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2SC5198 - A1941 Replacement
2SC5198 - A1941 Replacement
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Old 13th October 2021, 07:48 PM   #11
Leema6 is offline Leema6  Sri Lanka
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Join Date: Oct 2021
Quote:
Originally Posted by Mooly View Post
The bias generator is usually a transistor that is in contact with the main heatsink. It could be any shape or type.
Thanks it has two of S9014 transistors

Quote:
Originally Posted by MikePP View Post
Yeah , the third man - here for instance:
Thanks...

I Changed every ceramic capacitor on the board with brandnew ones
check each ceramic cap with multimeter they showed original value
but after replacing there is no hum or minus voltage on speaker out
but both side a1013 Getting extremely hot after few seconds,
as i see i need to find the 5198 and 1941 for sure
i think this board cannot handle 5200 and 1943
but both running with c2073 and A940
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Old 13th October 2021, 09:01 PM   #12
MikePP is offline MikePP
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Join Date: Jun 2019
Quote:
Originally Posted by HighTec View Post
Well, one thing is for sure, that video shows how not to repair an amplifier. Inadequate soldering iron, the lifted pads, bodged wires all over the place etc.
Treat the PCB like you would treat a fine woman !

I can't bear to watch it, never mind listen to the dreadful background noise, or the shaky video


That guy is a butcher, and he's butchered that board


Quote:
Originally Posted by Mooly View Post
You would have to be able to identify the bias generator and determine how to initially link it out and then when/if you fix the amp how to alter the values to get a suitable bias current.


The bias generator is usually a transistor that is in contact with the main heatsink. It could be any shape or type.

See pic - I've arrowed them



Quote:
I Changed every ceramic capacitor on the board with brandnew ones
check each ceramic cap with multimeter they showed original value
but after replacing there is no hum or minus voltage on speaker out
Why would you do that ?
Ceramic caps rarely fail. were you 'upgrading' them? lol
Attached Images
File Type: jpg board.jpg (524.6 KB, 124 views)

Last edited by MikePP; 13th October 2021 at 09:06 PM.
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Old 14th October 2021, 01:16 AM   #13
Ian Finch is offline Ian Finch  Australia
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Join Date: Apr 2010
Location: Coffs Harbour, NSW
2SC5198 - A1941 Replacement
Ceramic caps are cheap and you can buy a bagful of mixed values for next to nothing. Hence you replace them when you have nothing else on hand to try. There's obviously inexperience and lack of understanding of basic electronics here so I don't hold much hope for our friend's repair.

I suggest Leema6 puts the wreck aside until later, when they have some experience with PCBs and have done some real, systematic electronics study - not just watching random "me too" DIY dummy videos. In the meantime, a much simpler kit or better still, a finished "chipamp" module of no more than say, 15W power output would be very cheap and make a much better, safer start. Before touching any PCB, he/she needs to learn to solder quickly and properly. Only use an adjustable temperature iron if you know how to set it accurately and use the right type of easy-working solder. Most people find that safe, 100% tin solder can be very difficult and slow to work with, which leads to damage of the PCB and there is a point where that damage is too much to have a reliable amplifier. Stop before making it worse.

Last edited by Ian Finch; 14th October 2021 at 01:20 AM.
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Old 16th October 2021, 03:12 AM   #14
Leema6 is offline Leema6  Sri Lanka
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Join Date: Oct 2021
i will take this as advice,
i'm still learning some stuff

Checked Voltage between transistors

C5198 BASE + EMITER I'M GETTING 0.5V
COLLECTOR + BASE 45V
COLLECTOR + EMITER 45V

A1941 BASE + EMITER I'M GETTING -0.5V
COLLECTOR + BASE - 45V
COLLECTOR + EMITER -45V

C2073 BASE + EMITER I'M GETTING 0.5V COLLECTOR TO BASE AROUND 35V
A940 BASE + EMITER I'M GETTING -0.5V COLLECTOR TO BASE AROUND 35V

A1013
BASE + EMITER I'M GETTING 6.0V
COLLECTOR TO BASE AROUND 35V
THERE ARE TWO C1815 TRANSISTOR BEFORE A1013
BASE + EMITER I'M GETTING 5.0V
COLLECTOR TO BASE AROUND 35V

AS YOU GUYS SEE WHAT COULD BE THE PROBLEM RESISTORs Value are all ok to me
A1013 getting 35v and could it be higher ampere course this to heatup
i didn't measure ampere
C1815 won't heat

WHEN I TESTING I DIDN'T TURN ON THE SPEAKER I MEAN SPEAKER PROTECTION KEEP TURNING OFF
TESTING USING LIGHT BULB

ANY IDEAS GUYS?
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Old 16th October 2021, 10:12 AM   #15
Ian Finch is offline Ian Finch  Australia
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Join Date: Apr 2010
Location: Coffs Harbour, NSW
2SC5198 - A1941 Replacement
We can't help you without knowing the circuit/schematic diagram. There may be someone who has completed the kit and has it working but they still may not know what damage has to be repaired before it can possibly work.

In case you aren't aware, the speaker protection must turn the speakers off and remain in that state if it is going to protect the amplifier from faults which likely remain in the shorted or open output stage semis and open circuits where the PCB traces are torn and lifted from the board. Can you also be certain that you fully and correctly repaired the copper tracks and solder joints there? I doubt it, by the mangled and charred appearance of the board, but I have already suggested that you do something else before just making things worse and "worser". Ease-off and think about your progress so far - do you really think that continuing to burn the PCB is going to fix it?

There is a way to simplify problems like this by fitting only one pair of output transistors rather than the two supplied, when looking for problems. That is also an opportunity to test the power and driver transistors by comparing the test results you measure according to the best, verified test advice for power transistors that you can find. If you find differences, fit those that measure correctly and check the assembly with no load (no speaker).

There are plenty of "me too" and "idiot" videos and suggestions on the internet - hopefully you can recognise and ignore them.
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Old 16th October 2021, 10:39 AM   #16
Ian Finch is offline Ian Finch  Australia
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Join Date: Apr 2010
Location: Coffs Harbour, NSW
2SC5198 - A1941 Replacement
Apologies, I meant to write "them" instead of "the amplifier" in line 3, above.
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Old 16th October 2021, 06:34 PM   #17
HighTec is offline HighTec  Croatia
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Location: Sibenik, Croatia
@ Leema6,

try to 'reverse engineer' the PCB. Trace the PCB copper tracks and put it on the paper. Since it's a one side copper clad board, it should be easy for you to copy the sucker. Then it will be easy for us and you to resolve the problem.
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Old 17th October 2021, 09:46 PM   #18
Leema6 is offline Leema6  Sri Lanka
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Join Date: Oct 2021
Quote:
Originally Posted by Ian Finch View Post
We can't help you without knowing the circuit/schematic diagram. There may be someone who has completed the kit and has it working but they still may not know what damage has to be repaired before it can possibly work.

In case you aren't aware, the speaker protection must turn the speakers off and remain in that state if it is going to protect the amplifier from faults which likely remain in the shorted or open output stage semis and open circuits where the PCB traces are torn and lifted from the board. Can you also be certain that you fully and correctly repaired the copper tracks and solder joints there? I doubt it, by the mangled and charred appearance of the board, but I have already suggested that you do something else before just making things worse and "worser". Ease-off and think about your progress so far - do you really think that continuing to burn the PCB is going to fix it?

There is a way to simplify problems like this by fitting only one pair of output transistors rather than the two supplied, when looking for problems. That is also an opportunity to test the power and driver transistors by comparing the test results you measure according to the best, verified test advice for power transistors that you can find. If you find differences, fit those that measure correctly and check the assembly with no load (no speaker).

There are plenty of "me too" and "idiot" videos and suggestions on the internet - hopefully you can recognise and ignore them.
Quote:
Originally Posted by HighTec View Post
@ Leema6,

try to 'reverse engineer' the PCB. Trace the PCB copper tracks and put it on the paper. Since it's a one side copper clad board, it should be easy for you to copy the sucker. Then it will be easy for us and you to resolve the problem.
PROBLEM SOLVED

FIRST I WILL TELL THE STORY OF THIS AMPLIFIER
This is a really rat house when i get this from friend and every single wire was bitten by rat,
what i did was cleaned everything and re wire the all connection by looking at there ribbon cable pattern,
i didn't know about that LIGHT bulb safety,
when i first turn on the amplifier there is some weird sound and music played with that sound and
suddenly blow away two C5198 transistor and Two A1941,
and again i bought c5200 and tried with that safety method then i replaced few of burned c1815 A940 and C2073
then i came up with this hum issue then i replaced every 2a104J ceramic capacitor with new one,
Then again a1013 heated a lot when turning on
I Checked every single part of the transistor they were all good,
Then i found out that c5200 and a1941 collector leaking to Heat sink not fully but tiny current leaking to heatsink
Yes i used mica sheet but somehow that thermal paste had some conductivity
I cleaned heatsink and removed every excess thermal paste,
then i checked voltages and finally A1013 heating up a little but then i understand it's normal
Now Amplifier is fully working without any issue,

Thanks everyone who help me by there words,
Hope this will help someone
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