[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