MRV-F345 fan cooling? - diyAudio
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Old 23rd June 2010, 07:33 PM   #1
jol50 is offline jol50  United States
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Default MRV-F345 fan cooling?

Anyone know how the fan works on this amp? Have one in the car the fan is not running. It got up to 137F on its temp display and I had to go, but no fan running. I could hold my hand on it but was hot. The fan does spin if you blow on it.
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Old 23rd June 2010, 07:48 PM   #2
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Google turned up several people with the same concern. There was one that said it had to go back to Alpine to be reprogrammed.
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Old 23rd June 2010, 07:57 PM   #3
jol50 is offline jol50  United States
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Nice, this is one I put PS and one channel in. It works nice far as audio except the input switch is weak. I suppose that means the IC runs the fan I didn't look while in there. The OM says nothing about it in fact the drawings in the manual don't even show the fan maybe early ones had it elsewhere or no fan. Only running highs with it but seems like it would come on by that temp, not wanting to screw it up again of course.
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Old 24th June 2010, 06:16 PM   #4
jol50 is offline jol50  United States
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Looked that stuff up and read, but not like Alpine is going to say why it does not work. Reprogramming an IC sounds a little out there to me but who knows.

I took it out of the car, will tear it apart when I get time and see what makes the fan tick. All else fails there is more than one way to make a fan run. One of the switches needs looking at too.

Unless someone has a schematic showing the fan, I don't have one.

Put another fan cooled amp in there and that fan is not running either, but it was cooler out and I didn't have time to run it for a while. And yes it sounds different lol! The vocal ranges are fairly different from the Alpine.
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Old 25th June 2010, 07:12 PM   #5
jol50 is offline jol50  United States
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There is what appears to be...an A1358 transistor that runs the fan. It is run by two SMD transistors but not found what runs them, it may be a 14 pin IC I'm not having luck finding ID of yet. There is a bigger square IC near that, it may run the fan. I'll hotwire it on all the time if need be. The three transistors seem to test good with no power. The traces to run the fan are tiny, it must not take much, but not seeing any other electronics in the cover near the fan. Not sure why the two SMD transistors to run the A1358 unless it works differently. The base of the A1358 is marked, it is similar to what is used for the channel drivers I replaced maybe the same didn't look.

I think the IC is a Fairchild VHC04 hex inverter, so would that be a PW modulator for fan speed? The SMD are in pin 4 and 8.
Details and datasheet on part: 74VHC04N
IC says:
0440H
VHC04
406545

According to this PC-BASED DC MOTOR SPEED CONTROLLER
They might be turning one or the other or both on to change fan speed?

Last edited by jol50; 25th June 2010 at 07:42 PM.
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Old 25th June 2010, 08:04 PM   #6
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The inverter changes positive pulses to negative pulses and vice-versa. It may be that it's being used as a buffer between the processor and the fan driver transistors.
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Old 25th June 2010, 10:33 PM   #7
jol50 is offline jol50  United States
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Yes looks like it runs off a toshiba TMP86PM47U on pins 11 and 12 maybe 10 also. Wonder if I can test it. Thing is most stuff blows the fan on startup to test, but the other amp I have does not. What do you do hold the solder gun on the temp sensor....it does have a temp readout, but I don't know what temp it should come on either. The IC is programmable the guy might have been right providing nothing else is broken. I have not tested the fan yet but it does turn fine. Not sure what voltage it runs have to trace the transistor to something I guess, it does have 5v think all those ICs run on it. IC says max 5.5v input.
PC-BASED DC MOTOR SPEED CONTROLLER

Guess I will put the scope on there later and look for some pulses.
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Old 25th June 2010, 10:40 PM   #8
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Without the service manual, it's difficult to offer suggestions for a problem like this (which may not actually be due to a failed component) but you should make sure that you don't short between the pins of the microcontroller or the logic IC. They may not be as rugged as op-amps or other ICs generally used in amplifiers.
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Old 25th June 2010, 11:33 PM   #9
jol50 is offline jol50  United States
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I'll try to fire it up on the bench later. It actually does have little test pads in most of the traces so you don't have to test on the ICs. I could get lucky and have a bad fan or something but I bet not, might be why it blew to start with though it should have shut down. But that channel runs subs too, that is the one you can run subs on half but not the other half, it has twice the outputs on that half.
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Old 27th June 2010, 05:28 PM   #10
ppia600 is offline ppia600  United States
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What about changing the value of the thermistor to induce the controller to kick the fan on earlier? Paralleling a resistor on the thermistor / or adding one in series depending on the circuit to trick the amp into thinking its super hot.
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