After a bit of work by some tuning with Nichicon UKW Caps and a great new Bourns Trimpod (that makes the Power-drive sense. adjust. now and fixed a diode problem in the Amp everything worked fine and i was pretty happy and couldnt wait to listen...
Till...
...I wanted to dial in the idlecurrent before and by that I shorted the Amp at the TP Points.
I kind of feel I damaged the Amp seriousely and would appreciate if its possible to help me out a bit to determin which parts got probably damaged by the cuircuit I've created, by showing you what happens, because my shematic reading abilitys are kind of limited.
I marked the short with the black line in the following pictures [the DMM clamps, I surely think touched TP2 and than the 0.1 Cap in front of it - TP1, was not hooked up at that point]
So as the short happened the blew was pretty heavy and I shut down the Amp immediately. After turning it on again, I saw smoke coming from R243[marked it with the red cross(the resistor is surely burned)] and then instantly the main Fuse at the PS burned trough also.
So by looking at the Images can someone determine what will be surely damaged especially? (maybe the following Transistors? Output Transistors?)
So I have the 0.1uf cap and the resistor here and about to change them, but im too afraid and don't have the courage to try turn it on yet as I don't know if following parts in thr cuircuit are pretty surely dead.
Thanks!
Till...
...I wanted to dial in the idlecurrent before and by that I shorted the Amp at the TP Points.
I kind of feel I damaged the Amp seriousely and would appreciate if its possible to help me out a bit to determin which parts got probably damaged by the cuircuit I've created, by showing you what happens, because my shematic reading abilitys are kind of limited.
I marked the short with the black line in the following pictures [the DMM clamps, I surely think touched TP2 and than the 0.1 Cap in front of it - TP1, was not hooked up at that point]
So as the short happened the blew was pretty heavy and I shut down the Amp immediately. After turning it on again, I saw smoke coming from R243[marked it with the red cross(the resistor is surely burned)] and then instantly the main Fuse at the PS burned trough also.
So by looking at the Images can someone determine what will be surely damaged especially? (maybe the following Transistors? Output Transistors?)
So I have the 0.1uf cap and the resistor here and about to change them, but im too afraid and don't have the courage to try turn it on yet as I don't know if following parts in thr cuircuit are pretty surely dead.
Thanks!
Ok thanks, yes my MM has it - so I can check them while they are still on the Board? - if I measure 0 at BaseE and 0 at BaseC the trans is dead?
If i find the transistors as replacements (comes out not that easy) - i have read something about transistor-matching. Is this a thing i have to pay attention in that AMP?
And what could be the worst outcome if just solder in any replacement i can find?....
i just kind of feel, getting them straight forward or even getting the Amp an upgrade (like with capacitors or resistors) with changing them isnt really that easy in that situation...i really hope this doesnt get over my abilitys... i really invested so much time and effort in the recap(from preamp to power supply) to get the Amp in a better state than ever before... And now im really feel i kind of fkd it up...
And what could be the worst outcome if just solder in any replacement i can find?....
i just kind of feel, getting them straight forward or even getting the Amp an upgrade (like with capacitors or resistors) with changing them isnt really that easy in that situation...i really hope this doesnt get over my abilitys... i really invested so much time and effort in the recap(from preamp to power supply) to get the Amp in a better state than ever before... And now im really feel i kind of fkd it up...
Digikey tells me that the 2SC5200OTU Transistor
would be a direct replacemant for the might dead 2SC5949-O Transistor
If thats true i would consider to change all 4 OT to that Trans and its PNP counterpart.
Or are there other Trans-Series that would be a good replacement that fit?
would be a direct replacemant for the might dead 2SC5949-O Transistor
If thats true i would consider to change all 4 OT to that Trans and its PNP counterpart.
Or are there other Trans-Series that would be a good replacement that fit?
Jep. Okay.
I would change the NPNs of both channels. Because every batch sounds different. Leave the PNP in, they sound completely different to the NPN anyway. You actually have two amplifiers per channel, one plus, one minus, which sound different because even the same parts sound different;-)
I would try TO-247 types later. These TO-3P ones sound very creamy and wide, but also a bit slow and don't get the notes together.
https://www.reichelt.de/?PROVID=278...MIsdH4-6vWiQMVIDsGAB1vIgcCEAAYASAAEgIMS_D_BwE
I would change the NPNs of both channels. Because every batch sounds different. Leave the PNP in, they sound completely different to the NPN anyway. You actually have two amplifiers per channel, one plus, one minus, which sound different because even the same parts sound different;-)
I would try TO-247 types later. These TO-3P ones sound very creamy and wide, but also a bit slow and don't get the notes together.
https://www.reichelt.de/?PROVID=278...MIsdH4-6vWiQMVIDsGAB1vIgcCEAAYASAAEgIMS_D_BwE
The 2SC5200 and its complementary 2SA1943 are good replacement parts.
Digikey has the ST and the EVVO brands. You will find Toshiba elsewhere (e.g. Farnell)
I never used EVVO parts so it's hard to comment on their quality.
Digikey has the ST and the EVVO brands. You will find Toshiba elsewhere (e.g. Farnell)
I never used EVVO parts so it's hard to comment on their quality.
So I have all Transistors on my Desk now (all pre drivers and Outputtrans) for both channels and ready to put them in. Thanks for your help.
If you say I can try TO-247 types. Are These different Types of trans. That can be replaced to the original? How do I found out which one is a good alternative?, do you have any recommandations?
I also read, that it is possible to drive the 2sc5200 and 2sa1943 with different drivertransistors... Right now im using the 5171 and 1930 ones.
What about other types? Heard good stuff about 1837's that can be used also?
Are there some recommandations to try out?
FYI: the 5200 and 1943 where already in the Amp and not the ones mentioned in the service manual.
For me the Amps sounds very dynamic, Lows and Highs are very differential and airy, like they come from two different Amps. I really like that. The Amp sounds very "correct", correct but not analytical. Just correct. For me the Bass is very fast and punchy, like that. Only the mids could be little smoother and softer because they come quite hard with like not much headroom.
How much impact on the sound would other trans combinations have?
Thx and Cheers
If you say I can try TO-247 types. Are These different Types of trans. That can be replaced to the original? How do I found out which one is a good alternative?, do you have any recommandations?
I also read, that it is possible to drive the 2sc5200 and 2sa1943 with different drivertransistors... Right now im using the 5171 and 1930 ones.
What about other types? Heard good stuff about 1837's that can be used also?
Are there some recommandations to try out?
FYI: the 5200 and 1943 where already in the Amp and not the ones mentioned in the service manual.
For me the Amps sounds very dynamic, Lows and Highs are very differential and airy, like they come from two different Amps. I really like that. The Amp sounds very "correct", correct but not analytical. Just correct. For me the Bass is very fast and punchy, like that. Only the mids could be little smoother and softer because they come quite hard with like not much headroom.
How much impact on the sound would other trans combinations have?
Thx and Cheers
Allright...Yeah thats what i will do in first place , just interested.
To my surprise only q214 from the OTs is dead.
indicator of other damaged Parts?
I solderout the pre drivers in some minutes...
To my surprise only q214 from the OTs is dead.
indicator of other damaged Parts?
I solderout the pre drivers in some minutes...
I would like to complement the original poster on the completeness and clarity of the information provided in the first post. Schematic, photos, description of what happened. This makes it much easier for the community to provide useful help.
Looks like you have gotten plenty already, so I will not pile on.
Thank you for this great example on how to do it!
Looks like you have gotten plenty already, so I will not pile on.
Thank you for this great example on how to do it!
Definitely "Q214"
Maybe the Short line was to the Ground side of the 0.1uf Cap?
Like that - does it make more sense?
Maybe the Short line was to the Ground side of the 0.1uf Cap?
Like that - does it make more sense?
Thanks. As I'm just pretty good at soldering and replacing Parts and not in schematic reading or fully understand the interactions between electrical parts or determing how the current flows, for me this is the at least necessary i can do and provide, so more knowledgeable people as me, can give me some help & advise. 🙂
So all the OTs and defect pre-trans are changed. Q212 was also dead... the Noname 5171 was the only one I could get from a serious dealer.
I checked with diode test and measured hfe from every trans before I soldering them in
They should all be alright now.
But...
The Amp powers on plays allright for 2-3 sec into L&R Speaker (for what i can hear in those few seconds) then switches off to the red LED and probably goes in the "protection mode"?. 😬🙄
The OTs keep getting hot in that switched off red LED mode...
The Amp Powers on with a "POP" from the speakers, that wasn't normal before - is this indicating something?
What could be the next steps or measurements I could do to detect, what's now or still wrong in the Amp?