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From: Sjouke Burry on 10 Aug 2010 19:54
Today, somebody donated an Akay AA-MBL radio/amplifier to me.
Not operational, on investigation two blown 15 amp fuses, by
the look of it, in the power amplifier.
Fuses replaced by 2X 6 amp , and to my surprise, everything
started working.

Now fuses dont blow just to surprise you.

So, how did the former owner manage to blow both?
From: William Sommerwerck on 10 Aug 2010 20:42
> Now, fuses don't blow just to surprise you.

No, they don't.

"Something" caused a momentary high current drain that popped the fuses,
which sacrificed their existance to save the equipment. What this
"something" was is not always obvious. It could have been due to cranking up
the volume and clipping the amp for an extended period. It could have been
due to brief high line voltage. It could have been due to kicking the power
cord, causing an intermittent connection at the wall socket or cable socket
on the amp. It could be due to thermal fatigue.

To answer the question you're /really/ asking, but didn't ask... It's quite
possible for fuses to blow without there actually being anything permanently
"wrong" with the amplifier. The probability that this amp is defective in a
way that will cause it to explode or burst into flames is small.


From: N_Cook on 11 Aug 2010 03:20
Sjouke Burry <burrynulnulfour(a)ppllaanneett.nnll> wrote in message
news:4c61e6ce$0$14123$703f8584(a)textnews.kpn.nl...
> Today, somebody donated an Akay AA-MBL radio/amplifier to me.
> Not operational, on investigation two blown 15 amp fuses, by
> the look of it, in the power amplifier.
> Fuses replaced by 2X 6 amp , and to my surprise, everything
> started working.
>
> Now fuses dont blow just to surprise you.
>
> So, how did the former owner manage to blow both?


Self-healed capacitor short?


From: nesesu on 11 Aug 2010 14:54
On Aug 10, 4:54 pm, Sjouke Burry <burrynulnulf...(a)ppllaanneett.nnll>
wrote:
> Today, somebody donated an Akay AA-MBL radio/amplifier to me.
> Not operational, on investigation two blown 15 amp fuses, by
> the look of it, in the power amplifier.
> Fuses replaced by 2X 6 amp , and to my surprise, everything
> started working.
>
> Now fuses dont blow just to surprise you.
>
> So, how did the former owner manage to blow both?

Where in the circuit are the fuses? If they are line fuses, it is
pretty hard to develop enough current through the power transformer
[?] to blow 15A fuses. If there is an outlet for a phonograph after
the fuses, it could have been a short plugged into that.
I did have one set that the 'line' capacitor failed and it was blasted
to oblivon so the set worked fine with a new fuse. The only clue that
the cap had been there was a bit of blackening near the tie strip and
two short leads with nice copper balls on the ends. Someone must have
taken the bottom off and removed all the bits of plastic and paper
since there were none present.

Neil S.
From: Sjouke Burry on 11 Aug 2010 17:14
nesesu wrote:
> On Aug 10, 4:54 pm, Sjouke Burry <burrynulnulf...(a)ppllaanneett.nnll>
> wrote:
>> Today, somebody donated an Akay AA-MBL radio/amplifier to me.
>> Not operational, on investigation two blown 15 amp fuses, by
>> the look of it, in the power amplifier.
>> Fuses replaced by 2X 6 amp , and to my surprise, everything
>> started working.
>>
>> Now fuses dont blow just to surprise you.
>>
>> So, how did the former owner manage to blow both?
>
> Where in the circuit are the fuses? If they are line fuses, it is
> pretty hard to develop enough current through the power transformer
> [?] to blow 15A fuses. If there is an outlet for a phonograph after
> the fuses, it could have been a short plugged into that.
> I did have one set that the 'line' capacitor failed and it was blasted
> to oblivon so the set worked fine with a new fuse. The only clue that
> the cap had been there was a bit of blackening near the tie strip and
> two short leads with nice copper balls on the ends. Someone must have
> taken the bottom off and removed all the bits of plastic and paper
> since there were none present.
>
> Neil S.
The fuses sat right in the centre of the power amplifier print.
I wold guess protection of the output stage.
The mains fuse was oke.
The set is still playing as I type this.
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