[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