TUBES- DIY trouble shooting for Dummies, lol

 THE HOME MADE TUBE TESTER 

Good ol' Phil has a video showing the age old trick to find a bad tube and
replace it. If you take your amp to a shop you usually get charged the minimum one hour rate to do what is a simple DIY. It is not unusual to find a shop that has to farm out to a tube amp tech as many shops even if they are in house got their training from a school that focuses on consumer electronics which are all solid state. The point is that it often is actually cheaper to buy a whole new set of tubes which gives you the bonus of swapping out your whole set in an emergency or taking your time and swapping out one at a time. Add to that you have no down time which can be weeks.

In the video it mentions a stick. No stick? Then use the stick I have used for decades ...a damn 'pencil' it is the perfect stick. On the other hand you may have a chopstick kicking around.

POWER TUBES

BIAS OR NO?

In basic Rock player terms a tube amp is meant to have its power tubes matched. The power tubes are the large ones. The small ones are preamp tubes. A tech can meter the power tubes and adjust them. The maker supplies a schematic and in it it says what they feel they should be set at. If you have an amp with two power tubes (or more) that came in your new amp and one dies you change it and then it is recommended to have a tech match it to the others.

BIG BUT

Big names have often went bolistic because their amp has lost its sound after doing all this. They are correct!!! In short an unbiased amp may indeed sound better.

MY POINT ?

If you do not have the money just swap out the offending power tube. If it sounds OK ... then fine. You will not damage the amp.

the fine print

While sitting here writing I have the back off my Plexi 

checking tubes. I am getting crackle like you get from moving

a noisy pot at random. Some days none, some days relentless.

Today just a bit with long periods without. I change out one Pre

and will do one at a time if it does not stop. So far no noise

but I will have to give it about a half hour. 

an hour later

I freaked!!! I could not hear even a low hum from the speaker!!!

I plugged a cord in and messed with the jack. No it was not

blown. 

I then hooked it up and it was still dead quiet!!!

I started playing. It was noticeably louder and clearer

...and as I said dead quiet.

Thank you god :-)

a day later

The AMPTATA T5 CHECKER 

A Toy? ...I just discovered this little device a stripped down tube tester. It is for checking and doing your own BIAS on specific power tubes. There are 3 models each covering different power tubes. You get the one that has your amps power tubes. At $35.00 USD with free shipping on Ali Express it is worth the risk. I ordered one. If it only works once I will be ahead of the game. Shop time has to be a minimum of $35 no matter where you live. If all it tells me is that I have a bad tube I am still ahead even if I can't sort out any BIAS thing. I am sure that you have to adjust from inside the amp and you have to know where to and not kill yourself. But like I said just knowing which tube is toast is worth it.

2 weeks later

WTF ...my amp cut out & went dead  at rehearsal today!!!

A fuse did not blow ...but I was crapping myself.

It did not distort or get noisy so I start thinking

all about big bills and a wait well into the new

year because this or that tube or part can not be found.

Out came the screwdriver,

I must thank the gods ...it was another preamp 12ax7

I can't complain they are all about 3 years old.