[baronbeehive]

PCBs and tube amps: not a good combination in my experience. P2P all the way.

 
Absolutely!

 

[Maxx134]

I'm going to take a guess here and say that one of your heater wires are connected to the grid or wrong pin..

Edit :
Why?
Your grid voltage is elevated about amount of heater voltage amount.

 

[Maxx134]

You don't have to pull out board to test.
Test for continuity with amp off.
The two tubes on each side should have continuity on same pins for heater.
Edit:
So the point is,
NO other pins should read continuity with the heater pins!
Pull out tubes with amp off for this test.


Also, side note, never turn on amp without tubes.
As this power supply likes to see a load with tubes,
or the zenner diode gets more hot.

 

[baronbeehive]

I'm going to take a guess here and say that one of your heater wires are connected to the grid or wrong pin..

Edit :
Why?
Your grid voltage is elevated about amount of heater voltage amount.

 
OK thanks Maxx, that sounds possible. So I'm either going to have to get a large handled screwdriver - the cordless shredded one of the screw heads, or take it back from whence it came.

 

[baronbeehive]

You don't have to pull out board to test.
Test for continuity with amp off.
The two tubes on each side should have continuity on same pins for heater.

 
I don't get how to do that, continuity from a pin to where?

 

[Maxx134]

You don't have to pull out board to test.

Test for continuity with amp off.

The two tubes on each side should have continuity on same pins for heater.

I don't get how to do that, continuity from a pin to where?

1-Locate the heater pins.
2-Set your tester to ohm meter at lowest setting only.
3- touch one end probe on either heater pin,
And other probe to other pins, one at a time,
to see if any low reading which would indicate continuity...

 

[baronbeehive]

1-Locate the heater pins.
2-Set your tester to ohm meter at lowest setting only.
3- touch one end probe on either heater pin,
And other probe to other pins, one at a time,
to see if any low reading which would indicate continuity...

There are 2 heater pins - 7 & 8 so touching 7 at one end and 8 at the other would indicate continuity of a circuit? Then if there is continuity at another pin other than those 2 pins the heater circuit has been connected up wrongly to the other pin which indicates continuity? Sorry if that's garbled!

 

[baronbeehive]

I've just checked for continuity between pins 7 & 8, and others, and the wiring is correct on all tubes ie. continuity only with pins 7 & 8.
 
So it's back to square one!
 
What does that grey 2 core wire do on the reverse of the board?

 

[SonicTrance]

 
The 4 cathode 330ohm resistors are the ones in the cathode bypass joints on the component side I believe.
The 4 anode 330ohm resistors are the ones in the reverse side I believe.
I'm  assuming it doesn't matter which leg of the resistor I measure to?
 

Hi Baron!
 
Its' the other way around. The anode resistors are on component side. One of them is mysteriously burnin. Cathode resistors are on top side of board. You have them soldered in parallel to the Rifas and Mundorf E-Caps.
 
It does matter from which resistor leg you measure. If you measure before the voltage has passed the anode resistor you are measuring B+. If you measure after the resistor you are measuring plate voltage.

 

[baronbeehive]

  Hi Baron!
 
Its' the other way around. The anode resistors are on component side. One of them is mysteriously burnin. Cathode resistors are on top side of board. You have them soldered in parallel to the Rifas and Mundorf E-Caps.
 
It does matter from which resistor leg you measure. If you measure before the voltage has passed the anode resistor you are measuring B+. If you measure after the resistor you are measuring plate voltage.

Hi Sonic!
 
Of course that's what I meant ha ha

.
 
I'm beginning to slowly realize what it's about, voltage is bound to be affected by resistance, thanks for your patience

.
 
OK, so have you any ideas why its burning?

 

[coinmaster]

 Grid pin 1 to ground -0.6

That would do it. Check the area around that pin for shorts, etc.
Learn how to use a continuity tester. Most multimeters haver a contuity setting that will beep on continuity, if not just measure resistance and very low ohms means continuity. 
Check everything from the bottom of the coupling capacitor up until it hits the grid resistor and the grid and make sure nothing is connected that should not be.
Also check the continuity from ground to the opamp pins. The small circle on the opamp indicates pin 1. Only pin 3 should show continuity, if any of the others are then the opamp is toast or there's a short.

 

[Maxx134]

Yes if looks like there is some type of short on the grid pin and if that is the main grid, not the WCF grid,
then need to check all coimmaster said.

If it is the WCF grid, then check the WCF cap wires that may be touching, or not on proper position..

My guess s(yes again) is a mistake with cap connection..
Make sure solder joints are not covering two different points
.

 

[baronbeehive]

  That would do it. Check the area around that pin for shorts, etc.
Learn how to use a continuity tester. Most multimeters haver a contuity setting that will beep on continuity, if not just measure resistance and very low ohms means continuity. 
Check everything from the bottom of the coupling capacitor up until it hits the grid resistor and the grid and make sure nothing is connected that should not be.
Also check the continuity from ground to the opamp pins. The small circle on the opamp indicates pin 1. Only pin 3 should show continuity, if any of the others are then the opamp is toast or there's a short.

 
Thanks Coin. I'm guessing that the black thing marked "OPA..." with 8 contacts is the opamp? So I check each of these 8?
 
The grid resistors are the 2 brown 300ohm ones at top right with the red wire near and bottom left by the red wima?
 

 

Yes if looks like there is some type of short on the grid pin and if that is the main grid, not the WCF grid,
then need to check all coimmaster said.

If it is the WCF grid, then check the WCF cap wires that may be touching, or not on proper position..

My guess s(yes again) is a mistake with cap connection..
Make sure solder joints are not covering two different points
.

 
Can't see visually any shorts on the trace from the grid pin but haven't used the continuity check yet.
 
The WCF wires look OK, (red and black wires in pic), and in correct position. There is a question about the pads on this WCF cap though that I remember from the original mods.
 
The only solder covering two different points is on the cathode bypass joints which is OK. Maybe something like that on the reverse of the board possibly?
 
Thanks guys for giving up your Saturday evening

.

 

[coinmaster]

Thanks Coin. I'm guessing that the black thing marked "OPA..." with 8 contacts is the opamp? So I check each of these 8?

Yeah only with continuity, not with voltage so leave the amp off. Just measure the pins from ground. Pin 3 should be the only one with a continuity reading.
 
 

The grid resistors are the 2 brown 300ohm ones at top right with the red wire near and bottom left by the red wima?

Not sure but with a continuity test you can find out, just measure from grid.
 

 
If it is the WCF grid, then check the WCF cap wires that may be touching, or not on proper position..

From his previous statements it is the top grid that is the issue, the wcf grids look fine. Plus it's the anode resistor that's burning which would make since if the top triode is running at near 0v grid.

 

[baronbeehive]

So far everything appears to check out visually, and with continuity test comparing the bad circuit with the other right hand circuit: grid to grid resistors, and to other modded components, and opamps check out. There's continuity where there should be and no continuity where there shouldn't be. I haven't compared to the left hand side circuits.
 

 
 

 
Just out of interest I looked at the pic of the reverse. I don't see how anything could have pierced the new blue heater wires. It looks like the right hand circuit heater wires were the ones that were moved being closer to the resistor. Do the wires have to go from pin 7 of one tube to pin 7 of the other because that could have been mixed up. It looks like on the stock, (red wires), they were connected pin 7 on one tube to pin 8 on the other and visa versa.
 
I also checked the 2 output wires coming from pin 3 of each of the 2 right hand circuits in case that was wrongly connected. The output wires were about the only change on the reverse side from stock apart from the resistor/rifa combo. The left hand circuit wire was connected to one of the output pins on the left 3 pin xlr however the right hand circuit wire was connected to one of the output pins on the left 3 pin xlr as well as all the 3 pins on the right 3 pin xlr which can't be right can it?
 
It looks from the pic like the output wires are coming from pin 4 not pin 3.
 
That's weird they are definitely coming from pin 4 which is correct looking at the old pics, so I don't know what I measured from pin 3, it says r-out and l-out on the component side. I've had enough for now.