Hitachi HA270 amplifier - right speaker channel not working

Good evening, I don't want to seem know-it-all, but in my opinion, it’s the power integrated circuit that manages the right channel that failed. Here is a model of this component https://www.aliexpress.com/maintain.html. I should clarify that not all of them are like this one, but at the time, this model was widely used, and for someone who has the skill to solder components, it is quite easy to replace it. I myself did this, without ever having done it before, on an old Philips vinyl board; it was a TDA2005R. I changed it by applying new thermal paste between the component and the heatsink, and it was back to like new.

Here is a Google Image link https://www.google.be/search?num=10&hl=fr&site=imghp&tbm=isch&source=hp&biw=1016&bih=619&q=circuit+int%C3%A9gr%C3%A9+de+puissance+TDA2005&oq=circuit+int%C3%A9gr%C3%A9+de+puissance+TDA2005&gs_l=img.3...2140.14830.0.15588.36.13.0.23.23.0.86.930.13.13.0...0.0...1ac.1.7wLECLWziK0&gws_rd=ssl#hl=fr&tbo=d&site=imghp&tbm=isch&sa=1&q=circuit+int%C3%A9gr%C3%A9+de+puissance&oq=circuit+int%C3%A9gr%C3%A9+de+puissance&gs_l=img.12...508646.508646.0.509946.1.1.0.0.0.0.56.56.1.1.0...0.0...1c.1.iADMgm6RuqY&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.&fp=4ac5206dcda4ff34&bpcl=38897761&biw=1016&bih=619 that will show you a multitude of power integrated circuits.

But I will still attempt a more in-depth search, namely a schematic of the main printed circuit of the amplifier, and I will come back to give you updates, whether I find it or not.

Best regards, STARGATE43.

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Anyway!!! I didn't think it was that old, it dates back to 78-79, and the components weren't yet reduced to the size of those I showed you, they were much more "coarse" than that. Here is a photo of the inside of your amp http://img714.imageshack.us/img714/1965/0aa008.jpg, but I must admit I'm a bit defeated, I can't even see the components that managed the power, I have a little doubt, but to avoid saying something wrong, I will refrain.

I will still go a little further.

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I think this is the part http://www.datasheetking.com/photos/img/2sb557.jpg, with the identifier 2SB654, but back then we simply called it a transistor, not a power integrated circuit, and it's still rare to find this kind of part, but is it feasible?

If you zoom in on the photo, you'll clearly see the markings on the transistor on the right http://www.acontrecourant.fr/wp-content/uploads/2009/07/Hitachi-HA-270-in.JPG

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Thank you,

I will look into that. I need to go buy this component in PARIS and I will keep you updated.

Best regards

CHT

Hey yes... and it's not going to be easy to take apart the card that is above. The problem is finding the components. I haven't found anything available online yet.

See you soon

CHT

Hello

Result:

The transistors were tested by a friend. They are good. I bought new ones just in case. In fact, since this is second hand, it was a defective fuse that had been discreetly bypassed that caused the failure. Preliminary tests are promising. Then, after a few hours of operation, it's the left speaker output that's causing problems: power drop and sound distortion...

Thank you for your help.

Happy holidays.

Hello CHT and Merry Christmas, well you had to know about the fuse, right? Never bypass a fuse, good lord!!!
A little suggestion regarding the left channel, does the balance potentiometer work properly? Does it crack when you turn it? Be careful, it's still old gear you have there in your hands, it might cause it to break down one after another when starting it up, it's like with old cars, right? I certainly don’t wish that, but your amp is going to have its little old-age diseases.

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An electric wire was placed (hidden) under the right channel fuse ... I put the balance on Left and the right channel is cut off. It's normal. I tried all the sources: tuner, Aux, and cassette player.

Ok, but does it crack when you turn the balance knob or not? Also, just so you know, any of the potentiometers might be the cause, not necessarily the balance one.

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No crackling on all the pots. The sound saturation in the left channel exists even at low volume. I should point out that I swapped the speakers to test them.

From what I've read, you were able to find some transistors just in case, as you said. Now, it might be one of them that has failed, at least for the left channel, which saturates even at low volume.

No false contact at the level of the printed circuits??? Are the circuit traces in good condition??? No micro-breaks, which are sometimes difficult to detect with the naked eye, to be tested one by one with an ohmmeter. Back then, they weren't yet micro-traces, so it is possible to test them.

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To test the transistors, they were desoldered and resoldered by the friend mentioned above who knows about electronics. We'll have to take everything apart again to check unless the said failure is the result of a known malfunction.

In fact, everything is possible with these old clunkers, and sometimes the breakdowns are so obvious that we overlook them even more quickly.

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I dismantled everything. I did not detect any bad soldering. The left channel remains unchanged: reduced power and sound saturation. Only the right channel works normally.

Really strange, and none of the potentiometers crack when you turn them? Now, speaking of potentiometers, it might be the balance one that is faulty over time, that one however, I think will be more difficult to find.

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While waiting for a diagnosis, I connected my speakers to the right channels (A and B). The balance doesn't crackle, and both potentiometers work as if the two channels were connected. When adjusting the balance to right or left, the corresponding speakers are connected or not.

Really strange your issue, I'm not pulling my hair out yet, but I'm not far from it ;-)

Have you been able to check all the solder joints related to the left channel? It could also be a faulty diode, which is harder to check though.

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Hello,

I have exactly the same problem with my old Sony amplifier. One of the two output channels that connects to the speakers has failed...

So I ended up connecting both speakers to the last remaining channel, but it's not really convenient since the sound comes out in stereo...

As a last resort, do you know any repair shops or stores that might be able to resolve this issue in Paris?

Hello,

I ended up replacing the transistors. No change. The left channel is still saturating with a low sound level, and the left VU meter barely moves. Curiously, when I turn off the speakers, either A or B, the VU meters indicate that the right and left channels are functioning at the same sound level.

As for getting it repaired... an equivalent amp costs €350 at FNAC, and it took me 4 hours to dismantle, replace the transistors, and reassemble everything. I had to take EVERYTHING apart, even the transformer...

Interestingly, when I turn off the speakers either A or B, the level meters indicate that the left and right channels are functioning at the same sound level.

And that's not really the case, of course?

The difference in sound level is still there? As well as the distortion?

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