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Post subject: Bassman 100T tube replacement question
Posted: Wed Nov 05, 2014 10:13 am
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How do you know if and when the smaller valves (12Ax7 AT7 etc) need replacing.
If the auto bias shows all green (meaning the 4 power tubes are ok) if one of the smaller valves is dieing, how would you know?


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Post subject: Re: Bassman 100T tube replacement question
Posted: Wed Nov 05, 2014 2:09 pm
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Low , or no power in most case.

You'll need to replace 6L6's few times before need to replace 12XX7 tubes


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Post subject: Re: Bassman 100T tube replacement question
Posted: Wed Nov 05, 2014 6:56 pm
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Sometimes the preamp tubes can be troublesome, especially if they become microphonic or develop other issues. Frequently I've seen them fail in hybrid amps with no warning or degradation before they simply cease to function. If they sound clean at low drive and are not generating feedback they are probably ok. A tube tester is a really good thing to have. Sometimes you can find one cheap on eBay. Usually though when most people notice something that doesn't sound right they just re-tube. The problem with that is new tubes are sometimes not exactly perfect either, at least not 100% of the time and only with a tube tester do you know that it is working right. Over time all tubes very gradually degrade in performance. but sometimes preamp tubes go really, really quickly with little or no warning. On an amp as new as yours they SHOULD be fine. But then again so should the power tubes. People tend to think a Chinese or Russian made tube is going to last as long as the old USA made ones. They absolutely do not.


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Post subject: Re: Bassman 100T tube replacement question
Posted: Thu Nov 06, 2014 2:32 am
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Im my opinion , it is better and accurate to have some 12XX7 in spare than a tube tester. Cheaper too.

Same for 6L6

So many tube failure can't be see with a tube tester.

If tube is bad you must buy one anyway


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Post subject: Re: Bassman 100T tube replacement question
Posted: Thu Nov 06, 2014 9:53 am
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:idea: :arrow: Owning a tube tester and a full compliment of replacement tubes is mandatory in this day and age.

Gone are the days of popping into a TV & Radio repair shop and using their tester and picking up any new RCA; GE, or Sylvania tube you might need on the spot.

New Old Stock American made tubes are going for small fortunes nowadays and with good reason.

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Post subject: Re: Bassman 100T tube replacement question
Posted: Thu Nov 06, 2014 6:32 pm
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Thanks for the replies.

So what do you think are the best replacements to put in these? 6L6's I mean.
I swapped the Chinese groove tubes that it came with for a set of Russian Svetlanas.
But wondering if I should stick to the groove tubes when the time comes for a new set.


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Post subject: Re: Bassman 100T tube replacement question
Posted: Fri Nov 07, 2014 2:10 am
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love-boat-captain wrote:
Thanks for the replies.

So what do you think are the best replacements to put in these? 6L6's I mean.
I swapped the Chinese groove tubes that it came with for a set of Russian Svetlanas.
But wondering if I should stick to the groove tubes when the time comes for a new set.



Did you check 6L6's bias ?

I often use JJ's and Electro Harmonix


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