Edcor XPWR131-120 Power, Edcor CXC125-10H-200mA choke, R30 is 120k ohm. I originally had a 47 uf cap in C4 spot and had about 380VDC across R30. I changed it to a 10uf and the V lowered to about 360VDC. I'm using the two 260 volt legs on the power transformer. Any suggestions? Can I use a non polarized cap for C4, seeing as I don't have any electrolytics of that value? Oh, forgot to mention this is for a 45 tube amp. Filament and B- are 2.45 V and -177 VDC.
Yes, some builders have used polypropylene caps for that position, and even an entire amp build.
360 volts is a bit high for a 45. I run mine at 320 volts and 30 mA, which is over spec but seems to work fine. But then all my tubes are flea market and Ebay finds from a long time ago when they were cheap. They were all under $10 each.
The voltage will drop considerably once the 45's are installed and biassed up.
Without the 45's in their sockets verify that turning the bias pots changes the voltage on the 45 grid pins. Set each pot to its most negative voltage.
Install both 45's, power up then adjust the pots until each 45 draws 25 to 30 mA. Then measure the B+ voltage. It will probably be below 300 volts. If you need to make changes in the cap value, repeat the above steps since the current depends on the B+ voltage and you will likely be increasing the voltage, so the current will increase as well.
The pots will interact a bit since turning up the current lowers the B+ a bit, so the other tube will lose a milliamp or so. Old tubes will take some time to settle in, especially if they haven't been used in a long time......set them to 25 mA or so and let them cook for several hours (playing music is OK). Then recheck the bias and set to the desired current.
I'm sure there is something, but I can't think of anything now. Electrolytics are popular because they were the only option in the size VS capacitance department. In the past 20 years ceramics have chased electrolytics out of the low voltage high capacitance market, and film caps are becoming cost competitive for high voltage applications.
Without the 45's in their sockets verify that turning the bias pots changes the voltage on the 45 grid pins. Set each pot to its most negative voltage.
Install both 45's, power up then adjust the pots until each 45 draws 25 to 30 mA. Then measure the B+ voltage. It will probably be below 300 volts. If you need to make changes in the cap value, repeat the above steps since the current depends on the B+ voltage and you will likely be increasing the voltage, so the current will increase as well.
The pots will interact a bit since turning up the current lowers the B+ a bit, so the other tube will lose a milliamp or so. Old tubes will take some time to settle in, especially if they haven't been used in a long time......set them to 25 mA or so and let them cook for several hours (playing music is OK). Then recheck the bias and set to the desired current.
I'm sure there is something, but I can't think of anything now. Electrolytics are popular because they were the only option in the size VS capacitance department. In the past 20 years ceramics have chased electrolytics out of the low voltage high capacitance market, and film caps are becoming cost competitive for high voltage applications.
That's because without the power tubes installed, the capacitors are charging to their maximum value, and just sitting there, as there is nothing to pull the voltage back down. As you are observing.
With a 260-0-260 xfmr, CLC power supply with 47 uf first C, and a 5AR4 rectifier, I guesstimate you will get about 327 volts B+ with the power tubes drawing current.
Win W5JAG
I think the information you are looking for is here on the tubelab site:
Tubes and Applications | Tubelab
Tubes and Applications | Tubelab
The pots set the plate voltage for the 5842. 175 is usually the best choice for distortion.
I run my 45's on 320 volts at 30 mA. I have a set of NX483's (a 5 volt 45) that I pulled out of a flea market Sparton radio about 14 years ago. They had 1929 date stickers on them. Now almost 90 years later they are still playing just fine. YMMV
The CD went away when I put it all on the web site over 10 years ago. It had less info and no pictures. When I started selling the boards, my customers were mostly tech's and engineers in the same plant where I worked. If they had an issue, I was easy to find. It was one of them that convinced me to do the web site.
I run my 45's on 320 volts at 30 mA. I have a set of NX483's (a 5 volt 45) that I pulled out of a flea market Sparton radio about 14 years ago. They had 1929 date stickers on them. Now almost 90 years later they are still playing just fine. YMMV
The CD went away when I put it all on the web site over 10 years ago. It had less info and no pictures. When I started selling the boards, my customers were mostly tech's and engineers in the same plant where I worked. If they had an issue, I was easy to find. It was one of them that convinced me to do the web site.
Thanks, George and others for your help. I finally figured out what to do. 5842s running 180V and 45s running 300V. On vinyl it kinda farted out until I got the volts up on the 45s. Now it sounds just superb! A little more detail than the SSE. It really is a marvelous little 2 watts
Thanks again for the help.
Thanks again for the help.Apologies for resurrecting an old thread, but it seemed to be the most relevant. I am just starting the initial checks on a TSE board with just the rectifier tube in at the moment - if I read the comments right the B+ I have at the moment, 340V with 4.7uF for C4, will drop once I get the power tubes in and biased, but does this go for the B-, which is 200V at the moment? Also, I seem to have a high voltage for the filaments on the 5842's (pins 9-3?), at over 8V - will this drop under load as well? The filament voltages for the outputs tubes are pretty much spot on, at 2.48V
Decided to go through the rest of the setup - all is good, I actually had to go back to 47uf for C4 to get the B+ to where I wanted it. On the bench with the headphones hooked up, running at a B+ of 300v, 45 tubes biased at 28ma, and sounding superb. A tiny bit of hum, but that should go away once I have boxed it up and got the cable routing sorted out.
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