AMC CVT 3030
Anatech,
I am in Toronto and my AMC 3030 is in the shop with my repair person and he is trying to figure out the best way to put in tube sockets for the soldered ones.
I saw some of you posts and was hoping you might be able to advise what he can do to as he is skeptical about doing it although he would have liked to.
He bought ElecrtoHarmonix 6ea7s to replace the EL 34s as well.
Any thoughts?
Thanks,
Darrell
Anatech,
I am in Toronto and my AMC 3030 is in the shop with my repair person and he is trying to figure out the best way to put in tube sockets for the soldered ones.
I saw some of you posts and was hoping you might be able to advise what he can do to as he is skeptical about doing it although he would have liked to.
He bought ElecrtoHarmonix 6ea7s to replace the EL 34s as well.
Any thoughts?
Thanks,
Darrell
Re: AMC CVT 3030
I am in Toronto and my AMC 3030 is in the shop with my repair person and he is trying to figure out the best way to put in tube sockets for the soldered ones.
I saw some of you posts and was hoping you might be able to advise what he can do to as he is skeptical about doing it although he would have liked to.
He bought ElecrtoHarmonix 6ea7s to replace the EL 34s as well.
Any thoughts?
Thanks,
Darrell [/B][/QUOTE]
Hi Darrell,
I own a CVT2030 and gave my daughter for her birthday a CVT3030. I converted them both to the "socket" version.
To convert the standard version to socket you will need a table saw and lots of patience!. Yes I did say table saw...
Before you remove the circuit boards with old tubes make a mark about 1/4"/ 5mm below the head of the tube on the inside of the chimney. This notch will have to be cut out of the heatsink/chimney so that when the tubes are extended by the sockets they will not hit the inside of the heatsink. The fans will do their normal duty.
When I created the socket upgrade program at Weltronics I had a special de-solder adapter that fit inside the 100watt weller iron. It had 8 holes and was about 1 inch round. When hot it was slid over all 8 pins at one time and melted the solder letting the tube pull right out. You and I no longer have this capability so you have to clip off each leg of the tube at the circuit board and unsolder each one at a time. I still do one occasionally but after a couple ales I don't really care how many legs I have to cut off🙂
After cleaning the large tube holes align the appropriate leggs over the holes and solder away. After the upgrade you will have to bias each tube and a differential supply at the bottom of the circuit board. Let me review the upgrade and post it here.
As far as the 6EA7's I'm not sure. I have tried ALL types of the sovtek/EH tubes and liked them all. they all biased properly without undue current draw and adapted into the circuit without smoke. If they are close to the same specs would say go for it. So whats a little smoke? Nah, just kidding! I would like to know how they sound though. I will find the info for biasing and get right back to you.
Dave
I am in Toronto and my AMC 3030 is in the shop with my repair person and he is trying to figure out the best way to put in tube sockets for the soldered ones.
I saw some of you posts and was hoping you might be able to advise what he can do to as he is skeptical about doing it although he would have liked to.
He bought ElecrtoHarmonix 6ea7s to replace the EL 34s as well.
Any thoughts?
Thanks,
Darrell [/B][/QUOTE]
Hi Darrell,
I own a CVT2030 and gave my daughter for her birthday a CVT3030. I converted them both to the "socket" version.
To convert the standard version to socket you will need a table saw and lots of patience!. Yes I did say table saw...
Before you remove the circuit boards with old tubes make a mark about 1/4"/ 5mm below the head of the tube on the inside of the chimney. This notch will have to be cut out of the heatsink/chimney so that when the tubes are extended by the sockets they will not hit the inside of the heatsink. The fans will do their normal duty.
When I created the socket upgrade program at Weltronics I had a special de-solder adapter that fit inside the 100watt weller iron. It had 8 holes and was about 1 inch round. When hot it was slid over all 8 pins at one time and melted the solder letting the tube pull right out. You and I no longer have this capability so you have to clip off each leg of the tube at the circuit board and unsolder each one at a time. I still do one occasionally but after a couple ales I don't really care how many legs I have to cut off🙂
After cleaning the large tube holes align the appropriate leggs over the holes and solder away. After the upgrade you will have to bias each tube and a differential supply at the bottom of the circuit board. Let me review the upgrade and post it here.
As far as the 6EA7's I'm not sure. I have tried ALL types of the sovtek/EH tubes and liked them all. they all biased properly without undue current draw and adapted into the circuit without smoke. If they are close to the same specs would say go for it. So whats a little smoke? Nah, just kidding! I would like to know how they sound though. I will find the info for biasing and get right back to you.
Dave
Dave,
Thanks for the prompt response,. I forwarded your answer to my repair person and he might need more info.
Seems like a fair bit of work. He was going to go to Home Depot to get a hole saw to see of that would work. If you have done it and are happywith the results, it might be worthwhile. Otherwise I will just let him solder the new tubes in and live with them.
Dont know much about tubes but did like the EL34s and dont know what 6ea7s are.
Sounds like Weltronics depended on you for all the socket upgrades.
Darrell
Thanks for the prompt response,. I forwarded your answer to my repair person and he might need more info.
Seems like a fair bit of work. He was going to go to Home Depot to get a hole saw to see of that would work. If you have done it and are happywith the results, it might be worthwhile. Otherwise I will just let him solder the new tubes in and live with them.
Dont know much about tubes but did like the EL34s and dont know what 6ea7s are.
Sounds like Weltronics depended on you for all the socket upgrades.
Darrell
Hey Darrell,
'ya know, I never thought of the hole saw trick. I guess it would be the same thing too. I gotta remember that one! I dont have the docs for the biasing yet. I have a ton of paper to go through to find it. I retained some of the schematics and upgrade info.
I want to check in on the 6ea7 tubes. they ought to be interesting.
I'll let you know about the biasing info soon.
Dave
'ya know, I never thought of the hole saw trick. I guess it would be the same thing too. I gotta remember that one! I dont have the docs for the biasing yet. I have a ton of paper to go through to find it. I retained some of the schematics and upgrade info.
I want to check in on the 6ea7 tubes. they ought to be interesting.
I'll let you know about the biasing info soon.
Dave
Hi Darrell,
You can not sub an EL 34 with a 6EA7. They are completely different tubes. The 6EA7 is a dual type type, the power section has vastly reduced ratings. I think you were told 6CA7 (EH).
Don't waste time with a circular hole. That simply complicates everything, including tube replacement. The original instructions from Dave were to cut the heatsink in two places so as to remove a section to provide clearance for the tube. A 6CA7 is wider that an EL 34. Both will fit after the work is done. I do prefer 6CA7's myself. Electroharmonix is an excellent choice.
Which shop is it? I may know them.
-Chris
You can not sub an EL 34 with a 6EA7. They are completely different tubes. The 6EA7 is a dual type type, the power section has vastly reduced ratings. I think you were told 6CA7 (EH).
Don't waste time with a circular hole. That simply complicates everything, including tube replacement. The original instructions from Dave were to cut the heatsink in two places so as to remove a section to provide clearance for the tube. A 6CA7 is wider that an EL 34. Both will fit after the work is done. I do prefer 6CA7's myself. Electroharmonix is an excellent choice.
Which shop is it? I may know them.
-Chris
Its not a shop. just a guy who was referred to me from toronto-audiophiles web group and he has done a number of repairs for me to date. Email me off line if interested in his name and number
You were right about the 6CA7s. I got it wrong. Seems to be simpler if he just solders them in and I will livbe them.
Can you describe the difference b/w the EL34s and 6CA7s?
Darrell
You were right about the 6CA7s. I got it wrong. Seems to be simpler if he just solders them in and I will livbe them.
Can you describe the difference b/w the EL34s and 6CA7s?
Darrell
Hi Darrell,
A 6CA7 is a beam tetrode, the EL-34 is a true pentode. I find that a 6CA7 seems to be a tougher tube in my experience. The EL-34 has a "kink" in it's characteristics, I think near cutoff. Just going on memory.
Interestingly, some early data sheets (early Tung-Sol) for the 6CA7 show it as a pentode with the exact same kinks as the pentode. So I guess it depends on what make of tube you buy as well.
My view on your amp is simple. If your are going to keep it, install the sockets. I would simply do a pair of straight cuts through the heatsinks for the above mentioned reasons. That was the original method that was given to me by Dave.
Dave was an invaluable help to me when I was doing warranty work on AMC products. He didn't have to assist me, and yet he did. I still am very grateful to you for that Dave! 😉
-Chris
Edit: Curious about who your tech is. I may say hello.
A 6CA7 is a beam tetrode, the EL-34 is a true pentode. I find that a 6CA7 seems to be a tougher tube in my experience. The EL-34 has a "kink" in it's characteristics, I think near cutoff. Just going on memory.
Interestingly, some early data sheets (early Tung-Sol) for the 6CA7 show it as a pentode with the exact same kinks as the pentode. So I guess it depends on what make of tube you buy as well.
My view on your amp is simple. If your are going to keep it, install the sockets. I would simply do a pair of straight cuts through the heatsinks for the above mentioned reasons. That was the original method that was given to me by Dave.
Dave was an invaluable help to me when I was doing warranty work on AMC products. He didn't have to assist me, and yet he did. I still am very grateful to you for that Dave! 😉
-Chris
Edit: Curious about who your tech is. I may say hello.
Thanks Chris.
I forwarded you message and I am waiting for his reply and a "cost" for the work. The Tubes are the 6CA7 from ElectroHarmonix. Dont want to spekd a fortuen given that there seems to be a fair bit of labour involved in poutting in sockets. IIRC AMC charged a flat fee for it? Any idea?
Its Stephen Nitikman. He does the ss and tube repairs. He teaches electronics etc. at a school in Toronto.
Darrell
I forwarded you message and I am waiting for his reply and a "cost" for the work. The Tubes are the 6CA7 from ElectroHarmonix. Dont want to spekd a fortuen given that there seems to be a fair bit of labour involved in poutting in sockets. IIRC AMC charged a flat fee for it? Any idea?
Its Stephen Nitikman. He does the ss and tube repairs. He teaches electronics etc. at a school in Toronto.
Darrell
Hi Darrell,
Stephen Nitikman, I don't think our paths have ever crossed before. I was hoping I knew him.
6CA7EH is a very good choice. An undervalued brand if you compare it to others. I have no complaints with them at all.
The labour involved is mostly removing the old tubes. Tell Stephen to destroy the tubes and pull out the pins one by one. You will waste too much time removing them the nice way. That should lower the labour bill. 😉 Installing the new sockets is dead easy after that. So is cutting the heatsinks.
Dave had a special octal desoldering tip made up. He may have had a set figure. I never had to do one (I refused to do it under warranty for the fixed rate). For him, the job was straight forward and I had a feeling he did a few.
I hope that helps you out.
-Chris
Stephen Nitikman, I don't think our paths have ever crossed before. I was hoping I knew him.
6CA7EH is a very good choice. An undervalued brand if you compare it to others. I have no complaints with them at all.
The labour involved is mostly removing the old tubes. Tell Stephen to destroy the tubes and pull out the pins one by one. You will waste too much time removing them the nice way. That should lower the labour bill. 😉 Installing the new sockets is dead easy after that. So is cutting the heatsinks.
Dave had a special octal desoldering tip made up. He may have had a set figure. I never had to do one (I refused to do it under warranty for the fixed rate). For him, the job was straight forward and I had a feeling he did a few.
I hope that helps you out.
-Chris
Any specific ideas for tweaking a 3030? I'm also gonna install tube sockets, now it's running with two siemens' and two sovteks. 🙁
Cheers,
Simon
Cheers,
Simon
Hi Simon,
I've never attempted to tweek one of these. I suspect that the JJ or Electroharmonix tubes would be an upgrade. The other big thing would be better output transformers. Bigger iron.
One thing I see that I don't like is the side mounting of the tubes. I'd be tempted to strip the old chassis and rebuild it so the outputs were in their normal mounting plane (vertical). There may be some things you can do to improve things. While I did work on them it was strickly to make them go and meet specs, under warranty.
Dave, can you provide any insights on these?
-Chris
I've never attempted to tweek one of these. I suspect that the JJ or Electroharmonix tubes would be an upgrade. The other big thing would be better output transformers. Bigger iron.
One thing I see that I don't like is the side mounting of the tubes. I'd be tempted to strip the old chassis and rebuild it so the outputs were in their normal mounting plane (vertical). There may be some things you can do to improve things. While I did work on them it was strickly to make them go and meet specs, under warranty.
Dave, can you provide any insights on these?
-Chris
Chris, the opts definitely seem to be the weakest link; they really look tiny when compared to other el34pp opts. I guess for a complete make-over there's too much compromises in the amp to get me going in the first place. The insides of the amp really look commercial; all pcb's, plenty of plug-in connectors, thin wire and probably lowest-end resistors and caps. Still a good tutorial on how cheap components can do the job when the design is good. I guess I might try the usual tricks as lower esr caps, better quality coupling caps and volume pot. Any guesses on the bandwith of those opts?
Cheers,
Simon
Cheers,
Simon
Hi Simon,
The components are not terrible quality. If you attempt to replace any caps, stay to the same values. You might have better luck bypassing the filter caps. Since the temperature is high in the case, some electrolytics may be tired.
I am still looking at the output transformers as being the thing that would upgrade the sound the most. New output tubes would really help as well. Don't go nuts and replace resistors with metal film types. That won't buy you as much as you might think.
-Chris
The components are not terrible quality. If you attempt to replace any caps, stay to the same values. You might have better luck bypassing the filter caps. Since the temperature is high in the case, some electrolytics may be tired.
I am still looking at the output transformers as being the thing that would upgrade the sound the most. New output tubes would really help as well. Don't go nuts and replace resistors with metal film types. That won't buy you as much as you might think.
-Chris
I realize this is a late post on subject, but I recently worked on a CVT3030 that I though had a bad output transformer. What I found was that a circuit board section between 2 of the transformer pins had become electronically "active" and thus was causing a short (~50 ohms) between the two. This is a rather rare occurance, but the circuit board will usually have a "waffle" appearance, and as in my case, also very dark colored. I cut out this small section, and
the transformer works fine. Not sure if this is a common failure on these.
the transformer works fine. Not sure if this is a common failure on these.
Hi Doral,
I haven't seen this with these amps. Most likely some moisture allowed a small current to flow that over time produced a carbonized track.
-Chris
I haven't seen this with these amps. Most likely some moisture allowed a small current to flow that over time produced a carbonized track.
-Chris
Hello Chris,
Whomever worked on it before me apparently was under the impression the output board circuitry was bad as many of the components had lifted legs. I also found a bad fet switch in the mute circuit not allowing one channel through. The amp is fully functional now, but unfortunately, the original owner removed the housing around one of the fans that also holds the output circuit board, so I will have to somehow fabricate one. I was looking at the preamp circuit, and was surprised to see electrolytics in the audio path. I feel this in a definite area for improvement/mods.
Whomever worked on it before me apparently was under the impression the output board circuitry was bad as many of the components had lifted legs. I also found a bad fet switch in the mute circuit not allowing one channel through. The amp is fully functional now, but unfortunately, the original owner removed the housing around one of the fans that also holds the output circuit board, so I will have to somehow fabricate one. I was looking at the preamp circuit, and was surprised to see electrolytics in the audio path. I feel this in a definite area for improvement/mods.
Hi Doral,
All electrolytics are not bad, and if they are biased they are much "less bad". You can try to bypass them with film types. Just make sure your work is neat.
You may need to try and restore those PCB's also. Sorry to hear "TIM" got there before you did.
-Chris
All electrolytics are not bad, and if they are biased they are much "less bad". You can try to bypass them with film types. Just make sure your work is neat.
You may need to try and restore those PCB's also. Sorry to hear "TIM" got there before you did.
-Chris
Not sure if it's really worth putting a lot of time in. The amp is OK, just not what I am accustomed to. I just finished restoring/upgrading a rare (non-existent?) Golden Tube Audio SE-60. Could not find anyone to extend any information on the amp, so I was on my own. The circuit has quite a few differences from an SE-40, and apparently had at some time, current runaway problems. I am now in the middle of reverse engineering a Cary V-12 with build out sheets I obtained from Cary since there are no existing schematics available. I have a pair of the ouput trannies,
and what's left of a blank chassis, so we will see how that goes. Nice talking to ya.
and what's left of a blank chassis, so we will see how that goes. Nice talking to ya.
I just stumbled upon this thread. I have a 3030 that i bought second hand about a year ago. It came with 4 new tubes instead of the old ones, which the previous owner said was worn out.
It's 6l6gc tubes, dont really know the manufacturer, but it's definitly Russian (that's why a can't read the name😀 ).
It was a heck of a job to replace them
, and i was a fool not to find sockets for them.
I've also changed a few resistors that was fried, the high voltage electrolytics, just for safety, and later one of the trimmers for bias, that suddenly went. I found out, because the amp suddenly made some very scary noise, and very loud pop's in one channel, and the tubes for the right channel lit like 200W light bubbles
It´doesn't sound like they were hurt though, i like the sound of the amp very much. ( My first tube amp).
All the best
Ebbe
It's 6l6gc tubes, dont really know the manufacturer, but it's definitly Russian (that's why a can't read the name😀 ).
It was a heck of a job to replace them
, and i was a fool not to find sockets for them.I've also changed a few resistors that was fried, the high voltage electrolytics, just for safety, and later one of the trimmers for bias, that suddenly went. I found out, because the amp suddenly made some very scary noise, and very loud pop's in one channel, and the tubes for the right channel lit like 200W light bubbles
It´doesn't sound like they were hurt though, i like the sound of the amp very much. ( My first tube amp).
All the best
Ebbe
Hi Ebbe,
I am pretty sure you are supposed to have EL-34's in there. 6CA7's may have been installed (I hope) but it wasn't designed for 6L6's. I like the 6L6GC tube, I just don't like sticking the wrong tube into amplifiers.
The worst case would be some 5881's. They are another thing again, a low powered 6L6GC with a 25 watt plate.
-Chris
I am pretty sure you are supposed to have EL-34's in there. 6CA7's may have been installed (I hope) but it wasn't designed for 6L6's. I like the 6L6GC tube, I just don't like sticking the wrong tube into amplifiers.
The worst case would be some 5881's. They are another thing again, a low powered 6L6GC with a 25 watt plate.
-Chris
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