fuse/ power supply question or problem on amplifier

[ian nicoll]

Our amplifier was on yesterday and suddenly stopped working, the T1A fuse on
the 240V side of the transformer had blown, for no apparent reason. I did an
250V insulation test on the 240V side of the t/f and it was clear, there
didn't appear to be a short circuit on the 240V side of the t/f or an
interwinding fault or a fault to earth on the LV side, the connector from
the LV side is connected to a rectifier board with, I presume, some current
limiting feature. As far as I could see there was no obvious fault component
in the amplifier.

I didn't have any T (antisurge) fuses so I used a F1A quick blow fuse. The
amplifier worked fine last night but today the fuse blew within a few
seconds (or less) or the amplifier being switched on (using the button on
the front which switches the 240V circuit).

The amplifier is a Marantz about 12 years old.

Is it possible that using a quickblow rather than an anti surge fuse has
caused the fuse to blow the second time. Is there likely to be some current
limiting device on the rectifier board? Any other pointers things or things
I should look for.

Thanks

Ian

 

[Asimov]

"ian nicoll" bravely wrote to "All" (09 Sep 03 15:33:44)
--- on the heady topic of "fuse/ power supply question or problem on amplifier"

in> From: "ian nicoll" <newsnicoll@btinternet.com>
in> The amplifier is a Marantz about 12 years old.

in> Is it possible that using a quickblow rather than an anti surge fuse
in> has caused the fuse to blow the second time. Is there likely to be some
in> current limiting device on the rectifier board? Any other pointers
in> things or things I should look for.

in> Thanks

in> Ian

Yes, a fast fuse will go... well... faster! What can happen with a fast
blow fuse in an application requiring a surge rating is that one might
switch the power at the instant the line voltage is at maximum and the
fast fuse goes pfffft... If the slo blow one goes again then worry...

Asimov
******

.... Power is obtained by current meeting resistance

 

[Asimov]

"ian nicoll" bravely wrote to "All" (10 Sep 03 08:23:57)
--- on the heady topic of "Re: fuse/ power supply question or problem on amplifier"

in> From: "ian nicoll" <newsnicoll@btinternet.com>

in> Thanks for answers.

in> The original fuse is stamped T1A 250V, it also has four coloured bands
in> on the glass body (like a resistor) they are brown, black, red and a
in> thicker blue line. What do the colours signify?

The colours represent the current in milli-amperes so brown, black, red
would be 1,000 milli-amperes or 1 ampere. The last blue band would
similarly likely represent the voltage rating, in this case your 250V.

The significant symbol is the letter "T" which represents a slo-blo fuse
for use with inductive or capacitive surges. They are designed to blow
with up to 400% of the rating outside a time period of about 2 seconds.
A similar ampere rating fast blow fuse will open within 0.3 seconds, so
rest assured the fast blow fuse you tried to use never stood a chance.

No need to "special" order a fuse. "T" fuses are very ordinary.

Asimov
******

.... Power is obtained by current meeting resistance