#1
Edit : Some of the questions i have below have been answered, but read it all if possible to confirm what i've managed to conclude towards the end is correct, like someone said below, i don't want to be zapped.

Ok so, opened up the amp, to see if i'm going to be able to do the whole tube change and biasing prior to receiving the tubes, i can't figure out what i'm ment to be turning when i put in the new tubes.

There's ment to be 2 turnable pots, one for setting the bias, and one to do with " hum reduction? "

Also, should i check what the amp's bias is before removing the old tubes? Even if blackstar told me what the bias is ment to be set at ?

And what are " Test points " , what do i use them for , where would i find them?

Here are the pics

http://i44.tinypic.com/2u8xu3c.jpg
http://i39.tinypic.com/2gv6g4m.jpg

The whole thing : http://i39.tinypic.com/11rgot1.jpg

One more thing I can see the v1,v2,v3,v4 ( i thought they were in a row, but now i can see where the matched pairs go where , now where would the new phase invertor go? ( ecc82 ) , v4?

And since all power amp tubes are the same, i can just randomly put any on either v5-v8?

Edit : Just contacted blackstar and got this info from them , basically they said to bias it to 100mv , and they told me to disregard milliamperage and just set the reading to mv. Does that sound right?

ok now regarding the questions, they said the phase inverter is v1, i've always known phase invertors to go either v3 v4?

And i've asked about the bias adjuster location
He said the white thing within the blue thing ( there's 2 , one near the preamp tubes, and one near the big thing, i'm assuming transistor? ) He said the bias adjuster one is the one near the heat sink Here's a pic

http://i44.tinypic.com/2ptnqdt.jpg

Now regarding test points that i'm going to adjust the bias in regards to , he said it's the 2 metal parts hanging of the plastic thing, near " Con 1 " . Said that i'm going to use the black probe of the multimeter on one of the metal legs, and red one on the other one , here's a pic

http://i39.tinypic.com/2rxcrat.jpg ( near con 1 )

Can someone verify all this? Thanks so much
Last edited by weirdzaid at Aug 14, 2013,
#2
One trim pot is in the second picture.


No offense but you really should take it to a tech with all the questions you have. Ask them to show you. If you don't know what a trim pot is then this is over your head at this point and time.

See con 1? See the back of the tube pins right next to it? All you have to do is lay your hand down and you will get the shit zapped out of yourself. Nothing starts the day like a 300V hit to the hand. You won't be jerking off for months...

And V1 or V2 or V5 doesn't matter....it matters what were they are in the circuit. V1 is not always the input gain stage tube. You need the schematic to see.

I am not trying to be an ass, just trying to keep you playing guitar instead in the hospital.
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
Last edited by R45VT at Aug 14, 2013,
#3
I'm obviously " diy " since i can't take it to a tech, hence asking for help, if i do take it to a tech now, ill take it to a tech again and again. and i'm not rich , yet.

Trying to get my facts right before i start this, if i didn't care and wouldn't mind being zapped, i wouldn't have opened a different thread asking for safety tips, and another thread to get my facts right.
#4
Quote by R45VT
One trim pot is in the second picture.


No offense but you really should take it to a tech with all the questions you have. Ask them to show you. If you don't know what a trim pot is then this is over your head at this point and time.

See con 1? See the back of the tube pins right next to it? All you have to do is lay your hand down and you will get the shit zapped out of yourself. Nothing starts the day like a 300V hit to the hand. You won't be jerking off for months...

And V1 or V2 or V5 doesn't matter....it matters what were they are in the circuit. V1 is not always the input gain stage tube. You need the schematic to see.

I am not trying to be an ass, just trying to keep you playing guitar instead in the hospital.


As much as I agree with you, he wants to learn how to do it himself. He's in touch with Blackstar directly. He's following my blog so I'm assuming he is following the safety practices.

TS- remember that blog is for 'my' amp and somewhat Splawn specific. You may not have a hum cancelling pot. And my amp doesn't have 'test points' built in. I originally created the tutorial for the Splawn web site. Hopefully it is generic enough that can be helpful to others. I made it because I was unsatisfied with the 'How to Bias' information I was finding on the web.

Just continue to work with Blackstar on this - I can't answer your questions but you are on the right path. Ask them which variable resistor (trim pot) is the one to adjust the amp bias. Ask them to verify the bias range - 100mv seems high to me but again, I don't know much about your amp. Ask them to describe the function of each of the preamp tube slots (hint - there are 'two sides' if you will to most preamp tubes so you'll know if they start talking about V1a and V1b. Yes, check your amps current bias and plate voltage before you swap.

Honestly, I'd just focus on the preamp tubes for now and forget about the power tubes. If you think for some reason that the amp is biased too cold or too hot I could understand. Also, chances are that if you know the bias range you want and ask a distributor for a matched set - you won't need to bias at all. As a matter of fact, if you do get new power tubes, I'd suggest you just pop them in and play and see what you think.
Last edited by 311ZOSOVHJH at Aug 14, 2013,
#5
Quote by weirdzaid
I'm obviously " diy " since i can't take it to a tech, hence asking for help, if i do take it to a tech now, ill take it to a tech again and again. and i'm not rich , yet.

Trying to get my facts right before i start this, if i didn't care and wouldn't mind being zapped, i wouldn't have opened a different thread asking for safety tips, and another thread to get my facts right.
Take it to a tech, tell him you're interested in how this works and have him show you through the process. Throw him extra bucks for the time he spends teaching you stuff.
#6
Quote by 311ZOSOVHJH
As much as I agree with you, he wants to learn how to do it himself. He's in touch with Blackstar directly. He's following my blog so I'm assuming he is following the safety practices.

TS- remember that blog is for 'my' amp and somewhat Splawn specific. You may not have a hum cancelling pot. And my amp doesn't have 'test points' built in. I originally created the tutorial for the Splawn web site. Hopefully it is generic enough that can be helpful to others. I made it because I was unsatisfied with the 'How to Bias' information I was finding on the web.

Just continue to work with Blackstar on this - I can't answer your questions but you are on the right path. Ask them which variable resistor (trim pot) is the one to adjust the amp bias. Ask them to verify the bias range - 100mv seems high to me but again, I don't know much about your amp. Ask them to describe the function of each of the preamp tube slots (hint - there are 'two sides' if you will to most preamp tubes so you'll know if they start talking about V1a and V1b. Yes, check your amps current bias and plate voltage before you swap.

Honestly, I'd just focus on the preamp tubes for now and forget about the power tubes. If you think for some reason that the amp is biased too cold or too hot I could understand. Also, chances are that if you know the bias range you want and ask a distributor for a matched set - you won't need to bias at all. As a matter of fact, if you do get new power tubes, I'd suggest you just pop them in and play and see what you think.



Normally I am all for helpin people but this is above his level. With 300+ volts DC a few multimeters away from the bias test point....
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#7
Quote by R45VT
Normally I am all for helpin people but this is above his level. With 300+ volts DC a few multimeters away from the bias test point....

Stupid Blackstar.

I guess I was hoping it is the other pot in the middle of the board. IIRC mine is in the middle of the board and the hum canceller is closer to the power section.

I wasn't attacking you as you already know. I do however remember not knowing very much about amps and wanting to learn this myself. That was a big reason I created the tutorial after I learned how. If it had not been for a few people on this board answering my questions I would be taking my amps to a tech too.

#8
Back to my 2nd main question , are the 2 metal prongs on the plastic near Con1 , infact the test points ( http://i41.tinypic.com/2a6ry8l.jpg Coloured it in purple ) ? Literally one end of the multimeter to one leg, and other to the other one ? ( one safety question related to this, i want to always work with one hand on the amp, for safety reasons , but probing the 2 test points is going to have to be with 2 hands, or i can try hold both probes in one hand , so anyways , is it safe?

And is the bias trim pot infact there? {White on top of blue box thing http://tinypic.com/view.php?pic=2ptnqdt&s=5 )

Again as preciously mentioned in another thread i'm taking all precautions possible reading blogs, watching videos etc. But i want to know that i have my facts correct.
Last edited by weirdzaid at Aug 14, 2013,
#9
Quote by 311ZOSOVHJH
Honestly, I'd just focus on the preamp tubes for now and forget about the power tubes. If you think for some reason that the amp is biased too cold or too hot I could understand. Also, chances are that if you know the bias range you want and ask a distributor for a matched set - you won't need to bias at all. As a matter of fact, if you do get new power tubes, I'd suggest you just pop them in and play and see what you think.


This
#10
311z, firstly thanks a whole bunch for helping out and answering many of my questions, but my primary reason to change tubes is the amp isn't sounding as optimum as it should be, as it had been, i'd understand if you aren't familiar with my amp , i've sent the 2 pictures i've uploaded here to blackstar aswell to confirm ( A Tech said it on the phone, but be safe safe rather than sorry )
#11
No worries. I don't mind helping where I can. I'm not an amp tech though. My knowledge is pretty limited actually. If he was saying that Con1 is the test points then yes, that is where you put the mulitmeter leads in.

Keep in mind, you have to do this while the amp is turned on and you will be exposed to potential lethal voltages. Normally I say keep one hand in your pocket (jeans not shorts) and one hand to do the work. That will obviously be hard with the test points inside the amp and so close together. Do not use one hand to hold both leads. You don't want those two leads to touch. Think about how you jump a car battery.

The absolute safest bet is to get a Bias Probe like the one in my blog. They are cheap. $25 is nothing in grand scheme of life. You can get them on eBay and also places like www.eurotubes.com. Actually I got a pretty decent one from www.tedweber.com. That way you don't have to worry about this aspect and all you will have to do is turn that screw with a screwdriver to bias up or down.

PS: I still say to just get some preamp tubes like I suggested in your other thread first. I'd be shocked if new power tubes make much difference tonally. I can sense small tonal changes with power tubes but it is super super faint and not OMG That Sounds Soo Much Better.
Last edited by 311ZOSOVHJH at Aug 15, 2013,