Cymbal bias procedure?

0 Members and 1 Guest are viewing this topic. Read 1274 times.

harryf

  • Jr. Member
  • Posts: 117
Cymbal bias procedure?
« on: 12 May 2010, 03:59 am »
Ok i got both my cymbal's up and running.They smell a bit funny like new electronics burning in but sound fine.Except....One plays half the volume of the other.
So i fooled around trying to set bias.I did the procedure that is called for in the manual and got .002.The problem is .002 is what my dvm reads just sitting around.
So what do you reasure ohm's volt's what?I thought volt's?
If the bias was out on one it would cost me a bit of power but not 50% right?So i have some kind of problem?
With my boards i have absolutly no room for error as far as where you mount them in the top cover.
In fact i had to cut a bit off one board for it to fit in the lansing chassis.This one play's loud.
The other one touch's on both ends.Could this be a problem?It play's lower.
I do notice the longer you play this amp it start's to lose even more power.
I hAVE no red plates.No  burning smell.Both smell the same in fact.
So what does it sound like.Well i was shocked.I have never heard a less warm tube amp.
I used auricap's and two multicaps.Kwami's and takman carbon's.Gold pin eh tubes.
i realise this amp might need to be biased and definitly need's breaking in.
It is clear as a bell.I am useing klipsch heresy II's right now so i'm sure with my better speakers it will sound different.

poty

  • Full Member
  • Posts: 616
Re: Cymbal bias procedure?
« Reply #1 on: 12 May 2010, 11:47 am »
...I got both my cymbal's up and running. ...One plays half the volume of the other.
So i fooled around trying to set bias.
It's the last thing you should do.
...I had to cut a bit off one board for it to fit in the lansing chassis. This one plays loud. The other one touchs on both ends. Could this be a problem? It play's lower.
Yes, you should check this first. I think there may be the problem.
I do notice the longer you play this amp it start's to lose even more power.
Something is heating more and more, I suppose.
I did the procedure that is called for in the manual and got .002.The problem is .002 is what my dvm reads just sitting around.
So what do you reasure ohm's volt's what?I thought volt's?
Hmmm, "procedure" in the manual mentions several points of measurement:
1. "The LED should be red, and then switch to green after about 20 seconds. This indicates both heater and high voltage circuits are working."
2. "Measure power supply" - means  voltage on "+" of C300 (should be 280V) and C304 (should be 6.2V).
3. "and plate voltages using a DVM." - means voltage in the point of joint of the resistors R308, R309, R307 (should be 140V).
Don't forget: "Due to tube variations, these voltages will range as much as +/-10V."

I do not understand your ".002" completely.

harryf

  • Jr. Member
  • Posts: 117
Re: Cymbal bias procedure?
« Reply #2 on: 12 May 2010, 02:20 pm »
It say's to put your dvm into m+ and m- then measure.I get .002.Reading your post i realise i probably need to ground to the chassis then put the red end probe of the dvm in each hole seperatly.Duh!Then turn the screw for 0 v
So i swaped in the tube's from the lower playing amp into the louder amp.I found one of my sovtech's 5ar4's did indeed cause the louder amp to play with less volume.About 10%.Lucky for me i have so many hagerman project's i just swaped tube's and got that 10% back.
i then swaped driver's between amps and found a bit of volume too.Say 5%.
So i need to find 35% more.I will check voltage's internaly today.
The sound on the one loud amp has already started to open up.
I have a few resored or in the process of being resored vintage amp's.This is the polar oposite of what that warm vintage sound.Its really interesting as i never thought a tube amp could sound so detailed.The transformer's are cool,really cool.The chassis seems to soak up the heat.

harryf

  • Jr. Member
  • Posts: 117
Re: Cymbal bias procedure?
« Reply #3 on: 12 May 2010, 02:23 pm »
Oh i ment my dvm read's .002 just sitting around not touching anything.It it's natural error.It also read that when oi put the probes in m+ and m-

harryf

  • Jr. Member
  • Posts: 117
Re: Cymbal bias procedure?
« Reply #4 on: 12 May 2010, 04:13 pm »
Well i found the problem!!!A loose speaker connector.All is fixed.I'm happy as a clam.
I'll post a review in a few week's when everything break's in.