One thing I noticed is that when the volume drops, the bias 1 red light goes out while the bias 2 stays lit.
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Ampeg SVT-II appreciation thread
- Thread starter i_got_a_mohawk
- Start date
No the Hifi Ayon tubes. I could get a one off Sextett for 230 but if one would need a replacement I´m looking at 115.
Im probably gonna go with a more standard make of tubes though.
Im probably gonna go with a more standard make of tubes though.
There are resistors on the power tube board that are designed to blow like fuses. This helps protect the transformer. There are also flyback protection diodes from the tube plates to ground that need to be checked.
There is an internal fuse that can be checked. There are a number of reasons why an amp can fail to turn on. A visual inspection is a good start but a tech would take readings with a volt meter and other test equipment.
Best to have a tech look at the amp.
A WORD OF WARNING: Be very careful poking around inside the amp. The power supply electrolytic capacitors can remain charged long after the amp is turned off and unplugged. The zap can melt a steel screwdriver, imagine what it can do to you. The voltages are potentially lethal. Normally you would take some voltage readings to ensure that they are fully discharged. If not, a discharge tool is used to drain them. See the link below:
Technical - Amplifier | TalkBass.com
Thanks for the warning! Ive got some experience with electronics so I know what I´m doing. or better: know what I shouldn't do.
The fuse has blown itself. now want to see what the tube board looks like... I want to try to figure out if the tube blowing caused the problem or if a problem caused the tube and fuse to blow. of course once I get the chance the tech will be on it with me but thats another three weeks down the road. but until then Im letting curiosity and learning have its way.
once again: is there someone with the PDF of the schematics? please drop me a PM
Thanks
The fuse has blown itself. now want to see what the tube board looks like... I want to try to figure out if the tube blowing caused the problem or if a problem caused the tube and fuse to blow. of course once I get the chance the tech will be on it with me but thats another three weeks down the road. but until then Im letting curiosity and learning have its way.
once again: is there someone with the PDF of the schematics? please drop me a PM
Thanks
I would. Looking at Ayon's website is making my Spidey Sense tingle, and not in a good way. First I'm hearing about them so I could be wrong, but $6000 US for an audio amp???
The warning of being zapped is standard boilerplate that comes with any advise.
For the schematics, go here and search for "SVT II": Link Removed
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not zapped yet!
Thanks for the schematics
So the fuse is gone as is the 5ohm protection resistor. the schematic recommends ferrite beads now... I´m not sure what I should use now. I´m guessing two 10 ohm 1/4 watt resistors won't do the trick these seem a little heftier. do you perhaps know if the fuse is slow or fast blow? mine doesn't say... and unfortunately a search led to different people saying different things...
anyway that was as far troubleshooting as i feel comfortable on my own. thanks for the advice!
And yeah jimmy, some people really enjoy just spending money... although I must say the stuff looked quite pretty in the shop. my upstairs neighbour has a 16.000 euro audio amp... never listens to music though... he does refuse to buy a car from his money.
Thanks for the schematics
So the fuse is gone as is the 5ohm protection resistor. the schematic recommends ferrite beads now... I´m not sure what I should use now. I´m guessing two 10 ohm 1/4 watt resistors won't do the trick these seem a little heftier. do you perhaps know if the fuse is slow or fast blow? mine doesn't say... and unfortunately a search led to different people saying different things...
anyway that was as far troubleshooting as i feel comfortable on my own. thanks for the advice!
And yeah jimmy, some people really enjoy just spending money... although I must say the stuff looked quite pretty in the shop. my upstairs neighbour has a 16.000 euro audio amp... never listens to music though... he does refuse to buy a car from his money.
The ferrite bead on plate of each power tube (pin-3) shown on the schematic is intended to suppress high frequency pulses. The resistance of the ferrite changes and knocks it down. By not using a plate resistor, they can get a little more out of the 6550. All the current Ampeg SVT use this bead. The part that I use is a Murata BL01RN1A1F1J axial bead. It has leads on it like a resistor. It's an inexpensive part, about $0.29US each. I buy them from Digikey (part number 490-10999-1-ND) or Mouser (81-BL01RN1A1F1J ), both these companies have a presence in Europe. Replace all six. It is important when installing the bead to ensure that the leads do not short against any of the nearby traces. Ampeg started installing a nylon spacer on each lead to offset the part from the board.
The 1N4007 diodes D1 (and the other five) should be removed if it hasn't been already.
The part that I talked about in a previous post that acts as a fuse is the screen resistor. It is R2 in the schematic segment. It is a 220 ohm (yes 220R not 22R as on the schematic), ½W, fusable, flameproof metal film resistor. The part number that I use is a 220R Vishay NFR25H, the data sheet is attached. Again, replace all six of these resistors.
As for the fuses, for 220-240VAC the external fuse (F1) is 5A sloblo 250V, the internal fuse F2 is 1A 250V SLOBLO; for 120VAC the external fuse (F1) is 10A sloblo 250V, the internal fuse F2 is 1.5A 250V SLOBLO.
Thanks B-O-T
Well the diodes are still there... on four of the tubes the fuse resistors are still there. they where 22r´s as the schematic says. so out are the diodes you say? and the 22r´s and in are the 220r´s? and out are the 5 ohm resistors and in are the beads. sounds more than doable.... while I´m at it Ill see if I can install some high quality jacks. I´ve read these give some trouble.
Thanks a bunch! its always great to solve the low hanging fruits before the professional comes in and does it for more money than I would have earned doing my own job in the same time. plus fun is being had!
Well the diodes are still there... on four of the tubes the fuse resistors are still there. they where 22r´s as the schematic says. so out are the diodes you say? and the 22r´s and in are the 220r´s? and out are the 5 ohm resistors and in are the beads. sounds more than doable.... while I´m at it Ill see if I can install some high quality jacks. I´ve read these give some trouble.
Thanks a bunch! its always great to solve the low hanging fruits before the professional comes in and does it for more money than I would have earned doing my own job in the same time. plus fun is being had!
The changes make it in line with current production. 220R vs 22R is easier on the tubes. Anyways, talk about it with your tech. Those diodes are on the current schematics but there is a note, DNP which means do not place. They are no longer installed during manufacturing.
Rather than replacing the jacks, consider scrubbing and cleaning them, with Deoxit.
would there be much difference in sound between these two resistors being installed?
seems all of the used SVTII's out there could possibly have either of these resistor values installed...
No difference that you would hear, it is more about a longer tube life. The amp might put out a few (literally) less watts. The larger resistor lowers the voltage seen at the screen by small amount. Ampeg wouldn't be doing this on all their current SVT's if there wasn't some benefit, however small.
The choice is yours, do whatever you feel is best.
Whatever resistors you decide to use, given the low cost, buy some extras. If a tube goes down the road, if you have them you will be able to get the amp back in service quicker.
nooooooooooooooo
Did some work on the amp, got a great deal on a sextet of tubes and now I want to put the misses together but I labeled two of the many wires with the same number and can't figure out which is which. does anyone have a gunshot from the bottom of the amp without the bottom plate?
the offending wires are coming from the right transformer they are the top two wires on the left side.
Did some work on the amp, got a great deal on a sextet of tubes and now I want to put the misses together but I labeled two of the many wires with the same number and can't figure out which is which. does anyone have a gunshot from the bottom of the amp without the bottom plate?
the offending wires are coming from the right transformer they are the top two wires on the left side.
Not sure if the image below will help, note that this one is wired for british VAC. The wire colors are important and can help. Attached is an SVT II wiring diagram showing how the power transformer is connected. One mistake with these wires and you can really blow something in the amp.
Here's a link to my photobucket album: SVT-II by Eric Andersen with a bunch of gut-shot pics that my amp tech (talkbass member timv) took when he went through my 93 SVT-II. I'll bet the pic you need is in there, plus serveral more that you'll dig!
Very pleased to have picked up an SVTII from a fellow TBer a couple of weeks ago. Wow, what a great piece of kit. I've been coveting this head for years and finally managed to grab one.
So far I've only played it at low level in my lounge room but will be putting it to the test over coming months with the band... and look forward to seeing how it compares to my SB300.
What I've noticed so far is that once it warms up it develops that real sweet tube tone (at low volume) and sounds just great. In that way I think I can say it sounds better to me than the SVT-VR I sold a few years ago. Early days yet, and I look forward to winding it up for some tube compression and OD.
So far I've only played it at low level in my lounge room but will be putting it to the test over coming months with the band... and look forward to seeing how it compares to my SB300.
What I've noticed so far is that once it warms up it develops that real sweet tube tone (at low volume) and sounds just great. In that way I think I can say it sounds better to me than the SVT-VR I sold a few years ago. Early days yet, and I look forward to winding it up for some tube compression and OD.
I've got an NV115 which I use along with my SB300 as my mini stack, but being 8ohms it's not compatible with the SVTII. I'm looking at possibly getting an SVT212AV cab as replacement for my mini stack setup. Just wondering if someone can please help, has anyone got experience of an SVT and SVT212AV in combo? Can the 212 handle a bit of punishment?
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I have pushed my SVT212 pretty hard with my SVT without problems.
From what I've heard so far of the SVTII, comparing it to my SB300, the SVTII seems a bit more natural sounding to me. The SB sounds fantastic and I love it, but to me has a subtly effected sound. Like the sound is processed a tiny bit so that it sounds like it does. The SVTII sounds more pure, simple, and less affected.
I love my SB and the way it sits in the mix of my band is amazing and I look forward to seeing how the SVTII sits.
I love my SB and the way it sits in the mix of my band is amazing and I look forward to seeing how the SVTII sits.
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