Info on this pair of A1943/C5200

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#81
what i think i told you a few times before but you dont seem to care or understand ...so what's the point ?

last time ...
1) use your multimeter to trace where the power goes
2) attach black lead to ground ( can also be the speaker output ground )
3) check if there is voltage present in the midle pin of any output transistor ( expect to see 40 something volts .
4)if you dont find any check the right pin of the output transitor (any)

if you find the power supply voltage in the midle pin ( 40-42 volts ) means that your amplifier is an efp and the only way to keep it safe ( beyond heatsinks and vents ) is to remove one transistor that i will show you from the pcb....use small pieces of isolated wire and find a way to attach it on the heatsink so it can sense temperature and adjust idle respectivelly ....


none of the forum members told you that obviously and since you are replacing outputs to your amplifier you need to check /verify bias and adjust if needed ...

New outputs unless completelly identical with the old ones will require bias adjustment

Finally when i say identical that doesnt of cource mean 2SA1943 number ...will mean batch number brand and so on and on ...

this is the only way to achive a grater annount of safety that will guarantee that the amp's margine will increase from 40% to almost 75% ... still i think that requesting 100% for long periods will never happen since power supply and heatsink are too small

regards sakis
 
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#82
sakis said:
what i think i told you a few times before but you dont seem to care or understand ...so what's the point ?

last time ...
1) use your multimeter to trace where the power goes
2) attach black lead to ground ( can also be the speaker output ground )
3) check if there is voltage present in the midle pin of any output transistor ( expect to see 40 something volts .
4)if you dont find any check the right pin of the output transitor (any)

if you find the power supply voltage in the midle pin ( 40-42 volts ) means that your amplifier is an efp and the only way to keep it safe ( beyond heatsinks and vents ) is to remove one transistor that i will show you from the pcb....use small pieces of isolated wire and find a way to attach it on the heatsink so it can sense temperature and adjust idle respectivelly ....


none of the forum members told you that obviously and since you are replacing outputs to your amplifier you need to check /verify bias and adjust if needed ...

New outputs unless completelly identical with the old ones will require bias adjustment

Finally when i say identical that doesnt of cource mean 2SA1943 number ...will mean batch number brand and so on and on ...

this is the only way to achive a grater annount of safety that will guarantee that the amp's margine will increase from 40% to almost 75% ... still i think that requesting 100% for long periods will never happen since power supply and heatsink are too small

regards sakis
Click to expand...

sakis, thanks for all the help.

The amplifier power transistors are in:

cpf --> power goes directly to the emmiter of the output transistors
 
#83
then this is abviously a copy of ESP P3a and idle should be according to specs arround 75ma ...it could work with less and it will not need any modification to operate stable regarding temperature

then the only problems unsolved is the size of heatsink which will limmit the 100% operation of the amplifier for long periods

secondly this amplifier is not designed to operate in this voltage at 4ohms loads ...transistors will blow ...

kind regards sakis
 
#84
sakis said:
then this is abviously a copy of ESP P3a and idle should be according to specs arround 75ma ...it could work with less and it will not need any modification to operate stable regarding temperature

then the only problems unsolved is the size of heatsink which will limmit the 100% operation of the amplifier for long periods

secondly this amplifier is not designed to operate in this voltage at 4ohms loads ...transistors will blow ...

kind regards sakis
Click to expand...

sakis, thanks again.🙂

I have bought two 80mm CoolerMaster 80mm CPU fans, which i will fit behind the heatsink.

But the problem is the power supply for this fans, I have a old PSU of my PC, but I do not know how to start the PSU by itself. Googling it, i found i need to attach two wires to auto Boot the PSU.

But which two wires?

Thanks in advance.
 
#87
sakis said:
just out of ciouriosity ..... is this amplifier to be used in a home application or it will be used for something else ??

seen many power hungry people from your country ....
Click to expand...

No no, this amp is for my personal home use only.

But I listen loud. Lots of bass heavy songs are actually in my list, and i listen for extendend periods of time on weekends only.😀
 
#89
Stolen design

That is a Norge amplifier, you can see it on the PCB print.

Someone did tell me that brand (and most other hifi manufacturers in this part of the world) uses some public domain designs - though never seen an internal shot of one.
Click to expand...

The preamp PCB is a picture-perfect direct copy of the ESP P97 design. None of my circuits is 'public domain', and the person who built this amplifier is a cheat and a thief.

It is likely that other parts of the amp are also stolen, but the maker doesn't have enough sense to include a decent heatsink. I suggest that the owner of the amp contact me to let me know how to contact the maker, as he has violated my copyright for the PCB artwork.

I'm not at all happy 😡
 
#91
Hi, first of all I want to thank all the members of diyaudio for the unending support to fix my & my friends amplifier.

Amp:
An externally hosted image should be here but it was not working when we last tested it.

http://www.freeimagehosting.net/cf142

Today I will speak about my amp's mod. Well according to the truly knowledgeable members of this forum, the amp have a small heatsink to handle 75 watts of power @ 4 ohms per channel.

Even considering the fact that the transformer being a 300 VAC plus, this 2 pair of A1943/C5200 will be dumping 150 watts of heat to this heatsink while the rest 150 watts goes to the speakers.

I was given the idea to buy a pair of PC coolling fans and fit them at the back of the heatsink.

An externally hosted image should be here but it was not working when we last tested it.

http://www.freeimagehosting.net/d13f4

Before going to the shops of our local electronic market I measered the fins of the heatsink. It is a ~80mm & square sized. I a bought a pair of CoollerMaster 80mm silent fans.

An externally hosted image should be here but it was not working when we last tested it.

http://www.freeimagehosting.net/b96e7

I had a old PSU lying around of late, so used it to power these fans. To do this I also bought a pair of 4 pin Molex to Fan input adaptors.

An externally hosted image should be here but it was not working when we last tested it.

http://www.freeimagehosting.net/f609a

An externally hosted image should be here but it was not working when we last tested it.

http://www.freeimagehosting.net/c4620

I used very small amount instant glue(drops of) to stick the fans at the back of the heatsink fins. All went ok & the fans are sturdily fixed at the back of the fins as of now.

An externally hosted image should be here but it was not working when we last tested it.

http://www.freeimagehosting.net/09f74

Now, my amp runs super cool.

Before if i kept the PC volume at half & amp volume to 40%, and play ultra bass heavy tracks like "Handle This" by Basstronics, this song simply sucks any amp completely dry, the heatsink used to become very hot in just 5 mins time.

Now when i play the same song at the same volume levels, i find the heatsink is running super cool. I also played with this type of bass heavy songs at 50% volume for over half an hour & now the amp simply refuses to heat up. FAN SURELY MAKE WONDERS WITH HEAT.!!!!😀

All the credit goes to you guys for giving me the idea of what & how to do all this.

diyaudio is diyaudio. Period.

Thanks to all of you. I will sit with my friends amp to replace the transistors by tomorrow.

Chow!!!
 
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