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Dynacord Powermate 1000 Protect Error

#1 User is offline   Rocket 

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Posted 29 December 2007 - 08:47 PM

Hi All,

My dads band had a bit of a disaster at a gig at the weekend. As they came to start the second spot, their Powermate 1000 suddenly completely died and would not power on at all. They had to cancel the gig and go home shamefaced (the first time my dad has had to completely cancel a gig in 30 years - they've always been able to at least cobble together some sort of temporary solution to a problem).

Anyway, as of the next morning, the desk powers up with the 'Protect' LED lit. I understand this indicates that the desk has muted itself and shut down the outputs to protect itself. I've checked the ventilation areas - they aren't blocked. I've also had a peek inside and checked that both the fans are running OK, which they are.

Has anyone any other ideas what could have caused this, or what can be done to diagnose or solve the problem further. it doesnt seem to be the most obvious fault (I.e. a fan problem) so were now sat with a desk thats in protect mode, and no idea how to troubleshoot it.

If it can't be solved then it's off to a specialist, but nothing can be done over the xmas/new year period, so I'd like to take a further look at it in the meantime if possible.

Cheers

Sam

(N.B. Ironically, they went through the whole rig about 6 weeks ago discussing what they would do if each component were to fail on a gig. They worked out that they could work temporarily around most problems, bar the desk failing! With this in mind, they invested in a second hand Powermate 1600, to use for larger gigs and as a backup. Having carried it as a spare to the past few gigs, they decided not to bring it to this one as space in cars and vans was limited. The one gig they don't have the spare...the desk breaks down! Talk about sods law!)

#2 User is offline   Mixermend 

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Posted 29 December 2007 - 10:07 PM

Although I am not familiar with this actual model - there are a few things that you might be able to check.
Firstly, check the fuses on the power amplifier boards - there may be quite a few, as this amplifier probably has several different positive and negative voltage supply rails. If the fuses are OK (check visually and with a continuity tester) - then try and measure the DC power supply voltages to make sure that they are all present and correct.

If they are all present and correct - then measure any voltage present at the amplifier output BEFORE the muting relay, possibly the easiest place might be at either end of the output coil. Measure the voltage with respect to earth. Should be a few 10's of millivolts only.

It is quite likely to be many 10's of volts (thus triggering the protection) - meaning that you possibly have an output transistor failure. If this is the case - you need the schematic diagram and probably some existing experience faulting power amplifier circuitry.

JG
John Godsland
Orchid Electronics
Audio Engineers Helping To Make Music!

#3 User is offline   Kennyp 

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Posted 02 March 2016 - 08:18 PM

Hi,
Just stumbled across this forum and I'm interested in this topic. This seems to be a common fault in these desks. I too have a Powermate 1000 Mk1 and it recently developed an intermittent fault where the Aux 1 output would cut out meaning that I would suddenly have no monitor. I left it with a friend who works at electronics and he told me that there was a capacitor burned out and a leaky diode. He replaced them and it seems to have cured the problem but I've now noticed the protect light coming on a couple of times and I'm wondering if this could be connected to the repair job that I had done or is it just coincidence? Could it be that this desk is very sensitive to condensation as it happened when I was on tour and the gear sat in the van overnight on pretty cold nights. Luckily I'm using powered speakers (fed from the main outs on the desk below the Aux outputs) so when the protect light is on it doesn't kill my sound. The protect light seems to stay on for about an hour or so and then goes off again.

This post has been edited by Kennyp: 02 March 2016 - 08:36 PM


#4 User is offline   KevinE 

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Posted 30 March 2016 - 03:37 PM

the protect led is driven off the main amp section so if you've got that, it means the amp itself is unhappy at something. I dont think they're particularly bothered by humidity any more than other equipment but you can get a build up of muck..possibly damp muck eg smoke fluid residue or booze on the rear grille and circuitry immediately behind that grille. Any leakage here can cause intermittent protect problems and eventual failure..sometimes catastrophic :)
Kevin Edwards

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Staffordshire Moorlands

#5 User is offline   warrenstuart 

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Posted 30 March 2016 - 06:34 PM

View PostKevinE, on 30 March 2016 - 03:37 PM, said:

Any leakage here can cause intermittent protect problems and eventual failure..sometimes catastrophic :)


Hmm I've got one here that I wouldn't say has gone catastophic but I've had easier repairs... I think when the mains fuses kept blowing they substituted it with a nail to see if that would do the trick :-(

Any idea of a good source for the flameproof resistors? RS is out of stock city and I ordered some off of ebay but I'm not convinced they're flameproof...

Warren.

#6 User is offline   KevinE 

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Posted 04 April 2016 - 04:17 PM

Well....I ended up buying a load after another dealer sent me a mixer where they'd replaced them with standard resistors twisted together to form the double units. I can't remember where they came from, but if its the 0.22R 5W ones, they're here on ebay:

Noble RGC55 series
Kevin Edwards

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Staffordshire Moorlands

#7 User is offline   warrenstuart 

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Posted 06 April 2016 - 10:57 AM

View PostKevinE, on 04 April 2016 - 04:17 PM, said:

Well....I ended up buying a load after another dealer sent me a mixer where they'd replaced them with standard resistors twisted together to form the double units. I can't remember where they came from, but if its the 0.22R 5W ones, they're here on ebay:

Noble RGC55 series


That's the guy I get my double 0.22R from but it's not those it the small 1/8w flameproof resistors, there are some 10R, 68R & 100R values that are commonly used.
Basically every final transistor is BCE short all ways round and as a result quite a lot of surrounding components have suffered the consequences I'm afraid :-(

Warren.

#8 User is offline   KevinE 

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Posted 06 April 2016 - 02:56 PM

I think Newark do them, MCCFR0W8 series
Kevin Edwards

K. Edwards Electronics Engineers
Staffordshire Moorlands

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