Cracking glass and problems with my first build

[halfbackstrat]

I may have just found something, i connected my multimeter to the centre pin of the ratio control and then to the appropriate part of the relay board, encompassing both connections of that shielded wire. Sometimes it shows 0 resistance as it should but most of the time it shows no connection (resistance beyond my multimeters capability of reading!
Is it possible if this connection being broken would stop the OD controls working when the relay was engaged.
This wire is marked "V" on the ceriatone layout

[Kassie]

I may have just found something, i connected my multimeter to the centre pin of the ratio control and then to the appropriate part of the relay board, encompassing both connections of that shielded wire. Sometimes it shows 0 resistance as it should but most of the time it shows no connection (resistance beyond my multimeters capability of reading!
Is it possible if this connection being broken would stop the OD controls working when the relay was engaged.
This wire is marked "V" on the ceriatone layout

Think so.. how does it read to ground? And with potentiometer twisting..
You could clean the contacts and resolder. Then also check the other gain wires... ( the designated resistor on the board.. and from that resistor to the gain trimpot etc.).

[halfbackstrat]

Ratio: The resistance of the middle pin to ground varies linearly as the pot is turned. 100k resistance to ground when the pot is at 10, which makes sense.

0 resistance leading from the centre tap of the level control to the 180k resistor on pin 7 V2.

Just about to check the trim pot.

Your help is so greatly appreciated Kassie.


Edit: Centre tap of trim pot connection to 68k resistor on pin 2 of V2 shows a good connection. The connection of the centre tap to ground is also operating correctly. As is the centre tap of the level control to ground

[Kassie]

Checked continuity on all connections on the relay boards and I they all seem fine.

Ok here is the thing.. I am going through your pictures. And at the powertubes your wiring looks a mess...

You see the grid resistor. (3k3?) And the white/orange wires from the PI. Try to move them away from the OT primaries.. The resistor is going up as per Ceriatone pictures, but study some dumble pictures.. if you want to leave it as Ceriatone.. make sure the PI wires are crossing perfectly other wires.. or move them up in the air earlier. Also your OT primaries should go to eachother pronto from both the tubes and be twisted tightly.. there is high current going in those which can cause crosstalk and magnetic fields and thus oscillations (instability).. Move the green wire (your B+ to the output tubes) also a bit in the air but not as high as the grid resistors.

Don't know if that solves the problem, but do it just in case.. make it neater.

[Structo]

It is not unheard of to get a brand new pot that is defective.

I had a couple on my 100w build.
On the volume pot which was a NOS Allen Bradley, it would rotate about 1/3 of the way then go to full volume.

Best course of action when building an amp is to measure everything to make sure you are installing not only a component of the correct value but also that it functions correctly, as in the case with a pot.

Measure from the wiper to one side and rotate the pot to ensure the travel and resistance is correct for the taper of the pot.

[halfbackstrat]

Thanks Tom, I've checked how well the ratio level and od trim pots function thanks to this but I'll now go through and check everything!

[renshen1957]

JJ Tesla 12AX7. The crack is as you indicated across the base of the tube between the pins.

Hi,

I have both EH and JJ 12AX7 crack in a vintage integrated amp, also the PI.

No problem with NOS tubes or Jolida (Shuguang selected) tubes.

Best regards,

Steve