Working on a Ampeg V4B. Changing all the E-Caps, adding a bias pot, changing the screen resistors to 1K/5W. Now I am looking at the AC mains. It has a 3 wire power cord but it also has a death cap/polarity switch and a 10 amp fuse between the AC convenience jack and the fuse holder for the 6 amp fuse.
What is the 10 amp fuse for?
I am planning on getting rid of the 10 amp fuse, the death cap, and the polarity switch. Any reason not to proceed with my plans?
Thank You
Link to the original Ampeg Schematic......
http://www.freeinfosociety.com/media/images/1555.gif
Ampeg V4B
Moderators: pompeiisneaks, Colossal
Re: Ampeg V4B
I don't know as much about the late 70's ampegs vs. the earlier ones. The 10A fuse seems superfluous. I'd get rid of the death cap if the polarity switch isn't 3 position. I'd leave the switch there...doing nothing.
Re: Ampeg V4B
That is what I was thinking. Abandon the 10 amp fuse (but why is it there?) get rid of the death cap, and disconnect the polarity switch. I am kind of following this schematic. I see it a lot on the Internet, but I do not know how legitimate it is.
Thanks
http://www.ampix.org/albums/ampegamps/v4bpowramp.pdf
http://www.ampix.org/albums/ampegamps/v4bpreamp.pdf
Thanks
http://www.ampix.org/albums/ampegamps/v4bpowramp.pdf
http://www.ampix.org/albums/ampegamps/v4bpreamp.pdf
Re: Ampeg V4B
That schematic is pretty good.
The V4-B is an early (non-distortion) model V4 (or VT-22) minus the reverb section and with the added Ultra-Low switch and RC network. Otherwise they are the same.
I'd follow the advice as you've been given here. I'd have the cable in go via a fuse to the courtesy outlet so that if anything plugged in there develops a fault you won't be relying on your amp power lead to be able to handle the fault, and the amp itself fused as normal.
Definitely remove the death cap and disconnect the polarity switch as it's not needed now this has a grounded power lead.
As an aside, since you've got access to one of these, it would be great if you could help fill in the missing piece of documentation on the RC values for the Ultra Low switch (see the question marks on the schematic you posted).
If you can see them without tearing the amp apart that would be really useful to have documented.
The V4-B is an early (non-distortion) model V4 (or VT-22) minus the reverb section and with the added Ultra-Low switch and RC network. Otherwise they are the same.
I'd follow the advice as you've been given here. I'd have the cable in go via a fuse to the courtesy outlet so that if anything plugged in there develops a fault you won't be relying on your amp power lead to be able to handle the fault, and the amp itself fused as normal.
Definitely remove the death cap and disconnect the polarity switch as it's not needed now this has a grounded power lead.
As an aside, since you've got access to one of these, it would be great if you could help fill in the missing piece of documentation on the RC values for the Ultra Low switch (see the question marks on the schematic you posted).
If you can see them without tearing the amp apart that would be really useful to have documented.
Re: Ampeg V4B
Hey Paulster -
Yes, I will wire the mains in that manner.
Ampegs are about the most difficult and confusing amps I have ever had my hands inside of. The original Ampeg schem can differ quite a bit from the later, dual schem that I posted. So it is confusing which schem I should be using as far as component values are concerned. Also, the dual schem does not call out the component number that corresponds to the stenciled PCB. I guess what also happens is the original schem tries to incorporate a few different configurations of this chassis. Perhaps I should just follow thew new print to avoid the back and forth headache.
If you guys think it is important I will pull the board for the pots that has the caps in question. It is kind of a lot of work, these Ampegs are not very user friendly. Just looking down at the board I do see some tropical fish caps...... So I can pull it, and take some pics and data if you like.
This is the second Ampeg I have worked on (the other was a B-25) and they are just a struggle for me. The switching is kind of confusing, and the PCB's are more demanding and time consuming than all the hand wired stuff I am use to.
What ever....
Thank You
Yes, I will wire the mains in that manner.
Ampegs are about the most difficult and confusing amps I have ever had my hands inside of. The original Ampeg schem can differ quite a bit from the later, dual schem that I posted. So it is confusing which schem I should be using as far as component values are concerned. Also, the dual schem does not call out the component number that corresponds to the stenciled PCB. I guess what also happens is the original schem tries to incorporate a few different configurations of this chassis. Perhaps I should just follow thew new print to avoid the back and forth headache.
If you guys think it is important I will pull the board for the pots that has the caps in question. It is kind of a lot of work, these Ampegs are not very user friendly. Just looking down at the board I do see some tropical fish caps...... So I can pull it, and take some pics and data if you like.
This is the second Ampeg I have worked on (the other was a B-25) and they are just a struggle for me. The switching is kind of confusing, and the PCB's are more demanding and time consuming than all the hand wired stuff I am use to.
What ever....
Thank You
Re: Ampeg V4B
Here's what I've done with several old BF/SF Fenders--
Disconnect the polarity switch and make it an on/off switch for the courtesy outlet.
On your Ampeg, I'd wire the extra fuse in series with the switch/outlet so the courtesy outlet is independently fused from the amp. Make it something reasonable, say 2 or 3 amps, for running a pedalboard.
Disconnect the polarity switch and make it an on/off switch for the courtesy outlet.
On your Ampeg, I'd wire the extra fuse in series with the switch/outlet so the courtesy outlet is independently fused from the amp. Make it something reasonable, say 2 or 3 amps, for running a pedalboard.
Rich Gordon
www.myspace.com/bigboyamplifiers
"The takers get the honey, the givers get the blues." --Robin Trower
www.myspace.com/bigboyamplifiers
"The takers get the honey, the givers get the blues." --Robin Trower
Re: Ampeg V4B
If you could do me a favor, I'd like to see a picture of the inductor. (I've had my chances and didn't think about it...) I've got several gut shots of V series amps, but I don't see anything that looks like a multi-tap inductor. MM wants a lot for one, and I would assume it's a low current device that should be pretty inexpensive.
Re: Ampeg V4B
You are going to have to give me some guidance. Multi tap inductor??jaysg wrote:If you could do me a favor, I'd like to see a picture of the inductor. (I've had my chances and didn't think about it...) I've got several gut shots of V series amps, but I don't see anything that looks like a multi-tap inductor. MM wants a lot for one, and I would assume it's a low current device that should be pretty inexpensive.
When I read "inductor" I think of a choke, which my V4 does not have. So what are you wanting me to take a picture of?
Re: Ampeg V4B
If you use the first schematic you posted, find the mid-range pot...it's in the right-middle of the schematic below the third section of the 6K11. Follow the wiper down to "Toriodal Inductor". My assumption is that it doesn't see any power, so the toroid could be 1 to 2 inches in diamter, and the wire, pretty light gauge. It might be on the back of the front panel, near the midrange switch.
Re: Ampeg V4B
Jay
It's a 1" core toroidal inductor of 800mH, with taps at at 100mH and 300mH.
The same inductor, on a small PCB mount, is used in the SVP-CL, so may be available as a spare part from Ampeg.
If I was in the States I'd have ordered one by now to get some more measurements off (like the DCR figure), but if someone wants to take up that challenge...
Paul
It's a 1" core toroidal inductor of 800mH, with taps at at 100mH and 300mH.
The same inductor, on a small PCB mount, is used in the SVP-CL, so may be available as a spare part from Ampeg.
If I was in the States I'd have ordered one by now to get some more measurements off (like the DCR figure), but if someone wants to take up that challenge...
Paul
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Re: Ampeg V4B
OK, I spoke too soon. I was thinking of something like a small verb tranny. Sorry about that. It is located on the pot PCB which I managed to set free from the front panel. I guess you get use to these Magnavox Ampegs after awhile.
OK, so I have access to the little toroid. Is there some way I can help one of you guys at this point?
OK, so I have access to the little toroid. Is there some way I can help one of you guys at this point?
Re: Ampeg V4B
MM shows the AV4-MC inductor, as an $85 part, fwiw.
I swear I had all the Baxandall R's and C's written down, but now I can't find them.
This schematic shows it as a short:paulster wrote:As an aside, since you've got access to one of these, it would be great if you could help fill in the missing piece of documentation on the RC values for the Ultra Low switch (see the question marks on the schematic you posted).
I swear I had all the Baxandall R's and C's written down, but now I can't find them.
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Re: Ampeg V4B
I think that schematic has an error on the Ultra Low switch or it'll be Ultra Quiet as well, and the resistor values are really difficult to read as well.
I posted the tone stack values in the other Ampeg thread on here (https://tubeamparchive.com/viewtopic.php?t=9844).
I wouldn't want to buy MM's part because I don't know whether they've just plumped for the 800mH value with the right taps rather than reverse-engineer an original. As the SVP-CL has been in production until very recently (and I imagine some of the current heads use the inductor too) it should be pretty easy to get an original from Ampeg to properly reverse-engineer.
Once I get to the stage of finalising the layout for a hybrid V4/V4B I might even pull the inductor out of my SVP-CL temporarily to get a repro made, but that project's a little way out yet.
I posted the tone stack values in the other Ampeg thread on here (https://tubeamparchive.com/viewtopic.php?t=9844).
I wouldn't want to buy MM's part because I don't know whether they've just plumped for the 800mH value with the right taps rather than reverse-engineer an original. As the SVP-CL has been in production until very recently (and I imagine some of the current heads use the inductor too) it should be pretty easy to get an original from Ampeg to properly reverse-engineer.
Once I get to the stage of finalising the layout for a hybrid V4/V4B I might even pull the inductor out of my SVP-CL temporarily to get a repro made, but that project's a little way out yet.
Re: Ampeg V4B
It is mounted to the control pot board on the backside of the control panel.
I have a V2 in now probably the same inductor, about 2" diameter, yellow tape. I will try to get a pic for you. I just buttoned it all back up after service. If the owner is slow coming to pick it up I may have chance to open it back up and take a few pics.
Oddly enough, I have a SVT and a V2 both Magnavox era , a Selmer 100W and a Sunn PA 200 series all in the shop at the same time. The Selmer is the Coolest of the bunch 4x el34 all mullard mustards, sounds great.
I have a V2 in now probably the same inductor, about 2" diameter, yellow tape. I will try to get a pic for you. I just buttoned it all back up after service. If the owner is slow coming to pick it up I may have chance to open it back up and take a few pics.
Oddly enough, I have a SVT and a V2 both Magnavox era , a Selmer 100W and a Sunn PA 200 series all in the shop at the same time. The Selmer is the Coolest of the bunch 4x el34 all mullard mustards, sounds great.
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HI ! I'm Having the Same Problem with my Ultra Lo Switch
paulster wrote:I think that schematic has an error on the Ultra Low switch or it'll be Ultra Quiet as well, and the resistor values are really difficult to read as well.
I posted the tone stack values in the other Ampeg thread on here (https://tubeamparchive.com/viewtopic.php?t=9844).
I wouldn't want to buy MM's part because I don't know whether they've just plumped for the 800mH value with the right taps rather than reverse-engineer an original. As the SVP-CL has been in production until very recently (and I imagine some of the current heads use the inductor too) it should be pretty easy to get an original from Ampeg to properly reverse-engineer.
Once I get to the stage of finalising the layout for a hybrid V4/V4B I might even pull the inductor out of my SVP-CL temporarily to get a repro made, but that project's a little way out yet.