Boston Acoustic Sub Power Supply Not Supplying Power

-
Daves69

Daves69

Well-Known Member
Joined
Feb 20, 2011
Messages
7,523
Reaction score
6,259
Location
WestOfChi
Well here I go again.
This PS is from a Boston MCS-95
Had some popping going on with the sub woofer lately and now I have nothing. Not even the is led lit to show power on. Power in fuse and switching diode are good per what I have found on the net. Then I ran across a fix one person did on a bad capacitor. It looks like I have two that are suspect.
So my questions to the electronic wizards is.......
Could this have been the popping issue?
Do you think it's worth trying to replace these caps in the pictures?
BAAmpPS1.jpg
BAAmpPS2.jpg
 
That could have been the popping.
Is this the audio amp itself or just the power supply?
Anything wrong in a switching power supply and it won't work at all.
You have a 50/50 chance that replacing those caps will fix it.
Look also for any swollen electrolytic capacitors, or any with broken open scored marks on the ends.
 
Thanks for the reply. Just the power supply. Has a little darker area under the switching diode but I didn't see any other visual problems with it, the amp, or the crossover..............
BAAmpPS3.jpg
 
Just wondering if you recently changed ignition system or other that might be generating spikes.
If the random pop is still present after this is repaired you can suspect another something is generating spikes. In my experience, finding replacement caps can be the hard part. Like using 2 polarized caps to create a bipolar cap then how/where to mount these 2 not fitting that original space. Good luck
 
RedFish said:
Just wondering if you recently changed ignition system or other that might be generating spikes.
If the random pop is still present after this is repaired you can suspect another something is generating spikes. In my experience, finding replacement caps can be the hard part. Like using 2 polarized caps to create a bipolar cap then how/where to mount these 2 not fitting that original space. Good luck
Click to expand...
Thanks RF,
Actually this is 7 year old "Shy-Neese" home theater equipment. My junk runs through a Blackout Buster UPS / Surge Suppress. Hopefully that works as it should.
For the caps I do have a Radio Shack PN to look for (272-1053 or .1uf 250volt). Hope both leakers are the same. I haven't pulled them yet.
We also have a Fry's in the area, or I'll try Jameco online for parts.
 
Replace the two caps only. Fortunate to have a Radio Shack still around.
Got lucky I guess!
Green is good! (on this a red indicates no input from receiver)...............
BAAmpPS4.jpg

(so far, so good)
And the culprits...........
BAAmpPS5.jpg


Thank you all for your input.
 
cool

and i was just about to suggest the ballast resistors
 
Darthomas said:
Never seen capacitors squirt goo before....
What are they doing in China?
Click to expand...
Lol, They are laughing at us for buying this stuff!
Well, it's a Shy-Neese made sub woofer :( The new caps from R Shack are Taiwan-eese and :eek::eek: They look exactly like the old ones with same numbers :eek::eek:.
 
Please help! I don’t know anything about circuit boards or subs but my Boston mcs 95 stopped working. I pulled out the circuit board and found this. Look normal? Could anyone tell me anything from seeing that??

AD985730-47BA-4219-A5F6-7E8FDE09DEEB.jpeg


A9F74B12-0CB5-49DA-AF23-B99CEC87F3C0.jpeg
 
Hi Santiago. I have to say you definitely have an issue there. Short of taking mine apart again, I found another picture I can provide you from my repair. Like my first picture in the thread but from a slightly different angle, you can see it does not show signs of getting hot like yours. BTW, Mine still works but I've put it on a switched outlet so that it's not on all the time.
upload_2020-2-20_9-21-56.png
 
Yes you most definitely have a shorted component in that board. Get an ohm meter and read across that C13 electrolytic capacitor. Should initially.have a reading and then move slowly towards open. If you have close to zero ohms then it's shorted and will need replaced. Also check the diodes for a short. They should conduct in one direction only (black negative lead on the line side red lead on the triangle). If you have conduction in both directions then its shorted. You might have to unsolder one side of these components to get an accurate reading. You can fix the burnt circuit board runs using wire across them.
 
You must log in or register to reply here.
-

Back
Top