915P ->L7915CV, insulated central pin from radiator of course), got 0V on 15V rail. With this temporary setup (photo, only -15V regulator) and disconnected -15V pin from input board (tested that pin only when disconnected, i don't get it short to ground) i get constant -15V (looks like PSU is working fine?).
Any clues where to look next? 🙂 Thank a lot everyone!
Got a problem with my AVR1909. Problem began with unit going into protection mode after ~5-10 min. Checked power supply voltages and found that -15V is pretty low (~ -14), drops to ~ -13 and and around that moment protection mode kicks in.
Changed regulator (KIA7915P ->L7915CV, insulated central pin from radiator of course), got 0V on 15V rail. With this temporary setup (photo, only -15V regulator) and disconnected -15V pin from input board (tested that pin only when disconnected, i don't get it short to ground) i get constant -15V (looks like PSU is working fine?).
Any clues where to look next? 🙂 Thank a lot everyone!
I replaced both -15V and +15V regulators, -15V (7915) output capacitor and input zener diode (33V). When i disconnect -15V rail output i get nice -15V from the regulator, with both -15V rails connected i get 0V. +15V rail is fine. Maybe someone has any ideas where to look next? 🙂 Thanks!
There's obviously something shorting -15V to ground.
Arm yourself with the service manual and look for potential culprits. Could be a decoupling capacitor or a bad opamp or something.
Have you checked the rectifier diodes, just in case?
Arm yourself with the service manual and look for potential culprits. Could be a decoupling capacitor or a bad opamp or something.
Have you checked the rectifier diodes, just in case?
Quite often in these cases a decoupling cap has got old and faulty.
Sounds like one on the turn and is becoming low impedance hence dropping voltage.
Sounds like one on the turn and is becoming low impedance hence dropping voltage.
Here's a short schematics of +15/-15 regulators daughterboard. 7915 IN is -24V, 7815 IN is +24V. I checked all diodes here, they seem fine. Changed ZD504 zener (-24V input) and C527 (-15V output) cap.
Is there any chance that -24V input smoothing cap (large 4700 uf/35V) could be at fault or is it most likely short along -15V rail somewhere? BTW, strange thing there, schematics says it should be 2200uF, also 2200 etched on the PCB itself, but the cap there is 4700 uF (with factory glue around) 🙂
Did you check the 24V rails are correct voltage? If so its likely after the 15V regulator. Very leaky cap could pull the rail down - eventually protection kicks in by itself or regulator shuts itself down and provokes protection circuit?
Its not uncommon to see issues due to old electrolytics in the protection circuit itself - probably wise to replace those anyway.
Its not uncommon to see issues due to old electrolytics in the protection circuit itself - probably wise to replace those anyway.
Yes, -24V is steady even when -15V is 0V (short) with rails connected.
I think that regulator shuts itself off before protection circuit kicks in in this case. Will check the protection circuit anyway, thank you 🙂
Looked throughly every board along -15V rail, caps visually seem fine to me. Will look further.
I think that regulator shuts itself off before protection circuit kicks in in this case. Will check the protection circuit anyway, thank you 🙂
Looked throughly every board along -15V rail, caps visually seem fine to me. Will look further.
Looks like found one shorted op-amp along the -15V rail, but still have short in this part of protection circuit (picture). Disconnecting R188 makes it go away and amp turns on fine.
Replaced C179, ceramic SMD cap C180 not shorted, all resistors and Q143 seem fine for me. Red points (come from input/output board) measure ~ +3.6V each, does that trigger protection circuit? Thanks a lot for any ideas 🙂
Replaced C179, ceramic SMD cap C180 not shorted, all resistors and Q143 seem fine for me. Red points (come from input/output board) measure ~ +3.6V each, does that trigger protection circuit? Thanks a lot for any ideas 🙂
I also have a failing Denon 1909. Getting the fast flashing red power light (ASO / DC protection error) after about 15 min operation. Blasting with a fan to keep it cool seems to help but still fails after a few hours.
Have already opened it up to clean out dust and poke around. Suspect the 15v regulator may be the issue, it's the only part that seems to get hot (60C+ on the heat-sink) and have seen a few references to the transistors failing. I measured the voltages at the plug below the transistor daughter board as +16.10v and -14.46v. Not sure if this is the correct point or what the acceptable range is?
I'm fairly handy with a soldering iron but don't understand the circuits that well. Doesn't look too hard to replace the KIA7815API & KIA7915PI. Is it ok to replace with L7915ACV & L7815CV, not sure what the difference is? Anything else I should be looking at?
How long do I need to disconnect the power for before taking apart so i'm not going to get zapped by the capacitors?
Already have a replacement amp for my main system but would like to use this in another room. Besides I hate throwing away good stuff when it has the potential to be fixed.
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Found these on ebay:
10 x 7815 insulated Voltage Regulator KEC KIA7815API (10 pcs) NEW | eBay
10 x 7915 insulated Voltage Regulator KEC KIA7915PI (10 pcs) NEW | eBay
I guess they would be a good start?
10 x 7815 insulated Voltage Regulator KEC KIA7815API (10 pcs) NEW | eBay
10 x 7915 insulated Voltage Regulator KEC KIA7915PI (10 pcs) NEW | eBay
I guess they would be a good start?
Well I managed to pop the regulator daughter board out without having to take anything else apart.
Took a couple more voltage readings from the regulator pins before removing:
KIA7915PI : -26v in / -14.4v out
KIA7815API : 24.5v in / 15.8v out
Guess I go ahead and try replacing the KIA7815API & KIA7915PI?
Feels like i'm just replacing random parts but don't have any other ideas. Maybe replace the 2 capacitors as well?
Took a couple more voltage readings from the regulator pins before removing:
KIA7915PI : -26v in / -14.4v out
KIA7815API : 24.5v in / 15.8v out
Guess I go ahead and try replacing the KIA7815API & KIA7915PI?
Feels like i'm just replacing random parts but don't have any other ideas. Maybe replace the 2 capacitors as well?
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Ordered the new voltage regulators. Don't know if it will work but want to try something before giving up.
15v rails don't seem that far out to me but it does still work for some time before failing. Hard to get it to fail while opened up as it only seems to happen when the heat builds up. They are the hottest components in there and do seem to be a common failure point on old Denons. Makes sense that if one of the rails drifts too far out it could trigger the protection circuit.
Will update how I get on next week...
15v rails don't seem that far out to me but it does still work for some time before failing. Hard to get it to fail while opened up as it only seems to happen when the heat builds up. They are the hottest components in there and do seem to be a common failure point on old Denons. Makes sense that if one of the rails drifts too far out it could trigger the protection circuit.
Will update how I get on next week...
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Done the repair, had it running for a few hours in a hot room with no errors so hopefully it's fixed. Post fix voltages were -14.7v & +15.7v so looking a bit better than before. It also feels like it's running a lot cooler now, maybe old failing regulators produce more heat?
Didn't take any pic's, not overly proud of my soldering. Scorched the board and screwed-up one pad getting the old regulators off, not too bad apart from that.
If it does still fail again I'll just have to go back to my faithful 22 y/o Marantz PM-65.
Didn't take any pic's, not overly proud of my soldering. Scorched the board and screwed-up one pad getting the old regulators off, not too bad apart from that.
If it does still fail again I'll just have to go back to my faithful 22 y/o Marantz PM-65.
I have the same AVR-1909 and my problem is lower volume for LEFT channels (A and B only), also the amp has once gone to protect mode (loud pop from the speakers and power button flashing red).
I have tested HDMI and RCA inputs and same problem occurs. With multimeter, 50hz test sound gives 0,17V for rights and 0,05V for the lefts so something is clearly wrong there.
Any advice for this? Its a nice AVR so I dont wanna toss it to scrap just yet.
I have tested HDMI and RCA inputs and same problem occurs. With multimeter, 50hz test sound gives 0,17V for rights and 0,05V for the lefts so something is clearly wrong there.
Any advice for this? Its a nice AVR so I dont wanna toss it to scrap just yet.