[Maxx134]

You will have to check the headphone jacks in front for wiring issue.
It may even be something as simple as the single ended jack having the center right contact and the last contact (ground) reversed..

 

[baronbeehive]

You will have to check the headphone jacks in front for wiring issue.
It may even be something as simple as the single ended jack having the center right contact and the last contact (ground) reversed..

 
Just checked:
 
1 - Right hand headphone to right hand XLR output, brown has continuity to brown
2 - Right hand headphone to right hand XLR output, blue has continuity to blue
3 - Right hand headphone to right hand XLR output, blue has continuity to black (ground) - therefore short here.
4 - Right hand headphone to left hand XLR output, blue has continuity to black (ground) - because of short.
5 - Left hand headphone to left hand XLR output, brown has continuity to brown
6 - Left hand headphone to left hand XLR output, blue has continuity to blue
7 - Left hand headphone to left hand XLR output, black has continuity to black
8 - Left hand headphone to right hand XLR output, black has continuity to black
9 - Left hand headphone to right hand XLR output, black has continuity to blue - because of short.
 
All correct except nos. 3, 4, and 9.
 
This all appears to be down to the fact that the right hand ground, or black, wire hasn't been connected to the ground pin on the headphone jack because I didn't think that it was originally. Anyway, now to connect the ground wire and see what happens........!!

 

[baronbeehive]

You will have to check the headphone jacks in front for wiring issue.
It may even be something as simple as the single ended jack having the center right contact and the last contact (ground) reversed..

 
I haven't touched the SE jack.
 
Quote:

   
.........
This all appears to be down to the fact that the right hand ground, or black, wire hasn't been connected to the ground pin on the headphone jack because I didn't think that it was originally. Anyway, now to connect the ground wire and see what happens........!!

 
Well, I've done that and still got the problem!
 
It can't be the 3 core wiring which I've checked again and it can be seen visually whereas the 6 output wires can't be seen visually all the way. The problem is the continuity between XLR pin 1 - ground, and XLR pin 2, -ive, right hand side. The connections on the board look straightforward from the pics, just one connection to one of the tube pins. I haven't checked the ground wires because they are inaccessible. So what combination of negative wires or ground wires crossed could cause that?
 
Ground and -ive wires crossed possibly, or wrong connection at the tube pin which is not likely given that there is a similar connection on the left hand side and I didn't get that wrong. 
 
Or could the problem be back in the right hand middle circuit somewhere?

 

[Maxx134]

To find the location of the error,
you simply have to divide and separate the two sections...

first section is the board to the XLR ..
second section is the XLR to the front headphone Jack's..

so you simply disconnect and label wires at the XLR Jacks in the rear ..

Then test with those connections apart..

so you can find out if the short is on the side eminating from the board,

or the wires going to to the front...

Remember the wires are twisted so easy to mix up if not color coded..

the rear XLR are your midpoint to disconnect,
because they joined both board outputs and front jacks together ..

 

[baronbeehive]

The problem seems to be with the right hand -ive output which is going to ground. I disconnected the wires and its not that so there must be a short somewhere from the right hand -ive output tube pin.
 
Looks like I'm going to have to get the board out to see what's going on there

.

 

[Maxx134]

The problem seems to be with the right hand -ive output which is going to ground. I disconnected the wires and its not that so there must be a short somewhere from the right hand -ive output tube pin.

Looks like I'm going to have to get the board out to see what's going on there .

You tested each wire individually (separate) and other prob to chasis?

So are you say the wire from board negative wire grounded?

There is one positive tube(circuit) and one negative tube(circuit).

The tube that had the burnt resistor should be the wire but we tracing the location of the short by disconnecting the wires from the XLR jacks.

You only needed to do this on the side you had problems (right).

Anyways we cannot rule out that there could be a soldering mistake there.

The reason for testing wires is to locate the area of short so if the wire grounded is coming from the board side then ,
Before you pull out, recheck the soldering and connections on the resistor anode area.

 

[baronbeehive]

You tested each wire individually (separate) and other prob to chasis?

So are you say the wire from board negative wire grounded?

There is one positive tube(circuit) and one negative tube(circuit).

The tube that had the burnt resistor should be the wire but we tracing the location of the short by disconnecting the wires from the XLR jacks.

You only needed to do this on the side you had problems (right).

Anyways we cannot rule out that there could be a soldering mistake there.

The reason for testing wires is to locate the area of short so if the wire grounded is coming from the board side then ,
Before you pull out, recheck the soldering and connections on the resistor anode area.

 
I disconnected the ground and -ive output wires from the right hand XLR, these were the 2 wires that were showing continuity at the XLR when there shouldn't be continuity.
 
I then tested at the right hand XLR with the other probe at the +ive output connection on the board.:
 
1 - The +ive pin tested correctly. This output wire was left on because it was not causing the problem.
 
I then tested at the right hand XLR with the other probe at the -ive output connection on the board, the connection from pin 3 of the faulty tube circuit.
 
2 - The ground pin only showed continuity. This indicates that it wasn't the output wire causing it, because I had disconnected it. So the right hand -ive output connection from the board was obviously going to ground.
 
I then tested at the right hand ground XLR pin with the other probe at the chassis ground:
 
3 -  It showed continuity correctly and none of the other pins showed continuity which was correct.
 
I then tested the ground output wire at the XLR end with the other probe at the chassis ground. This wire I had disconnected:
 
4 - It showed continuity correctly showing ground.
 
Then I tested the right hand -ive output wire at the XLR end with the other probe at the chassis ground. This wire I had disconnected:
 
5 - It showed continuity indicating a short somewhere before, or at the board -ive output connection.
 
Then I tested the disconnected right hand -ive output wire at the XLR end with the other probe at the -ive output connection on the board:
 
6 - It showed continuity which is what you would expect in a correct circuit but....
 
Then I tested the distconnected right hand ground wire at the XLR end with the other probe at the -ive output connection on the board:
 
7 - It also showed continuity indicating that the -ive wire was grounded.
 
Not much point checking the soldering around the anode resistor because it melts every time I switch on due to the power draining out. But this was a pre-existing problem, it was not the soldering that caused it. The other connections look good.
 
Edit:
 
I also tested the suspect right hand circuit tube pins 3 and  5 with the other probe at chassis ground, and both pins were grounded which was incorrect.
 
These results taken with the tests on the bad circuit continuity I did on the last page indicating continuity on many parts of the bad circuit which should not have been the case, I believe indicate that somewhere on the circuit on the board is the problem, not in the wiring. That could explain the incorrect continuity readings in the bad circuit that I found during testing.

 

[Maxx134]

I believe pins 3&5 go together in WCF circuit, and so should read same.

The question is if the output wire from that board was connected when you performed that continuity test.
The output wire from board needed to be disconnected at the XLR.

You have a grounded output but maybe only grounded for the instance of the time it take the big coupling cap to charge.
That is, if the big coupling cap is improperly connected at wrong side of the resistor..

Compare that big coupling cap connection point to the others.

Also verify the output wire from board is disconnected at XLR when doing checking those pins 3&5.

 

[baronbeehive]

I believe pins 3&5 go together in WCF circuit, and so should read same.

The question is if the output wire from that board was connected when you performed that continuity test.
The output wire from board needed to be disconnected at the XLR.

You have a grounded output but maybe only grounded for the instance of the time it take the big coupling cap to charge.
That is, if the big coupling cap is improperly connected at wrong side of the resistor..

Compare that big coupling cap connection point to the others.

Also verify the output wire from board is disconnected at XLR when doing checking those pins 3&5.

 
Yes there is continuity between pins 3 and 5 in the good circuits.
 
Yes I disconnected the ground and -ive wires from the XLR's when I did the continuity test.
 
So to check the connections around the cap, which big coupling cap do you mean?
 
So to sum up, it can't be a wiring problem because I disconnected those -ive and ground wires and then tested at the XLR's.
 
Therefore I think I'm right in saying that somewhere on the bad circuit is a short, or bad connection and that would explain all the false continuity readings that I was getting on the bad circuit only. I've looked at some of these readings and I can't see what could be shorting without actually looking on the reverse side. For example the only possible thing may be a wrong connection of the -ive wire at the wrong tube pin indicated by continuity between pins 5 and 6, but I can't think of anything else. Nothing seems to be physically close enough to cause a short.
 
I've discounted the opamps for the moment because the grounding issue looks more likely.
 
So I think I need to look somewhere around grid pin 1. This had a wrong reading of  -0.6v, measured from ground to pin1. Also the anode resistor, which had a wrong reading of  44.3v. All other voltage readings were good.
 
So how would I find the exact location of the short?
Do I need to take more voltage readings?
Will capacitance readings tell me anything?

 

[Maxx134]

So to check the connections around the cap, which big coupling cap do you mean?
....

So how would I find the exact location of the short?
Do I need to take more voltage readings?
Will capacitance readings tell me anything?

The wire soldered to the negative pin must be touching ground if your reading ground.
You reading ground on the pins.
Leave meter on it and see if the value changes.
If it stays near zero there is a ground connection, as the amp it not on so the grid can't control that.

Disconnect any tube AND tube socket .
Extra Tube sockets are known to short.

Test again those pins without tube to verify it is the connection.

Also,
I was talking about the huge Decoupling cap.
It's the only "large" one there, and supposed to be connected as in pic.

If the cap was connected on wrong end of resistors (either end - anode resistor or cathode resistor)
Then you would initially see ground, but value would change as cap charges.

Anyways, just a visual look at the big caps (47uf I think you have)
Would easily tell you if one Cap is misplaced.

 

[baronbeehive]

The wire soldered to the negative pin must be touching ground if your reading ground.
You reading ground on the pins.
Leave meter on it and see if the value changes.
If it stays near zero there is a ground connection, as the amp it not on so the grid can't control that.

Disconnect any tube AND tube socket .
Extra Tube sockets are known to short.

Test again those pins without tube to verify it is the connection.

Also,
I was talking about the huge Decoupling cap.
It's the only "large" one there, and supposed to be connected as in pic.

If the cap was connected on wrong end of resistors (either end - anode resistor or cathode resistor)
Then you would initially see ground, but value would change as cap charges.

Anyways, just a visual look at the big caps (47uf I think you have)
Would easily tell you if one Cap is misplaced.

Yes.......
 
I'm reading ground on the ground pin with other probe on negative output on board with wire disconnected, which indicates short around that negative connection somewhere.
 
I'm also reading ground on the end of the disconnected negative wire with other probe on ground with wire disconnected which indicates short around that negative connection somewhere.
 
I'm also reading ground on the end of the disconnected ground wire at the XLR end with the other probe at the -ive output connection on the board which indicates short around that negative connection somewhere.
 
The meter stays at or near zero.
 
I've removed the tubes so the readings are with them out.
 
All decoupling caps are connected at the same ends of the resistors, therefore if it was that it could only be the solder joint.

 

[Maxx134]

Have you doubled up on the wiring?
If so maybe make sure they not mixed/crossed.

 

[baronbeehive]

Have you doubled up on the wiring?
If so maybe make sure they not mixed/crossed.

 
No.
 
Looks like I will have to take the board out and you think that whatever is wrong should be able to be traced fairly easily?
 
If I do have to take the board out, do I need to do any more tests first?

 

[baronbeehive]

The wire soldered to the negative pin must be touching ground if your reading ground.
................

 
Not sure because...........
 

   
 
...........
 
Then I tested the disconnected right hand -ive output wire at the XLR end with the other probe at the -ive output connection on the board:
 
6 - It showed continuity which is what you would expect in a correct circuit but....
.........

Therefore it is connected to the -ive output on the board. How can it be connected correctly to the board at that end and connected correctly to the XLR end as well yet be shorting out. Possible I suppose but I think it must be something else in the circuit.

 

[Maxx134]

If you pushed your leads of caps or resistors or the wire in the board too far they will extend and touch the metal surfaces on other side such as frame or screws .
Especially when you insert wires soldering they will slip in far if not Careful.

Something is creating contact,
But just to have continuity from one side to the other (board to XLR end) should not be confused with continuity from any point of testing, to the metal frame (ground)..