Ummm...yeah. Didn't even think about the pin-out, LOL.
For the record, I see about 5.5V on my 5842 filaments. Since this is not intentional, I guess a lower value needs to be calculated by the end user. I'm getting about 6.6V out of the supply in 45 mode, though I imagine it is lower when 300Bs are in there. I wonder if that has anything to do with why I don't care for the 300Bs as much.
For the record, I see about 5.5V on my 5842 filaments. Since this is not intentional, I guess a lower value needs to be calculated by the end user. I'm getting about 6.6V out of the supply in 45 mode, though I imagine it is lower when 300Bs are in there. I wonder if that has anything to do with why I don't care for the 300Bs as much.
You are using an Edcor power transformer? If so that explains it. I have been using Hammonds. Even my Lexan amp which uses a severely underrated Allied 6K56VG (made by Hammond) runs at 6.3 volts with 45's. I have been known to put 300B's in the same amp. This really heats up the little 120 mA transformer, but it is now about 6 years old. I still get 6.1 volts when doing this. I have stuffed 2A3's into this amp but the transformer smells funny and is too hot to touch after 1/2 hour of use. Didn't measure the voltage though.
The Simple P-P on the bench has a 272JX transformer. The "6.3 volt" filament winding measures 7.2 volts. The 600 VCT winding measures 660 volts (both measured under load). I also have a 372HX, but it isn't hooked up right now.
Different pinout, eh? I guess that explains why the 6c45p's went "poof" after I plugged the 45's in. I was adjusting the bias for one channel, and suddenly there was a flash in both 6c45p's and they both went dark. No big loss since they apparently weren't any good to me anyways, guess I'll hunt down a pair of real 5842s. Hopefully I didn't damage anything else, but I'll start the checkout procedure from the beginning just in case. The 45's and rectifier seem to still be glowing happily away at least, but I'll pull them all out until I'm sure everything's still right.
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A new pair of real RCA 5842's came in the mail today, so I'm really to pick up where I left off. I'm going to start the checkout procedure from scratch, of course, to make sure I didn't damage anything. I do have a question about one step, though...
Put a meter from the grid of the output tubes to ground. One meter for each tube. Power up the board. Each meter should read a negative voltage. With ONE HAND BEHIND YOUR BACK carefully adjust one of the bias pots (R12 or R23). The negative voltage for the corresponding output tube should change. Set it to the most negative voltage, and then adjust the bias pot for the other channel. Set them both to the most negative voltage. Power OFF the board. Do NOT touch the board for 5 minutes after the power is disconnected.
What kind of negative voltage should I be seeing at this step? A few volts? A hundred?
Put a meter from the grid of the output tubes to ground. One meter for each tube. Power up the board. Each meter should read a negative voltage. With ONE HAND BEHIND YOUR BACK carefully adjust one of the bias pots (R12 or R23). The negative voltage for the corresponding output tube should change. Set it to the most negative voltage, and then adjust the bias pot for the other channel. Set them both to the most negative voltage. Power OFF the board. Do NOT touch the board for 5 minutes after the power is disconnected.
What kind of negative voltage should I be seeing at this step? A few volts? A hundred?
Okay, two more stupid questions and then I'm done. It's already working fine and making music, but I want to be sure on a couple things before I call it quits.
1: I'm only able to get 165 volts on the plates of the 5842's, but the manual says 175. Is that good enough?
2: I'm a little confused about what the output bias should be. I want to set it to 25ma. My Radio Shack multimeter is reading .025 amps (the range is set to auto). Do I want .025 amps or .25 amps?
1: I'm only able to get 165 volts on the plates of the 5842's, but the manual says 175. Is that good enough?
2: I'm a little confused about what the output bias should be. I want to set it to 25ma. My Radio Shack multimeter is reading .025 amps (the range is set to auto). Do I want .025 amps or .25 amps?
1) This is fine and pretty normal. The Raytheon 5842s I have vary quite a bit in how they bias in this amp. Just try to get them as high as you can.
2) If you are measuring per Georges instructions, you should set your meter for VOLTS when you place it across the 10 ohm resistor. You want to bias your 45s to 25mA (0.025A), but you are doing this by measuring voltage across the 10 ohm sense resistor. Ohm's Law says V=I*R, so 0.025 * 10 is 0.250V or 250mV.
2) If you are measuring per Georges instructions, you should set your meter for VOLTS when you place it across the 10 ohm resistor. You want to bias your 45s to 25mA (0.025A), but you are doing this by measuring voltage across the 10 ohm sense resistor. Ohm's Law says V=I*R, so 0.025 * 10 is 0.250V or 250mV.
It did sound rather... unremarkable when I tried it out with the bias set wrong. What surprised me was that it had more than enough gain to drive my backloaded horn speakers. I only had to turn the preamp up about 1/4th of full volume to get satisfying sound levels.
Actually, that brings me to another dumb question: What's a good value pot to use for the volume knob? 100k logarithmic?
Actually, that brings me to another dumb question: What's a good value pot to use for the volume knob? 100k logarithmic?
Okay, I'll remove R8 and R19 tonight. It definitely didn't like the 100k with the other two resistors still in. There was very heavy reverb, and for some reason vocals were recessed into the background. Almost like somebody was singing from inside a cavern.
Without the pot it sounded normal, but I did notice a very slight reverb on certain recordings, but only on vocals. This may just be the recordings themselves, maybe my previous amp wasn't revealing enough for me to notice it. I'll have to listen to more records to be sure.
Without the pot it sounded normal, but I did notice a very slight reverb on certain recordings, but only on vocals. This may just be the recordings themselves, maybe my previous amp wasn't revealing enough for me to notice it. I'll have to listen to more records to be sure.
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It seems like my amplifier is completely operational at this point, so thanks again for the help! I'm pretty convinced the reverb I'm hearing in some vocals is just how they were recorded. I played a few folk records and I didn't notice it. What's surprising me most about this amp is how many slight tempo and rhythm changes I'm noticing in recordings I've listened to a million times before. Very, very impressive.
Now I just have to build a proper enclosure for it. I might try to duplicate Tubelab's lexan amp so I won't have to remount any of the caps on the bottom of the PCB.
Now I just have to build a proper enclosure for it. I might try to duplicate Tubelab's lexan amp so I won't have to remount any of the caps on the bottom of the PCB.
The TSE was my first working SE amp, though the SSE followed shortly after. It's still on a breadboard, but I listen to it often. I rediscovered a *lot* of my old music with this amp...for months I was listening to all kinds of old pop, classic rock, any live recording I could find, etc. I also discovered how lousy some of my recordings are. 
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