Hi
I've come across a few emitter-follower/common collector push-pull power amp circuits where NPN / PNP are collector-connected to +ve and -ve respectively, but am working on a repair of a Deltec Precision Audio DPA 50S from circa 1987 where the PNP / NPN power transistors are connected the opposite way (PNP and NPN emitter to +ve and -ve respectively).
The driving circuitry is therefore a bit more complex than I'm used to seeing and it's giving me a brain-block without any schematic to look at... Does anyone have any information that could be of help please?...
kehall
Member
Last Activity: 03-19-2023, 10:53 AM
Joined: 03-14-2011
Location: Warrington, Cheshire, UK
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DPA 50S common emitter push-pull schematic
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Re: Acer AL2416 AL2416W 24" 1920x1280 LCD Monitor
Just a final update - the monitor worked perfectly with the replacement 1.25A fuse. -
Re: Acer AL2416 AL2416W 24" 1920x1280 LCD Monitor
MOSFETs installed today and installed the "J" 1.25A Fast Blow fuse and works perfectly.
I would say at this point that 4A is overrated, and indeed they are 'M' marked not W. (I'd have expected 1.25A to be completely underrated and blow immediately otherwise).
Will soak for next 24 hours.
Keith.Leave a comment:
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Re: Acer AL2416 AL2416W 24" 1920x1280 LCD Monitor
Nice thought but not quite - I need a working monitor to find out what the correct operating current is, and although I've repaired 2 of these already which were just cap replacements, they have now gone, and the only one left (that I get to keep for my troubles!) is waiting for replacement FETs on one side so I can't remove the good side fuse to test as it doesn't stay on long enough for a reading, and doing that where a short caused the blow is a bad idea.
Does anyone have a monitor they've...Leave a comment:
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Re: Acer AL2416 AL2416W 24" 1920x1280 LCD Monitor
Has anyone measured the current flow to determine suitability?...Leave a comment:
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Re: Acer AL2416 AL2416W 24" 1920x1280 LCD Monitor
Back on topic though, this is the 3rd Acer 2416w i'm repairing, the other two were just cap swaps, but this one, after it first shut down, the user stupidly kept trying to turn it back on until it stayed on (even hitting it int he process), then until you guessed, big pop, and now a less simple repair!Leave a comment:
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Re: Acer AL2416 AL2416W 24" 1920x1280 LCD Monitor
thanks for the link... I didn't find any bad ones in the 245 although there is another thread on here talking about it, burnt sacrificial resistors and things but my flickering must be something else, or they all do it and only I notice it!...Leave a comment:
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Re: Acer AL2416 AL2416W 24" 1920x1280 LCD Monitor
yep, all of them....Leave a comment:
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Re: Acer AL2416 AL2416W 24" 1920x1280 LCD Monitor
Thanks... I know someone who has a couple of 4A very fast blow in a 1206 package left over from another job but its rated at 63V not 24V, not 100% sure if it would be suitable.
Interestingly it is marked with an 'S' which according to your table is 2A but it is definitely a 4A rated fuse ??? see [URL="http://cpc.farnell.com/multicomp/mc12cf-004/fuse-smd-1206-ff-4a/dp/FF02246?Ntt=4a+smd+fuse"]http://cpc.farnell.com/multicomp/mc12cf-004/fuse-smd-1206-ff-4a/dp/FF02246?Ntt=4a+smd+fuse[/URL]...Leave a comment:
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Re: Acer AL2416 AL2416W 24" 1920x1280 LCD Monitor
I ordered exactly the same from same seller on 26th March! Just waiting for them to arrive now, by your experience I'm probably looking around next Thursday to arrive.
Where did you source the fuses, may I ask? I have one blown due to the shorted mosfets that I need to replace.
Interesting you also have a Samsung 245bw - I'm suffering from a case of flickering backlight (all caps swapped on psu, even on inverter board, none of them tested faulty anyway for what its worth), and still...Leave a comment:
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Re: Samsung Syncmaster 245BW
To be honest not really seen much wrong with the caps on my panel, the worst in terms of ESR is the 10uF/50v in middle of the psu board.
The psu board contains
1000uF/35v
1000uF/35v
82uF/450v
100uF/50v
10uF/50v
47uF/50v
1uF/50v
22uF/50v
47uF/50v
47uF/50v
68uF/63v
1000uF/10v
1000uF/10v
2200uF/10v
470uF/35v
Do you think increasing the value of the 4x220uF/35v on the backlight to say 330uF or more would help with the flicker issue?...Leave a comment:
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Re: Samsung Syncmaster 245BW
Thanks, as I'm currently using the monitor I don't want to dismantle it until ready to swap caps, but want to get the parts sorted out first - does anyone have a list of the main culprit capacitors - I've already got noted the 82uF 450v primary filter in case thats a cause of the flicker, but what else, please, in case I don't already have in stock?
Regards,
Keith.Leave a comment:
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Re: Samsung Syncmaster 245BW
Whilst I may do just that out of precaution, given some of the tales earlier in the thread about blowing other components, this monitor has always had this flicker that I can recall (yes I know probably should have mentioned sooner whilst in warranty!), however I want to know if anyone else has seen it (and if it's what is being referred to earlier on in the thread).Leave a comment:
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Re: Samsung Syncmaster 245BW
Hi, sorry if hijacking a thread but had read mention of flickering earlier on and wanted to clarify/ask a question please in terms of the flickering.
I have a 245B which is just over 3 years old now, I use it with DVI connection 1920x1200 on Custom Magicbright with brightness/contrast (5/50) as anything else is just too bright..
However there is a persistent background 'flicker' which you can see and I'm sure its giving me headaches... you can mostly 'forget' about it but it is there and I don't think it's helping my head!...Leave a comment:
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