OD3 tube life

[q]

Still struglling with my Foreplay and noticed that the OD3 is getting blacker around the towards the bottom inside
Is this a good sign of something not quite right or is this normal. The Foreplay has less than 100hrs on it and can sound great one time than not so much after awhile. Is the variable perfomance of the Teflon cap something I should look into?
I just went through this pre with a magnifiying glass and fixed any joints that looked questionable which is when I saw the OD3 tube's wear. The problems with sound quality are on both channels and the last time I listed the metered values no one mentioned that there was any odd values or results
thx in advance
q

[Grainger49]

q are you saying that you have a Teflon cap or caps in your FP III?  Yes, Teflon caps do not sound that good when first installed and need cycling, forming or burning in.

Even if you used a Teflon bypass on the OD3 you should have broken it in first:

Link To My Fast Break In Post

I can't tell you about the black on the OD3.  I don't have one.

The voltages should be within 15% of those listed in your manual.  If not those are the only ones that you need to post.

[q]

sorry I got this all confused
I used the Cap that came with the kit, I didn't substitue any parts
I did however find something. While trying to make sure that things that shouldn't be touching don't. One of the carbon resistors fractured why genlty moving it. The body looked like it got too hot. I have some replacements ordered and hope that this may have been the problem with the sound all along. Could this bad resistor affect both channels? if so should I try and replace both? It's pretty darn tight in this part of the build, hopefully i don't screw anything else up
Oh well, it's worth it, Ive learned alot from this build. Hopefully I get to hear the ForeplayIII in it's full glory soon
thx
q

[Paul Joppa]

Yes, the carbon composition resistors (220 ohms) are fairly fragile, and an internal crack could easily let some signal through imperfectly, affecting the sound.

I'm not sure this is what you are describing, but the glow on the internal surface of gas regulator tubes such as the 0D3 will usually only cover a portion of the surface. When it covers the whole surface, the tube is saturated and can't regulate any more.

[q]

Yes, the carbon composition resistors (220 ohms) are fairly fragile, and an internal crack could easily let some signal through imperfectly, affecting the sound.

First,Thank you very much for your help. Sorry to be a noob
Is this a good time to replace these resistors with a "boutique" part?

I'm not sure this is what you are describing, but the glow on the internal surface of gas regulator tubes such as the 0D3 will usually only cover a portion of the surface. When it covers the whole surface, the tube is saturated and can't regulate any more.

The glow does not cover the whole surface, just some carbon like build up on the inside surface of the tube. This is located at the base.
once again, thanks!
q

[Grainger49]

Replace a 220 ohm carbon composition resistor only with the same carbon composition (CC) resistor if this is the one that seems damaged.  The 220 ohm CC resistors are located on pin 2 and pin 7 of each 12AU7 tube.  They are shown on page 33 of the manual.

These are selected for their specific use, that is they are grid stopper resistors.  They are not considered signal path resistors that would benefit from a tantalum resistor.  If you change the type of resistor you might increase the noise or RF interference in the preamp.

I still can't help on the OD3.

[q]

Thanks,glad I asked and glad this forum is here.
Any suggestions on a source other than what comes up with google?
thx
q

[Grainger49]

If you are asking for a source of 220 ohm CC resistors then call Eileen. 

Contact Info:

http://www.bottlehead.com/contu/cntu.html

[q]

Thanks once again, I didn't think about sourcing components like this from Eileen. Thought they were in the business of design and providing a complete kit. With the new move and new dac i didn't want to bother them with something as simple as a carbon resistor. I