Mackie VLZ-Pro 24.4 Consoles

[bgavin]

I have a friend who is a service tech for mixing consoles.
He said the chronic weak spot in my 24.4 console is the power supply.

The # 1 failure of these consoles is the +16V regulator IC...due to heat degradation.
The IC that's goes bad is located on the supply's heat sink located directly above the screened vent in the bottom case.
The failure of the IC (LM317t) is a combination of a lack of cooling, dried up heat sink compound and two dried up caps.
These are electrolytic capacitors (10uf @ 50V) on the power supply PCB.

My question is, does anybody have any knowledge about the size spec for the 10uF / 50V caps? He says the stock caps are rated 85C, and to make sure to get 105C because of the heat.

We also discussed internal fans to cool this area.

[gg1978]

Re: Mackie VLZ-Pro 24.4 Consoles

LM317T is just a standard variable linear regulator.. No fancy switching here.. No idea about the size, but 105C rated caps are always a good idea around linear Vreg's that are either dropping a large amount of voltage, or passing a lot of current.. I forget the exact limit for current on a 317T, i'm thinking either 1.5 or 2.5A, but you have to have a large heatsink for those kinds of currents..

[Wizard]

Re: Mackie VLZ-Pro 24.4 Consoles

317T is 1A MAX. Better get a efficient transistor and have 317T drive that transistor instead for higher current capacity and less heat.

Cheers, Wizard

[bgavin]

Re: Mackie VLZ-Pro 24.4 Consoles

Thanks for the replies.
The tech told me this console is quite reliable as long as the IC has working heat paste and the 10uF/50v caps are good.

We discussed at length adding a pair of A/C fans, in a push-pull arrangement to positively cool the PSU. He said this will add years of life to a solid console.
I have to get this done before our torrid summer season sets in.

I have a four day event in mid-May, and it will probably be hot.

[Wizard]

Re: Mackie VLZ-Pro 24.4 Consoles

The datasheets is explict on 1A and it did say with infinity cooling (overkill).

There are versions of higher current 317 regulators and they are large package but it is prudent to design a circuit using a 317T to drive a voltage regulating transistor that can handle higher current if you can use a low drop voltage transistor (less heat).
We could have you use buck regulator but the noise would get into audio circuits so I decide against this unless one design a 100-500KHz buck regulator.

Cheers, Wizard

[hardwareguy]

Re: Mackie VLZ-Pro 24.4 Consoles

A good high temp general purpose capacitor is what you need here. I'd select a long life type.