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Yamaha HTR 5650 - Power on Immediate Power Off

Were there any insulating mica between heatsink and regulator case? Some of the regulators have the metal tab as live, depending on manufacturer. For the middle regulator, measure resistance between middle leg and tab or heatsink, amp powered off/unplugged. Download the datasheet of components you used (on mouser/digikey site) and check the pinout.
 
mbz said:
Were there any insulating mica between heatsink and regulator case? Some of the regulators have the metal tab as live, depending on manufacturer. For the middle regulator, measure resistance between middle leg and tab or heatsink, amp powered off/unplugged. Download the datasheet of components you used (on mouser/digikey site) and check the pinout.
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Thank you! There was only thermal paste on the originals, but no micas. I’ll post the data sheets here. I was somewhat worried about the 79m05 because of the c suffix. Is the suffix related to the case and tab configuration? I’m 90% sure this is the issue.

Is that regulator likely fried along with the toasted resistor? Anything else that may have been damaged in the 1 second of powering on?
 
Original IMG_3094.jpeg
Replacement
IMG_3091.jpeg

Looks like you nailed it? Input pin on the replacement is linked to the top of the case *face palm* I have to slow down and not rush these things. Another learning lesson though. Glad it was on this unit and not something more valuable.
 
The 79M05 is probably ok since the input pin would have been connected to GND, ie, the harmful current did not pass through the IC. You should check the datasheets of the other regulators to ensure not a similiar fault, then find some mica insulators, also the mounting screw needs to be insulated from the IC...
 
mbz said:
The 79M05 is probably ok since the input pin would have been connected to GND, ie, the harmful current did not pass through the IC. You should check the datasheets of the other regulators to ensure not a similiar fault, then find some mica insulators, also the mounting screw needs to be insulated from the IC...
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Ok cool! I will check the other data sheets. Would it be a safe bet to just put insulators on all 5? Also, instead of them being screwed down individual there is a bracket that holds them all in place. Is this going to cause an issue?
 
Musicman524 said:
Would it be a safe bet to just put insulators on all 5?
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No real harm in doing this, the mica would reduce the thermal transfer so better without. I'd prefer to have a clear understanding of what's happening and take actions accordingly, ie, mica on 79M05 and no mica for others provided datasheets indicate tabs are not live.

Musicman524 said:
Also, instead of them being screwed down individual there is a bracket that holds them all in place. Is this going to cause an issue?
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No, provided metal bracket does not make contact with the metal tab (which it won't)
 
mbz said:
No real harm in doing this, the mica would reduce the thermal transfer so better without. I'd prefer to have a clear understanding of what's happening and take actions accordingly, ie, mica on 79M05 and no mica for others provided datasheets indicate tabs are not live.


No, provided metal bracket does not make contact with the metal tab (which it won't)
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Ok awesome: thank you so much for all of your help!! I think I have some micas around and if not I will order: I’ll check the other data sheets. I did notice the note on the original that says the radiation fin is connected to pin 2 which is the input. Is this relevant?
 
Musicman524 said:
I did notice the note on the original that says the radiation fin is connected to pin 2 which is the input. Is this relevant?
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Yes, exactly what we are talking about, in this case mica must be used.
For 79M05 the middle pin is the input (+7...+10Vdc) so connecting it directly to the heatsink(=GND) will blow the fuse....
 
mbz said:
Yes, exactly what we are talking about, in this case mica must be used.
For 79M05 the middle pin is the input (+7...+10Vdc) so connecting it directly to the heatsink(=GND) will blow the fuse....
Click to expand...
makes sense. The only reason I’m asking is because the original also had no mica, but did have pretty thick layer of thermal paste.
 
The case of voltage regulators is not always live, if they have a metal tab then it's a safe bet, some are just black plastic so probably not live, best approach is to first check the manufactures data sheet then listen to the OCD and resistance check in turn each leg to case.
 
Rebel said:
I inherited a Yamaha HTR 5650, looks pretty good. Powers on (relay clicks and lcd screen turns on) then Immediately powers off. Unit does not flash a message when it powers off, just blanks out. I went through a reset procedure I found, I tried it twice it does the exact same thing afterwards. It will stay on in diagnostic mode but other than that nothing much. I have a pretty good meter and know how to diagnose some stuff, also have a capacitance meter. Any help is appreciated, Thanks.
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Mine was doing this as well. I followed the operators manual troubleshooting instructions which seemed to fix it for now. I just went into diagnostic mode by pressing the two buttons and then pressing the power button and then unplugged it for about 40 seconds. I turned it back on and it worked fine. I am not sure what caused the receiver to go itno protective mode in the first place so that will be the next step. Plugging everything back in one at a time and making sure there is no shorts in the speaker wires.
 
mbz said:
The case of voltage regulators is not always live, if they have a metal tab then it's a safe bet, some are just black plastic so probably not live, best approach is to first check the manufactures data sheet then listen to the OCD and resistance check in turn each leg to case.
Click to expand...
Do you know if plugging a cabinet fan into the outlet on the back of the receiver would cause any issues. It's in a fairly small cabinet with an open back and front but still got quite hot so I installed a cabinet fan to keep it cool. That seemed to work for about a year. Then it went into protection mode. I got it working again but I'm not sure what caused it to go into protection mode in the first place. I guess just trouble shooting one input at a time and double checking all the speaker wire would be the first step.
 
JrStingray said:
Do you know if plugging a cabinet fan into the outlet on the back of the receiver would cause any issues.
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Should be ok-ish provided the fans power consumption does not exceed max limits of the switched outlets (100W).
The fan will not be kind to the amps power supply probably injecting some noise however you identified a potential problem and did something about it. Where possible the amp should be freestanding with good air circulation however that is not always possible.

JrStingray said:
I'm not sure what caused it to go into protection mode in the first place.
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Whenever the amp goes into protection it's best to read the protection info, these items are complex, you may do more damage by old school repair techniques...
 
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