Valve Itch phono

[Salas]

Now I'm more confident using again FT-1 seeing the other cap is good.

That one held better than the one in the other channel. Throw the bad one away not to get mixed with good ones.

 

[merlin el mago]

Soldered both caps, tome to listen & report how it goes.

 

[Salas]

Also test to see, at the moment you power up, maybe the voltage at C3 overshoots the 200V FT-1 spec until the tubes settle bias so it grills this kind of capacitor in the long term?

 

[merlin el mago]

Now I'm enjoying your work Salas, but I will measure tomorrow for sure.

 

[Salas]

Did you check the C3 max power-on voltage?

 

[merlin el mago]

Still not, I will tell us asap, thanks for your interest Salas.

 

[Salas]

REC button on your Brymen DMM is MIN/MAX function. If already hooked up to measure voltage and REC is activated, when you power on it captures instant MAX voltage.

 

[merlin el mago]

You are the best one, thanksssss

 

[merlin el mago]

Attached pic of measurement, left pic max. voltage, right pic stabilized voltage.

 

[Salas]

It shows that the drifted FT-1 unit wasn't grilled by turn on peaks because of its 200V spec.

 

[merlin el mago]

Yes, I used 200V rated RIAA caps because I see in your schematic 165VDC

 

[Salas]

...Also measured correctly biased. 165V point noted on the schematic, 162V in your build. Within 2%. Very close when considering there are differences in tubes bias details between samples or alternative types.

 

[Salas]

In any case, better using 250V or higher for C3 & C4 when possible. Especially so for C6. For peace of mind.

 

[Salas]

What make are your E283CC special quality tubes? Telefunken, Siemens, Mullard?

 

[merlin el mago]

If I remember well are Siemens gold pins bought to Erno Borbely.....

 

[merlin el mago]

In any case, better using 250V or higher for C3 & C4 when possible. Especially so for C6. For peace of mind.

I can't get reasonable priced 250V teflon caps for RIAA but at least my peace of mind is guaranted using C6 3.9uF Mundorf Silver Gold Oil rated 1000V.....

 

[Salas]

After some months check again if the C3 values remain correct since there's been a negative capacitance drift incident with an FT-1 in one channel. Maybe it was simply random, maybe there is a tendency.

 

[Salas]

Yes, I used 200V rated RIAA caps because I see in your schematic 165VDC

With 7N7 in the output stage and those modified resistor values around it, Ip should be closer to 9mA and C6 voltage bias 170-175V.

 

[Salas]

If I remember well are Siemens gold pins bought to Erno Borbely.....

10000 hours anti vibration low noise tubes. Alike the 6N2P-ER.

 

[merlin el mago]

Voskhod triple mica?