There's most likely something wrong with chassis grounds, since that is what you changed. It is most likely someplace other than the power transformer, since it passed several tests and it's fairly easy to wire.
The most obvious choice is a mis-wiring where the chassis is connected to DC. Begin by tracing all the places the circuit grounds to the chassis to the circuit board to see if it goes where it's supposed to.
Some people post photos of their wiring, which helps.
The most obvious choice is a mis-wiring where the chassis is connected to DC. Begin by tracing all the places the circuit grounds to the chassis to the circuit board to see if it goes where it's supposed to.
Some people post photos of their wiring, which helps.
Apology
Oh damn, I'm a complete and utter jackass. I was using the damn grounding lug on the terminal strip as the point were the B+ connects to the power supply. I've looked the amp over a hundred times and not noticed it because all the power supply caps make it difficult to see. I'm really sorry for wasting everyones time on this. I couldn't for the life of me figure it out. I had rebuilt the power supply to bring down the B+ voltage when I put on the new transformers. And during the rebuild accidentaly used the gronding lug. I'm going to re-build it again and this time not use the grounding lug. Again, I'm really sorry. Thanks to Sy, Tubelab, Paulb and PRNDL for helping me. If it's any conselation I've learned a lot and practically pulled apart and rebuilt the entire amp.
Oh damn, I'm a complete and utter jackass. I was using the damn grounding lug on the terminal strip as the point were the B+ connects to the power supply. I've looked the amp over a hundred times and not noticed it because all the power supply caps make it difficult to see. I'm really sorry for wasting everyones time on this. I couldn't for the life of me figure it out. I had rebuilt the power supply to bring down the B+ voltage when I put on the new transformers. And during the rebuild accidentaly used the gronding lug. I'm going to re-build it again and this time not use the grounding lug. Again, I'm really sorry. Thanks to Sy, Tubelab, Paulb and PRNDL for helping me. If it's any conselation I've learned a lot and practically pulled apart and rebuilt the entire amp.
You don't have to apologize for wasting anyones time. Look at it this way, it may have been frustrating for you at times, but is was a learning experience for you, and anyone who reads the thread. We all have to learn from our (or others) mistakes, and at least for you it only cost you a hand full of fuses and some time. It could have been worse, touching the amp and something grounded at the same time while the ground wire was disconnected could have been a real shocking experience.
I have made the same mistake with the lug strips, granted it was a long time ago, but if one person avoids this mistake, we have furthered the vacuum tube hobby.
I have met people who would have stuffed in a 20 amp fuse and tried to make voltage measurements. By the time you smell the power transformer, it is already toast.
Power transformer too small?
I'm afraid the the power transformer might be undersized for this application. It's gotten pretty hot (too hot to keep my hand on the top of). It's 100ma, in your experience should this be large enough for a SE 6V6GT with an out put of about 4.5 watts? I'm wondering if maybe 125ma or even 150ma would run cooler.
I'm afraid the the power transformer might be undersized for this application. It's gotten pretty hot (too hot to keep my hand on the top of). It's 100ma, in your experience should this be large enough for a SE 6V6GT with an out put of about 4.5 watts? I'm wondering if maybe 125ma or even 150ma would run cooler.
The power transformer is on limit (45 mA anode current + 4.5 mA screen current = 49.5 mA at zero-signal and 54 mA at maximum signal for each tube). Use a bigger one if you can.
Chek the anode current and the voltage across 330 ohm/1W resistor in cathode (12.5 V).
See this (pag. 2): http://www.mif.pg.gda.pl/homepages/frank/sheets/135/6/6V6GTA.pdf
Chek the anode current and the voltage across 330 ohm/1W resistor in cathode (12.5 V).
See this (pag. 2): http://www.mif.pg.gda.pl/homepages/frank/sheets/135/6/6V6GTA.pdf
If the transformer is made by Hammond the heat is common. I have been using Allied electronics power transformers in tube amps for over 10 years, below, at and above the maximum ratings. They are made by Hammond. They all get hot. Transformers run right at the maximum ratings get too hot to keep your hand on for more than 10 or 20 seconds. I have only had one fail in 10 years, and it got wet during a hurricane.
If this makes you nervous, you can use a transformer with a higher current rating. If the voltage rating is the same, the actual B+ voltage will increase slightly. This is because it is wound with heaver wire which has a lower resistance. Make sure that your amp is not running near the maximum voltage before installing a bigger transformer.
If this makes you nervous, you can use a transformer with a higher current rating. If the voltage rating is the same, the actual B+ voltage will increase slightly. This is because it is wound with heaver wire which has a lower resistance. Make sure that your amp is not running near the maximum voltage before installing a bigger transformer.
I'm glad to hear that Hammond power transformers tend to run warm. It's information like this that makes me appreciate this forum and the internet in general. I would have no way of knowing what is normal otherwise. I sent and e-mail to Wade (designed the curcuit) and asking whether he thought I should get a larger transformer. I'll see what he recommends.
I checked out your web site. It's pretty impressive. I don't see many people experimenting with new tube curcuits. I figured electrical engineers would love this stuff.
I was reading a thread (from January) today that you contributed to and had a question for you. In the thread you mention swapping out the 6V6s in you SE amp with KT88s and 6L6s (quote provided below) which really interested me. Is it normal to be able to subtitute these tubes for 6V6s? I would love to try these tubes in the amp I just built. Let me know what you think.
A 6L6 will draw a lot more filament current than a 6V6, a KT88 will draw even more. The bias current will also be different. This may be an issue if your power transformer is marginal already.
These tubes all share the same pinout, but are not normally considered interchangable. In some cases, where the other components are capable of dealing with the increased current demands these substitutions can be made. The SimpleSE in question used Edcor 5K ohm output transformers and a power transformer from an old HP audio oscillator. Every thing else is the same as used in my 6L6 - KT88- EL34 amps, so the substitution was not an issue.
I can not open the schematic link that you provided, so I don't know the details of your circuit. If your power transformer has enough filament capacity to deal with 6L6's you could try them. You need to have meters attached across the cathode resistors so that you can watch the current. If 6L6's draw too much cathode current in your design, your already warm power transformer will be a HOT transformer. I know that KT88's draw a lot of current. I have used Electro Harmonix KT88's in my amp, they draw about 90 mA of cathode current each. Add that to the driver current ant you are looking at 200 mA total. Too much for a 100 mA transformer. The max current for the Edcor output transformers isn't specified, but I have run them at 80mA with good results.
These tubes all share the same pinout, but are not normally considered interchangable. In some cases, where the other components are capable of dealing with the increased current demands these substitutions can be made. The SimpleSE in question used Edcor 5K ohm output transformers and a power transformer from an old HP audio oscillator. Every thing else is the same as used in my 6L6 - KT88- EL34 amps, so the substitution was not an issue.
I can not open the schematic link that you provided, so I don't know the details of your circuit. If your power transformer has enough filament capacity to deal with 6L6's you could try them. You need to have meters attached across the cathode resistors so that you can watch the current. If 6L6's draw too much cathode current in your design, your already warm power transformer will be a HOT transformer. I know that KT88's draw a lot of current. I have used Electro Harmonix KT88's in my amp, they draw about 90 mA of cathode current each. Add that to the driver current ant you are looking at 200 mA total. Too much for a 100 mA transformer. The max current for the Edcor output transformers isn't specified, but I have run them at 80mA with good results.
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