What does it mean that your plate voltage is 61 percent of your plate current? You're in way over your head - take @agedhorse's advice.
Enjoy the benefits of a premium membership!
Upgrade Account
-
TalkBass has been independent since 1998. Add your voice.
Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
Join free Log in
Want zero display ads or expanded classifieds tools? Compare plans.
First time putting new tubes into Peavey VB-2
- Thread starter Billythebass1
- Start date
-
- Tags
- first time peavey time tubes vb-2
- Feb 12, 2006
- 60,986
- 5
- 220,768
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Ummm, where are you reading 48V? That has nothing to do with the plate current, which is in completely different units (mA). You are now comparing bananas with bacon. I have no idea what you are doing (and I know this stuff pretty well).
I'm guessing that you are measuring the bias voltage (which then should be -48.1V, it's negative in respect to ground)...that tells you nothing, really.
Hold your horses...the "PC" value on the box indicates the measured value in the vendor's tube matching equipment, this is not a static value that you can use for setting the idle plate current (which is what biasing is about) in your amp..... I suggest that you stop here and hire a tech.
Hold your horses...the "PC" value on the box indicates the measured value in the vendor's tube matching equipment, this is not a static value that you can use for setting the idle plate current (which is what biasing is about) in your amp..... I suggest that you stop here and hire a tech.
Two Leggs
Commercial User
- Feb 20, 2018
- 70
- 87
- 62
- Disclosures
- Pro Audio Repair shop , SVC Mesa Boogie
Why is it that folk buy themselves a tube amp and then consider it fine to go prodding around inside with no idea what they are doing? Inside a 200W tube amp is no place for a neophyte to be. It’s a place where it’s easy to seriously damage yourself or worse just to save a few dollars!
OP please heed the advice that @agedhorse and myself have given you and take it to a tech.
OP please heed the advice that @agedhorse and myself have given you and take it to a tech.
Mmmmmm, bacon wrapped bananas. drool
I wonder if you would be where you are now if everyone told you to take it to a tech? How does anyone ever learn? The bias point on this VB-2 reads 48.1 with my multi meter. which I take to mean -48.1 millivolts DC. Like bb5000 says But this must mean something to somebody? It is a ‘learning amp’ like one guy said and not one to take to work. And I’m not so dumb as to touch any of the capacitors! So if anyone can help with some kind tips on my next steps then please let me know.
Two Leggs
Commercial User
- Feb 20, 2018
- 70
- 87
- 62
- Disclosures
- Pro Audio Repair shop , SVC Mesa Boogie
You learn by going to tech school and start with basics and work,your way through. My tech school lasted at least 1800 hours and after that you learn the do’s and don’ts and if your lucky your instructor knows about tube amps. Don’t be a “Primitive Pete”!and get yourself hurt.
And if I had any questions Mr. Horse would be the first person I would ask and probably the only one .And you can take that to the bank.
Last edited:
Could be preamp tubes as well
He's probably measuring bias voltage sounds within range id assume its preset so bias might not be adjustable.
He said metallic sound.
Sounds like basic microphonic preamp tube.
Tubes are ten years old he's not killing any endagered species here guys.
Just butt ancient factory tubes ....relax.
He's probably measuring bias voltage sounds within range id assume its preset so bias might not be adjustable.
He said metallic sound.
Sounds like basic microphonic preamp tube.
Tubes are ten years old he's not killing any endagered species here guys.
Just butt ancient factory tubes ....relax.
- Feb 12, 2006
- 60,986
- 5
- 220,768
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Without knowing WHAT you are measuring, there's no way to know if the value you are reading is volts or mV.
Where are you measuring this voltage?
Note that there may be several versions of this amp, but the only schematic I have would preclude the reading being mV.
We learn by studying the basics, we learn how tubes work, how the circuits work, how they fail and why. We learn troubleshooting skills so that we an identify what measurements are correct and what are not so that we can identify where the malfunction is occurring. Adding global feedback completely skews the impression of what is normal and what is not.
Capacitors are the least of your worries, though they carry with them the grandest of internet stories and folklore.
Where are you measuring this voltage?
Note that there may be several versions of this amp, but the only schematic I have would preclude the reading being mV.
We learn by studying the basics, we learn how tubes work, how the circuits work, how they fail and why. We learn troubleshooting skills so that we an identify what measurements are correct and what are not so that we can identify where the malfunction is occurring. Adding global feedback completely skews the impression of what is normal and what is not.
Capacitors are the least of your worries, though they carry with them the grandest of internet stories and folklore.
Here are some comments from the person ( BbbyBld ) who designed the VB-2
"The VB-2 plate is 550V and it will do 225W easy while staying class AB. 75W per pair is also easy if you have reliable EL34s, which were not available for decades until about 4 years ago when JJ made theirs. It's all about controlling the screens, the power supply, and the output transformer. Also, the efficiency of a class AB amp changes with output power. The efficiency goes way up at near clipping."
I had this amp, and retubed it , the easiest way is to get tubes from Peavey, they will have a matched set, you'll have to give them the numbers on the tube bases
The bias set-up is kinda similar to an old traynor YBA-3
Here's another snippet from another thread about the VB-2
"On the vb-2, per the schematic and layout documentation that I have from peavey, the power tubes are as follows:
A B A B A B
the A's are connected in paralell, the B's are connected in paralell. There are no "pairs" as far as the audio part of the amp. The heaters are in series in pairs though.
Also, the stand by on the vb-2 is not what you think it is.
The vb2's standby turns the screens of the power tubes on and off. This configuration allows you to put the head in standby, and use the preamp as a D.I., or to drive another power amp, or what ever. When the power switch is on, everything is on. Heaters, B+ etc etc. (except the screens)
Hope this helps a little.
P.S. the vb-2 is an awesome tube amp. el34's as P. Traynor intended them. Thanks BBYBLD!"
I believe BbbyBld, still posts on TB, might want to PM him
"The VB-2 plate is 550V and it will do 225W easy while staying class AB. 75W per pair is also easy if you have reliable EL34s, which were not available for decades until about 4 years ago when JJ made theirs. It's all about controlling the screens, the power supply, and the output transformer. Also, the efficiency of a class AB amp changes with output power. The efficiency goes way up at near clipping."
I had this amp, and retubed it , the easiest way is to get tubes from Peavey, they will have a matched set, you'll have to give them the numbers on the tube bases
The bias set-up is kinda similar to an old traynor YBA-3
Here's another snippet from another thread about the VB-2
"On the vb-2, per the schematic and layout documentation that I have from peavey, the power tubes are as follows:
A B A B A B
the A's are connected in paralell, the B's are connected in paralell. There are no "pairs" as far as the audio part of the amp. The heaters are in series in pairs though.
Also, the stand by on the vb-2 is not what you think it is.
The vb2's standby turns the screens of the power tubes on and off. This configuration allows you to put the head in standby, and use the preamp as a D.I., or to drive another power amp, or what ever. When the power switch is on, everything is on. Heaters, B+ etc etc. (except the screens)
Hope this helps a little.
P.S. the vb-2 is an awesome tube amp. el34's as P. Traynor intended them. Thanks BBYBLD!"
I believe BbbyBld, still posts on TB, might want to PM him
Last edited:
I’ve PMd BbbyBld but without reply. Thanks jastacy, I’ve wound the bias point down to 43.5 volts and the distortion has reduced. This was quoted to me by the UK distributor who emailed Peavey. A much better response than the local Peavey service centre. I may drop it lower by a touch another evening but I’ve run out of time tonight. Getting there I hope.
