Hello!
I had a small time hobby of DIY electronics while I was in school, which is over 10 years back. From amongst the things I built those days, there is this STK4392 based stereo amplifier that I'd like to start using now. This hasn't been in use for quite a long time. Well, at least 10 years of no usage.
From what I remember, this had a good enough audio quality. Nothing was broken. But the thing I built was just way too bloated with two transformers and two separate full bridge rectifiers just because I needed two different voltages. Either because I did not know about voltage regulators at that time, or maybe it is something new, this silly two transformer approach is what I had done. One is an 18-0-18 1Amp, and the other is 12-0-12 5Amp custom-wound.
The 'bloated' work goes on as it has a cassette tape mechanism, an FM tuner pcb, an AM tuner, mic input and aux input with one pre-amp board for each of those! An LED light 'visualization' thing that used to move like the computer based music player visualization. Then one long board that says its for '3 way tone control'. Bass, Treble, kind of things.
Anyway, I want to use just the STK based Amplifier and its dependencies inside a new enclosure/cabinet and use it as just an amp to which I can connect some music source.
The STK PCB says it needs 26 - 0 - 26 volts AC. These points go towards the on board bridge rectifier diodes, and the circuit goes on. The problem is that the transformer connected, which worked as well, is 12-0-12 5 amp! How did it work when the board needs 26-0-26 but the transformer was 12-0-12? :| Funnier thing is that the board says 26-0-26 AC I had connected 12-0-12 DC as the wires were from the bridge rectifier board I had! With all these mistakes, I clearly remember it worked!
As I'm sure it worked, can I still use it with me new reorganized and minimized amplifier? Or, as it is a transformer, and it is 10 years old, should I just get a new one? And if a new one, should I get a 26-0-26 like the PCB says, or 12-0-12 like I had used and it worked, or 39-0-39 like it says on the datasheet( STK4392 pdf, STK4392 description, STK4392 datasheets, STK4392 view ::: ALLDATASHEET ::: ) ?
I think the pre-amplifier circuits were used because the audio sources were the FM, and AM radios along with the magnetic head of the cassette tape mechanism. Is this preamplifier still required for modern day music sources?
I had a small time hobby of DIY electronics while I was in school, which is over 10 years back. From amongst the things I built those days, there is this STK4392 based stereo amplifier that I'd like to start using now. This hasn't been in use for quite a long time. Well, at least 10 years of no usage.
From what I remember, this had a good enough audio quality. Nothing was broken. But the thing I built was just way too bloated with two transformers and two separate full bridge rectifiers just because I needed two different voltages. Either because I did not know about voltage regulators at that time, or maybe it is something new, this silly two transformer approach is what I had done. One is an 18-0-18 1Amp, and the other is 12-0-12 5Amp custom-wound.
The 'bloated' work goes on as it has a cassette tape mechanism, an FM tuner pcb, an AM tuner, mic input and aux input with one pre-amp board for each of those! An LED light 'visualization' thing that used to move like the computer based music player visualization. Then one long board that says its for '3 way tone control'. Bass, Treble, kind of things.
Anyway, I want to use just the STK based Amplifier and its dependencies inside a new enclosure/cabinet and use it as just an amp to which I can connect some music source.
The STK PCB says it needs 26 - 0 - 26 volts AC. These points go towards the on board bridge rectifier diodes, and the circuit goes on. The problem is that the transformer connected, which worked as well, is 12-0-12 5 amp! How did it work when the board needs 26-0-26 but the transformer was 12-0-12? :| Funnier thing is that the board says 26-0-26 AC I had connected 12-0-12 DC as the wires were from the bridge rectifier board I had! With all these mistakes, I clearly remember it worked!
As I'm sure it worked, can I still use it with me new reorganized and minimized amplifier? Or, as it is a transformer, and it is 10 years old, should I just get a new one? And if a new one, should I get a 26-0-26 like the PCB says, or 12-0-12 like I had used and it worked, or 39-0-39 like it says on the datasheet( STK4392 pdf, STK4392 description, STK4392 datasheets, STK4392 view ::: ALLDATASHEET ::: ) ?
I think the pre-amplifier circuits were used because the audio sources were the FM, and AM radios along with the magnetic head of the cassette tape mechanism. Is this preamplifier still required for modern day music sources?
It looks like a single-supply chip. The maximum allowable power supply voltage is 56 V.
It says that the recommended supply voltage is 39 Volts. That's not 39-0-39. It's 39-0.
Maybe it's wired with one end of the transformer to ground and the center tap unused? The 26-0-26 would make sense, then.
Where is the rest of the datasheet?
It says that the recommended supply voltage is 39 Volts. That's not 39-0-39. It's 39-0.
Maybe it's wired with one end of the transformer to ground and the center tap unused? The 26-0-26 would make sense, then.
Where is the rest of the datasheet?
Thank you for the response 🙂
I have the PCB right here with me, on the tabletop. So, I'm looking at it, and posting so that no mistakes or guessing could happen.
The 0-26-26 AC-in on the PCB goes to the anode of 2 of diodes. The transformer is a center tapped one, and each 12v wire goes to one IN5402 diode. The cathodes of these two diodes merge on the PCB tracks and goes through a big 2200 capacitor, and finally to the rest of the circuits. As these two diodes merge on the circuit, the two rails of 12-0-12 gets added up to give 24 volts? :| The '0' of the 12-0-12 is connected to the ground on the PCB.
If its becoming 24v likes I addumed, then based on the '40%' rule there would be 33.6v after the bridge rectifier? Now it's all making sense :|
Well, sorry for the incomplete datasheet.
Here they are, in two pages:
Page-1 --> STK4392 datasheet(1/2 Pages) SANYO | AF Power Amplifier
Page-2 --> STK4392 datasheet(2/2 Pages) SANYO | AF Power Amplifier
If I use 26-0-26, wouldn't the end be 52v + 40% = 72.8v which is higher than the Vmax suggested on the datasheet which is 56v?
I have the PCB right here with me, on the tabletop. So, I'm looking at it, and posting so that no mistakes or guessing could happen.
The 0-26-26 AC-in on the PCB goes to the anode of 2 of diodes. The transformer is a center tapped one, and each 12v wire goes to one IN5402 diode. The cathodes of these two diodes merge on the PCB tracks and goes through a big 2200 capacitor, and finally to the rest of the circuits. As these two diodes merge on the circuit, the two rails of 12-0-12 gets added up to give 24 volts? :| The '0' of the 12-0-12 is connected to the ground on the PCB.
If its becoming 24v likes I addumed, then based on the '40%' rule there would be 33.6v after the bridge rectifier? Now it's all making sense :|
Well, sorry for the incomplete datasheet.
Here they are, in two pages:
Page-1 --> STK4392 datasheet(1/2 Pages) SANYO | AF Power Amplifier
Page-2 --> STK4392 datasheet(2/2 Pages) SANYO | AF Power Amplifier
If I use 26-0-26, wouldn't the end be 52v + 40% = 72.8v which is higher than the Vmax suggested on the datasheet which is 56v?
I had an APC UPS whose battery was supposed to be replaced. Instead, I got a higher kVA UPS and I'm happy about its perfomance. So, this older UPS is good for its transformer!
I opened up the UPS.
The battery was 12v 7AH, and one of the thickest red wires from the transformer is directly connected to the battery's positive terminal. The black wire to the negative terminal came from the PCB though. That has an equally thick wire gauge(those awg numbers).
The transformer looks custom done for APC. There is no terminal annotation on the transformer. In fact there are no terminals on it, but wires come from within the windings from multiple areas. I have managed to isolate three groups of wires. One had 10 ohms resistance, another had 1 ohm resistance and the last group had .4ohm resistance.
So, wire groups are like:
Blue, Brown and Black, thinner gauge [total 3 wires] - 10 ohms and 8 ohms
White and Black, same thinner gauge [total 2 wires] - 1 ohm resistance
White, Red, Red and Black, thick gauge [total 4 wires] - .4ohm and .2 ohm
Based on the readings done so for, the higher resistance, but thinner wires are the higher voltage lower current windings, and the lower resistance thick *** wires are lower voltage higher current windings.
The transformer looks perfect without any visual damage. Not even scratch or dust! The wires and windings are of good quality, and hence you can just hold on any single wire and suspend the transformer without it breaking off from the cable and falling onto the floor! The transformer I get from the local stores are not like that! They are cheap brass colored and the wires dont come from inside, but instead are soldered on the terminals. They break if you just pull with sufficient force. The APC transformer is bigger and at least 10-15 times heavier than the normal electronic store transformers.
Please help me figure out if my assessments about the wiring connections based on the continuity test and resistance test are right or wrong 🙁
I opened up the UPS.
The battery was 12v 7AH, and one of the thickest red wires from the transformer is directly connected to the battery's positive terminal. The black wire to the negative terminal came from the PCB though. That has an equally thick wire gauge(those awg numbers).
The transformer looks custom done for APC. There is no terminal annotation on the transformer. In fact there are no terminals on it, but wires come from within the windings from multiple areas. I have managed to isolate three groups of wires. One had 10 ohms resistance, another had 1 ohm resistance and the last group had .4ohm resistance.
So, wire groups are like:
Blue, Brown and Black, thinner gauge [total 3 wires] - 10 ohms and 8 ohms
White and Black, same thinner gauge [total 2 wires] - 1 ohm resistance
White, Red, Red and Black, thick gauge [total 4 wires] - .4ohm and .2 ohm
Based on the readings done so for, the higher resistance, but thinner wires are the higher voltage lower current windings, and the lower resistance thick *** wires are lower voltage higher current windings.
The transformer looks perfect without any visual damage. Not even scratch or dust! The wires and windings are of good quality, and hence you can just hold on any single wire and suspend the transformer without it breaking off from the cable and falling onto the floor! The transformer I get from the local stores are not like that! They are cheap brass colored and the wires dont come from inside, but instead are soldered on the terminals. They break if you just pull with sufficient force. The APC transformer is bigger and at least 10-15 times heavier than the normal electronic store transformers.
Please help me figure out if my assessments about the wiring connections based on the continuity test and resistance test are right or wrong 🙁
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