Mackie M1400 poweramp problem

One of my designs has been sitting in the local venue for over TEN YEARS. One level pot went scratchy in that time and we also gave the heatsinks a blow-through.

$300 doesn't buy you very much in the way of a power transformer or decent output devices and heatsinking + fans.

I've heard of these amps in the UK. Not 'Warrior' brand is it ? They came with ten year warranties but the company only lasted about 18 months. Killed by the warranty claims.

Graham

Isn't using a vacuum cleaner as the rack cooling blower, a bit noisy ... ? :-)

Arfa

output

It's a Wharfedale 1800 and the dealer price was around 450 not 300. I know it's not good enough for you but I really don't give a shit.

I had a guy offer me a crown Micro Tech 1200 for $250 and turned him down. It was pretty beat up looking, the rear rack ears were bent and who knows what abuse it may had suffered. I'd rather add $200 and buy another Wharfe.

Yeh but the HEPA filter does wonders :)

Seems to me that you have a problem with anything made in China. We all know that you get some crap made there but sometimes some good stuff comes from there. Most of my amps are British made (Matrix) but I have a couple of Chinese made amps, one Audiohead and the other T.amp brand from thomann.de which look like the same amp to me, both have been in service on the road for about 3 years now without trouble.

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. That amp got replaced with another Chinese made T.amp from Thomann which has also given me no problems.

Seems to me that you have a problem with anything made in China. We all know that you get some crap made there but sometimes some good stuff comes from there. Most of my amps are British made (Matrix) but I have a couple of Chinese made amps, one Audiohead and the other T.amp brand from thomann.de which look like the same amp to me, both have been in service on the road for about 3 years now without trouble.

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. That amp got replaced with another Chinese made T.amp from Thomann which has also given me no problems.

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.

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 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.

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.

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!)

I don't remember looking closely but I don't think they were particularly domed. It was at least 2 years ago when it died. I do remember that everything looked very clean in there. The amp had an easy life in a church install but for some reason the power transformer got shorted on the primary thus blowing the mains fuse every time. Since it was a custom part I enquired with Toroid International about purchasing a replacement but it would have cost about £150 as I guess they were not making these in volume any more. When I saw that I could just replace the whole amp for the same money it was a no-brainer.

Good point. I don't remember seeing any "country of design" on the literature. I just "assumed" it was a wholly Chinese product.

If it's a Korean design, that would explain a lot of things.

I'm hoping Toshiba will come out with a direct-replacement 100GB (or larger) vertical-recording hard drive. But I'm not holding my breath.

By the way, there's an "open" group called RockBox that makes improved operating systems for many jukeboxes, including iRiver models.

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. 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 so they must serve some other purpose in the driver stage?? Here is a recent pic of my 700D in the rack that fell over. Lucky all the other equipment wasn't in the rack when it fell backwards.

Below the Crown amp is a rare Sound Code Systems 2350A MOS-FET amp someone gave me after they couldn't find anyone to repair it back in 1998. It needed a new set of outputs 2SK134/2SJ49 TO3 case that had been discontinued and unavailable at the time. I did find a set on the internet and repaired the amp successfully. It's been used on and off as a source for 18" subs in a tri-amped band PA setup since then without any problems. It too is a quiet amp having a similar cooling system to the 700D. It's heat sink includes a bristled radiator which is unique.

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The Mackie amp was repaired. A tiny tiny pcb trace/via hole for one of the predrivers were open circuit. This happened probably when the drivers shorted. Now everything's OK!

Regards

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

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

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

Graham

Aluminium actually.

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

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

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.

No, those are the smaller ones nearby.

Graham

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