I’ve finished repairing a Marantz PM00AV and both modules were blown. I replaced them from a Chinese supplier and it’s been on the bench for a few weeks run up daily with no issues. The gout who sold me the amp was probably aware that he had dropped it. The amp fell on the volume pot, smashing it off its daughter board and breaking the board itself. My feeling is it put full power into both inputs and that’s what blew it. The chips themselves have the circuit for dc sending and dropping a relay, so each models has a speaker protection circuit as it’s a Dolby surround amp. Anyway, I remade the fibreglass board and bridge the tracks where broken and repaired the pot- which is 50k 4 gang with motor- so rare as rocking-horse.
You may want to replace the STK module with two TDA based power amps, discretely built on a small separate PCB's. Check the power supply voltage. It has been done, seems to work fine.
If you open it right,all you need is to connect new transistors through wires and put them onto the heatsink of the amplifier.It looks bad but it works good
thanks! that's right, those transistors in that ic are just missing their cases. i was concerned about the looks. i have another bad ic just like it; thinking of doing a transplant if i can get it open without messing it up.
+Vintage Electronics Geek Thanks for watching! Shelved the unit for now; I have not forgotten it. Either find a donor unit or get a another module. I should be able to get it fixed; I think the board itself was ok; I did both resistance and voltage checks (not sure if I showed this on camera).
An incorrect bias in an amplifier can easily result in the output stage behaving like a short circuit. This is why when amplifiers fail it is very important to make sure the bias is correct. It seems in this case, the bias went wrong causing the output stage to pass a large current until failure.
No sir, I don't. But I remember that the 4-page datasheet had one. You would have search for it online and download it. There was also an online PDF databook called "Catalog de 5000 diagramas de Amplificadores." Might be in there.
I just downloaded the pdf I mentioned. There seems to be a working circuit in there. Here is a link I found in case you haven't checked it out yet: docs.google.com/viewer?a=v&pid=sites&srcid=ZGVmYXVsdGRvbWFpbnxnZXJhcmRvY3Vyc29zZW5hfGd4Ojc2MzIwMDRlNzhmZGEx There seem to be other links, too.
You have somewhere in your receiver a short and you need to test where the short is coming from. Another place it could be coming from is your speakers if two wires are touching each other in the inside of your speaker connectors. This will only happen if you don't have connectors in the inside and instead smoldered them in place. That rarely happens when buying one and it blows so take a good luck.
The devices can blow open rather than show the short inside them, making testing confusing as many are looking for a short. The reason it blew could be a crossed speaker wire of faulty speaker of lack of air flow during hot running conditions.
I wish I could have repaired it. I have another complete defective module; I might try to take parts out of this one and put them in in the other one, if I can get the other one open easily enough and remove the transistor dies from this one. Not that it would make sense to do this...
Your not testing the transistors. Those things glued to the top are thermistors to detect overheating. The 3 legs of the transistor are soldered beneath, you can follow the tracks out from under them. usually they are the 1st 3 and the last 3 legs of the larger device. I have a blown technics one. I heard they often blow open somewhere in the device rather than measure short at the legs so it can be confusing trying to check them. The replacements are fakes built with cheaper transistors. There is a board available that you can build up a better then original circuit to replace the device rather than use the fake devices.
I’ve finished repairing a Marantz PM00AV and both modules were blown. I replaced them from a Chinese supplier and it’s been on the bench for a few weeks run up daily with no issues. The gout who sold me the amp was probably aware that he had dropped it. The amp fell on the volume pot, smashing it off its daughter board and breaking the board itself. My feeling is it put full power into both inputs and that’s what blew it. The chips themselves have the circuit for dc sending and dropping a relay, so each models has a speaker protection circuit as it’s a Dolby surround amp. Anyway, I remade the fibreglass board and bridge the tracks where broken and repaired the pot- which is 50k 4 gang with motor- so rare as rocking-horse.
Cool! You really put some effort into this. I wish I was still like that. 😅
You may want to replace the STK module with two TDA based power amps, discretely built on a small separate PCB's. Check the power supply voltage. It has been done, seems to work fine.
Thanks for the info! I am going to take a look at the unit again. In the basement somewhere...
If you open it right,all you need is to connect new transistors through wires and put them onto the heatsink of the amplifier.It looks bad but it works good
thanks! that's right, those transistors in that ic are just missing their cases. i was concerned about the looks. i have another bad ic just like it; thinking of doing a transplant if i can get it open without messing it up.
Try heating it with hot air on the edges
good idea! i use heat sometimes, but didn't think of it in this case. thanks!
Give it a try on some non important IC to see if it works with heat
i'm just gonna go at it....slowly....
I've heard the same thing in regards to fakes....you fix the amp or shelf it? ~Jack, VEG
+Vintage Electronics Geek Thanks for watching! Shelved the unit for now; I have not forgotten it. Either find a donor unit or get a another module. I should be able to get it fixed; I think the board itself was ok; I did both resistance and voltage checks (not sure if I showed this on camera).
An incorrect bias in an amplifier can easily result in the output stage behaving like a short circuit. This is why when amplifiers fail it is very important to make sure the bias is correct. It seems in this case, the bias went wrong causing the output stage to pass a large current until failure.
Thanks for the feedback!
STK 082 is available here
Great great great...hermoso el circuito..
How can I fix one like this?
There is a video on UA-cam from someone that shows this. I don't repair them.
hey sir do you have a circuit which based on stk2038 ?
No sir, I don't. But I remember that the 4-page datasheet had one. You would have search for it online and download it. There was also an online PDF databook called "Catalog de 5000 diagramas de Amplificadores." Might be in there.
@@OldSchoolElectronics thank you sir. I saw that datasheet in chineese too. But i couldn't understand it
I just downloaded the pdf I mentioned. There seems to be a working circuit in there. Here is a link I found in case you haven't checked it out yet: docs.google.com/viewer?a=v&pid=sites&srcid=ZGVmYXVsdGRvbWFpbnxnZXJhcmRvY3Vyc29zZW5hfGd4Ojc2MzIwMDRlNzhmZGEx
There seem to be other links, too.
You have somewhere in your receiver a short and you need to test where the short is coming from. Another place it could be coming from is your speakers if two wires are touching each other in the inside of your speaker connectors. This will only happen if you don't have connectors in the inside and instead smoldered them in place. That rarely happens when buying one and it blows so take a good luck.
thanks jesse! i plan on getting back on this thing soon. it's in a box somewhere....
The devices can blow open rather than show the short inside them, making testing confusing as many are looking for a short. The reason it blew could be a crossed speaker wire of faulty speaker of lack of air flow during hot running conditions.
First time when I see inside of the stk.
I wish I could have repaired it. I have another complete defective module; I might try to take parts out of this one and put them in in the other one, if I can get the other one open easily enough and remove the transistor dies from this one. Not that it would make sense to do this...
Your not testing the transistors. Those things glued to the top are thermistors to detect overheating. The 3 legs of the transistor are soldered beneath, you can follow the tracks out from under them. usually they are the 1st 3 and the last 3 legs of the larger device. I have a blown technics one. I heard they often blow open somewhere in the device rather than measure short at the legs so it can be confusing trying to check them. The replacements are fakes built with cheaper transistors. There is a board available that you can build up a better then original circuit to replace the device rather than use the fake devices.
STK 082
Akai amplifier