Continuing with silly questions... I plugged my soldering iron into the variac. Same problem. I removed the AC wires from the board and tested them. Same problem. And again with my worklight.
I tested the bare secondary wires with this variac a few days ago and it worked OK. It's got to be an intermittent short in the variac.
I tested the bare secondary wires with this variac a few days ago and it worked OK. It's got to be an intermittent short in the variac.
Turns out it was a bad variac. I broke my own rule of not buying cheap tools and picked one up off ebay for $40. Not a deal if it doesn't work!
So... one new variac and I'm now up and running.
I ended up taking the amp to Peter Fletcher-Haynes at Vacuum Tube Supplies in Denver to check it out anyway, as this is my first AC and tube project. He's a fantastic guy, agreed to see me on a Sunday so I could sit next to him while he tested it out. It was a lesson well worth the $75, I got loads of construction tips and he thoroughly explained some things that were confusing me.
I've just got to clean up some wiring and button it up, then I'll post pics.
So... one new variac and I'm now up and running.
I ended up taking the amp to Peter Fletcher-Haynes at Vacuum Tube Supplies in Denver to check it out anyway, as this is my first AC and tube project. He's a fantastic guy, agreed to see me on a Sunday so I could sit next to him while he tested it out. It was a lesson well worth the $75, I got loads of construction tips and he thoroughly explained some things that were confusing me.
I've just got to clean up some wiring and button it up, then I'll post pics.
Sounds great, I'm working on mine... gotta order a couple more parts that got omitted the 1st time from partsconnexion, but I have to get my chassis built too so the delay isn't too bad.
Do you live near Denver? I live in Lafayette... I'll have to look up Vacuum Tube Supplies, I'd like to have some tubes tested and my neighbor has some old Macintosh pieces that no longer work properly. I may have a look at the power amp, it sounds like it's not biasing a power tube right, but I don't even want to get into the preamp, it is too complicated... lots of controls.
Hey, we're neighbors! I live in Erie. If you want to give the preamp a listen, shoot me a PM. My power amp at the moment is a Rotel integrated 40wpc 30-year old beast I've had since I was 14, so the Aikido isn't in it's best light but you're welcome to have a hear.
I'm doing a Honey Badger next, it's the perfect project at the perfect time.
Yeah, I can't recommend VTS enough. He's a brilliant British guy whose been working on "valve" amps for probably longer than I've been alive. I found him to be generous with his knowledge, very happy to teach, and a guy who has been blessed with loving his work. His shop alone is worth the trip.
I'm doing a Honey Badger next, it's the perfect project at the perfect time.
Yeah, I can't recommend VTS enough. He's a brilliant British guy whose been working on "valve" amps for probably longer than I've been alive. I found him to be generous with his knowledge, very happy to teach, and a guy who has been blessed with loving his work. His shop alone is worth the trip.
Wow, you're only a few miles away... For sure, I'd love to check it out. What's a Honey Badger?
I'm running a Tubelab SSE w/EL34s and Omega single driver speakers, you are also welcome to stop by and run the amp with your Aikido. The SSE is running off the volume control in my music player right now, it can't quite get to full volume without a preamp but it's still pretty loud.
The Honey Badger is an amp designed by a guy on this forum, the boards are available through the DIYAUdio store. It's designed to be easy to build, delivers 150wpc (depending) and there's loads of support here. I've heard they are going to have a parts kit and chassis available too.
http://www.diyaudio.com/forums/solid-state/192431-diyab-amp-honey-badger.html
http://www.diyaudio.com/forums/solid-state/211905-diyab-amp-honey-badger-build-thread.html
PM sent with my contact info.
http://www.diyaudio.com/forums/solid-state/192431-diyab-amp-honey-badger.html
http://www.diyaudio.com/forums/solid-state/211905-diyab-amp-honey-badger-build-thread.html
PM sent with my contact info.
And it works! One of my cheap Russian 6H8Cs didn't make the trip from the Ukraine, so I started it up with 2 perfectly matched brand new Sylvania 6SN7GTAs in the input position (after verifying it didn't blow up with the HT trafo on w/o tubes). I was worried but had to try it out.
I'll post some pics of the complete preamp. So far it sounds great, no buzz/hum.
I'll post some pics of the complete preamp. So far it sounds great, no buzz/hum.
I have 335V B+ and 7.2V (!) at the heaters. I have an old and cheap multimeter, but it read 9.2V measuring a 9V battery so I think it's not too far off.
The heaters are regulated and I used the resistors for 6.0V that were supplied with the PCB. Does anyone have any advise for getting the heater voltage down? I am using a separate Hammond filament trafo with center tap.
Also, after a few hours it is sounding very good! It was not a cheap project so I am happy the results have been worthwhile.
The heaters are regulated and I used the resistors for 6.0V that were supplied with the PCB. Does anyone have any advise for getting the heater voltage down? I am using a separate Hammond filament trafo with center tap.
Also, after a few hours it is sounding very good! It was not a cheap project so I am happy the results have been worthwhile.
The bottom resistor sets the heater voltage...I would doublecheck, the top resistor JB sends is usually 124 ohms...I think for 6.3V you need 499ohm on the bottom resistor...you will want to doublecheck the manual for the formula...or look at the LD1085 datasheet...its pretty straightforward.
you should be within 0.1V of heater voltage...if you are that high I would think it is a resistor in the regulator sequence that is off.
Love the chassis!!!
you should be within 0.1V of heater voltage...if you are that high I would think it is a resistor in the regulator sequence that is off.
Love the chassis!!!
Yup, the resistor values were off, shoulda checked that considering there were A LOT of mistakes in the documentation and in the parts I was sent. He sent three 49.9r, a 116r and a 104r for r20/21. None of which are the correct values for anything.
Oh well, I'm lucky it was close enough to 6.3V to not damage the tubes. Off to order 2 resistors, sigh....
Here's a few pics of the finished preamp:
Love it!
Funny, my first tube project was the SSE, and I think might still be my favorite. I have done a couple PP amps but there really is some magic to the SE topology that I could never begin to explain.
I abandoned my 300b project and reporposed the guts, xformers, and chassis to essentially the JELabs EL34. I must say I finally got it up and running last night and WOW!!! The SSE has a rival...
Allied 6K7VG PT, James 6123 OPTs, 6SL7 inputs, EH EL34 power tubes. Only mod I made to the circuit is utilizing one red LED for the 6SL7 cathodes happily running around 2.5mA (passing about 1.7V). I am running the EL34's at around 78mA, a little hot but no red plating after hours of listening. This one is a keeper...
Funny, my first tube project was the SSE, and I think might still be my favorite. I have done a couple PP amps but there really is some magic to the SE topology that I could never begin to explain.
I abandoned my 300b project and reporposed the guts, xformers, and chassis to essentially the JELabs EL34. I must say I finally got it up and running last night and WOW!!! The SSE has a rival...
Allied 6K7VG PT, James 6123 OPTs, 6SL7 inputs, EH EL34 power tubes. Only mod I made to the circuit is utilizing one red LED for the 6SL7 cathodes happily running around 2.5mA (passing about 1.7V). I am running the EL34's at around 78mA, a little hot but no red plating after hours of listening. This one is a keeper...
I noticed a very pronounced shift at maybe around 40 hours of burning in. Mid bass gained a lot of clarity and detail, and high treble was smoothed out. I've been extremely happy with mine, it just keeps getting better.
Dave, I'd be interested in hearing yours as well sometime. How does it change your sound?
Dave, I'd be interested in hearing yours as well sometime. How does it change your sound?
I was horrified for the first 5 minutes, then it got better and better and I got happier and happier.
I shut it off after a couple hours because the heater voltage was too high, ordered the new resistors last night priority mail so it shouldn't be too long before it's up and running again. $7 shipping for $.19 resistors, lol. I'd love to bring it by and check out those speakers you built!- Status
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