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Post by blues77 on Nov 22, 2010 11:44:55 GMT -7
Hello,
I bought a Route 66 about a year ago on eBay. A few months ago I had in in to a technician to troubleshoot some static sounds coming from the amp. He had a difficult time getting the bias set correctly which leads me to my question. I opened up the amplifier and noticed that the bias resistor (or at least I think it's the bias resistor) appears to have been replaced. It looks older than the other components. I wanted to ask people if this is the stock resistor or not, and if it isn't, what should the stock resistor be? Also, based on the photo are there any other components in the bias circuit that aren't stock? If anyone else has some photos of an unmodified Route 66 bias circuit I would love to see them!
Thanks for your help Mike
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Deleted
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Post by Deleted on Nov 22, 2010 12:57:11 GMT -7
Here is the bias circuit in my 2004 Route 66. Your amp looks to be a little older. That would explain the different components.
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Post by blues77 on Nov 22, 2010 16:09:07 GMT -7
Thanks doc001. I emailed the service guys at Dr. Z about this and this is the response I got.
"That is not a stock bias resistor. A 68K resistor is what we use on new Route 66s. This sets the range for the bias pot to operate in. Some pairs of tubes will require the resistor to be changed if the bias can’t be dialed in."
From the photo you posted you have a 56K bias resistor. Maybe yours was changed at some point. Does anyone have a 68K bias resistor? I just want to make sure that the person who replied to my email didn't make a mistake. I want to return the bias circuit back to its stock values.
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Post by Deleted on Nov 22, 2010 17:40:24 GMT -7
I sent my amp to Z for service and a retube at one point. That is the resistor they put in it. I'm sure whoever answered your email had the proper info. They have their stuff together at the Z shop.
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Post by blues77 on Nov 24, 2010 14:01:11 GMT -7
If a stock bias resistor is 68K and it looks like I have a 33K resistor in there now would that mean that the voltage on the control grid could potentially be lower (i.e more negative) than on a stock Route 66 since the resistor is dropping less voltage. If this is the case then would that mean that the amp could potentially be biased colder than on a stock Route 66. I'm just trying to figure out what I would essentially be doing by replacing the 33 K resistor that is in there now with a 68K one. Thanks in advance for your help!!
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Post by Deleted on Nov 24, 2010 15:58:08 GMT -7
I'm not sure, but your tech should be able to tell you that. If it was me I'd go with resistor Z recommended. Maybe someone will chime in with an answer that is more helpful.
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Post by blues77 on Nov 30, 2010 12:04:35 GMT -7
Hi doc001,
I wanted to check this thread again to see what tolerance they used on the bias resistor and noticed that your photo was removed. Any chance you could tell me what colour is the tolerance band on your bias resistor? I'm putting in a new resistor to replace the "non-stock" one I currently have which should help in biasing the amp.
Thanks!!
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Post by Deleted on Nov 30, 2010 12:35:33 GMT -7
I can see the pic on my computer.
Anyways...the tolerance band is gold. What is that? 5%?
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Post by blues77 on Nov 30, 2010 14:44:57 GMT -7
Thanks and yes that's 5%.
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Post by Deleted on Nov 30, 2010 15:15:05 GMT -7
You are welcome.
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