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Dynaco-Doctor Forum Welcome! Need support, you got it. Or share your ideas and experiences. |
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Dynaco-Doctor Forum Welcome! Need support, you got it. Or share your ideas and experiences. |
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In Reply to: Re: 1 Channel Dynaco st70 posted by paul cbc on May 22, 2003 at 20:09:25:
It's likely that if you re-insert the output tubes the original sockets will work fine - for a time but that's the problem - you just don't know when one of them will let go. This is how you got here in the first place. Replacing them all is just good insurance plus while your under the chassis it's a good time to get the whole job done.It's hard to say if the output tubes (on the side with the high bias) are defective - probably not. You have placed them in the other channel (I think you said) and they functioned well so they're probably OK. If they have been harmed with the saturation problem as I suspect, the worse that can happen is that you will probably fry the replacement cathode resistor again. BTW, you can replace the 15.6 ohm resistor with a 10 ohm / 3W resistor but if you do it is _mandatory_ that you set the bias to be 1.0 volts (as opposed to 1.56 volts)
1.7 is a little high (representing 54mA per tube) but is not too serious. However if this is the bias you are getting with the bias pot fully counterclockwise, this indicates a problem with the bias supply - you should look into the bias tweak or updating the bias supply.
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Follow Ups
- Re: 1 Channel Dynaco st70 - Joe Curcio 22:17:40 05/22/03 (3)
- Re: 1 Channel Dynaco st70 - paul cbc 18:57:07 05/23/03 (2)
- Re: 1 Channel Dynaco st70 - paul cbc 18:43:45 05/25/03 (1)
- Re: Why 3 watt cathode resistors? - Russ57 10:26:20 05/28/03 (0)
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