[colliedoggy]

Could someone help me with what components are soldered and what values on the top side of the pcb for the mk viii se?
 
 
I believe that there may be a resistor on the top side of the board of value 180 Ohms in parallel with each cathode bypass cap. This is the value I get with my DMM rather than the 330 Ohms marked on coinmaster's schematic for the mk vi+ .
Is this correct?
 
What other components are not visible without removing the board?
 
Thanks 

 

[SonicTrance]

  So is the continuity between pins 5 and 6 on only one of the 6N30P sockets in the right hand circuit, or both of them? 
 
If only one, is it the +ve or -ve socket?
 
Presumably, this short is with no valves in the sockets, is it?

Just so you know, Baron has a MK6. So no 6N30P sockets there.

 

 

[Maxx134]

Yep different pins that's why I not stated the pins, but a OK as same idea

 

[SonicTrance]

  Could someone help me with what components are soldered and what values on the top side of the pcb for the mk viii se?
 
 
I believe that there may be a resistor on the top side of the board of value 180 Ohms in parallel with each cathode bypass cap. This is the value I get with my DMM rather than the 330 Ohms marked on coinmaster's schematic for the mk vi+ .
Is this correct?
 
What other components are not visible without removing the board?
 
Thanks 

The cathode resistors are on top side of board. Also some ceramic resistors in the psu and a couple by the relay.
 
As far as I know the MK8 usually has 150 ohm cathode and plate resistors. 180 ohm will also work of course. Tubes will run cooler at lower current.

 

[colliedoggy]

Ahh!
 
In my unit the plate resistors actually fitted are 180 Ohms, so that explains things.
 
Thanks

 

[Maxx134]

The anode/cathode resistor values are the only difference between amp components to get that I recall,
and all extra components to install are same.

 

[baronbeehive]

  So is the continuity between pins 5 and 6 on only one of the 6N30P sockets in the right hand circuit, or both of them? 
 
If only one, is it the +ve or -ve socket?
 
Presumably, this short is with no valves in the sockets, is it?

 
Hi colliedoggy, welcome!
 
The continuity is on only one, the suspect right hand circuit. I don't know if it is the +ve or -ve but it is the one with the -ve output going from it.
 
Yes tubes are out.
 

Just look at the board trace in the center of the socket it clearly shows two pins connected I don't have time to pull up pics but it is from first triode of WCF circuit to second triode.
As long as they don't have continuity to chassis ground you should be good .

 
I can't see the connection from the board trace but it is definitely pins 3 and 5 that are connected as confirmed by the other good circuits. On the bad circuit they are grounded, as I said by a possible short with pin 6.
 

  Those are pins 3 and 6 that should be connected. Check.

 
No, pins 3 and 5. Pin 6 is only connected in the bad circuit as indicated by continuity check, not in the other circuits.
 
Thanks for the help, I'm getting nowhere, having checked again the connections, joints and so on and I can't see anything amiss, and I've run checks to try to see as well. Maybe I should just send it back and stop wasting everyone's time.
 
Before doing that I will of course try to wrench out the opamps, how do I test them to check they're OK? I still don't see how they could cause a grounding issue though.

 

[colliedoggy]

   
Hi colliedoggy, welcome!
 
The continuity is on only one, the suspect right hand circuit. I don't know if it is the +ve or -ve but it is the one with the -ve output going from it.
 
Yes tubes are out.
 
 
I can't see the connection from the board trace but it is definitely pins 3 and 5 that are connected as confirmed by the other good circuits. On the bad circuit they are grounded, as I said by a possible short with pin 6.
 
 
No, pins 3 and 5. Pin 6 is only connected in the bad circuit as indicated by continuity check, not in the other circuits.
 
Thanks for the help, I'm getting nowhere, having checked again the connections, joints and so on and I can't see anything amiss, and I've run checks to try to see as well. Maybe I should just send it back and stop wasting everyone's time.
 
Before doing that I will of course try to wrench out the opamps, how do I test them to check they're OK? I still don't see how they could cause a grounding issue though.

Apologies about the pin numbers but now I realise that you have the mkvi+ and I have the mk viii se which have different output valve pin outputs
 
Chin up and keep going! 
 
I haven't got enough acquaintance with the circuit and your problem yet to be able to judge whether the op amps could be the source. But you could always try swapping them from one left to right channels and see if the problem moves. There is a cheap tool to pull them from their sockets cleanly and without fear of damage.to the pins, which is referred to as an 'IC puller'. Essentially they are just a pair of tweezers with right-angled, inward-pointing tips. They cost a couple of quid..Before I had a pair of those I used to just carefully prize up one end a tiny amount, then the other, etc,. incrementally, until the chip could easily be pulled out with forefinger and thumb.

 

[coinmaster]

A short between 5 and 6 would immediately blow the fuse on startup. The only way that could be shorted is a broken WCF cap or some really bad wiring or a tube short. 
What is this -ive you are referring to?

 

[baronbeehive]

  Apologies about the pin numbers but now I realise that you have the mkvi+ and I have the mk viii se which have different output valve pin outputs
 
Chin up and keep going! 
 
I haven't got enough acquaintance with the circuit and your problem yet to be able to judge whether the op amps could be the source. But you could always try swapping them from one left to right channels and see if the problem moves. There is a cheap tool to pull them from their sockets cleanly and without fear of damage.to the pins, which is referred to as an 'IC puller'. Essentially they are just a pair of tweezers with right-angled, inward-pointing tips. They cost a couple of quid..Before I had a pair of those I used to just carefully prize up one end a tiny amount, then the other, etc,. incrementally, until the chip could easily be pulled out with forefinger and thumb.

 
Hey, thanks for the tip about the opamp tool, I was wondering if I had anything suitable in the cutlery drawer and was contemplating getting an ice lolly and using the stick to lever it out! With all the mods it would be difficult to do by hand because everything else is in the way.
Are you modding your MKVIII then?
 

  A short between 5 and 6 would immediately blow the fuse on startup. The only way that could be shorted is a broken WCF cap or some really bad wiring or a tube short. 
What is this -ive you are referring to?

 
Well there is definitely continuity there such that I was thinking about removing the tube socket to see if there was any solder or anything stuck there, but first I wanted to be sure it was nothing else in the circuit. I've tried looking underneath the socket and it all looks clear. Looks like the tube short is ruled out because I'm testing with tubes out.
 
So would the amp still work with a blown fuse, because if it's just that it would save a lot of hassle.
 
The -ive is the -ive output marked on the board by the tube pins of the faulty tube circuit going from there to the output XLR, and the other one is the output on the board just by the fuses, (-ive and +ive).

 

[SonicTrance]

So would the amp still work with a blown fuse, because if it's just that it would save a lot of hassle. 

No, with a blown fuse no AC enters the amp.

 

[coinmaster]

I take it back, 5 and 6 being shorted is normal. I forgot they wired it a little funky from the way I look at the diagram. It's just the output to the WCF. 

 

[coinmaster]

I pulled my mk6 board out of the trash and I don't see any -ive marked anywhere so I have no idea what you are talking about if you can take a picture that would be great.
 
Other then that start with what you know. The grid voltage is grounded which would cause the original symptoms you were having. Switch the opamp in the problem area out with one of the other ones and see if the issue moves around with it.

 

[coinmaster]

Today is a glorious day, I finally purchased another MK6 lol. I turned off my brain and just clicked the buy button before logic and reason returned to me 

Also the fact that I'm constantly waiting on parts made me realize that my prototypes will never be a good way to just listen, at least not anytime soon. Dear god help my bank account.

 

[baronbeehive]

  I pulled my mk6 board out of the trash and I don't see any -ive marked anywhere so I have no idea what you are talking about if you can take a picture that would be great.
 
Other then that start with what you know. The grid voltage is grounded which would cause the original symptoms you were having. Switch the opamp in the problem area out with one of the other ones and see if the issue moves around with it.

 
Mk VI - trash - you have no respect lol.
 
This pic shows the right -ive board output to the XLR, the other 2 outputs are just down below the 2 fuses.
 

 
 

  Today is a glorious day, I finally purchased another MK6 lol. I turned off my brain and just clicked the buy button before logic and reason returned to me 

Also the fact that I'm constantly waiting on parts made me realize that my prototypes will never be a good way to just listen, at least not anytime soon. Dear god help my bank account.

 
I gave up worrying about my bank account long ago

.