YAMAHA A-S701 - tear-down, thoughts about the internals & few measurements

[restorer-john]

The banana plug terminals (threads) are pretty poor quality actually. I may have a donor set here, depending on what the owner (my friend) wants to do with his RN-602 that has died.

Personally, I'd just use bananas into the sockets and be done with it.

 

[Roland68]

Michel binding posts/banana sockets used to be popular after-market replacements. I don't know if the connection is any better, but they do look nice (if that matters). <https://www.turntableworld.co.uk/ca...hell-big-mother-binding-posts-pack-of-4-p3523>

Of course you can do that and the quality is more than sufficient, but I would never use uninsulated binding post terminals on an amplifier, too much can happen.
I once saw someone blindly trying to plug in an RCA cable and the plug ended up in the uninsulated speaker terminals. Nice cloud of smoke...

Such insulated brass binding posts cost €5 - €15 for 4 pieces.

 

[bboris77]

The banana plug terminals (threads) are pretty poor quality actually. I may have a donor set here, depending on what the owner (my friend) wants to do with his RN-602 that has died.

Personally, I'd just use bananas into the sockets and be done with it.

Sorry for my ignorance, but is it ok to use banana plugs on a binding post that cannot be screwed down tightly? I would assume that the contact surface would not be as great if one was to use a banana plug without tightening the binding post first.

Here is a video of the issue:

 

[DSJR]

The strength of the terminal may be compromised if the outer part cannot be screwed down and a banana plug is accidentally tugged sideways.

Is it just the UK and maybe Europe later on after the low rated DIN plug went out of fashion, that has uses 4mm plugs as standard (BFA version or otherwise?) for very many decades now, starting I believe with the Quad II valve amps and maybe others of that time? So many customers using bare wires used to have ONE STRAND of speaker cable floating free and risking a short circuit, but in normal use, we never had an issue with banana plugs.

 

[Doodski]

The strength of the terminal may be compromised if the outer part cannot be screwed down and a banana plug is accidentally tugged sideways.

Is it just the UK and maybe Europe later on after the low rated DIN plug went out of fashion, that has uses 4mm plugs as standard (BFA version or otherwise?) for very many decades now, starting I believe with the Quad II valve amps and maybe others of that time? So many customers using bare wires used to have ONE STRAND of speaker cable floating free and risking a short circuit, but in normal use, we never had an issue with banana plugs.

Yes, all of the above I think applies.

The thing about attempting to use standard banana jacks is that the hole in the back of the case sheet metal is much larger than a standard banana jack has? I think it is. Take a close look at the video and you'll what I mean. The steel has been punched out to a large diameter hole.

 

[Roland68]

Sorry for my ignorance, but is it ok to use banana plugs on a binding post that cannot be screwed down tightly? I would assume that the contact surface would not be as great if one was to use a banana plug without tightening the binding post first.

Here is a video of the issue:

This depends on whether the plug contact for the 4mm banana plugs is in the rotating part or in the fixed inner part. There are both options.
If it is in the rotating part, you have unfortunately lost.
Addendum:
If the plug contact is in the inner part, it doesn't matter.

 

[AudioSceptic]

Of course you can do that and the quality is more than sufficient, but I would never use uninsulated binding post terminals on an amplifier, too much can happen.
I once saw someone blindly trying to plug in an RCA cable and the plug ended up in the uninsulated speaker terminals. Nice cloud of smoke...

Such insulated brass binding posts cost €5 - €15 for 4 pieces.
View attachment 358902View attachment 358903

Good point, but the same current & voltage is present there as on speakers. Better to be safe, though.

 

[AudioSceptic]

Sorry for my ignorance, but is it ok to use banana plugs on a binding post that cannot be screwed down tightly? I would assume that the contact surface would not be as great if one was to use a banana plug without tightening the binding post first.

Here is a video of the issue:

That definitely needs replacing.

 

[AudioSceptic]

The strength of the terminal may be compromised if the outer part cannot be screwed down and a banana plug is accidentally tugged sideways.

Is it just the UK and maybe Europe later on after the low rated DIN plug went out of fashion, that has uses 4mm plugs as standard (BFA version or otherwise?) for very many decades now, starting I believe with the Quad II valve amps and maybe others of that time? So many customers using bare wires used to have ONE STRAND of speaker cable floating free and risking a short circuit, but in normal use, we never had an issue with banana plugs.

I'd forgotten about BFA and also Speakon. Much safer and I'd use those if they fit. I never liked bare wires and screw-down terminals. Apart from the shorting risk, they tend to loosen over time.

 

[Doodski]

I'll post this again.>>>

The thing about attempting to use standard banana jacks is that the hole in the back of the case sheet metal is much larger than a standard banana jack has.
I think it is.
Take a close look at the video and you'll see what I mean.
The steel has been punched out to a large diameter hole.
Look very closely and it can be seen that the hole punched in the steel is as big as the big part of the banana jack.
Cannot fit regular banana jacks on that steel plate.

 

[AudioSceptic]

Yes, all of the above I think applies.

The thing about attempting to use standard banana jacks is that the hole in the back of the case sheet metal is much larger than a standard banana jack has? I think it is. Take a close look at the video and you'll what I mean. The steel has been punched out to a large diameter hole.

I suppose you could use washers but it wouldn't be ideal. Would a Speakon be a better fit?

 

[Doodski]

I suppose you could use washers but it wouldn't be ideal. Would a Speakon be a better fit?

Very good question and it would be such a upgrade.
Here are details on the fit clearances and steel back plate on the Yamaha.
One can see the large black plastic block that the bananas mount on and the tiny bit of gold plated wire leads that solder to the circuit board.
There might be enough clearance inside the Yamaha but that is not clear.
Refer to image and diagrams for indication of what clearance might be available.

 

[AudioSceptic]

Very good question and it would be such a upgrade.
Here are details on the fit clearances and steel back plate on the Yamaha.
One can see the large black plastic block that the bananas mount on and the tiny bit of gold plated wire leads that solder to the circuit board.
There might be enough clearance inside the Yamaha but that is not clear.
Refer to image and diagrams for indication of what clearance might be available.
View attachment 358971
View attachment 358972
View attachment 358973

I've never seen a Speakon in person but it looks like they might a bit large. In any case they would need a fair bit of bodging. <https://en.wikipedia.org/wiki/Speakon_connector>

 

[bboris77]

That definitely needs replacing.

The question now is where I can purchase this TE102 module from? Part number seems to be either WU987400 or WU987600 according to the service manual. I’m hoping that consumers can buy these parts. Replacing it seems fairly trivial in terms of disassembly and soldering.

I would much rather use the original part rather than trying to frankenstein something Ill fitting in there.

 

[Doodski]

The question now is where I can purchase this TE102 module from? Part number seems to be either WU987400 or WU987600 according to the service manual. I’m hoping that consumers can buy these parts. Replacing it seems fairly trivial in terms of disassembly and soldering.

I would much rather use the original part rather than trying to frankenstein something Ill fitting in there.

It will be a combination of 1- TE102 plus 1-TE101. Not a quantity of 2-TE102. There must be a difference between the part IDs at the exploded diagram otherwise they would simply name them as being the same. Be cautious because they do make parts that could be apparently identical but come as different.

Yes, MODing the back plate would be intensive. The steel is soft and not easily worked while keeping it straight and attractive for future use.

Try the country you are in for Yamaha parts. Contact the service department or the parts department and ask if they will sell to the end user.

You might get lucky and get used parts from @restorer-john if the unit he is working on for a friend is deemed for parts only.

 

[restorer-john]

It will be a combination of 1- TE102 plus 1-TE101. Not a quantity of 2-TE102. There must be a difference between the part IDs at the exploded diagram otherwise they would simply name them as being the same.

One is left, the other is right. (note the positions of the red vs blk).

 

[Doodski]

One is left, the other is right. (note the positions of the red vs blk).

Yes, and the PCB thru-holes are spaced differently too.

 

[bboris77]

So, some good news. Yamaha Canada is willing to sell me the part for about $35 including shipping. They are saying that the correct part is WU987400.

The part is not stocked so it may take up to 5 weeks but I’m ok with that. The replacement process should be fairly easy but I would appreciate any advice from the experienced repair people here who may have performed this replacement before.

 

[Doodski]

So, some good news. Yamaha Canada is willing to sell me the part for about $35 including shipping. They are saying that the correct part is WU987400.

The part is not stocked so it may take up to 5 weeks but I’m ok with that. The replacement process should be fairly easy but I would appreciate any advice from the experienced repair people here who may have performed this replacement before.

I vaguely remember a Yamaha with bad binding posts. That's why I was suspect about the diameter size of the holes in the rear panel sheet metal. Otherwise...

Is Yamaha Canada sure it is a 1 piece part?
Because the diagram shows it is a 2 piece assembly.

The unit will need to be disassembled into bits and pieces so that you may access the Amplifier PCB underside where the soldering will take place.
So...

You need to remove:
- top cover.
- the back panel steel sheet metal piece.
- the smaller PCB above the amp PCB.
- the amplifier PCB take it out of the chassis.

That's roughly the procedure.

Keep in mind that the connectors are usually all different sizes and types although sometimes there are duplicates. That can make life difficult. So take lots of pictures to reference to and use a Sharpie felt pen to make a slash across the connector before pulling them apart. The odds of the slashes being identical on multiple connectors is near zero and so this is a good method for identifying the proper place to plug them together. Just a little slash with the felt pen and not huge.

... and then you can work the binding posts and remove them and resolder in new ones. Don't take shortcuts and try to bend the amp PCB while it is in the chassis and attempt to access the PCB solder points. That will maybe break stuff, cause a short on the PCB due to poor soldering due to poor visibility when soldering.

and... Enjoy yourself... Don't get stressed out and make a mistake.

 

[bboris77]

I vaguely remember a Yamaha with bad binding posts. That's why I was suspect about the diameter size of the holes in the rear panel sheet metal. Otherwise...

Is Yamaha Canada sure it is a 1 piece part?
Because the diagram shows it is a 2 piece assembly.

The unit will need to be disassembled into bits and pieces so that you may access the Amplifier PCB underside where the soldering will take place.
So...

You need to remove:
- top cover.
- the back panel steel sheet metal piece.
- the smaller PCB above the amp PCB.
- the amplifier PCB take it out of the chassis.

That's roughly the procedure.

Keep in mind that the connectors are usually all different sizes and types although sometimes there are duplicates. That can make life difficult. So take lots of pictures to reference to and use a Sharpie felt pen to make a slash across the connector before pulling them apart. The odds of the slashes being identical on multiple connectors is near zero and so this is a good method for identifying the proper place to plug them together. Just a little slash with the felt pen and not huge.

... and then you can work the binding posts and remove them and resolder in new ones. Don't take shortcuts and try to bend the amp PCB while it is in the chassis and attempt to access the PCB solder points. That will maybe break stuff, cause a short on the PCB due to poor soldering due to poor visibility when soldering.

and... Enjoy yourself... Don't get stressed out and make a mistake.

When you say 2 piece assembly - do you mean two different binding post modules with 4 posts each? Because, the one for the right speaker is working perfectly fine. I only need the one for the left speaker (which is on the right side lol). Unless you mean the 4-post module comes in two parts. What would the other part number be?