Sony TA-N7B restoration

[US7IGN]

I was asked to restore this beautiful amplifier.
It is in not very good condition with marks of previous intervention.

So, I removed the bottom cover and saw that someone was already inside, and the previous owner had a cat.

Also, someone removed the foam rubber, which collapsed over time and caused corrosion, resoldered some places, but did not touch a single electrolytic capacitor.

It seems to me, or did someone change the fusible resistors to ordinary ones, and even more power (R121)?

I spent two days searching the forums for information on the best options for replacing original parts and did not see only with what modern analogues could be replaced Q130 (2SC1962), Q131 (2SA835), Q103, 203, 104, 204 (2SK30A) transistors and D154, 254 (1T22AM) diodes. Also wondering what would you recommend to replace RV101 and RV102 pots? Thank you!

 

[Vint Age]

Hey welcome to AK! Check this thread out:
https://www.audiokarma.org/forums/index.php?threads/sony-ta-n7b-transistors.696077/#post-9452170

 

[US7IGN]

Check this thread out:
https://www.audiokarma.org/forums/index.php?threads/sony-ta-n7b-transistors.696077/#post-9452170

Thanks, I started searching there, but some questions still remained. Perhaps I will leave all the original good transistors for which I can not find a replacement.

 

[ivandezande]

I was asked to restore this beautiful amplifier.
It is in not very good condition with marks of previous intervention.
View attachment 2790953 View attachment 2790954 View attachment 2790955
So, I removed the bottom cover and saw that someone was already inside, and the previous owner had a cat.
View attachment 2790956 View attachment 2790957
Also, someone removed the foam rubber, which collapsed over time and caused corrosion, resoldered some places, but did not touch a single electrolytic capacitor.
View attachment 2790958
It seems to me, or did someone change the fusible resistors to ordinary ones, and even more power (R121)?
View attachment 2790959
I spent two days searching the forums for information on the best options for replacing original parts and did not see only with what modern analogues could be replaced Q130 (2SC1962), Q131 (2SA835), Q103, 203, 104, 204 (2SK30A) transistors and D154, 254 (1T22AM) diodes. Also wondering what would you recommend to replace RV101 and RV102 pots? Thank you!

2SA835 > TTA004B

The diodes are germanium. Leave them.
The FET’s would have to be converted from surface mount.

 

[rottalpha]

I was asked to restore this beautiful amplifier.
It is in not very good condition with marks of previous intervention.
View attachment 2790953 View attachment 2790954 View attachment 2790955
So, I removed the bottom cover and saw that someone was already inside, and the previous owner had a cat.
View attachment 2790956 View attachment 2790957
Also, someone removed the foam rubber, which collapsed over time and caused corrosion, resoldered some places, but did not touch a single electrolytic capacitor.
View attachment 2790958
It seems to me, or did someone change the fusible resistors to ordinary ones, and even more power (R121)?
View attachment 2790959
I spent two days searching the forums for information on the best options for replacing original parts and did not see only with what modern analogues could be replaced Q130 (2SC1962), Q131 (2SA835), Q103, 203, 104, 204 (2SK30A) transistors and D154, 254 (1T22AM) diodes. Also wondering what would you recommend to replace RV101 and RV102 pots? Thank you!

Nice JP unit.
Is there a reason for not sending this amp out to someone familiar with these amps?
Where’s the amp located?

 

[US7IGN]

Hello! I think it's all about the money. The owner decided not to change the big capacitors yet. Maybe later he will be able to buy them. So far I have ordered everything else - fusible resistors, capacitors and most of the transistors and diodes.

The amplifier is located in Ukraine. I often get devices after such repairs and forced to redo after other masters

 

[US7IGN]

The first parts arrive and I begin to deal with this device. I wonder if someone has already replaced transistors here, or were they installed at the factory with different letters?
Q35 (2SC1173) has Y but others (Q36, Q37) has O

 

[US7IGN]

It seems that someone has very randomly changing parts before. Maybe it is the best way to get better sound from any amp

 

[Oilmaster]

2SA835 > TTA004B
The diodes are germanium. Leave them.
The FET’s would have to be converted from surface mount.

Be careful and nuanced with that kind of advice:

2SA835/2SC1962 = EBC
TTA004B/TTC004B = ECB

The Sony 2SA835/2SC1962 have not only that unique leg layout, but also a specific body size & heatsink lip.
Using ECB TO-126 will result in ugly hook-ups, turning such heritage amp into a DIY unit

Besides that, the 2SA835/2SC1962 have high bandwidth, high Hfe, low Cob, something that the industry is depriving us from since a decade or two.
In any case, finding NOS 2SA835/2SC1962 is the best option; sonic and mechanical wise

 

[Oilmaster]

Hello! I think it's all about the money.

Sure, first they spent between $1000 to $1500 to buy it in Japan and have it shipped, import duties etc, then looking for low cost fix

 

[US7IGN]

In any case, finding NOS 2SA835/2SC1962 is the best option; sonic and mechanical wise

Thank you! I'm very appreciative of your time and consideration!
As you already understood, the process itself is interesting for me in this repair, so I carefully study all the information. I have a couple of ideas for mounting the parts so that it's not ugly and efficient. Although the owner does not seem to care what his amplifier looks like. He finds it impractical to even paint such horrible surfaces. Ok, my task is to return the sound to the amplifier.

 

[ivandezande]

Be careful and nuanced with that kind of advice:

2SA835/2SC1962 = EBC
TTA004B/TTC004B = ECB

The Sony 2SA835/2SC1962 have not only that unique leg layout, but also a specific body size & heatsink lip.
Using ECB TO-126 will result in ugly hook-ups, turning such heritage amp into a DIY unit

Besides that, the 2SA835/2SC1962 have high bandwidth, high Hfe, low Cob, something that the industry is depriving us from since a decade or two.
In any case, finding NOS 2SA835/2SC1962 is the best option; sonic and mechanical wise

I think the point was to use a new production part. I don’t trust any Sony transistors.
Yes should have noted pinout.

 

[US7IGN]

So, I replaced Q109/209 2SA639S with 2SA1319 and Q110/210 2SA896 with 2SB649AC.
Then I found that instead of 2SC1962, C1670 was installed on the board as Q111/211 and I replaced them with 2SD669AC.
Also C1663 was installed as Q130/230 instead of 2SC1962. Perhaps they can also be replaced by 2SD669AC

 

[US7IGN]

Due to medical issues, I spent a week in hospitals and only recently continued to work on this amplifier on the sly.
I replaced some of the diodes, and cleaned others.

I replaced all electrolytic capacitors with the Panasonic FC 105C.

Also replaced most of the transistors on main boards. Can this be called a matched complementary pair?

Instead of C1663/A835, I used TTC004B/TTA004B, bending the legs and wearing an insulating tube.

Also new pots

 

[US7IGN]

Today I assembled the amplifier with the exception of the output stage. You need to rest before the most responsible stage. So far, the turning on has shown that I did not make mistakes when replacing parts.
I replaced all the fusible resistors with the correct ones.

The relay and switch contacts were dirty, but not badly damaged.

 

[US7IGN]

I replaced some of the diodes, and cleaned the diode bridges and decided to leave them.

"Matched" pairs of transistors and "identical" capacitors C307/C407 in the channels)

Also I found open R127 and replaced it.

 

[US7IGN]

Today I finally assembled this amplifier. Unfortunately, I do not have suitable acoustics to evaluate its sound, so I will have to wait for the owner's feedback. It seemed to me that the amplifier was heating up and the radiators could be larger...

 

[US7IGN]

 

[Arye]

Hello US7IGN, I also obtained an N7B amp from Japan. Concerning the restoration process did you need to match the BJT d44h11/d45h11?
Regards Arye

 

[US7IGN]

Hi Arye!
I have bought two dozens of them and choose with closest parameters.