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> Changing Tubes In My 6505+ 112
Himansu C Kerkar
post Oct 1 2014, 07:30 PM
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Hi Friends

I have a 6505 + 112 Amp which I have been using consistently for over 2.5 years since I joined GMC.
Almost like playing everyday.

These days the amp sounds a little dull even when cranked up and I do not know what is wrong with it.

They say that if the tubes give off a slight bluish light you should replace them and mine have turned slightly bluish just slight

Sadly my amp does not roar like it would 2 years back even at high volumes

Feedback and noise has also gone up these days.

Though the amp has been noisy but these days it makes more noise than the days when it was new

Should I replace the tubes ??


Which Ones should I replace them with??

Which tubes are good??

I love playing Thrash metal like Testament and would love a fuller sound like Dark Roots album


What would be the cost of replacing these??

Are Tubes very expensive??



Thanks

This post has been edited by Himansu C Kerkar: Oct 1 2014, 07:44 PM
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Chris S.
post Oct 1 2014, 08:48 PM
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I checked out TheTubeStore and they have a Metal Package for the 6505+ head which has 6 Electro-Harmonix 12AX7 tubes and 4 TAD 6L6GC-STR tubes for $191.50 USD.

There are plenty of other options with different prices ranges as well.

As for the tubes glowing blue, I've never experienced it myself but from what I've read it online it's not necessarily a bad thing (possibly some oxygen left in the tube during manufacturing) - the key factor is how they sound.

The tubes in my Blackheart Little Giant started to go and I noticed some slight 60 cycle hum and a flatter, more dull tone so I swapped them out yesterday and the amp is back to life.

That's my two cents, I hope it was of some use!
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Todd Simpson
post Oct 2 2014, 02:01 AM
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That sounds like a killer pack for your tube job!!! You can go crazy selecting tubes but thats a fine selection.

QUOTE (Chris S. @ Oct 1 2014, 03:48 PM) *
I checked out TheTubeStore and they have a Metal Package for the 6505+ head which has 6 Electro-Harmonix 12AX7 tubes and 4 TAD 6L6GC-STR tubes for $191.50 USD.

There are plenty of other options with different prices ranges as well.

As for the tubes glowing blue, I've never experienced it myself but from what I've read it online it's not necessarily a bad thing (possibly some oxygen left in the tube during manufacturing) - the key factor is how they sound.

The tubes in my Blackheart Little Giant started to go and I noticed some slight 60 cycle hum and a flatter, more dull tone so I swapped them out yesterday and the amp is back to life.

That's my two cents, I hope it was of some use!



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GregH
post Oct 2 2014, 04:26 AM
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Gassy tubes (tubes that glow blue) are not uncommon. That, by itself is not reason to change them out.
However, the sounding dull can be a symptom of aging tubes (among other things). If you are using the amp a lot, 2 1/2 years is not an unreasonable amount of time to need tubes. If you had access to a tube checker, you can test them one at a time to find the bad one (or ones). Without one, you could get a preamp tube (12AX7) and move it from spot to spot and see what difference it makes. The power amp tubes (6l6) really should be replaced as a set.
Or you could just replace them all and figure the old ones could be spares in a pinch.
On most tube amps, after replacing the output tubes (that's the 6l6s) someone should go in and adjust the bias. Bias is the amount the tubes are turned on with no signal coming in. The bias in a 6505 is set by the factory so cold that you really don't need to worry about it.

Note: On any tube amp, the voltages inside are rather high, probably around 500 volts DC in your amp. You really don't want to come in contact with it. Use caution and standard precautions when you change tubes.
Always unplug the amp before working on it.
Make sure it has been off for a while. The filter caps can retain a potentially lethal charge for a half an hour (sometimes longer, depending on the design).
A lot of people work with one hand in their pocket if they are near exposed circuits (that keeps the voltage from going through your body if you get your hand somewhere it really shouldn't be).
It's really not hard but some caution is warranted.
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