Used mesa.1 power tubed was changed.Need to be pairs?

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diddlydan

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Hi there,hard to get much info in the title.Basically im picking up a used lonestar special online.Cant try before i buy so i was asking as many questions as possible.I asked about the tubes and he said he did change 1 power tube.But arent they supposed to be changed in pairs so they match?I do know mesa color codes matched pairs(green,yellow etc) so for example if a yellow power tube was replaced with another yellow power tube, would it be ok to change 1 at a time?Cheers
 
Yes, always. Unless it's a single ended amp. Then it only has one output valve.

Reason being, they work in pairs, they wear in pairs.
It's no biggie, if the price is right. And personally, changing valves is something I do to 2nd hand amps whatever their history, on taking ownership.
 
So it wont cause any damage?He says it woks fine anyway but im weary now hes mentioned it
 
If it's too big a mismatch, then it'll sound terrible. If a valve fails, it could take a it's screen grid resistor. Depending on how the circuit is, it could cause the other to redplate depending on the circuit. I'm not familiar with Mesa. But Fender and Marshall, their 100 watt output sections. When you lower the bias one side, you increase the bias on the other.

You can never know what has gone on with a set of second hand valves. Whether you buy them individually or in an amp. Which is why the first thing I do, is change them
 
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