Sony TA-N80ES left channel died and I am not sure why, can I get some advice on the repair?

I just got a new (old) ta-n80 es amplifier and I had cleaned it, recalibrated it and thought I had it working, held the bias well, came out of protection etc. So I go to test it and get no sound. I tried a few things but nothing worked so I pulled the left channel input and put that into the fixed left input while the right channel was still in the variable input I also disconnected either just the left channel, or both I do not remember 100% from the pre amp while still keeping them connected to the power amp to see if tapping the connectors would produce anything. Before I could even try tapping the connector the amp almost immediately started smoking and shot into protection. After this I pulled it out with a heavy heart and started disassembling to see what went wrong. I found out that the driver transistors for the left channel, three of the six output transistors for the left channel, one of the 10 ohm emitter resistors, a zero ohm resistor and the left speaker relay had all gone. While very annoying especially after just spending a bit of money on this amp this is all fairly easy to replace even if the transistors might not be cheap. However I am making this post mainly to ask why this happened. Is the screwing around with the inputs the reason for this? I do not really understand why this would be an issue but admittedly I do not have a ton of experience with a/b power amps. I had it running on idle for atleast an hour to adjust the bias and it showed no signs of issues. I did redo the solder joints for the transistors but I checked for shorts or otherwise unwanted bridges and found nothing. And the 1 hour plus idle session was after this. While I had no sound during testing I also am not familiar with the setup and it is very possible I just connected something incorrectly. Since the dc offset adjustment was working I doubt that there was a relay that wasn't engaging or otherwise something obstructing the signal. I checked the manual on instructions that might caution the user to not use it in the way I did but I did not find anything like this either. Ofcourse that doesn't have to mean much but if there was such a confirmation I would feel much more at ease with repairing the amp by just replacing these components.

After some more searching and reading I figured out that the d312 diode is also gone. I have read that it is unobtanium but I am sure that some modern replacement will work.... The same diode on d311 is not shorted but it gives some unexpected readings (1.7 voltage drop one way, 0.3 the other) so I think I probably will have to replace both.

I will check all the other fusible resistors for shorts but for now I am planning to order:

Q404 2SA1306A-0 (toshiba) -> MJE15033G (onsemi)
Q403 2SC3998B-Y (toshiba) -> MJA15032G (onsemi)

both C3423 transistors read ok with a multi meter so I do not believe they need to be replaced.

C3856 (sanken) -> 2SC3856 (sanken) if chip one stop allows me to order there, otherwise 2SC5200N (toshiba) (non obsolete version of a transistor successfully used on a thread from years ago). I can also order these from digikey but they do not have the A1492.
A1492 (sanken) -> 2SA1492 (sanken) same story with chip one stop, otherwise I will probably opt for the 2SA1943N (toshiba)

As for the known bad resistor I will just order whatever is available locally that has the correct specs of 1/2 watts and being fusible. I am not sure yet if that is all that needs to be replaced. Input on this regarding the cause of the problem would be really helpful.

As for the relays I was thinking of just ordering the set sold on ebay for 12 euros, but it is not a priority. I think the old one might still work even if the plastc got very hot, even if it is just to test.

I would also really appreciate some input on the HZ3ALL diodes. In the aforementioned thread the suggested replacement was the Bzx55c2v7 which has some different specifications like a lower impedance rating and a higher max power dissipation. I do not know what should be prioritised in this instance in terms of specs but the Bzx55c2v7 has since also gone out of production so it is not an option.

Also mentioned in the thread was the UPA68HA UPA68 Dual N-Channel JFET being faulty. I checked it for shorts on my board and there weren't any but I do not know if that is enough to know if it actually ok or not.

As for the actual reason this happened, I am still not sure. When the left channel blew up I could hear sound through the left speaker so the speaker cables atleast on the left channel where connected. I am not sure if sound being produced in this situation means that there is no short or not.

Sorry for the likley disjointed post. I originally posted this to audiokarma and updated it as I went along. However during this process I noticed that a lot of the information that ended up being useful came from this website. As such I figured that it would make more sense to ask on here.
This is my first post here so I am sorry if I am not following some rules correctly. While I am sad that I killed my newly acquired amplifier I am also excited to potentially get it up and running again.
 
For now I have decided to go ahead and order:

15032g 3x
15033g 3x

2sc5200 10x
2sa1943 10x

bzx55c2v7 10x (a different variant was still in stock luckily)

10hm 1/2 watt 5% fusible 10x

I decided to order a bunch of spares should something go wrong again so I can both keep testing if one attempt does fail and I had to order more than 50 euros in value anyway to avoid shipping costs, so the extra spares are essentially free anyhow. I will order the relays on ebay as I do not know much about relays and the service manual just says relay under the part description.
 
@Citizen124032 thank you for taking the time to try and help me. I have since tested all the resistors on both mainboards and the protection circuit and I found some more defective components.
Listed it would be:
Main board a
Transistors:
Q401 2SC3514-Q
Q402 2SA1383-Q

Q308 2SA1360-0
Q309 2SA1383-Q

Q312 2SA1360-0
Diodes:
D311 hz3all X(maybe)
D312 hz3all X(maybe)
Resistors:
R316 100 ohm 1/2 W fusible
R401 1k ohm 1/2 W fusible

Main board b
Transistors:
Q404 2SA1306A-0 x
Q403 2SC3298B-Y x

Q453 2SC3298B-Y x
Q454 2SA1306A-0 x
Resistors:
R402 10 ohm 1/2 W fusible x
R403 10 ohm 1/2 W fusible x
R404 10 ohm 1/2 W fusible x
R405 10 ohm 1/2 W fusible x
R406 10 ohm 1/2 W fusible x
R407 10 ohm 1/2 W fusible x
R408 10 ohm 1/2 W fusible x
R410 10 ohm 1/2 W fusible x
R421 47 ohm 1/4 W carbon
R469 47 ohm 1/4 W carbon

R501 4.7k ohm 1/4 W carbon
12x metal plate 0.33 ohm resistor not all are gone, only the three for the output transistors that died, however the values are kinda off on some of them)
R411->R416
R466->R461
The x is for parts I have ordered replacements for already. I have not checked any fuses as I haven't found any yet...
DSC_1546.JPG
 
Last edited:
I made some mistakes on the previous list. Here is a corrected version.

Main board a


Transistors:
Q401 2SC3514-Q -> KSC3503 (Onsemi)
Q402 2SA1383-Q X -> KSA1381 (Onsemi)


Q308 2SA1360-0

Q309 2SA1383-Q X -> KSA1381 (Onsemi)

Q312 2SA1360-0


Diodes:
D311 hz3all X (maybe) -> BZX55C2V7
D312 hz3all X (maybe) -> BZX55C2V7


Resistors:
R316 100 ohm 1/2 W fusible
R401 1k ohm 1/2 W fusible

Main board b


Transistors:

Q404 2SA1306A-0 X -> MJE15033GOS (Onsemi)
Q403 2SC3298B-Y X -> MJE15032GOS (Onsemi)

Q405 2SA1492 X -> 2SA1492 (Sanken) and/or 2SA1943N (Toshiba)

Q407 2SA1492 X -> 2SA1492 (Sanken) and/or 2SA1943N (Toshiba)

Q410 2SC3856 X -> 2SC3856 (Sanken) and/or 2SC5200N (Toshiba)


Resistors:
R402 10 ohm 1/2 W fusible X
R403 10 ohm 1/2 W fusible X
R404 10 ohm 1/2 W fusible X
R405 10 ohm 1/2 W fusible X
R406 10 ohm 1/2 W fusible X
R407 10 ohm 1/2 W fusible X
R408 10 ohm 1/2 W fusible X
R410 10 ohm 1/2 W fusible X
R421 47 ohm 1/4 W carbon
R469 47 ohm 1/4 W carbon

R501 4.7k ohm 1/4 W carbon
12x metal plate 0.33 ohm resistor (not all are gone, only the three for the output transistors that died, however the values are kinda off on some of them)
R411->R416
R466->R461

I still need to find what would be a suitable replacement for the 2SA1360 which I believe pairs with the 2SC3423.
 
@madis64 I bought a ta-n80 that was working. I brought it home and calibrated it which went fine. I hooked it up in my set up and turned it on but did not get any sound. I eventually decided to connect the left channel to the fixed input while keeping the right channel on the variable input. I also disconnected the cable from the pre amp. When I did this the left channel started smoking and the amp went into protection. I disconnected everything opened it up and I have now found the given list of defective components. My questions are as follows:

What would have caused the amp blowing up? Would me screwing around with the input cable be able to short the amp ? I would normally expect such behavior from a speaker terminal short instead. I had the amp on idle for an hour without issues while it kept a stable bias.

Of the mentioned defective components there are quite a few that are no longer available in their original form. I have found some possible replacements from reading a bunch of ta-n80/77 repair threads but I would like some input on whether they are ok as replacements or not, specifically the zener diodes.

There are also a few components I have yet to find replacements for, tips regarding those would be great as well.

For the final question I would like some general advice. I am not sure what to do with testing. I would like to prevent more damage but the dim bulb tester I have uses a 60 Watt bulb. I also do not know whether some of the components I have tested are actually ok or not.
 
I brought it home and calibrated it which went fine. I hooked it up in my set up and turned it on but did not get any sound.
Ok, that is the first obvious problem and - aftersight is the biggest wisdom of all - you should have stopped there.
What happened next - as you describe - does not make much sense.
But since you now have an obviously blown amplifier at your hands then the path is as usual - download SM, check components, replace defective ones, power up under DBT, measure everything etc etc etc :)
But keep us posted step by step - in shorter jumps...
 
Fixed input seems to be DC coupled - you fed DC somehow into the amp?
I don't think so, I essentially connected a cable to it with nothing as the input but I do not believe that this could cause anything. I also checked my speaker connectors and there wasn't a short. Maybe the left speaker cable shorted to ground somehow? How would I do the DBT with this amp? I only have a 60 watt bulb, should I buy a larger one? Or will it just take longer to charge the capacitors at 60 watts. I have also since checked the pre amp and it is working ok so there not being any sound was indeed a bad sign in the first place and not me having set it up incorrectly.

I have already essentially checked all the components in the signal path except for some of the ceramic capacitors which I do not believe are a cause of concern. The broken components are the ones I have listed out earlier in the thread.
 
How would I do the DBT with this amp?
What exactly are your skills and technical capabilities - DBT, DMM, scope, soldering THT/SMD...?

The main problem is in your initial posting - you had no sound. Now you need to find a cause of that (in addition to the release of magic smoke).

Edit:
Can you upload some photos of the amplifier internals? Sometimes it helps to understand the playground.
 
What exactly are your skills and technical capabilities - DBT, DMM, scope, soldering THT/SMD...?
I am pretty good at soldering. I have repaired amps before but usually simpler designs from the 70s and it is also most definitely not my forte, I mainly work on record players. I do not know what THT is. I was able to calibrate the dc offset which to me indicates that a signal was going to the speaker terminals. I have some pictures of the boards but the amp is now in pieces so pictures of the internals might be difficult.

Before I changed the thermal paste for the transistors:

95edd996-e12f-4c44-8ed5-164676904ede.jpg
e392eb8f-4b13-418c-a6bf-5adce0d1d935.jpg


The two main boards after removing the broken components:
c8fae311-5da8-4b9c-adaf-ca0ae7223d27.jpg
fb9b737b-6626-4d77-825e-1c99b3b9e149.jpg


I believe that the amp has been repaired before. The driver transistors weren't all the same as the ones listed in the service manual and some of the resistors are different even if they are measuring correctly. The thermal paste was also still wet, so I cannot imagine that it has been long since it was last changed. There are some resistors, mainly next to the two relays on mainboard a and on the protection circuit that differ from the service manual. However since both channels have the same exact differing resistors I assume that the modification was made with intent and makes sense...
 
D312 HZ3A1L zener approx 2.5 - 2.7 V
UPA68 Dual N-Channel JFET
Check for the Idss by connecting the gate to the source (Vgs=0V), a 9V block battery and a mA meter (drain to plus, gate-source to minus).
As for the actual reason this happened, I am still not sure.
A faulty polar cap can take the amp down. Recapping might become neccessary.
Q401 2SC3514-Q
Q402 2SA1383-Q
pre drivers...
Q308 2SA1360-0
Q309 2SA1383-Q
VAS cascode...
Q312 2SA1360-0
Temp comp for bias...
D311 hz3all X(maybe)
D312 hz3all X(maybe)
Protection zeners...
Q404 2SA1306A-0 x
Q403 2SC3298B-Y x
Drivers...
Q405 2SA1492 X -> 2SA1492 (Sanken) and/or 2SA1943N (Toshiba)
Q407 2SA1492 X -> 2SA1492 (Sanken) and/or 2SA1943N (Toshiba)
Q410 2SC3856 X -> 2SC3856 (Sanken) and/or 2SC5200N (Toshiba)
Output...

RF... (#12)

Instability caused by...?
Check all polar caps and/or replace in advance - use tropical grade (105°).
Solderings, continuity, wires, connectors, &c.

You can use two bulbs of 60W in parallel for a suitable DBT.

A magnified & separated circuit diagram.
 

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Instability caused by...?
Check all polar caps and/or replace in advance - use tropical grade (105°).
Solderings, continuity, wires, connectors, &c.
Would you say that it is better to first recap it before testing? I would like to avoid changing too many things at once because if I make an error along the way it could be hard to figure out why what happened happened. Should I replace all the electrolytics? 2 60 watt bulb in parallel, ok will do thank you for the tip. Would you have any tips for what I should replace the 1360 transistors with? I read on a forum that you can bypass the 1360 in the bias circuit but I would like to prevent doing any mods before it is up and running again.
 
The image I posted in #14 has not the required detail due to the reduction of size...:(

Inspect the polar caps in advance of replacing them. Look for chaps with a bowler hat and/or swollen in size.
Corrosion on the pcb is also an indicator.

bypass the 1360 in the bias circuit
I would not recommend that, as this arrangement is a (fast) Sziklai video buffer in a bias application. Q313 is set at 1mA defined by R320, so Q312 takes the extra amount of current. This makes Q313 more sensitive to temp changes.
 
I would not recommend that, as this arrangement is a (fast) Sziklai video buffer in a bias application. Q313 is set at 1mA defined by R320, so Q312 takes the extra amount of current. This makes Q313 more sensitive to temp changes.
Thank you, I have now ordered the onsemi MJE350G as a replacement and the onsemi MJE340 for the complementary 2sc3423. I have ordered a bunch of spares as well.
 
Would you say that it is better to first recap it before testing? I would like to avoid changing too many things at once because if I make an error along the way it could be hard to figure out why what happened happened. Should I replace all the electrolytics?
I would first check all transistors and resistors (many of these are marked as fusible ones) in the power amp section starting from the back end and working towards the front (until the input stage). That would give you the scope of damage.
And then I would replace - without thinking twice - all lytics except the big ones.
 
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I would first check all transistors and resistors (many of these are marked as fusible ones) in the power amp section starting from the back end and working towards the front (until the input stage). That would give you the scope of damage.
And then I would replace - without thinking twice - all lytics except the big ones.
Thank you for the suggestion. I have done this and I have already ordered replacements with plenty of spares, wasn't cheap though, it is annoying that I could not find everything in one place but that is also kinda on me for not being patient enough with finding the proper modern substitutes. I will first replace the defective parts and attempt to turn the amp on with the DBT. If this is ok I will test it and if it tests ok I will probably replace the smeller ecaps like you suggest.
 
One thing I found is that
The main problem is in your initial posting - you had no sound. Now you need to find a cause of that (in addition to the release of magic smoke).
The mystery regarding the no sound has been solved. I just went up to check if there are any weird issues as I had not touched my setup since the amp had blown. Everything was ok no speaker wire shorts etc. So I grab my ta-4650 to use as a power amp with the e80es and wouldn't you know it, no sound. Turns out I had not pressed the output on button on the pre amp..................................................... So yeah that is the reason there was no sound.