Mostly just posting this because I am impressed. Never seen one of these later Marantz designs blow up this bad. Anyone got any ideas? I am assuming everything is probably blown...
The most blown up 170DC I have ever seen
- Thread starter goldswimmerb
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- blown up marantz 170dc repair
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Would say lightning but other channel is perfect...
From the looks of it all 4 outputs were fake. Which killed the drivers and I think just sent rail voltage everywhere
Doesn't look like it, fuse is the correct one. Looks to be a result of a fake set of output Transistors. Hoping that it didn't take out the input FET. As long as that is in tact shouldn't be too terrible...
I can't imagine anything burning MULTIPLE areas on a board without something being "bypassed".
That's what I thought as well, but from what I am seeing nothing looks to be bypassed. Will have to investigate more, unfortunately this one strays from there service manual a bit with the rear mounted board components...
catrafter
Marantz Specialist
I was once working part time at a CB (yeah, I know) radio shop. A trucker came in with two burned up 'linear' amps.
While I was looking at the carnage, he asked me 'what would happen if you hooked the two linear amps in line?' I told him 'you would have a burned up mess like you have now.'
There are no bounds to the inventiveness of a damn fool.
I hope you are able to save the amp.
Tom
While I was looking at the carnage, he asked me 'what would happen if you hooked the two linear amps in line?' I told him 'you would have a burned up mess like you have now.'
There are no bounds to the inventiveness of a damn fool.
I hope you are able to save the amp.
Tom
jd3rdcoast
Super Member
One channel on mine in mid surgery. Fully recovered now. Check for burnt traces on backside as well.
Well, replaced literally everything burnt and testing remotely out of spec, and so far so good. Only have it on the DBT at the moment but it seems stable there. Haven't checked bias yet, or tested with a speaker, but nothing is on fire!
Used KSA1220 and KSC2690 for my predrivers, KSA940 and KSC2073 for drivers, MJ21195/96 for outputs, a good number of KSC1845s on the input and differential side, and an old stock 2SA733 and KSC945 on the other side of the amp.
Will update when I put it through its paces.
Used KSA1220 and KSC2690 for my predrivers, KSA940 and KSC2073 for drivers, MJ21195/96 for outputs, a good number of KSC1845s on the input and differential side, and an old stock 2SA733 and KSC945 on the other side of the amp.
Will update when I put it through its paces.
Which #/size caps are those? I'd like to replace the main filter capacitor in here with minimal case modifications.
Hey, so I have it on the bench now, under load testing R749 starts smoking at around 9V RMS. Any ideas? My output looks like this one the scope:
Attachments
Figured it out, R759 had gone open without burning
Also, is the meter adjust procedure in the manual correct? My math tells me that 16v RMS as the max would only be 32 watts.
KSC945 EBC
2SC945 ECB
KSC945C ECB ( corrected -- oops )
Same goes for the 2SA733 and the Fairchild KSA733/KSA733C.
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It was a 945C
Working nicely now, just trying to figure out the meters, doesn't make sense to me that 16V RMS would be max on a meter that allegedly reads up to 170w
So far so good, discovered whatever shop butchered this one replaced both channels outputs with fakes, so had to go back and fix up the other channel. The "good" channel was running fairly hot even after swapping the outputs, wound up changing out the driver and predrivers with KSA1220/940 and KSC2690/2073 and everything seems nice and stable, as well as cool.
Love these later DC models, easy to work on and usually stable as can be, which can't be said for some of their earlier counterparts (cough cough looking at the 250M...)
Love these later DC models, easy to work on and usually stable as can be, which can't be said for some of their earlier counterparts (cough cough looking at the 250M...)
Steven Tate
CEO Flat Forehead Soc.
Nice work! That’s a beautiful amp you brought back from the dead. I haven’t heard one, but I know it’s reputation. Hope to hear one some day. 
