[baronbeehive]

  Are you saying there is continuity between 6 and ground? How are you measuring ground?

 
Yes, there are 2 separate things:
 
1 - continuity with ground with each of pins 3, 5 and 6 ie. each is grounded
2 - continuity between pins 3, 5 and 6 in whatever order ie each is connected with each of the others
 
I'm measuring ground by putting one probe in a screw hole in the chassis, or when the board is in, by putting it in a screw hole or in one of the 2 big holes near the PSU caps. The other probe touching the tube pins in turn.
 
BTW coin, I'm going out tomorrow to get the opamp extractor tool.
 
BTW Maxx, the engineer said that he didn't like all of the bunch of wires going in the small hole to the transformer, very tight fit and the hole has sharp edge.

 

[coinmaster]

If 3/5/6 is showing continuity with ground and there are no visual indicators  you may have damaged the board and shorted the pins to the ground plane as I did with mine. 

 

[baronbeehive]

  If 3/5/6 is showing continuity with ground and there are no visual indicators  you may have damaged the board and shorted the pins to the ground plane as I did with mine. 

 
Yes, that's why I was concerned about the pads, but the engineer did repair those. Is there any way of testing to find that out, by for example testing at different points along the plane?
 
One thing puzzles me, that is the intermittent nature of some of the test readings which has made testing quite tricky. For example when testing pins 3 and 5 to ground they give off continuous signals but when testing pin 6 it only gives a bleep of a few seconds before stopping and then will not give a reading again unless I reverse the probes. It looks like the short of whatever it is is only intermittent. I don't understand things like the direction of the current through the circuit but I know that diodes only allow current through one way only for example.
 
But to be sure I didn't make a mistake I made sure I repeated the tests several times until I was satisfied they were consistent.

 

[coinmaster]

 but when testing pin 6 it only gives a bleep of a few seconds before stopping and then will not give a reading again unless I reverse the probes.

That's what happens when u test continuity across a capacitor. You are charging the plates of the capacitor and they will not respond once fully charged unless the polarity is reversed. This means the B- connection is where the ground issue is which could be anywhere between the bottom of the cathode resistor to a bunch of places in the power supply. Although this would mean the fuse would trip after the relays kicked in so unless you broke it since u last had it on I'm not so sure. Check the bottom of the cathode resistor for continuity to ground.
 
 
As for 5 and 6 check the 2k resistor by the opamp.

 

[colliedoggy]

 
BTW coin, I'm going out tomorrow to get the opamp extractor tool.
 
 

Wait!
 
It just occurred to me that each op amp is adjusted for offset by its trimmer capacitor, which is the blue box nearby with the small screw on top of it. 
 
Whenever you change the position of one of the op amps, the op amp offset ought to be corrected for by adjusting the trimmer potentiometer (the blue box with the screw on top). 
 
Do you understand how that works?
 
( At the very least please label each IC so that you know which position it came from in the first place.) 

 

[colliedoggy]

I would like to point out at this time for the importance and necessity and cooling the amp not because of the tubes,
but mainly and specifically because of the Transformers winding for the driver stage...

If you look at the Transformer schematic (posted in thread), you will see that the winding for the driver Stage is the weakest link..

 

I finally found the Transformer schematic which was posted by SonicTrance in post #1621 on page 109 of this thread.
 
Are the same transformers used in the mk viii se?
 
Thanks

 

[Maxx134]

 
Are you saying there is continuity between 6 and ground? How are you measuring ground?

Yes, there are 2 separate things:

1 - continuity with ground with each of pins 3, 5 and 6 ie. each is grounded
2 - continuity between pins 3, 5 and 6 in whatever order ie each is connected with each of the others

I'm measuring ground by putting one probe in a screw hole in the chassis, or when the board is in, by putting it in a screw hole or in one of the 2 big holes near the PSU caps. The other probe touching the tube pins in turn.

BTW coin, I'm going out tomorrow to get the opamp extractor tool.

BTW Maxx, the engineer said that he didn't like all of the bunch of wires going in the small hole to the transformer, very tight fit and the hole has sharp edge.

BTW coin, I'm going out tomorrow to get the opamp extractor tool.

Wait!

It just occurred to me that each op amp is adjusted for offset by its trimmer capacitor, which is the blue box nearby with the small screw on top of it. 

Whenever you change the position of one of the op amps, the op amp offset ought to be corrected for by adjusting the trimmer capacitor. 

Do you understand how that works?

( At the very least please label each IC so that you know which position it came from in the first place.) 

Correct...
Forget swapping opamp.
Each pot is adjusted individually for each opamp.
So if you swap, You WILL get a DC offset resulting in a tiny pop sound when plugging in the headphones.
Also, marking the pots is useless because these trim pots have MANY turns...



Also, Coin is right, Baron does not have a problem with pin 6.

I would like to point out at this time for the importance and necessity and cooling the amp not because of the tubes,

but mainly and specifically because of the Transformers winding for the driver stage...


If you look at the Transformer schematic (posted in thread), you will see that the winding for the driver Stage is the weakest link..


 

I finally found the Transformer schematic which was posted by SonicTrance in post #1621 on page 109 of this thread.


Are the same transformers used in the mk viii se?

Thanks

You are right again...

 

[coinmaster]

The trimmers adjustments aren't critically important. They are there to adjust the 0 point of the opamp because the 100k RC resistor on pin 3 will draw a small current that will move the ground reference above ground but seeing how all the trimmers are already adjusted the offset won't be much if any. I've had 530v across my headphones for a few seconds as well as a couple hundred and a couple dozen volts dissipated through it. The 530v one had such a strong current that you could see the current flowing through the air when I pulled the alligator clip off it up until about 2 inches away.
My headphones still sound fine and still measure a perfect 311 ohms on both drivers, they are just metal coils afterall. The biggest problem with DC offset in headphones is the fact that with a high enough DC offset the coil gets displaced which screws with the sound. 
As for headphones not having any ability to dissipate heat, that's a load of bologna.
The pop sound always happens when any dc appears across the coil.

 

[colliedoggy]

So, just to be clear, the same transformers ARE used for both models. Check?
 
(I just corrected my error above where I referred to the trimmer pot as a trimmer cap!)

 

[baronbeehive]

  Wait!
 
It just occurred to me that each op amp is adjusted for offset by its trimmer capacitor, which is the blue box nearby with the small screw on top of it. 
 
Whenever you change the position of one of the op amps, the op amp offset ought to be corrected for by adjusting the trimmer potentiometer (the blue box with the screw on top). 
 
Do you understand how that works?
 
( At the very least please label each IC so that you know which position it came from in the first place.) 

 
I think I understand now that you've explained it. So how do you adjust it?
 
I assume that I could still check by swapping the opamps to see if it resolves the grounding issue nevertheless because the adjustment would not be critical, and so long as I put them back the same way they came out all would be well?
 

Correct...
Forget swapping opamp.
Each pot is adjusted individually for each opamp.
So if you swap, You WILL get a DC offset resulting in a tiny pop sound when plugging in the headphones.
Also, marking the pots is useless because these trim pots have MANY turns...



Also, Coin is right, Baron does not have a problem with pin 6.

You are right again...

 
So don't bother removing opamp after all?
 
So I do not have a problem with a grounded pin 6? I am thinking if coin is right about the board I may have to take it back and see if the engineer can fix it otherwise I'm not sure what to do now.

 

[coinmaster]

Nah, read my statement again. I said your reading of pin 6 meant you were reading continuity through the bypass cap, meaning the short is coming from the B- supply. Check the bottom of the cathode resistor for ground continuity. Don't bother adjusting the trimmers, the offset won't hurt and you won't be plugging in your headphones for it to matter anyway.
 
Switching out the opamp was to test if the opamp was defective because your grid voltage is 0. For now, just check the cathode resistor for ground and let me know because a 0v grid is irrelevant if your b- is grounded. 
Unless there's more to this picture or you are doing/understanding something incorrectly that is confusing us, I strongly suspect your board is defective (I blame your "engineer" 

)

 

[baronbeehive]

  Nah, read my statement again. I said your reading of pin 6 meant you were reading continuity through the bypass cap, meaning the short is coming from the B- supply. Check the bottom of the cathode resistor for ground continuity. Don't bother adjusting the trimmers, the offset won't hurt and you won't be plugging in your headphones for it to matter anyway.
 
Switching out the opamp was to test if the opamp was defective because your grid voltage is 0. For now, just check the cathode resistor for ground and let me know because a 0v grid is irrelevant if your b- is grounded. 
Unless there's more to this picture or you are doing/understanding something incorrectly that is confusing us, I strongly suspect your board is defective (I blame your "engineer" 

)

 
The cathode resistor is connected to ground, correctly I assume because the other circuits are the same. (I am measuring the resistor through the cathode bypass connection).
 
Edit: to clarify that the cathode bypass/resistor is connected to ground while the caps are charging but then when they are charged I no longer get the continuity to ground reading. This is the same for all the circuits not just the bad one.
 
NB: This may affect my previous test readings now that I know about the caps charging so if you need to clarify anything I did previously I can do a retest if necessary. (I don't think you will need to clarify anything because nobody understood what I said before

.

 

[baronbeehive]

Sorry about this guys, I didn't understand why I was getting that intermittent bleep on the tester before, now it is beginning to make sense. I've just tested pin 6 again and it's OK, an initial bleep while the cathode caps is charging and then no bleeps and longer grounded, same as other circuits and all OK!
 
So it's pins 3 and 5 now that are grounded!

 

[colliedoggy]

Great!
 
I have deleted my comment about adjusting the offset as I may have misunderstood how the circuit is working.

 

[coinmaster]

Hold up, the problem with pin 6 is that if your black probe was connected to ground as it should be and you are getting beeps while the cap is charging this means you have continuity to ground through the cap. The cathode resistor should not be connected to ground, the amp uses a bipolar supply.
Make it clear to me if the bottom of the cathode resistor is connected to ground.