Alpine mrv-f300 works fine for 10 min and then audio gets bad

[ivkata]

I got this amp here Alpine mrv-f300 its a 4 chanell v12 amp.will work fine for 10 min all audio chanels sound great and then distortion and gets worse ans worse.All chanels go bad at the same time ,any info is apresiated

 

[Perry Babin]

What do you mean when you state that 'all channels go bad'? Do the outputs in them fail and have to be replaced?

I'm assuming that you have the transistors clamped to the heatsink.

 

[ivkata]

well the amp will work fine for 10 min and will start distortions in all chanels.none of the output tested bad.if i let the amp stay overnight will work aggain for 10 min and the same.all transistor are clamped to the heatsink and none gets hot

 

[1moreamp]

Power supply issues maybe ???? at least that's what it sounds like with all 4 channels being effected evenly their only common thing is the power supply. perhaps its going into fault and not shutting down and or muting the channels, this would explain the unique symptoms.... Perhaps bad solder joints, thermally intermittent devices in the lower 16 volt regulators. Just sounding some ideas...

 

[ivkata]

just had it running for 10-11 min the same story.there is a pair of transistors near the power supply a1220a and c2690a that get kinna hot and i doubt they should couse are not mounted on any radiators,i can smell them hot

 

[Perry Babin]

On the upc494 (or whatever 16 pin IC they're using to drive the power supply, measure the DC voltage on all of the pins before and after it shuts down. Which pins have different voltage after it shuts down?

 

[ivkata]

i cant really do that now the amp have desided to play only bad.bad bad bad gate voltage is 0.8 no wonder why shitty audio comes out

kia 494 shows this

Pin 1: 1
Pin 2: 1
Pin 3: 3.8
Pin 4: 0
Pin 5: 1.7
Pin 6: 4
Pin 7: 0
Pin 8: 15
Pin 9: 0.8
Pin 10: 0.8
Pin 11: 15
Pin 12: 15
Pin 13: 5
Pin 14: 5.6
Pin 15: 5.3
Pin 16: 0.00

 

[Perry Babin]

Was the amp producing clean audio when you measured the DC voltage?

 

[ivkata]

nope all bad audio now and when i tested the kia494

 

[Perry Babin]

When the audio is distorted, does the amp have both positive and negative rail voltage on the output transistors?

Does it have both positive and negative regulated voltage on the power supply pins of the op-amps?

 

[ivkata]

I got both positive and negative 27 on the outputs.I see 4 kia6259 pre amps are those the one u want me to test couse i dont see and other op amps on the board

 

[Perry Babin]

Yes.

 

[ivkata]

ok they all have positive and negativ 15 on legs 4 and 8 .2 of them have 0 on legs 2,3 and on the out leg 1

 

[Perry Babin]

What do you mean by this "2 of them have 0 on legs 2,3 and on the out leg 1"?

Do the other two have something other than 0v?

 

[ivkata]

yes the other 2 have 15v on 1,2 and 3

 

[Perry Babin]

Do all of them have 0v on pins 5, 6 and 7?

 

[ivkata]

no those 2 have 15 v on those legs as well

 

[Perry Babin]

Does the audio change if you push on various points on the board?

Looking at the bottom of the board, do you see any solder connections with circular cracks around their center?

 

[lukej2000]

I got this amp here Alpine mrv-f300 its a 4 chanell v12 amp.will work fine for 10 min all audio chanels sound great and then distortion and gets worse ans worse.All chanels go bad at the same time ,any info is apresiated

I have the same amp - Alpine MRV-F300 and I have same problem. It runs perfectly and very loud for 10 minutes, then it starts buzzing and the output drops (gets quieter).

This affects all channels, in bridged mode and unbridged.

What could this be?

 

[starkeyg]

10 minute problem

Hello,

Had similar problem on a Clarian unit but only with one channel. Unit would work fine for just over ten minutes and then would start distorting badly.

Opened up unit, checked tightness of heat sink screws, put fresh silicon grease on power chips/heat sink. Touched up solder joints going to the main power amp chip, put things back and has worked fine since.

Believe the solder they are using now (no lead) is not as strong and the solder joints can crack / break. As things heat up, expansion causes the contact to get worse and the result sounds like ****. Car stereos do get quite a bit of vibration and shock.

Personally I am using silver solder which is harder and take a little more heat to melt, but is stronger.

For whatever it is worth, fairly easy to try.

Regards,
Greg