Mackie M1200

[Techknowman]

I searched the forum to make sure I wasn't duplicating something here.
I wanted to FYI anyone interested.
I started work on a Mackie M1200 amp. It is in protect constantly on one channel.
I pulled the main board out and found that the unit arced over from the -80V diode (D8) to the heatsink. it was very obvious. looking close the PCB with all the output transistors and all is very, very close to the heatsink and has little insulation to prevent such and issue. I cleaned the pcb and ground out the pcb that had carbonized.
I then took strips of kapton and made some 90 deg long strips to place between the PCB and heatsink.
The issue with protect looks like a leaky transistor (Q79) placing the unit in SOA fault.
I pulled R159 and the unit still went into fault. pulling R161 stopped the fault and the amp worked well and bias was correct.
Mackie-M1200 1400

[Jazz P Bass]

I just serviced a M 1400i.
The main board had really poor soldering.
The 6 pin AC connector had a really bad connection on the lower center pin.
Really bad.
This board was not preheated properly. The largest connections where all thin.
Total reflow of main board fixed the amp.
Thanks for the service manual.
I was curious about the idle current.
The manual states 8 mv across the test points.
As recieved the amp was set at 70mv,s.

[micri5446]

lol made in china...nuff said?

[Enzo]

No, not nuff said. It is too easy to just point to "China" on a product as the cause of any failure. Mackie and the rest don;t just pick up the phone and call China and tell them to slap some amp together and stick our name on it. For better or worse, the imported products are meeting Mackie's expectations and fulfilling Mackie designs. As a Fender authorized repair center, for example, I have had to repair a lot more poor solder jobs on hand wired domestic amps than I have on Fender CHinese imports.

[micri5446]

enzo i have been reading this forum for a while and finally decided to post because most people who speak know what they are talking about..you included sir are a true technician through and through but, i must disagree with you about chinese products...

as a service tech for many companies that produce in china, vietnam, thailand korea all i can say is that a unit is only as good as its weakest component. the engineering, manufacturing and quality control might be mint but, if that $.03 100ohm surface mount transistor is not made to the highest standard, the resistor probably will fail in constant usage situation. this seems far to common to me in products made in these countries that also produce the components.

listen, i know that some companies like hartke, loud, behringer, marshall gave their own manufacturing plants in these countries and are on top of quality control but, they still use components made in china ect..not made in usa or japan..that would be to costly.

i think it is sad what is happening in the industry of amps, keyboards ect...the big box stores are pushing this cheap crap onto people and selling an "insurance" policy to sweeten the deal. then when it fails in a year in 3 years and the consumer has no warranty left they bring it to a shop and decide , well hell, i only paid $350 for the amp, i don't want to fix it i'll get another one.....

and the cycle continues....buys another cheapy and has another experience.

i only say chinese lol is because, of the majority of stuff we see lately, it is real cheap. you cannot say that loud technologies are producing ampeg or crate to the same standards as slm.
marshall is manufactured in vietnam...dude, thats a jungle

i respect you man, but anything not made in north america or europe pretty much blows (circuits that is)
peace................mike

[Enzo]

But that is more or less what I meant. A company like Peavey has CHinese plants, and so does the company making cheap crap for K-mart. Any mass marketed product will see a certain amount of failures, but whether it is the construction or the components, if a lot of the product is falling apart, Peavey will make changes. K-mart might not. Point being that it is the company selling the product making that difference. My objection is not that CHina is blameless, but that a blanket statement of Chinese guilt is misplaced.

For example, the transformer wires on the Chinese Bugera amps that are burning up the Molex connector on the heater wiring. I see no difference between that and the Molex connectors burning up on the heater wiring pins on made in the USA PV Ultra amps. It is not the Chineseness of the contruction, it is the marginalness of the design spec. Yes, there are plenty of cases of Chinese crappy stuff, but Chineseness should not be a one size fits all indictment. SOmething good coming out of China doesn;t automatically become crap as it crosses our border.

[micri5446]

noted..

[tedmich]

lets hold off on the heated political discussions, you radicals!


(kidding)