Can I use old receiver power supply, to build a new amp

[robert1111]

Hello

My garage receiver broke down. Not even sure if the power supply works, the fuse needs to be replace, but I would love to use it in 2.1 amplifier build. Since Im very stupid with electronics, I would like to ask some help.

The receiver that I took out of the power supply, is Technics SA-EX500.

So basically what I would like to know is:

Is it possible to use it? I want to use it with a cinese class D amp. Wich one depends if it is even possible.

How do I know the voltage and amperage output? I could not find any info, only what is written on the receiver itself.

I have some pictures, of the unit. I can post later.

Thanks alot

 

[Mooly]

This doesn't look suitable for your needs unfortunately. The Technics uses a dual or 'split rail' supply of plus and minus 50 volts DC which is both unsuitable and to high in value for most Class D amps.

 

[robert1111]

I made some pictures, if It helps Power supply - Google Photos

So it can not be used for class D amp. But is there something I can use it for? AB class amp maybe? The goal would be to make something cheap out of it, and learn new stuff.

Thank you for fast reply.

 

[Mooly]

I looked at the service manual to see what the voltages were. The voltages used are high (-/+50 volts) and that puts it out of reach of many simple designs.

Something like this would be suitable, but it requires reasonable electronic knowledge to attempt it:

diyAB Amp - The "Honey Badger"

It sounds like you want something easy to build and cheap and I can't think of anything that fits the bill if you want to use that transformer.

Many of the Class D amps run well off a laptop type power supply which can be picked up cheaply.

The Technics could well have been fixable......

 

[robert1111]

Yes I do want something easy and fast. But the sad thing is that, those laptop brick amplifier, are not powerful. Well I quess, I have to find some other source for power supply . Than you for your time.

 

[kodabmx]

If you use full wave instead of bridge you might get 50V single ended supply for the following board...


TPA3255 300W+300W DC50V 3900UF/100V*2 Channel Digital Power Amplifier Amp Board | eBay

 

[robert1111]

Okey. I did a huge search in aliexpress, and I found many -/+50 volt mono amplifiers. Now I was thinking, why not make a subwoofer amplifier. Does that kind of combination work? I looked at the service manual, and I did not find schematics for the power supply. Not used to reading schematics. There is 7 pins coming out of the power supply, and there is a connection going out of the plate that is connected to it also. Is there anything I would need to change?

Thank you for helping guys. Sorry for totally noob questions.

Some examples:
L15D Class D Digital Mono Amplifier IRS2092S MOSFET IRFB4019 w/ Protective | eBay
LJM Audio L15D PRO Class D Digital Amplifier Board IRS2092 IRFB4019 Mono 300W Power Amplifier Board With Relay Protection -in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
Aiyima 1PC L15D PRO IRS2092S Audio Amplifier Board 300W Class D Digital Mono Amplifier Board With Relay Protection-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
IRS2092 IRFB23N15 D Class 30A D Amplifier Board / Mono / 350W/8ohm/700W/4ohm UPC1237 R179 Drop Shipping-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
IRS2092 amplifier board Class D IRFB4227 mono 350W better TPA3116-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group

 

[Mooly]

The transformer was shown on one diagram, the circuitry it connects to on another page as I recall.

With the greatest respect, it sounds like you are trying to run before you can walk Amplifiers running on 100 volts require respect, not just from the safety angle but also from the prospect of things turning ugly if mistakes are made.

The power supply consists of more than just the transformer. You need a rectifier and appropriate reservoir capacitors.

 

[robert1111]

BTW the first link of the examples is wrong.

Yep I´m trying to run before I can walk. I don`t know any other way.

I don´t understand why do I need rectifier if I want to use it with a board, that accepts DC current, and this power supply gives out DC. I understand this is needed, if I would use toroidal transformer. Am I correct?

Now coming back to not understanding the scematics. Yes I found where the power supply is, but I cant figure out the outputs. I got 5 pins. I understand the first one is -12, the second one is +12, fith one is ground, but I can´t figure out what are 3,4 and 6,7.

Did a little scetch.+ and - are probably not correct. I used LJM L15D pro schematics.

 

[planet10]

I have lots of dead receivers and asked the same question. Almost all of them had too high a voltage and not enuff current to power any of the amps i was interested. If you are someplace where you run on 110V and can find a way to wire the transformer (usually verbotten by the electrical compliance rules) then you could run the transformers at 220v off of 110 v and halve the available voltage out of the transformer.

dave

 

[Pano]

There are some Class-D amps that will run off +/-50V. I'll see what I can find.

 

[planet10]

Class D was not in the picture when i was looking.

dave

 

[Pano]

The Coldamps run on +/- 50V, but they are pricey. Would be better just to buy another old amp.

 

[tikiroo]

Search for L15D IRS2092 based class D amps. They work on voltages between +/- 35 to +/- 55 volts. Lots of deals for 2 mono boards.

 

[Mooly]

I don´t understand why do I need rectifier if I want to use it with a board, that accepts DC current, and this power supply gives out DC. I understand this is needed, if I would use toroidal transformer. Am I correct?

The mains transformer gives out AC voltages. These need to be rectified (changed to DC) and then smoothed out to give clean DC before they can be used to power any audio circuits.

If you apply AC direct to an amplifier then it will just instantly blow itself to pieces.

This shows the transformer and the power supply. The reservoir caps for the first diode bridge are off the page. That looks to be a low voltage supply for the small signal parts of the receiver.

 

[JMFahey]

This one will do very well with +/-51V supplies:
IRS2092 CLASS D Audio Receiver Power Amplifier AMP Kit 200W MONO Assembled Board | eBay

A friend of mine did same as you want to do, in his case to replace an unrepairable "200W" Bass amp power module.

The full thread, including lots of practical mounting and wiring data:
STK404-140S Question

it starts trying to repair the original power amp, then after it was deemed impossible , the Class D option was chosen, starting on post #30.

The finished, mounted and perfectly working Class D module:

1) Class D module mounted on a custom L shaped aluminum bracket, compared to original heat sink:

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

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

2) same bracket supports the original power supply on the other side.
Very clever guy.

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

3) the full assembly mounted insiden the original chassis.
Class D module is straight in front of original fan.
Not *strictly* necessary but it never hurts ... and in any case it was already there, so ....

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

 

[adason]

...or you can use your +/- 50V power supply as 100 V for tube preamp

 

[steveu]

The low voltage, high current comes from bridging outputs, and 2 or 4 Ohm loads. It's not really a class-D thing. The original UCD was +/- 42V, ie real close to +/-50. I would pick something rated for at least +/-60V, if you have to use a ready made circuit. The problem with most are that they are implementations of chip vendor applications circuits, and not discrete circuits like the UCD, so the operating range is influenced by chip limitations.
Years ago when I did more of this sort of thing, I fixed the amp and added a pair of 2n3773s (on heart sink) to each output, ~2 Ohm base resistors, so that the original outputs become drivers. Then it was able to drive a short while you take your time finding the problem. Of course this meant you had to live with most of the rest of the receiver. You could bypass the useless phono pre-amp, but one amp, for example, put the tone controls in the power amp feedback: Arrgh!
Its like rebuilding "classic cars". I don't have acres to store them while I use a modern product.

 

[DPH]

Also remember that these old receiver transformers probably aren't going to have the current capability (the A in VA rating of a xfrmr) to drive a 16 ohm load to max power, much less an 8 or 4 ohm load. Now, there's some novel ways to get around that for sure (line arrays anyone? ), but expect to be disappointed by the PSU.

Class-D will certainly help in squeezing every last bit of power out of it though! The IRS2092 modules already described are probably your best bet.

 

[robert1111]

Thank you guys. It seems to be damn complicated. I Guess that the first guy who said, it is too complicated was more than right. I´m too stupid to make it work .

Things have changed a bit. I found a bargain NAD T743. So what I need is a mono amplifier for subwoofer, no need for crossover because receiver has it, should be easy enought for a beginner.
I really like the JLM L15D pro or some other LJM product. Found a single one, DIY kit. So at least I can put it together myself, and have some soldering satisfaction . Just need to find a cheap power supply. I see everyone is using toroidal transformer, so I´m thinking using it too.