Mackie SRM1801

[clintronics]

Q1, Q2 FDP33N25 both check shorted. any advice on anything else that typically dies when these are shorted?

[soundguruman]

Q1, Q2 FDP33N25 both check shorted. any advice on anything else that typically dies when these are shorted?

1.the resistors, diodes, and previous transistor stages
2. The power transformer (disconnect from load, check that first)

[clintronics]

Are you familiar with this model? because there isnt a transistor stage. Q1 and Q2 are fed by U3

[clintronics]

My Yahoo Horoscope.
February 23, 2012
Virgo (8/23-9/22)
Usually you find helpful information when you look into the details of a project, but today it's not so simple. In fact, you're likely to only get more confused the deeper you dig. The best thing to do in that situation is to stop what you're doing immediately. Walk away for a while and let your brain get occupied with other ideas. When you come back later in the day, those details will suddenly help you understand. You'll immediately know what to do.

too funny

[Enzo]

And there is no power transformer either, it uses an SMPS.


I haven't had one of these blown up yet. I get the cracked solder on the little output filter board on EVERY freaking one.


If those are shot, I'd explore the health of the resistors and diodes in the gate drive circuit. If those are damaged, the IC may be bad. If those are OK, it may just be outputs. I'd also check out the series inductor L1 for arcs to the board or broken leads.


And I am shooting in the dark... my print for this amp - from a different model HD1801, but I think it is the same board - shows a two channel amp board. Is that the case here? And if so, do they bridge them? If they do, check the other channel's outs. The drawing charts several models the amp is used it, including yours.

[Enzo]

And of course, make sure the speaker itself isn;t toast.

[soundguruman]

Are you familiar with this model? because there isnt a transistor stage. Q1 and Q2 are fed by U3

And U3 being an integrated circuit, full of internal transistors.....it IS a transistor stage.
When power transistors blow, normally takes out several previous stages.
And so if you are unable to remove and test all related semiconductors, it will not get fixed.

[Jazz P Bass]

Can the schematic be posted?

[clintronics]

Thanks Enzo, that was more the type of response I was looking for. I have two of these both blown the same way, both have good speakers and are the Mono 1 channel version.

[clintronics]

Mackie made me sign a form saying I wouldnt do that

[Brian Swatton]

I've got one of these on the bench, I know I'm unlikely to get drawings.

I've found the smaller converter in the PS was hiccuping, I can measure a short across D24 which looks to be one of it's secondary rectifiers. It looks a pain to get at. I've not found any other obvious-to-check devices faulty so far, though I did find Enzo's output filter soldering issue too.

Can someone tell me if these PS boards will run up without the rest attached? or do they need loading/enabling?

I used to test & repair SMPS for a manufacturer by the way, so aware of general safety issues.

[clintronics]

I've got one of these on the bench, I know I'm unlikely to get drawings.

I've found the smaller converter in the PS was hiccuping, I can measure a short across D24 which looks to be one of it's secondary rectifiers. It looks a pain to get at. I've not found any other obvious-to-check devices faulty so far, though I did find Enzo's output filter soldering issue too.

Can someone tell me if these PS boards will run up without the rest attached? or do they need loading/enabling?

I used to test & repair SMPS for a manufacturer by the way, so aware of general safety issues.

try
techmail@mackie.com for schematics
they seem to be getting easier to deal with lately IMO.

[Brian Swatton]

Ah great, thanks, I'm on it

[clintronics]

I dont think supplies need to be loaded. But I seldom work on Mackie products so one of the other guys here would probably know that answer for sure. Definitely replace any shorted diodes.

[Brian Swatton]

Yes I'll certainly be changing the diode. I just maybe I might get a little forewarned If I can get some data out of Mackie I'll be happy.

Thanks again, cheers