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Re: I killed my Traynor - debug help?

1/24/2004 8:59 PM
Craig S
Re: I killed my Traynor - debug help?
I just connected Pin 3 of V5 directly to ground, and V3 of V6 to ground through the 10ohm resistor. I'm measuring .330 at the lowest resistance setting. Still too high?  
1/24/2004 11:32 PM
Don Symes

A datasheet is here:  
It looks like the tube is good for up to about 11W and a cathode current of up to 65mA. Depending on your plate (Va) and screen (Vg2) voltages and screen current, you can back out to your max viable cathode current.  
Sounds like you might want to start thinking about how to extend your bias voltage's maximum negative range.  
Maybe wire the bias pot as a 3-terminal voltage divider setup?
1/25/2004 7:42 PM
Craig S

There doesn't seem to be much difference in voltage when the pot is anywhere between 0-15K ohms. It's all around .310VDC.  
To decrease the cathode current, should the pot go to less resistance?  
This may seem like a dumb question, but when I'm taking these measurements, the tubes should be in? That's how I've been doing it.  
Thanks for all your help. I can live with the tubes biased at 31mA. It's a ton better than it was before.  
1/25/2004 10:24 PM
Don Symes

Yes, the tube have to be in.  
Lower resistance? Don't know until I see the circuit. If 31mA does it for you, that's great. I'd feel a little better knowing I had some headroom, though.  
Enjoy it for a while. Keep half an eye on the plates. When you feel like it again, compare some Fender or Marshall bias circuits with the setup you have and see if you want to dive back in.  
Stay Happy!
1/26/2004 12:18 AM
Craig S

Thanks for all your help. Without it, I would have ended up going to a tech about 3 weeks ago and probably would do so for amp work for the rest of my playing days. Now I am comfortable to open my amp up and play around with things.  
Thank you again. I'll let you know if (more like when LOL) I decide to tamper with the bias circuit. 31mA is good for me right now - time to finally play the amp.
1/30/2004 10:08 PM
Craig S

Everything is still good. I had a chance to really let the amp cook, and it was sounding better than ever. I will probably change the bias circuit in the near future though.  
I read on the Traynor forum that converting an amp from fixed bias to cathode bias is an improvement that will make the amp sound more compressed and browner.  
I was wondering if there are bias circuits that I should take a look at specifically, or any to stay away from? Or is this going to be kind of a crap shoot - if I want dirtier tones I should get a different amp. Maybe I just need to buy the Bassmaster.  

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