Tone Monster
Well-known member
What type of meter do I need? Anyone got a link to a vid perhaps? I looked on youtube and nothin 
Is there a CCV biasing tutorial anywhere?
- Thread starter Tone Monster
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LP Freak
Well-known member
You'll need a digital volt meter. You can get one at any home center. Doesn't need to be anything fancy it just needs to read DC voltage. You can pick one up for $20. I don't have a CCV and have never biased one so it would be better to have someone else who has chime in. It's not too hard to do but if you're not real sure of yourself it might be best to have somone do it for you. There's lethal voltages in the amp that can kill you if you're poking in the wrong spot.Tone Monster":2mbjg1ds said:What type of meter do I need? Anyone got a link to a vid perhaps? I looked on youtube and nothin
It would be helpful to suggest the method that is used at the shop for biasing the tubes in it and how long to wait before it stabilizes. While the manual states the plate voltages, I have heard that it is g2 that is important in determining if a power tube will hold up for an amp. Good information to have in the user's manual IMO.
dawnofdreamx97
Well-known member
50MkII":3a6166ip said:
either a regular JJ el34 or Winged C el34 will work. I suggest the winged C , they handle the high plate voltage and sound best.
steve_k
New member
Guys,
It's no different than biasing any other amp. As Nick says above, JJ or ARS E34L's will work, as will Ruby BHT's as will SED Winged C's. The CCV puts out 560PV. The screen voltage is what kills a tube though. Need to make sure you have a durable tube that advertises that they will handle high PV's.
To the OP, I use a Compu-Bias meter. You can order direct off their site. They are great because in one readout, you can get the bias mA, output wattage and plate voltage, without doing anything. The bias right is good too. Either way, go ahead and get one with a dual probe.
One caveat with the CCV that is a pisser, is that you still have to pull the chassis to get the probe and a tube to seat. If the head was a little deeper or taller, you wouldn't have to do this. HINT, HINT! One of my CCV's has an external bias, but I still have to slide the chassis out.
Anyway, here is your tutorial:
1) Unplug everything and remove the 4 chassis bolts and rear panel.
2) Reach inside and pick the chassis up by the transformers (the big red things) and slide the chassis out of the shell.
3) Remove the first power tube on the left (or farthest right) and plug in the bias probe.
4) Place the tube back in the probe socket.
5) If you have a second probe, put it in one of the inner sockets.
6) Plug in the electric cable, a speaker cable. Do not plug in a guitar, and turn down the MASTER VOLUMES.
7) Turn on the amp in standby and also MAKE SURE THE AMP IS ON THE HIGH POWER SETTING. You cannot bias on low.
8) Let it warm up a a minute then flip it onto RUN.
9) Read the bias and PV on one or both probes.
10) Anywhere that the bias settles in the 30-40mA range with the above mentioned tubes is fine. But, the bias between tubes should be within 10% of each other. I run mine at 35-38mA.
If you find the bias way too high or too low and need to adjust the bias, or if you have a set of tubes that are not matched and wish to change tubes, do the following to be safe. I usually just turn mine up on the side, powered up, but you need to be careful doing this. That CCV chassis is full and be careful where you fingers go. The safe way is:
1) Power down, let the tubes cool. Remove the power chord and speaker cable.
2) If you need to just rebias, leave the probe and power tubes in. If you need to change the quad, go ahead and pull the tubes. Leave the probes in.
3) Either set a few large books spaced apart where you can rest the amp on the transformers and do so, or tip the amp on its side and leaning against the wall so it won't tip over, or use an amp cradle.
4) Install power tubes.
5) Plug in the power cord and speaker cable. Power up in standby, on high power.
6) Flip the amp on run.
7) Locate the bias adjust screw. It will be the only thing in a CCV with a slot for a screwdriver.
8) Use an insulted flathead screwdriver and turn a small amount left or right and see which way your bias goes, up or down and then turn until the desired mA is reached.
Note - on the CCV, there is only one bias adjust for the quad. You cannot adjust inners and outers or singles. This is why it is important to have a new or known MATCHED QUAD.
9) Note the bias levels on both probes if you have two probes. They should match pretty close. Being off 3-4 mA is fine. Use the higher bias level if you have different readings.
I usually let mine set in run for 15 or 20 minutes then go back and check. They will drift a bit as they heat up. Readjust if needed. If you want, you can repeat all this with probes in the other two tube positions to check it out and make sure the quad is properly matched.
10) Put amp in standby and power down. Unplug everything. Remove the probes and replace the tubes in the slots you pulled them from.
Now is a really good time to experiment with different preamp tubes, with the chassis out of the shell. Once you are done:
11) Put the chassis back in the shell. Secure and install back panel.
Take extreme caution with the CCV when putt the chassis back in the shell. You want to hold the weight of the chassis a little by grasping the transformers. Some of the lugs on the pots are very near the bottom of the chassis, as is the MIDI board and the top side of the loop board. These have a bad habit of dragging across the foil in the bottom of the shell and getting a little piece of that grounding somewhere it shouldn't. If you put the chassis back in and see a little pile of foil at the front/bottom of the chassis looking from the front, remove and straighten out the foil and try again.
DO NOT PLAY the guitar through your amp with bias probes installed. Why? When you turn the volume up, strike a chord, pump the tube, you could really mess up here. With the probes in the sockets, the ground is broke which enables the probe to read voltage differential between pin 4 and 8. If you do something which exceeds the screen or bias supply and something goes to ground, it is also coming to you - via the guitar.
Also, use common sense. Stand on something insulated or wear shoes. Keep one arm behind your back or a hand in your pocket when you turn the bias screw. If you slip and the screwdriver goes somewhere else and your other arm is touching the chassis - you just made a circuit and you are going to get electrocuted.
Hope this helps.
Steve
It's no different than biasing any other amp. As Nick says above, JJ or ARS E34L's will work, as will Ruby BHT's as will SED Winged C's. The CCV puts out 560PV. The screen voltage is what kills a tube though. Need to make sure you have a durable tube that advertises that they will handle high PV's.
To the OP, I use a Compu-Bias meter. You can order direct off their site. They are great because in one readout, you can get the bias mA, output wattage and plate voltage, without doing anything. The bias right is good too. Either way, go ahead and get one with a dual probe.
One caveat with the CCV that is a pisser, is that you still have to pull the chassis to get the probe and a tube to seat. If the head was a little deeper or taller, you wouldn't have to do this. HINT, HINT! One of my CCV's has an external bias, but I still have to slide the chassis out.
Anyway, here is your tutorial:
1) Unplug everything and remove the 4 chassis bolts and rear panel.
2) Reach inside and pick the chassis up by the transformers (the big red things) and slide the chassis out of the shell.
3) Remove the first power tube on the left (or farthest right) and plug in the bias probe.
4) Place the tube back in the probe socket.
5) If you have a second probe, put it in one of the inner sockets.
6) Plug in the electric cable, a speaker cable. Do not plug in a guitar, and turn down the MASTER VOLUMES.
7) Turn on the amp in standby and also MAKE SURE THE AMP IS ON THE HIGH POWER SETTING. You cannot bias on low.
8) Let it warm up a a minute then flip it onto RUN.
9) Read the bias and PV on one or both probes.
10) Anywhere that the bias settles in the 30-40mA range with the above mentioned tubes is fine. But, the bias between tubes should be within 10% of each other. I run mine at 35-38mA.
If you find the bias way too high or too low and need to adjust the bias, or if you have a set of tubes that are not matched and wish to change tubes, do the following to be safe. I usually just turn mine up on the side, powered up, but you need to be careful doing this. That CCV chassis is full and be careful where you fingers go. The safe way is:
1) Power down, let the tubes cool. Remove the power chord and speaker cable.
2) If you need to just rebias, leave the probe and power tubes in. If you need to change the quad, go ahead and pull the tubes. Leave the probes in.
3) Either set a few large books spaced apart where you can rest the amp on the transformers and do so, or tip the amp on its side and leaning against the wall so it won't tip over, or use an amp cradle.
4) Install power tubes.
5) Plug in the power cord and speaker cable. Power up in standby, on high power.
6) Flip the amp on run.
7) Locate the bias adjust screw. It will be the only thing in a CCV with a slot for a screwdriver.
8) Use an insulted flathead screwdriver and turn a small amount left or right and see which way your bias goes, up or down and then turn until the desired mA is reached.
Note - on the CCV, there is only one bias adjust for the quad. You cannot adjust inners and outers or singles. This is why it is important to have a new or known MATCHED QUAD.
9) Note the bias levels on both probes if you have two probes. They should match pretty close. Being off 3-4 mA is fine. Use the higher bias level if you have different readings.
I usually let mine set in run for 15 or 20 minutes then go back and check. They will drift a bit as they heat up. Readjust if needed. If you want, you can repeat all this with probes in the other two tube positions to check it out and make sure the quad is properly matched.
10) Put amp in standby and power down. Unplug everything. Remove the probes and replace the tubes in the slots you pulled them from.
Now is a really good time to experiment with different preamp tubes, with the chassis out of the shell. Once you are done:
11) Put the chassis back in the shell. Secure and install back panel.
Take extreme caution with the CCV when putt the chassis back in the shell. You want to hold the weight of the chassis a little by grasping the transformers. Some of the lugs on the pots are very near the bottom of the chassis, as is the MIDI board and the top side of the loop board. These have a bad habit of dragging across the foil in the bottom of the shell and getting a little piece of that grounding somewhere it shouldn't. If you put the chassis back in and see a little pile of foil at the front/bottom of the chassis looking from the front, remove and straighten out the foil and try again.
DO NOT PLAY the guitar through your amp with bias probes installed. Why? When you turn the volume up, strike a chord, pump the tube, you could really mess up here. With the probes in the sockets, the ground is broke which enables the probe to read voltage differential between pin 4 and 8. If you do something which exceeds the screen or bias supply and something goes to ground, it is also coming to you - via the guitar.
Also, use common sense. Stand on something insulated or wear shoes. Keep one arm behind your back or a hand in your pocket when you turn the bias screw. If you slip and the screwdriver goes somewhere else and your other arm is touching the chassis - you just made a circuit and you are going to get electrocuted.
Hope this helps.
Steve
glip22
Well-known member
Nice work Steve. Rip the foil out. Trust me. The headshell makers use it and its the dumbest thing. It can cause lots of issues and does nothing to shield the amps. However as Steve said it can short various parts of the amp and ruin components also.drewiv":31zxyqap said:
lester
Well-known member
Give em the code guys.---------Maximum plate dissipation(EL34=25watts) divided by plate voltage X (anything between 0.5 to 0.7) X 1000
The factor 1000 is used to convert amps to milliamps.
Based on a plate voltage of 560 - I wouldn't bias them over 29mA (that's at 65 percent). I've been sticking around 60% for my deal lately.
The factor 1000 is used to convert amps to milliamps.
Based on a plate voltage of 560 - I wouldn't bias them over 29mA (that's at 65 percent). I've been sticking around 60% for my deal lately.
Tone Monster
Well-known member
Thanks Steve
steve_k
New member
johnpace2":24vprkm9 said:
That generic formula works great in a linear world. What this doesn't take into account is the OT resistance/impedance and its controlling effect at the screen grid. The "designed for Cameron Amplification by Mercury Magnetics" sticker on the OT isn't just sales gimmick. The relationship between bias supply and screen/plate supply/output is not a straight line and that formula, while good enough for government work is a starting point - you can somewhat disregard it.
Steve
steve_k
New member
psychodave":3w2gef7p said:johnpace2":3w2gef7p said:
I set mine cold... like around 28-29 mA.
...and I rarely use high power, so I'm actually a little colder.
Jack it up. That's where the harmonics are! I can't tell much difference between 40 and 50, but a lot of difference between 30 and 40 on the high setting. The low setting goes through such an impedance change that it really doesn't matter where it is set. The higher bias settings helps control the feedback and squeal on the clipping modes too as opposed to lower bias settings. Believe me....true story!
Steve
232cap
Well-known member
They are using a higher grid stopper resistor to allow the tubes to live at a hight PV, its the screens that fail not the plates fronm what I'v seen which isn't much. Look the JJ 34's in mine were biased at 54ma, normally a jj34 would die fast especially the latest ones I have been getting.
LP Freak
Well-known member
I'd say Dave's tone speaks for itself.steve_k":38r3bmcx said:psychodave":38r3bmcx said:johnpace2":38r3bmcx said:
I set mine cold... like around 28-29 mA.
Jack it up. That's where the harmonics are! I can't tell much difference between 40 and 50, but a lot of difference between 30 and 40 on the high setting. The low setting goes through such an impedance change that it really doesn't matter where it is set. The higher bias settings helps control the feedback and squeal on the clipping modes too as opposed to lower bias settings. Believe me....true story!
Steve
steve_k
New member
232cap":8rc84wfk said:
Yep.....and all you have to do to prove to yourself is run the bias up at idle to 50mA, which is over 100%, turn the lights down low, sip your cocktail and look for any signs of excess glow or red plating for a few minutes - you won't see any evidence of it. An effective way to bias a CCV is to turn the master up and run the bias up until you start to hear some background noise then back it down a bit. You will be sitting in the high 40's somewhere.
Steve