Sony TA 1120....cant still bring it to sound great

Nope.......i know of the all NPNs thingy going in there . My tech told me about the design months ago...

I will purchase 4 more NPNs today . The 21193s were purchased because of scarce availability of these and also for a future diy project .
 
2SA1306 Datasheet, Equivalent, Cross Reference Search
Type Designator: 2SA1306

Material of Transistor: Si

Polarity: PNP

Maximum Collector Power Dissipation (Pc): 20 W

Maximum Collector-Base Voltage |Vcb|: 160 V

Maximum Collector-Emitter Voltage |Vce|: 160 V

Maximum Emitter-Base Voltage |Veb|: 5 V

Maximum Collector Current |Ic max|: 1.5 A

Max. Operating Junction Temperature (Tj): 125 °C

Transition Frequency (ft): 100 MHz

Collector Capacitance (Cc): 30 pF

Forward Current Transfer Ratio (hFE), MIN: 70

Noise Figure, dB: -

Package: TO218

2SA1306 Transistor Equivalent Substitute - Cross-Reference Search
 
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The drivers look like originals. I've never seen a fake one with green case, but I haven't seen every fake transistor in the world.

Regarding the specs, they also look OK for a driver transistor.

Anyway, as said in many posts, the transistor model shouldn't have such an impact in performance to make a night-day difference. I've fixed amplifiers with "lower specs" transistors (as fitting cheap TIP41-42 and BD139-140 inside a Sansui amplifier with burned outputs and drivers), and the amplifier sounds as good as the original (at least, a listening test can't tell the difference, perhaps THD or some laboratory test are not as good as the original, but you can't hear anything wrong with the amp).

I'd ask for the square wave tests before keep swapping parts hoping they will "fix" some issue by some magic. If something is not OK in the amp, all the transistors you fit will reproduce the same fail, they will "sound" the same.
 
Yup that's what my tech says. That even with fake transistors a bang olufsen amplifier sounded so good that he copied the design and made a clone. And this sony has not impressed from the very start
 
He doesnot have an oscilloscope. Now what.... If the square wave is not produced , how do we go further ....
 
Without at least a scope it's nearly impossible to tell how the amp is performing. I've seen some nasty waves on amps that sounded pretty much fine. After repair they were better of course but I would never have known about the problem to start with if I couldn't look at the wave form.
This is especially important when using substitute parts as even if you pick a good replacement by the numbers they are not what the amp designers had in mind when building it. It could be a new component is causing oscillation or some other artifact that effects the sound.

I'd look into finding someone with a scope or trying to buy one. They make kits where you can use your computer as the scope which can bring the price down if used ones aren't available in your area.
 
I agree, at least a PC based oscilloscope is needed.

A free software as Visual Analyzer can show audio waves in a computer, using the sound card. Even without calibrating it, it's useful to see the shape of the waves. (you won't see an ultrasonic oscillation, but that would cause overheating the amp)

The only caution you need to take, to prevent burning the sound card, is the cards usually can take just a few volts, something like 1 or 2 volts. You need a 10X attenuator to check the amplifier output, and be gently with the volume control (just check low power levels). It can be done with a 10ohm + 1 ohm resistor in series, or a 4.7 ohm + 0.47. You clip the probes across the smaller resistor. Remember we don't need voltage accuracy, just to see if there is a major problem in the square wave shape.
 
The amp came to me this weekend .
The tech brought it for a listen to the other amps too.
I finally tested it with my speakers last night . These speakers have audax drivers and very satisfying tweeters .
I have to say this amp has something good there but its not quite reproducing it .
The sound is lacking in lushness and highs look restrained .there is a slightly raised noise floor compared to the bang n olufsen amp ...however the lows are strong n deep.

This amp does need those output transistors replaced...
 
Hello. As many techs had said here, the output transistors shouldn't have too much influence in the final sound (at least if they work).

Even you wrote in post #49 that another amp with fake transistors sounds OK.

Down here in Buenos Aires, I'm sure at least 1/2 of the transistors we buy are fake, and the amplifiers sound OK.

I suspect that in the full restoration, with so many parts replaced, some mistake was introduced in the amplifier. But you need an objective test to see this, that means, to see the waves in an oscilloscope. All the listening tests you can do will just introduce more doubts than certainties.

I'd invest some time setting a PC based oscilloscope (Visual Analyzer or similar, no affiliation), or selling the amp and buying another one.
 
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The amp came to me this weekend .
The tech brought it for a listen to the other amps too.
I finally tested it with my speakers last night . These speakers have audax drivers and very satisfying tweeters .
I have to say this amp has something good there but its not quite reproducing it .
The sound is lacking in lushness and highs look restrained .there is a slightly raised noise floor compared to the bang n olufsen amp ...however the lows are strong n deep.

This amp does need those output transistors replaced...

The output replacements are 2N3773 or BDX50.

See. https://redirect.viglink.com/?forma...ce095c98d1405804dda&type=M&term=2SD45
 
21194s . Today i got em.

HereView attachment 1207818
I hope you have had success with this amplifier. Please watch out, I believe that the MJL21194 transistor that you show in the picture is a counterfeit part. Its surface appears to have been sanded and the part number uses a different font. The one on the left (MJL21193) looks more like the genuine part, but you never know, unles you purchase them from a reliable source. There is a lot written about fake transistors, so I will not go into this in this thread.
 
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