The case of the possessed Sony TA-N77ES

[Nick89rs]

Hello!

Im reaching out for a little help here if its available. I came into possession of a Sony TA-N77ES a couple of months ago that was supposedly in working condition and "recently serviced"

Whomever serviced the amp clearly forgot to wave sage or something over this amp because it seems to be possessed.

On unboxing the amp it appears to be in immaculate condition. Excitedly I hook up my trusty Yamaha CX-800 preamp and start to stream a little music. The left channel is dead. No sound, no meter bouncing, nothing. I think to myself well crap, is has been a while since i used that preamp ill go grab the one from another setup and try that. I hook up my Yamaha C-45 and the same thing, dead left channel. frustrated i power everything off and go to sulk for a moment.

An hour or so later i try again, and this time everything works perfect. The amp powers right up i start playing some music from a tape and life is good! ....for about 10 mins then the left channel output goes to almost nothing with some...i dont know if i should call it distortion or popping or cracking from the left channel. I try hooking a CD player to the variable input. Same result.


I decided it was time to have the amp looked at by a pro. The trouble is i live in Maine...any of you familiar with Maine will know that there is nothing and no one here, its like me and 5 other people and a bunch of trees. So after locating one of the very few folks who still work on this stuff and driving 2 hours to drop it off its going to be repaired. Not the ideal start but hey at least itll be fixed.

A month later i get a call. The very nice gentleman cant get it to do anything wrong. He holds onto it for a few days and tells me to come get it. I show up and sure enough its been running steady into a dummy load and is just amplifying its little heart out.

I take this thing home and on the two hour ride we have a talk. I explain that ive been waiting a long time to own it and id really appreciate if this was the end of this little spat. The amp did not respond, it just sat there belted in and silent for the entire ride.

Sure enough once hooked up back at my house same exact problem. Sometimes it plays fine for hours after a power cycle, sometimes the channel is just dead, other times it plays at a very low output and distorted compared to the right.

Id like some help trying to fix it. I have a multi meter and i know its basic functions. Im also armed with good soldering iron and im decent with it. Im willing to buy a oscilloscope or anything else i need to beat this boss. I have a rudimentary understanding of circuits, i can point to parts and name them, a few i can even tell you what they do but i cant read a schematic and tell you what to do or where to look next and dont know the first thing about where or how to start troubleshooting this issue. If any of you are familiar with this amp or want to see someone new and motivated take their first steps into vintage audio repair id love the help.

Thanks,

Nick

 

[dr*audio]

The first thing to look at is the speaker relay. This is often overlooked and requires no test equipment to test it. Open the amp up, connect it to speakers and run some music through it at low level. Identify the speaker relay. It's a little plastic box about 1 1/2" on a side. Tap on the relay with a non metallic probe, like a Bic pen. If either channel cuts out, the relay must be replaced. Digikey stocks power relays. On the case of the relay is the part number and the specs; coil voltage and contact rating, in Amps. That's what you need to find a replacement. If it's mounted on a PC board you have to find one with the same pinout and spacing.

 

[spicer]

Hello!

Im reaching out for a little help here if its available. I came into possession of a Sony TA-N77ES a couple of months ago that was supposedly in working condition and "recently serviced"

Whomever serviced the amp clearly forgot to wave sage or something over this amp because it seems to be possessed.

On unboxing the amp it appears to be in immaculate condition. Excitedly I hook up my trusty Yamaha CX-800 preamp and start to stream a little music. The left channel is dead. No sound, no meter bouncing, nothing. I think to myself well crap, is has been a while since i used that preamp ill go grab the one from another setup and try that. I hook up my Yamaha C-45 and the same thing, dead left channel. frustrated i power everything off and go to sulk for a moment.

An hour or so later i try again, and this time everything works perfect. The amp powers right up i start playing some music from a tape and life is good! ....for about 10 mins then the left channel output goes to almost nothing with some...i dont know if i should call it distortion or popping or cracking from the left channel. I try hooking a CD player to the variable input. Same result.


I decided it was time to have the amp looked at by a pro. The trouble is i live in Maine...any of you familiar with Maine will know that there is nothing and no one here, its like me and 5 other people and a bunch of trees. So after locating one of the very few folks who still work on this stuff and driving 2 hours to drop it off its going to be repaired. Not the ideal start but hey at least itll be fixed.

A month later i get a call. The very nice gentleman cant get it to do anything wrong. He holds onto it for a few days and tells me to come get it. I show up and sure enough its been running steady into a dummy load and is just amplifying its little heart out.

I take this thing home and on the two hour ride we have a talk. I explain that ive been waiting a long time to own it and id really appreciate if this was the end of this little spat. The amp did not respond, it just sat there belted in and silent for the entire ride.

Sure enough once hooked up back at my house same exact problem. Sometimes it plays fine for hours after a power cycle, sometimes the channel is just dead, other times it plays at a very low output and distorted compared to the right.

Id like some help trying to fix it. I have a multi meter and i know its basic functions. Im also armed with good soldering iron and im decent with it. Im willing to buy a oscilloscope or anything else i need to beat this boss. I have a rudimentary understanding of circuits, i can point to parts and name them, a few i can even tell you what they do but i cant read a schematic and tell you what to do or where to look next and dont know the first thing about where or how to start troubleshooting this issue. If any of you are familiar with this amp or want to see someone new and motivated take their first steps into vintage audio repair id love the help.

Thanks,

Nick

When the channel is not working does the power meter still work, show output. If so I would suspect the protection relay, intermittent contacts, when going bad they sometimes, often have that symptom. If the power meter is not showing output probably not the relay. I would bet on a bad connection, bad solder joint, they show those symptoms too, often. If I had it on the bench and it acted up first thing I would do is give the unit a mechanical shock, pick it up in front and let it down with a bit of thump, see if the channel returns. You should have the schematic and though a digital VOM can be used a scope would be most useful probing for signal loss.

 

[Nick89rs]

When the channel is not working does the power meter still work, show output. If so I would suspect the protection relay, intermittent contacts, when going bad they sometimes, often have that symptom. If the power meter is not showing output probably not the relay. I would bet on a bad connection, bad solder joint, they show those symptoms too, often. If I had it on the bench and it acted up first thing I would do is give the unit a mechanical shock, pick it up in front and let it down with a bit of thump, see if the channel returns. You should have the schematic and though a digital VOM can be used a scope would be most useful probing for signal loss.

When the channel is on the fritz the meter is also showing low/no output to match what im hearing. I took the pannels off the machine last night. top sides and bottom. I will try to give it a bit of a drop and see if that does anything once im home from work.

 

[Nick89rs]

The first thing to look at is the speaker relay. This is often overlooked and requires no test equipment to test it. Open the amp up, connect it to speakers and run some music through it at low level. Identify the speaker relay. It's a little plastic box about 1 1/2" on a side. Tap on the relay with a non metallic probe, like a Bic pen. If either channel cuts out, the relay must be replaced. Digikey stocks power relays. On the case of the relay is the part number and the specs; coil voltage and contact rating, in Amps. That's what you need to find a replacement. If it's mounted on a PC board you have to find one with the same pinout and spacing.

i had posed this theory after some time googling the symptoms to the gentleman working on the amp. His conclusion was that if the meter was also effected it could not be the relay. Im not sure if thats true or not just letting you know i had been given conflicting information. Regardless i will try giving it a tap tonight if i can locate it inside the amp without taking things further apart. Replacement relays for the amp are available from Germany from a company that makes ones specific to the N77ES. It will take some time to get here but i feel like if this is my forever amp its worth having them on hand even if they arent bad this second.

 

[spicer]

When the channel is on the fritz the meter is also showing low/no output to match what im hearing. I took the pannels off the machine last night. top sides and bottom. I will try to give it a bit of a drop and see if that does anything once im home from work.

The meter showing no or low output pretty much eliminates the protection relay, not looking at the schematic but usually the case. Next thing one might do when not working is flex the boards a bit, looking for bad solder joint or connection. Next thing would be signal tracing following the schematic probing with a scope, possibly VOM. Isolating the problem to a board is the objective with an intermittent. It is possible there is a component failure somewhere in the signal chain.

 

[spicer]

i had posed this theory after some time googling the symptoms to the gentleman working on the amp. His conclusion was that if the meter was also effected it could not be the relay. Im not sure if thats true or not just letting you know i had been given conflicting information. Regardless i will try giving it a tap tonight if i can locate it inside the amp without taking things further apart. Replacement relays for the amp are available from Germany from a company that makes ones specific to the N77ES. It will take some time to get here but i feel like if this is my forever amp its worth having them on hand even if they arent bad this second.

I agree with the gentleman.

 

[dr*audio]

I looked at the schematic and the meters do come before the speaker relay, so if the meter shows no output, it's not the relay.
Are you using the fixed or variable input? Whichever you are using you might try the other ones.
There is a switch between the 2 sets of inputs. Could be dirty. Might have been overlooked. Try working the switch when the channel drops out, see if it comes back. Do it at a low level so the sudden burst of input doesn't make it start working, in case the problem is elsewhere.

 

[Nick89rs]

I looked at the schematic and the meters do come before the speaker relay, so if the meter shows no output, it's not the relay.
Are you using the fixed or variable input? Whichever you are using you might try the other ones.
There is a switch between the 2 sets of inputs. Could be dirty. Might have been overlooked. Try working the switch when the channel drops out, see if it comes back. Do it at a low level so the sudden burst of input doesn't make it start working, in case the problem is elsewhere.

I worked the switch a little and tried to get some deoxit into it, its a tough reach but im confident i at least scared it some with the stuff. No appreciable change from that. I took some pictures of the insides tonight, id really like to inspect for cold solder joints before i buy a scope, im just nervous about the hows and whens of disassembling this thing because it seems like most of what i want to see is going to require a pretty extensive disassembly that im worried im going to screw up.

Ill post the picture here in just a few. LOTS of transistors on the underside and i know they can be a culprit of cold joints but i didnt see anything obvious with my untrained eye.

 

[Nick89rs]

Underside.

 

[Nick89rs]

Power board? And top side.

 

[dr*audio]

If it's a bad solder joint it's not going to be on a power transistor on the output. There are several in parallel and it would take bad solder joints on multiple transistors to lose output like this. It could be a bad solder joint on the input connector on the driver board, or even a bad crimp on the wire. You can try carefully probing the wires on the input connector on the board. I can look at the schematic and tell you which one.

 

[dr*audio]

I think I know what it is. Find these 2 relays, RY301 and RY302 and tap on them.

 

[Nick89rs]

Ok, I found them. I can't test tonight because I'm past the hours where I can make noise in my workshop. I will give it a go tomorrow. Thank you for helping with this.

 

[Nick89rs]

Alright sportsfans, we have some progress. So a few observations from tinkering this morning. Tapping (even pretty harsh tapping) on those relays did not seem to make much of a difference, I thought at one point maybe it worked but it was at a point where I hit it VERY hard and it was only for a second.

When switching to mono both channels exhibit the very distorted and low volume play with matching meters. I just discovered this today and thought it was maybe noteworthy.

However I did make a exciting discovery. I went on a tapping mission and found that if I apply a decent amount of kinetic persuasion to this area of the heatsink the amp plays clean and beautifully for a while before returning to a dead or distorted left channel. This is the area the power board that those relays attach to.

 

[PE9ZZ]

Switching to mono just makes R_Ch to invert L_Ch so when that is bad it will be bad as well. Does LED D309 change brightness when the fault is present? Do voltages change? What does your scope show? If you have one that is. It will be essential in figuring out what's wrong here. The circuit itself is pretty simple. I've seen those double transistors (Q304) go bad, that could cause your issue. Flexing the board might fix them temporarily. Otherwise bad solder joints, cracks, yada yada. The meters are indeed before the speaker relays. Glued the schematic as I don't like to have them cut into pieces.

 

[dr*audio]

I think that the relays are just too far gone. If you had a scope you could probe that area and prove there is no signal after the relay.

 

[PE9ZZ]

Disagree. He tapped the relays like there's no tomorrow and it made no difference. I do suspect Q301. I've had several bad 2SK109s. This is another type (K244) but still. I do agree that this is the moment to get a scope and start probing away.

 

[Nick89rs]

ok, so i guess its time for a scope recommendation based on what both of you are saying. I had been looking at a DHO802. Is that an ok place to start? Please keep in mind ive only ever seen these things used on youtube, this will be the first time im ever putting my mitts on anything of the sort.

 

[PE9ZZ]

I'm not a big fan of Rigol, or Rochel (booger) as some say here in the Low Lands. I have a spectrum analyzer from them. The device itself is nice, the support software (Ultra somesuch - oh, Sigma) utter crap. But you don't need that for tasks like this. All these digital wonder boxes have a steep learning curve, you really must plow through a lot of YT tutorial videos. I have a Siglent SDS-1202 and it took me many months to stop worrying and start to love it. But now I do, I rarely touch my CRT scope (PM3055) anymore. But I will not abandon it. For some purposes the digital conversion is just an obstacle. But for simple scoping tasks inside this amp it should me more than adequate. Once you grok the basics you can use it to understand what's happening in this amp. And share screenshots like I do as well.