The one I fried may not be the same one you are looking at. I had two of them. I looked for it in my Amazon orders history and find two boost converter boards, neither look like the one I fried. Mine might have actually come from Ebay. There seems to be several variants of these things. This one is not regulated. The more voltage you put in, the more you get out. After poofing one rather quickly on a 19 volt brick, I wired the other one to a variable power supply and stopped turning the knob when I saw about 450 volts.....it has a 400 volt cap in it. Maybe it will live on 19 volts if loaded heavy enough to stay under 400 volts.
I'll try it again if I can find it, but I have decided to do something that ended in fireworks and lots of dead parts last time I tried it......DIY SMPS. Last time was about 15 years ago. Parts and computer modelling have both gotten a lot better since those days. So instead of collecting a bunch of Chinese modules, I bought a box full of parts. The rolls of wire to DIY the transformer just arrived. Maybe next week or so, I hide behind something and plug it all into the wall outlet.
I got my Chinese 6AK5 knockoffs today, for some reason I wanted to go the opposite direction of George and wanted to see if I can do an acceptable Marshall inspired 50V amplifier. I used the 6AU6 in place of triodes last time but think the 6AK5's (6J1P) will work better at this low voltage. I can't wait till I get my power tube, a 26A7 dual pentode common cathode in an octal tube. Rated at 50V into 2.5k Class AB1 a whopping 500mW. Might even use a 70V transformer for the output.
http://rtellason.com/tubedata/26A7-GT.PDF
I think I will do the 5E3 switched circuit first proposed in my 6K6 amp. I am reasonably far along on my latest guitar that I can easily switch back to it. I have to be a good ways into a project for me to pick it up again if I get distracted with other things. If I only have a day or two invested in something and set it aside it tends to collect dust for a while.
I also got some pencil tubes in today, some 6N28B-V's. Lets see if I can make a hybrid tube front end with PWM modal power amp. Anode voltage of 50V, gain 16-28. We are all over the map in this thread aren't we?
6N28B-V | Tubes Information
http://rtellason.com/tubedata/26A7-GT.PDF
I think I will do the 5E3 switched circuit first proposed in my 6K6 amp. I am reasonably far along on my latest guitar that I can easily switch back to it. I have to be a good ways into a project for me to pick it up again if I get distracted with other things. If I only have a day or two invested in something and set it aside it tends to collect dust for a while.
I also got some pencil tubes in today, some 6N28B-V's. Lets see if I can make a hybrid tube front end with PWM modal power amp. Anode voltage of 50V, gain 16-28. We are all over the map in this thread aren't we?
6N28B-V | Tubes Information
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I got to thinking about what the little 70 volt OPT's were really usable for since 400+ volts is likely not a realistic application for long term reliability. So the tubes that are sitting next to the board waiting for their turn in the hot seat (not so hot this time) are 6AK6's.
I saved a bag full of these for a battery powered tube guitar amp in the 2 to 5 watt range. The 6AK6 has a 945 milliwatt heater. They were the reason I got the Amazon / Ebay boost converters. I want about 250 volts from a 7.2 or 8.0 volt battery. Poor regulation could be a plus.
I have a bag full of US military versions from the 40's and 50's. Another tube with a low powered heater, as is the 6AQ6 triode. I have a bag full of them too.
I had some 26A7's, but for some reason I decided not to keep them, probably physical size and heater power.
Another twin pentode is the 28D7W. It needs a loctal socket which are available now, but makes 600 mW in AB2 from a 28 volt supply and can eat up to 100 volts on the plate. It's made for aircraft use so it will take being rattled about in a guitar amp. I also passed on them at purge time because loctal sockets were not available 10 years ago.
If one or more good sounding creations come from it, who cares?
The map thing doesn't bother me, I like when people have an idea and see where it leads them. What sparks the ideas can be totally unrelated. If I would have known of the 6AQ6's before shipping from the US went up I might have picked up some. I built a 6AK6 Deluxe 5E3 years ago and ran them about 250V. It worked quite well. Now days I would swap a Mosfet for the PI. Maybe a 6AK6 for the second position and a 12AY7 for the first.
I was debating between the 26A7 and the 28D7. Figured the 26A7 would be simpler without the AB2, but that was before seeing your results. Maybe the 26A7 might like being fed some grid current. No shortage of heat, 26V and 0.6A for the heaters. I was wondering why the plate dissipation was so low, 2W but with 16W already cooking.
I scratched my head over that (2 pentodes, only 8 pins) until I looked at the datasheet. Ah, only one pin for both screen grids!
I think the 500 mW is for a B+ of only 26.5 V (see attachment.) With 50V B+, you might in an ideal world see four times that output, a thundering two watts.
I have the same issue, and it seems, so do most people these days. I once read a very interesting book* written by a doctor who helps people with ADD to learn to manage their lives ( http://www.drhallowell.com/crazy-busy/ ).
In the book, Dr. Hallowell introduces the concept of what he now refers to as "culturally induced ADD". In a nutshell, as multitasking operating systems and the Internet started to take over our lives in the early 1990's, Dr. Hallowell began to notice that more and more people began to exhibit the symptoms of ADD, even though they did not actually have the medical condition.
By the way, starting endless projects, but having a hard time focusing long enough to finish any of them, is one of the classic symptoms of ADD, real or culturally-induced.
I'm pretty sure that TV, complete with constant ad breaks and channel-surfing, had already started to erode people's ability to focus, long before we had the additional challenges of computers and the Internet to deal with.
And now we have the "smartphone" epidemic (I dislike that term, since they seem to make people dumber, not smarter), which seems to be infinitely more addictive and infinitely more distracting than email and the Internet on your desktop PC ever were.
I've kept the curse of the smartphone out of my life, and regular TV too. The Internet alone is bad enough.
Then Netflix crept up and got a firm hold on family members; I might be lynched if I suggested getting rid of our subscription. Oh, well.
*Note: there is an entirely different book with the exact same title. This one is not written by a doctor, but by a pastor, and is very unlikely to contain any content worth reading.
Dr. Hallowell's book, on the other hand, is not only extremely informative, it contains a number of prescriptions for managing our "crazy busy" state of living, and actually getting some things done that need to be done.
Back on topic (what topic is that??), I found a 12.6V transformer in the junk-box. If I feed a pair of voltage doublers from it (one positive, one negative), I should get nominally 0V and +/- 35V rails. I think that will work for the MOSFET drivers needed to push a 12C5 into class AB2.
I'm pretty sure I have a few N-channel, TO220 power MOSFETs in a (static-safe) bag somewhere, too. I just have to find them and look up their specs to make sure they're okay for the job.
-Gnobuddy
Attachments
Tubelab's recent guarded comments about the $1 6W6 in disguise got me curious, and led me to waste an hour or two obsessively looking up data sheets for every 12-volt part number on the ESRC dollar list.
Once I had found a few potential power valves, I thought it would be really nice to find some $1 preamp triodes if they existed. I found nothing in the 12 V heater section, didn't even think of hunting through the 18 V section and so missed a good one there, and wasted a lot more time looking through 4V, 5V, and 8V parts and finding nothing.
But then I finally stumbled across the 6AQ6. Not quite the mu of a 12AX7, but enough of a family resemblance that I figured it would be usable in a lot of preamp circuits with only slight changes.
Your 2W 5E3 inspired my own 6AK6 amp. 225V from a voltage tripler and 48V Hammond transformer, MOSFET source-o-dyne, 6AG5 driving the MOSFET.
While your mini 5E3 is tuned for good overdrive, my 6AK6 amp is almost the opposite; the 6AG5 was a very successful experiment aimed at getting good clean tones, but it was hard to tame blocking distortion if you tried to overdrive it.
-Gnobuddy
Well things are looking up with my 26A7, you are right about the voltage. Might just push it to one watt. Yeah right, wonder when the plates will start to glow? Can't see much of the screens, it came in the mail today. Also got a 6SJ7, it looks questionable but I thought what the heck. Going to have to clean up my electronic bench. I have been throwing stuff on it as temporary storage, I have a job in front of me to get enough room to work on.
The one I have is shown in the attached image. It seems to be sold under half a dozen different names, but the one constant in all the ads I found is the number "390". The letters "ZVS" show up in many, but not all, of the ads.
The ad copy claims there is a jumper to select input DC voltage, and one of the ranges will accept up to 32 V DC.
My recollection is that another diyAudio user brought this module to my attention some months ago, and he said he had been running his off a laptop power supply, and using it to power a single-ended 6V6 amp of some sort.
Some months ago, I bought a class-D audio power amp module from the Canadian version of Amazon. The ad copy included the sentence "Output power: 100W+100W (Vcc = 36 V, RL = 6Ω, THD: 10%)". When I looked at the board, I found 32V filter capacitors right across the power rails.
Good luck!
-Gnobuddy
Attachments
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I think there are a lot of "390 volt" boost boards out there, and the reason for the 390 volt spec is the 400 volt output cap.
That's definitely NOT the same converter I have. I can't find it now, but your ad copy states "regulated" and dual range input. Mine did not, and did not look like that. Mine looked like a 12 volt to 240 VAC automotive power supply with half the parts missing.
I may look for one like yours the next time I order from Amazon. Depending on how the 6AK6 testing goes, I may want something that can make 250 VDC from 8 to 12 volts worth of batteries.
That's definitely NOT the same converter I have. I can't find it now, but your ad copy states "regulated" and dual range input. Mine did not, and did not look like that. Mine looked like a 12 volt to 240 VAC automotive power supply with half the parts missing.
I may look for one like yours the next time I order from Amazon. Depending on how the 6AK6 testing goes, I may want something that can make 250 VDC from 8 to 12 volts worth of batteries.
I had to pick and choose what to do today and tomorrow. I really should clean the house and make it look livable. Then there is the couple of guitars I need to fret and do the tuner holes, mount them and side dots. Thought about doing the circuit change of my 6K6 amp to the input circuit I started this thread with. Or try and get the latest quickie guitar body sanded and ready for finish and carve the neck.
Monday I am having surgery on my wrist and I'll have my right hand in a brace for a couple of weeks. I am going to have to really take it easy, I am not one to sit around if I can be doing something. So let's say I can manage the amp with mostly my left hand. Alright, decided.
I got most of the neck to shape, tomorrow make it look pretty. The body is done and second coat on it. I'll do a rough house cleanup after the neck. See, I can prioritize.
Monday I am having surgery on my wrist and I'll have my right hand in a brace for a couple of weeks. I am going to have to really take it easy, I am not one to sit around if I can be doing something. So let's say I can manage the amp with mostly my left hand. Alright, decided.
I got most of the neck to shape, tomorrow make it look pretty. The body is done and second coat on it. I'll do a rough house cleanup after the neck. See, I can prioritize.
All my woodwork must be done outside, and it's currently 22 degrees F (-5.5C), so the choice is made for me. I have some electric guitar and speaker cabinet projects waiting for the cold to go away. It has snowed for at least an hour 5 out of the last 7 days, none predicted for today though.
Yesterday I spent the whole day trying to wind the transformer for an SMPS for vacuum tubes experiment. It should have been an hour job but I kept messing it up.
Good luck, I hope it isn't serious.
Yesterday I spent the whole day trying to wind the transformer for an SMPS for vacuum tubes experiment. It should have been an hour job but I kept messing it up.
Good luck, I hope it isn't serious.
-5.5C? I get out in the garage at that temperature wearing just a pair of shorts. The surgery involves removing scar tissue that has formed around a tendon causing a lot of pain if I do the wrong movement. I was relieved when I heard it is common enough and not a problem and physio can sometimes get rid of it, in my case it didn't. It was a relief to know it was nothing too serious, I can assume the worst with my luck goes with health issues. I had an adverse reaction to some fire retardant on our uniforms at work (arc flash protection) and it had a lasting effect on me. That is why I end up at sub-zero temperatures cutting wood in shorts, the cold is a lesser of evils to putting on more clothes as they cause me pain. If I am going to spend a half hour or more I will put something more on. The wrist was suppose to be a simple thing but somehow a muscle that controls my thumb extending wasted away and I have limited movement with it now.
So it should go well but my luck medically has been spotty at times. The surgeon performing it is the best in in town for hand surgery, she spent a few years at the Mayo Clinic doing surgery. I think I will be in good hands.
So it should go well but my luck medically has been spotty at times. The surgeon performing it is the best in in town for hand surgery, she spent a few years at the Mayo Clinic doing surgery. I think I will be in good hands.
The neighbors can attest to my ability to shovel two 100 foot driveways full of snow wearing only jeans and flip flops. I do not have the ability to do woodwork in the garage, since my wife's car and a lot of other stuff fills it up. I wheel the job site table saw outside and use it, or set the other woodworking tools (belt sander, spindle sander, bench top band saw and drill press) on the table.
I have issues with my hands (pain and numbness) so I really prefer a clear bright day for table saw use. Cold doesn't bother me, but high winds (with blowing junk), snow, ice and rain does. Lately we have been receiving a mix of all of them 4 to 6 days a week.
Last week I saw something I had never experienced before. It would go from clear blue sky to white out snow and back to clear sky in a 20 to 30 minute period with steady high winds through the clear and snow. Twice the snow would accumulate up to half an inch, then melt off completely when the sun and wind appeared. This went on for several hours.
Last year the last snow storm came on April 1st after 2 weeks of good weather......fooled me.
I've been seeing similarly weird weather. A few weeks ago we woke up to bright sunshine, with snow still on the ground from the previous several days of intermittent snowfall. Not so odd so far, but as I drove to Walmart twenty minutes away, the sun disappeared, the sky turned grey, and it began to pour with rain.
I emerged from Walmart another twenty minutes later to find a black sky, no more rain, and a couple of inches of hail on the ground (and on the trunk lid of my car, where the small cosmetic spoiler kept the hail from sliding off.)
I drove from Walmart to the pet supply store fifteen minutes away, and during that drive the hail stopped, the sky cleared, and it was bright sunshine again. I bought my bag of cat-food and emerged from the pet store to find the sky black once more, and torrential rain splattering down. All this in the space of maybe an hour.
Actually I've noticed increasing amounts of bizarre weather for a number of years now, going back maybe as much as fifteen years. Like the time (I think in 2005) that the weather switched from bright sun to large windshield-smashing hail, and back, all in the space of 30 minutes - in Los Angeles, during summer!
-Gnobuddy
About a month ago in the middle of a rather ugly winter that brought us 15 consecutive days below freezing (with a $622 electric bill) and plenty of snow, and ice, we had a 80 degree day. It was a typical mid summer day, sunshine, gentle warm breeze, people driving their convertibles and rollerblading down the towns main street.....Then the next day.....the switch got turned back to winter. Record temperatures were not broken, they were smashed all over the eastern US.
Any time we had hail in Florida (not very often), it came in the summer, usually on the leading edge of one of those black nasty storm fronts.
Today the forecast was for another grey and gloomy day, but it turned out to be sunny and warm for this time of year. Unfortunately I spent most of the day inside on the phone dealing with government idiots, trying to get them to send me a corrected form I need to file my taxes. I am due a sizeable refund, and they have screwed it up constantly for almost 2 months. They are now 12 days past their 30 day maximum review period.
Any time we had hail in Florida (not very often), it came in the summer, usually on the leading edge of one of those black nasty storm fronts.
Today the forecast was for another grey and gloomy day, but it turned out to be sunny and warm for this time of year. Unfortunately I spent most of the day inside on the phone dealing with government idiots, trying to get them to send me a corrected form I need to file my taxes. I am due a sizeable refund, and they have screwed it up constantly for almost 2 months. They are now 12 days past their 30 day maximum review period.
I have my table saw in the garage and the cold did not bother me but as soon as the saw started and I caught the breeze from it I got cold. Too stubborn to go inside to get a jacket I finished the pieces that needed to be cut. The creek by my place freezes over in the winter but for the last two years it remained open or opened up by February. Some who have been here 50 years never seen that before. But staying away from politics and Russian tubes which can get you a two week vacation, had my surgery and fingers crossed all goes well. I was told I would be able to drive home and that part was fine, but to get my prescription filled and take some pills before the freezing wore off. I did. I would hate to feel this without the medication. It feels like someone beat on my arm with a baseball bat. I think I will 'really' be out of commission for a few days.
I did manage to carve and sand the neck of the latest guitar. What has been keeping me from finishing the other two was fret wire which came in the mail today. I think the three will have to wait a few days.
I will probably do some electronic breadboarding before that though. Less jarring poking parts into holes than hammering in frets.
I did manage to carve and sand the neck of the latest guitar. What has been keeping me from finishing the other two was fret wire which came in the mail today. I think the three will have to wait a few days.
I will probably do some electronic breadboarding before that though. Less jarring poking parts into holes than hammering in frets.
My sympathies go to you Nothern folk.
All I have to complain about is that all tube hobby work has been on hold coz I've been making the most of our remaining Southern summer, swimming, body surfing and snorkling on Kangaroo Island. Off there again for the Easter long weekend.
Keep warm,
Ian
All I have to complain about is that all tube hobby work has been on hold coz I've been making the most of our remaining Southern summer, swimming, body surfing and snorkling on Kangaroo Island. Off there again for the Easter long weekend.
Keep warm,
Ian
It sounds as though you're having a terrible time, Ian.
I've lived in the tropics, and I've lived in southern British Columbia. If you were homeless and had no clothes, the tropics is a better place to live - you won't freeze to death, and you can survive on food you can pick off trees. But otherwise, I much prefer the climate in this part of B.C. There isn't nearly as much sweating and fanning yourself involved.
The far north, up around the arctic circle, is something else entirely. I have no idea how people survive there - certainly I wouldn't last long, as I'm completely lacking in the requisite survival skills.
-Gnobuddy
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