Mackie micro serie 1202 first version

[noiro]

Hi I have a problem with an old Mackie 1202, that I have for over 20 years, I love this piece of equipement, easy to use and sound pretty decent, recently I notice that I have a hum, a noise through the master output and the headphone output that goes away after the mixier gets warm, take about 5 minutes and it does not come back, let it cool and here it is again, so I though that perhaps it was the two caps 2200uf of the power supply that was the cause, I changed those but still the same problem, perhaps it the two voltage regulator(transistor) of the power supply 7815A and 7915A but I'm not certain, I may try that anyway and see, caps were only $9 for 3, 7815A and 7915A are $2 each on ebay.

Anyone with a similar problem!

thanks!

 

[Enzo]

Don't throw parts at it, get out a scope and watch the power supplies. Are they up and stable or are they changing with the symptom? Is there excess ripple in them?

And it may not be a part at all. Over the years Mackie has had a problem with ribbon cables. I don't recall the insides of this unit, but the ribbon header female connectors get oxidized. Usually pulling them half way off and pushing them back down refreshes the contact surfaces.

 

[66521]

I agree with Enzo. Check connections. Rule of thumb is that about 80 per cent of problems with electronic circuits are connection related. Check and clean (if needed ) all connector points. Corrosion is electricity’s enemy. If you use isopropynol as a cleaning agent, make sure you rub surfaces well after application. Alcohol tends to spread the grease/dirt/bad corrosive stuff around on the surface so you have to remove it totally.