MY DMM has a 750v rating but has all the other whistles and bells ! Well I did not buy that VHT for nothing but The book on the amp gives a bunch of testing progressing through no tubes then preamp tubes then power. Checking different points on the turret board and other places here and there. The schematic has the test points and specs for testing which I could do either way and probably will just for my own education. I do appreciate everyones input. Hopefully all my double checking everything two or three times on each stage of this build will have everything covered and it will not blow sky high when it gets power. I have read enough to know to keep my hands clear and have a hand in my pocket while I am in there !.
Bias setting first time advise ???
- Thread starter Phoenix1
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That's sufficient
Good way to look at it! Take your time, be consistent and organised, and document well. I build amps to learn, and for my own pleasure.
Thanks ! This was a first time build after getting half way through the basically sme amp from StewMac who had so many substituted parts over the years they gave me my money back and took theirs off the sell list for a few months until theyredesigned their book on it and built one to make sure it all went together OK. They did give me a gift card and an apology for my trouble. I bought this Tube Depit kit and sterted it right away so sort of hit the ground running. this one does have some extra switches for SS and tube rectifier and some other feeeback type options to mess with the sound and tone. Thought that would be fun as I really dont want to mess with my two stacks which are bone stock but now will have better knowledge in case I want to give them a tune up or bump up the bias to a touch hotter !
dtier
Well-Known Member
Good idea to leave your other amps alone and do a build. Also a good idea to follow the section 8 of your instructions as close as you can as they will help you verify your wiring and avoid smoke. LBL will provide even more protection but may lower the expected readings from section 8. Don't forget to bypass it once your satisfied that you have no issues and are ready to set final bias according to @neikeel . I would have the VHT bias meters installed (when you install the power tubes) to monitor plate currents continuously until your done biasing. I like these analog bias meters myself. Of course heed al of the other great advice here as well.
Definitely been a ton of advise and have appreciated every bit ! Thats why I came here !
thanks !
Here is a good question ! I am starting this amp up slowly and by the book that came with it. First was to put power to the amp no tubes and check a few voltages and all checked really good ! Pilot is on and all is well. next says install the rectifier tube and did turned it on and checked the DC voltage on the big can caps ! Book says 492VDC plus or minus 10V. I am reading 533VDC.... a little over tolerance but the book tested at input 116VAC, I checked my house voltage and it is 123V. Wondering if this is ok or not to proceed ???
Pete Farrington
Well-Known Member
That’s fine.
All circuit voltages will go up and down with mains voltage.
Power supply voltages (eg heater, bias and HT) will directly track the mains voltage.
As I recall, your power company is allowed to let it rise to 127V continuously, with short term highs of 129.
All circuit voltages will go up and down with mains voltage.
Power supply voltages (eg heater, bias and HT) will directly track the mains voltage.
As I recall, your power company is allowed to let it rise to 127V continuously, with short term highs of 129.
Thanks I was not seriously worried about it as both my Marshall stacks work fine ! Anyway big news in my next post
Today I rolled my Silver Jubilee over to the doorway and in as close as possible as five foot speaker cords dont reach far and I turned it on and could not get a miliamp reading on pin 8 of each power tube so I freaked out and called the place Tube Depot and just got the answering machine. Now stress set in ! So after no answers and after closing time I would have to wait till next thursday when the main tech guy Jack comes in. And just walked away ! Fretted for the last two hours over this and went down to shut off lights finally and I said to myself there was a pop in the speakers when I shut off the power so knew it had to be close I just had to try again. So I powered it up and twisted the bias pot clockwise and this time had my bias meter in the sockets under the tubes and they moved in the wrong direction so twisted it back a little and turned the plugs around na d twisted the bias pot again and here the go !!! Kept twisting until I got up to about 35ma plugged in my guitar and twisted the master volume up and BOOM i got sound !!! Had it plugged into my big Marshall cabinet ! Well to make a long story short !!! It works !!!!! Works good too and no noise or anything !
Today I turned it onand could not get a miliamp reading on pin 8 of each power tube so I freaked out and called the place Tube Depot and just got the answering machine. Now stress set in ! So after no answers and after closing time I would have to wait till next thursday when the main tech guy Jack comes in. And just walked away ! Fretted for the last two hours over this and went down to shut off lights finally and I said to myself there was a pop in the speakers when I shut off the power so knew it had to be close. So I piwered it up and twisted the bias pot clockwiseand this time had my bias meter in the sockets under the tubes and they moved in the wrong direction so twisted it back a little and turned the plugs around na d twisted the bias pot again and here the go !!! Kept twisting until I got up to about 35ma plugged in my guitar and twisted the master volume up and BOOM i got sound !!! Had it plugged into my big Marshall cabinet ! Well to make a long story short !!! It works !!!
Today I turned it onand could not get a miliamp reading on pin 8 of each power tube so I freaked out and called the place Tube Depot and just got the answering machine. Now stress set in ! So after no answers and after closing time I would have to wait till next thursday when the main tech guy Jack comes in. And just walked away ! Fretted for the last two hours over this and went down to shut off lights finally and I said to myself there was a pop in the speakers when I shut off the power so knew it had to be close. So I piwered it up and twisted the bias pot clockwiseand this time had my bias meter in the sockets under the tubes and they moved in the wrong direction so twisted it back a little and turned the plugs around na d twisted the bias pot again and here the go !!! Kept twisting until I got up to about 35ma plugged in my guitar and twisted the master volume up and BOOM i got sound !!! Had it plugged into my big Marshall cabinet ! Well to make a long story short !!! It works !!!
