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Marantz 2215B popped it's top

Briant8

Briant8

Active Member
So, there I was....
I'm super stoked after a wildly successful 2250B recap last week. I carefully choose my next victim, the sweet little 2215B that has been waiting patiently for some lovin'.

Very methodically (as all you fantastic gurus recommend) I start with the:
Tone board: Recap, test = success
Power supply board: Recap, test = success
Phono board: Recap, test = success

I'm feelin' good right?

Main amp board: Recap, test =
Left channel normal, sounds great.
Right channel silence... Then more silence.

Check speaker connection, still silence...

Stand there scratching my head when the hum starts through the right channel.
Puzzled look etched on my face whilst the hum grows.
Puzzled look growing on my face whilst the HUM continues to grow!
It's steadily growing more ominous as my brain cloud finally dissipates and two brain cells finally meet up and scream at me to shut this warhead down; reach for the power switch and goes the big 2200uF/35V capacitor C722! [this was the original cap btw, was going to have to order C722 & C721]
As I'm doing my best Neo (a la The Matrix) imitation dodging scalding hot capacitor goo, I'm already looking to see which of the new caps I installed backwards.
Nope, nothing. The right and left sides are mirror images, everything installed properly and with identical specs.

The next morning:
(Left side continues to sound just fine, and bias was 8.9mV when I checked it)
Check my soldering, a little bit ugly but no bad joints, no bridges that I can identify. I didn't accidentally un-solder anything, don't think I accidentally cooked anything (besides C722...)

Ok, fire away!
 
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i had one recently in a tv that nearly went pop . i felt the heat then seen it getting bigger .. i got to the plug fast enough to stop it spewing out .. funny thing is i measured that circuit as dead before i swapped it ...
next tv was a cap getting hot that smooths power for the audio chip and sound is dead . removed chip and cap now cold . put it down to shorted chip but still cant work out why cap would heat up ..maybe you have similar thing going on here . ? all i can think is + side went more negative than - side or the other way round .
 
Pics as requested:
(I used 1uF Mylars in place of all 1uF electrolytics) just due to availability.
This receiver has a history of intermittent popping/crackling sounds upon warming up, btw.
So, maybe this cap was on its last leg anyways?


image.jpeg image.jpeg image.jpeg image.jpeg image.jpeg image.jpeg image.jpeg
 
Well,
Upon further examination of those pics and board, Its obvious that every component has a mirror image component, except R723/R729 & R724/R730.
R724/R730 are reversed on the bad right side (although this arrangement is what the SM specifies)
However, these two buck the mirror image trend.
Perhaps the smoking gun here?
(Someone has been in here before, and my guess is followed the SM in reinstalling R724/R730 instead of mirroring the other side)
Would this cause the bang, and if so, how did it last as long as it has?

image.jpeg image.jpeg image.jpeg
 
tonebells said:
C704 is backward. I don't know if that is what made it pop. Look up dim bulb tester.
Click to expand...

Good morning tonebells,
Thank you for your input!

(I'm still learning here, so please bear with me)

May I ask what brings you to that conclusion? C704 is placed properly as per the board (which of course can be incorrect) and is also oriented in the same manner as its brother C703 on the left side (which is working beautifully) with the negative leg towards the inside of the body.

(Again, the two sides seem to be mirror images of one another to me, with the exception of the resistor pairs that I mentioned above)

I appreciate any insight you would share, these things are still largely voodoo to me. But I'm learning! :)
 
gort69 said:
I think he meant C706. Definitely backwards.
Click to expand...

Sweet Baby Jesus!
(Good Lord, how many times must one look at something to see it accurately!?)
:eek2:

THANK YOU so much! :bowdown:
And hence why two (or 32) sets eyes are better than one....

(Curious as to why C706 didn't pop...... Hmmmmm)
I'll pull him out and test him. (If he still tests at 100uF is he still good to use?)
 
tonebells said:
That is a 6! There was some glue making it hard to read on the board I was looking at.
Click to expand...
Yep, tenacious glue that is!

What do we think about the resistors?
Are the ones on the right which are set per the SM correct or the ones on the left that are reversed the correct ones..... Hmmmm...
 
Not sure which resistors you are talking about, but resistors don't have polarity. They can go in the circuit in either direction
 
Those resistors are correct as far as I can tell. The bands for R723/R724 read as 8.2K ohm and that what the schematic and parts list call for in the service manual. And R729/R730 read 10 ohm and again exactly what the service manual specs for those positions.

No telling why the engineers decided not to mirror those particular positions but looks right unless those board markings are reversed. I'm not up to date on SM errors for this model.
 
MBuras said:
Those resistors are correct as far as I can tell. The bands for R723/R724 read as 8.2K ohm and that what the schematic and parts list call for in the service manual. And R729/R730 read 10 ohm and again exactly what the service manual specs for those positions.

No telling why the engineers decided not to mirror those particular positions but looks right unless those board markings are reversed. I'm not up to date on SM errors for this model.
Click to expand...
I know, it's weird...
Some of these caps have been replaced. What I pulled out doesn't seem typical from what I've seen.
I just wonder if the reversed pair (whichever one it is) was causing the popping noise that it originally was doing?
And it just doesn't make sense in my pea-brain that every single thing else is identical to the opposite side except these resistors...
Dang, I wish I was smarter!
Ah well, guess it's time to plug some things in and trust the DBT to protect us whilst figuring it out.... :-/
 
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