Mackie M1400 poweramp problem

[Eeyore]

Seems to me that you have a problem with anything made in China.

Not at all but the quality varies dramatically. I'm expecting to be going to
Shanghai / Ningbo quite soon in fact.

You might also remember some time ago when I posted for help with a dead
Studiomaster 700D. The fault turned out to be a bad power transformer
which was not economical to replace even by substitution with off the
shelf parts.

Only because our Indian sub-contractor had bankrupted the company. Those
transformers were custom made by Toroid International which is a highly respected
brand. I'm sorry you had that problem but it wasn't a design oversight for sure.

Graham

 

[Eeyore]

There is a difference between items made in China and designed in China. I
have plenty of Chinese-manufactured items that are of high quality. I have
many fewer that were _designed_ there. One is an iRiver H120 jukebox, which
is of very high quality.

The work I've seen come out of Kwan Asia is second to none. Orient Power /
Oritron is pretty good too.

As you imply, few Chinese know how to design well though, and if you get a good
relationship going they will freely admit this. I have met one good Chinese
designer though, a chap called 'Tim' Lau. He co-developed the QSC RMX series
with Pat Quilter AIUI.

Graham

 

[Eeyore]

Isn't iRiver Korean? We did some work with their products a while back,
had a couple of their engineers over here, I'm pretty sure they weren't
Chinese but I could be wrong.

A lot of Korean compnaies are moving their manufacturing to China. I could talk
volumes about that and the troubles it caused.

Graham

 

[Eeyore]

Do you remember looking at the 4-63 volt, 3300uf caps in your 700D? I just
replaced the banana jack on mine and those 4 caps looked like the tops
were puffed. I pulled the top off one and there is a convexed steel cap

Aluminium actually.

over the actual can under the heat shrink that makes these look domed. And
they appear also to run pretty warm discoloring the white glue used to
bond them to the pcb. The amp works fine otherwise and I've never had any
problems with it. It was formerly used to power A/V sub-woofers and had
been left on continuously for a couple years. Next trip to the electronics
shop will probably yield a new set just for my piece of mind.

Given its age, I would recommend replacing them. NO amplifier PSU electrolytics
last for ever. Do buy a decent brand. We used Sanwha which are great for the
price but not widely available. A Panasonic is probably your best bet. Sub-woofers
will give them more of a hammering than full-range too.

Graham

 

[Eeyore]

One reason I like the 700D is that the cooling system is efficient and the
fan had infinite control. It is as quiet as a mouse until you started to
drive it. It also draws fresh air directly through the front through a
foam cell filter and through a heat sink tunnel and doesn't expose the
entire amp to forced air dust and other contaminates.

I'm glad you appreciate the design considerations I put into it.

Mine suffered a fall while in a rack which broke the A channel banana jack off
or I wouldn't
have ever noticed those 4 caps. They're not big enough physically to be
for rail currents

Oh yes they are ! Quite comfortably so in fact. Do you know how to do ripple
current calculations ? These HE series show a ripple current rating of 2.5A each
but that's @ 105C and they don't get that hot.
http://www.rapidonline.com/producti...lytic+capacitor&moduleno=80204&catRef=11-3149

so they must serve some other purpose in the driver stage??

No, those are the smaller ones nearby.

Graham

 

[Arfa Daily]

I was beginning to think my posts were not making it out there until I saw
your reply (Arfa was right about the Virgin Media news server being
troublesome!)

Seems a bit better now Tim, although there still seems to be periods of time
when it is not accessible. It wasn't yesterday afternoon for a couple of
hours. I was beginning to think that something had screwed up on my machine,
but 'net access was ok, and the mail server was properly accessible. News
server access just suddenly returned ( I had a news post pending in the
outbox, and my machine will try to send it every 5 mins until it gets
success). I can't remember ever having had similar issues with the original
NTL server, which I had been on for many years since NTL were first cabling
up the country. The problems only seem to have been occuring since they
"migrated" I think was the word, to the 'new and better' Virgin Media binary
news server. Is this the same sort of issues that you have been experiencing
?

Arfa

 

[Arfa Daily]

Not at all but the quality varies dramatically. I'm expecting to be going
to
Shanghai / Ningbo quite soon in fact.



Only because our Indian sub-contractor had bankrupted the company. Those
transformers were custom made by Toroid International which is a highly
respected
brand. I'm sorry you had that problem but it wasn't a design oversight
for sure.

Graham

Ah ... Studiomaster. I will remember that Graham, when I next get one in
that's giving me some grief ...

d;~}

Arfa

 

[Tim Phipps]

Only because our Indian sub-contractor had bankrupted the company. Those
transformers were custom made by Toroid International which is a highly respected
brand. I'm sorry you had that problem but it wasn't a design oversight for sure.

Graham

I appreciate it wasn't a design issue just an unfortunate fault. I was
impressed to get a direct reply from Toroid Int. who did offer to supply
the part but the cost was prohibitive as it would have been a one off job.

I don't know who is making these T.amps for Thomann but they seem to be
pretty decent. I haven't opened mine to look but I've heard some say
that they are copies of an old Crest design.

 

[Eeyore]

Ah ... Studiomaster. I will remember that Graham, when I next get one in
that's giving me some grief ...

d;~}

Stop for a second to think how many tens of thousands were made and how few you
see.

I just bought a 700D on ebay btw for a club install that's going 3 way active
(for the HF drivers). You can see I do have confidence in my own products.

And you can always email me for repair tips.

Graham

 

[Eeyore]

I appreciate it wasn't a design issue just an unfortunate fault. I was
impressed to get a direct reply from Toroid Int. who did offer to supply
the part but the cost was prohibitive as it would have been a one off job.

It's a real shame about that. There was a repair oufit in Liverpool that had a small
supply of the TXs but they're long gone now.

I don't know who is making these T.amps for Thomann but they seem to be
pretty decent.

I've seen those. Maybe I'll get to find out who it is.

I haven't opened mine to look but I've heard some say
that they are copies of an old Crest design.

I doubt that on account of the fact that Crests are massively overengineered as a rule
(nhence expensive to build). Far more likely another QSC ripoff. If the output
transistors' collectors are grounded it's almost a dead cert.

Graham

 

[Tim Phipps]

I've seen those. Maybe I'll get to find out who it is.



I doubt that on account of the fact that Crests are massively overengineered as a rule
(nhence expensive to build). Far more likely another QSC ripoff. If the output
transistors' collectors are grounded it's almost a dead cert.

Graham

FYI it's these ones I'm talking about. I've also seen them branded as
Audiohead and C-mark.

http://www.thomann.de/gb/t-amp_ta2400.htm

 

[Eeyore]

FYI it's these ones I'm talking about. I've also seen them branded as
Audiohead and C-mark.

http://www.thomann.de/gb/t-amp_ta2400.htm

I know very well the ones you mean but from an external visual I can tell nothing.

Graham

 

[Arfa Daily]

Stop for a second to think how many tens of thousands were made and how
few you
see.

I just bought a 700D on ebay btw for a club install that's going 3 way
active
(for the HF drivers). You can see I do have confidence in my own products.

And you can always email me for repair tips.

Graham

Yes, I don't see that many. But always useful to have a 'contact' within a
company ...

Arfa

 

[neon]

it is not ringing but oscillating. tie the input to gnd and see if it is stil there.