PV11 troubleshooting help

[Dr.Greenthumb]

If I remember correctly, the PV 11 still had a two prong hard wired plug. Did someone modify it to take aftermarket power cords? If they did, they might have gotten into ground loop issues and disconnected the green wire.

Still has the 2 pronged plug. I looked online and found a pic of another PV 11 and it had the same green wire, twisted with the wires going to the power switch, that wasn't connected to anything.

I am going to replace the cord with a grounded one.

[admin]

Sounds like a fun project. Is there a specific place you plan to ground the unit (ie the chassis or circuit board)?

[AnotherJohnson]

Sounds like a fun project. Is there a specific place you plan to ground the unit (ie the chassis or circuit board)?

Looks likes it’s already on the chassis. That’s where it belongs.

[Dr.Greenthumb]

Hola...voltages seems to be ok. Noises are due to have tubes usually in wrong position or different types...here is what the the PV11 manual says:

The B+ puts the 12AU7 at max operating voltage for class A amplifier. With a grid voltage of -8, the plate current is maxed out at 22mA. Are the tubes supposed to be ran that close to the max? Unfortunately CJ was not willing to give me any info on correct plate voltages.

[AnotherJohnson]

As noted earlier, CJ will not facilitate transfer of their IP. They will put it on their bench and advise you of the feasibility of a repair and the cost, but they won’t help you DIY. It is a small company, and they are continuously under attack by Asian counterfeiters. They’re not going to make it easier to copy their stuff.

CJ are known (infamous some would say) for pressing their tubes. Roberto may know the voltages from bygone days when information flowed more freely. Maybe you could pm him and ask him directly.

[roberto]

That's a tough question. You could bring the tube to a lower bias current and have a listen, if your ears are happy, then that's ok. I really don't know if they do bring the tubes to their maximum potential current. I don't find any benefit to have a tube working that hard.

Happy listening!

[Toberius]

I replaced every diode and transistor in the power supply, along with every capacitor. I started going through checking the diodes and there were so many bad, I just replaced everything. The MPSU60 and MPSU10 were replaced with KSA1381 and KSC3503, respectfully. The replacements needed the pins (ECB) to be bent to be in the correct order as the original parts (EBC). I need the test point voltages to see how far off I am after the rebuild.

Hi, there is any reason to replace transistors? I have a PV10A and maybe I do that also.

Thanks.

[roberto]

The transistors basically belong to the regulator stage. If you have hum, these transistors are the suspect. If you have a clean S/R then you are OK.

Happy listening!