Sony TA-N77ES repair advice?

[restorer-john]

As the N77es is full of fusible resistors, we will be looking at them particularly hard. they are designed to save expensive semiconductors from death. There is about 14-17 of them, per channel and they are designed to smoke up in a problem situation.

Remember, they fail for a reason.

You won 't be recapping anything, until you have fixed the problem. That is for later, and only IF you feel like doing it. The capacitors in the TAN77es are likely absolutely 100% perfect, they were all top grade components.

Have a look at this component, it looks suspicious to me from your photo:


It is R366 in the right channel, a 100ohm 1/2 watt fusible. Test it and report back. Have a look at the clearance between the metal tab of Q359 and the copper behind it.

 

[restorer-john]

So, we are now working on two different pieces of gear in the same thread huh?

 

[Ds2000]

The motor would likely spin with a 3v D.C. Or so input directly. In other words, most of these are hobby motors from the likes of Maubichi. I'm also seeing some caps and what looks like a transistor on the board. Caps are known to fail, sometimes taking the speed governor transistor with them.
I'm thinking the motor is the last thing to fail,
Also, was the motor in the non working unit ok, as in did the remote volume function work on that one, or was it too far gone to check?

 

[Ds2000]

R-J, sorry 'bout that. I sort of jumped in. I should have suggested a new thread for the E-77 motor.

 

[TEKWRX]

So, we are now working on two different pieces of gear in the same thread huh?

Yeah, did I make a forum faux pas? I figured since they are a matched set, and we know exactly with part is the problem it might be a quick fix. I can start a new thread if it will makes things more streamlined. No big deal

 

[TEKWRX]

Also, was the motor in the non working unit ok, as in did the remote volume function work on that one, or was it too far gone to check?

The motor in the old one was good. The remote controlled volume worked just fine. How would i go about testing the caps on the motor board?

 

[TEKWRX]

Have a look at this component, it looks suspicious to me from your photo:

View attachment 909100
It is R366 in the right channel, a 100ohm 1/2 watt fusible. Test it and report back. Have a look at the clearance between the metal tab of Q359 and the copper behind it.

Wow, you have a good eye. Yes, that one looks like something happened to it compared to the others. Could be burned. I can take a macro shot if that would help. How would I test it? And should I wait until the DBT is ready?

 

[Ds2000]

Pm sent

 

[TEKWRX]

I've created a new thread for the pre-amp issues. We'll keep discussion here to the N77ES power amp. Sorry if things got cluttered and hard to follow

 

[TEKWRX]

OK, I just finished wiring the DBT. Can somebody take a look and let me know if I did anything wrong before I close it up and get to testing? Here are the incandescent bulbs I have on had: 72w, 100w, & 150w. Do I need to get anything else? Also, before I check the N77ES with the DBT, should i test it on a known good amp? I have a Sony TA-N220 on the shelf not being used, but it worked fine a few months ago when I pulled out of my system. I assume with that model, I should use the 72w? The specs on it are 100 wpc when run in 2 channel BTL mode (or 4x50w)

 

[restorer-john]

You aren't going to 'test' the N77es with your DBT. Yet. Patience.

You know it has smoked up some components. You know it has a fault. The DBT isn't going to help you just yet. It is for testing the amp in a non-destructive way after we have found the problems and fixed them first.

By all means plug your working N220 into the DBT and get used to the way turn-on lamps light and dim. Play some music through the N220 while it's connected to the DBT (with some speakers) and see the dynamic nature of the lamp in action and how that relates to current draw etc.

The wiring of your DBT looks good to me, but get a US based member to confirm. (Australian 240v fittings and colours are completely different and I'm used to them) It seems you are switching the active (blk), the neutral(wht) is connected and the earth is tied to the socket properly- I can't see a problem.

For the life of me, I cannot see why mains colours aren't standardised all over the world.

In Australia, we used to have black/red/green, now we have brown/blue/yellow-green and you have black/white/green- what a mess.

 

[restorer-john]

Test your DBT with the N220 and report back.

Then we'll start fault finding in the N77es. In the meantime, remove the top panel, right side panel and base plate.

 

[TEKWRX]

Thanks @restorer-john , I will play with the DBT with the N220 and see how it works. What wattage bulb would you recommend to use with that one?

I'll disassemble the rest of the N77ES tonight or tomorrow. I'd love to get to the bottom of the issue this weekend, so I can get an order placed online for replacement components early next week.

 

[restorer-john]

Use the smallest one you have, the 72w?

 

[TEKWRX]

Use the smallest one you have, the 72w?

OK. I grabbed a smaller one today when I was out. It's a 60w equivalent (43 actual watt). Also, is the 150w gonna be ok for the N77ES when it's ready? I can grab a 200w tomorrow if I need

 

[TEKWRX]

The DBT worked fine I think. I used the 42 watt and at first it got very bright and it looked like the top of the bulb burned a bit, but it could just be it's been so long since I've used an incandescent light and I'm just not used to that, lol. I could see the bulb dim with the music when I adjusted the gain on the amplifier. So just so I'm clear on the operation, if there is a short or some other problem with the N77ES, using the DBT will prevent from to much power surging through it and damaging other components? What will happen, the bulb won't light or will it burn out?

I removed the rest of the panels. Here is a picture of the underbelly. Please let me know if you need better/closer pictures of any particular section. I also have a macro lens for my Sony a6000 that I can get out if it will help

 

[restorer-john]

The bulb will not burn out, it will go full brightness if there is a high current draw (ie, a fault). By doing that, the voltage drop across the DUT (device under test) will be low, hence the dissipation in the DUT will be low and no further (hopefully) damage will be done.

If the bulb lights up fully bright and remains bright, there is a short/fault.
If the bulb lights up briefly and then dims to a lowish level (depending on the bulb and current draw) things are relatively normal.

Again, until we have done basic tests on the output stage and solved the other issues, do not power up the N77es amp through the DBT or at all.

It is Easter Saturday today and I will likely post back later with some tests I want you to do.

The output stage looks original, although the soldering looks pretty average for Sony. The devices are the correct ones and identical batch numbers and Hfe grading. We will test them all later today.

 

[TEKWRX]

@restorer-john I hope you're enjoying the holiday weekend. I went out and got a new meter, a Fluke 110+ so hopefully that will assist in troubleshooting correctly. I'm ready to go when you are (just letting you know. no rush)

 

[thymanst]

I saw the tan77 amp on CL, but passed because they have a history of burning up (info from forums a long time ago) they fixed the issue with the ta-n80es (but got rid of the meters) hope you can resurrect it.

 

[TEKWRX]

I saw the tan77 amp on CL, but passed because they have a history of burning up (info from forums a long time ago) they fixed the issue with the ta-n80es (but got rid of the meters) hope you can resurrect it.

Was that the one for $225? I missed out on that one by about an hour or so, they guy emailed me back and said it sold pretty much right away. I was kicking myself because I am a huge Sony fan and have a saved CL search that checks for just Sony products listed in the past 24 hours and I check it a few times a day usually. It was just bad timing that day. The one I bought and am trying to repair I bought from another gentleman knowing it had an issue and I paid considerably less that $225 I'm amazed at the condition of this one, probably a 9/10 cosmetically.

From everything I've read recently about the N77ES is that they are not really prone to failure, except for the meter lights. I think that gave it a "bad" reputation. If I'm not mistaken the N80ES has a tendency to run hotter. Either way, they are pretty much the same amp internally.

I have a proper soldering station arriving tomorrow (Hakko FX-888D) and have been watching YouTube videos on soldering techniques to brush up on my skills. I'm not a total novice, but it is usually a long time between projects for me I figured every little bit will help. I have faith I will bring this monster back to life