Mc Crypt PA-5000 fuse ratings

[Bernhard Kuemel]

Hi rat!

I was given a Mc Crypt PA-5000 amplifyer with the two internal fuses
missing. Fast 2 A fuses were blown by power up only, probably by
charging the capacitors. Fast 7 A worked, but are probably overrated.
The AC current measured with a multimeter goes up to 3.7 A peak during
strong deep basses. I read the unit is prone to dying (domed or leaking
capacitors) under high load so maybe 4 A fuses are still too high and a
more protective slow 3 A fuses may be sensible. What do you think? Which
rating are the original fuses?

Thanks, Bernhard

[Peter Larsen[_3_]]

Bernhard Kuemel wrote:

> Hi rat!

> I was given a Mc Crypt PA-5000 amplifyer with the two internal fuses
> missing. Fast 2 A fuses were blown by power up only, probably by
> charging the capacitors. Fast 7 A worked, but are probably overrated.
> The AC current measured with a multimeter goes up to 3.7 A peak during
> strong deep basses. I read the unit is prone to dying (domed or
> leaking capacitors) under high load so maybe 4 A fuses are still too
> high and a more protective slow 3 A fuses may be sensible. What do
> you think? Which rating are the original fuses?

I have a pair of McCrypt loudspeakers that are LD-Systems in disguise.

> Thanks, Bernhard

Kind regards

Peter Larsen

[FF]

Op 24-2-2011 20:58, Bernhard Kuemel schreef:
> Hi rat!
>
> I was given a Mc Crypt PA-5000 amplifyer with the two internal fuses
> missing. Fast 2 A fuses were blown by power up only, probably by
> charging the capacitors. Fast 7 A worked, but are probably overrated.
> The AC current measured with a multimeter goes up to 3.7 A peak during
> strong deep basses. I read the unit is prone to dying (domed or leaking
> capacitors) under high load so maybe 4 A fuses are still too high and a
> more protective slow 3 A fuses may be sensible. What do you think? Which
> rating are the original fuses?
>
> Thanks, Bernhard

Here (http://www.mikrocontroller.net/topic/144407) is a discussion in
German about the same amplifier. Schematics and board layouts are
included in that thread.

(side note: in his case R65 on the 4th page of the schematic was blown,
pls. note how Mc Crypt designed a 14V power supply from the 65V rail
voltage......)

YMMV, FF

[Bernhard Kuemel]

On 02/25/2011 07:18 PM, FF wrote:
> Here (http://www.mikrocontroller.net/topic/144407) is a discussion in
> German about the same amplifier. Schematics and board layouts are
> included in that thread.

The schematics are from a PA-8000, so the fuses may well be different.
Hmm, the drawing number (Zeichnungsnummer) is 'PA 5/8000 ...'. So maybe
the fuses are the same.

> (side note: in his case R65 on the 4th page of the schematic was blown,
> pls. note how Mc Crypt designed a 14V power supply from the 65V rail
> voltage......)

Ok, I think I understand the circuit. I don't understand enough about
electronics, though, to understand your point.

Bernhard

[FF]

Op 26-2-2011 0:43, Bernhard Kuemel schreef:
> On 02/25/2011 07:18 PM, FF wrote:
>> Here (http://www.mikrocontroller.net/topic/144407) is a discussion in
>> German about the same amplifier. Schematics and board layouts are
>> included in that thread.
>
> The schematics are from a PA-8000, so the fuses may well be different.
> Hmm, the drawing number (Zeichnungsnummer) is 'PA 5/8000 ...'. So maybe
> the fuses are the same.
>
>> (side note: in his case R65 on the 4th page of the schematic was blown,
>> pls. note how Mc Crypt designed a 14V power supply from the 65V rail
>> voltage......)
>
> Ok, I think I understand the circuit. I don't understand enough about
> electronics, though, to understand your point.
>
> Bernhard

On the fuse: I *think* it's safe to try the "next lower value" fuse for
the 5000, assuming the fuse in the drawing is for the 8000. However,
YMMV ;-)

On that 14V power supply: that design is rather crude, there's a lot of
dissipation in those power resistors. There are far more elegant ways to
design a 14V power supply for these LED's (e.g. separate transformer
windings, small SMPS etc).

According to the thread I mentioned, apparently there are quite a few
problems with this amplifier(s), and they are in no way suitable for
*real* PA work. BTW: in Europe they sell for 115 EURO = around 90 USD!

Pardon my English, I'm Dutch ;-)

FF

[Trevor]

"FF" > wrote in message
...
>BTW: in Europe they sell for 115 EURO = around 90 USD!

You might want to recheck that exchange rate calculation! The Euro is worth
more than the $USD.
(115 Euro is still pretty cheap of course)

Trevor.

[FF]

Op 26-2-2011 11:27, Trevor schreef:
> > wrote in message
> ...
>> BTW: in Europe they sell for 115 EURO = around 90 USD!
>
> You might want to recheck that exchange rate calculation! The Euro is worth
> more than the $USD.
> (115 Euro is still pretty cheap of course)
>
> Trevor.
>
>
<shame mode on> you're completely right....<shame mode still on>

FF

[Trevor]

"FF" > wrote in message
...
>>> BTW: in Europe they sell for 115 EURO = around 90 USD!
>>
>> You might want to recheck that exchange rate calculation! The Euro is
>> worth
>> more than the $USD.
>> (115 Euro is still pretty cheap of course)
>>
>>
> <shame mode on> you're completely right....<shame mode still on>
>

Turn shame mode off, we all make mistakes sometimes!

Trevor.

[FF]

>> <shame mode on> you're completely right....<shame mode still on>
>>
>
> Turn shame mode off, we all make mistakes sometimes!
>
> Trevor.
>
>
Thanks, it took me two hours to turn off the shame mode ;-)

FF