Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Mike_J on January 24, 2021, 11:59:36 am
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I put the power tube sockets so that pins one and eight are close to the bottom of the chassis as shown in the Hoffman layout. The rectifier tube was installed the same way. If you look at the picture of the way the wire to the power switch in red is running it is not like the 5f6a schematic or pictures I have seen of the chassis insides. They both have the wire and socket pin 8 on the lower left side. Does anyone see a problem with just rotating the socket 180 degrees. Would be like the 5f6a schematic and pictures I have seen of the way Fender wired the socket?
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fwiw;
I "align" all the filaments in the pre (4,5 up, 9down). IN the PA I align the sockets to be "best fit" for wiring
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That looks nasty!
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fwiw;
I "align" all the filaments in the pre (4,5 up, 9down). IN the PA I align the sockets to be "best fit" for wiring
I did the same for the preamp. Thanks for the "best fit" explanation for the PA. Attached is a picture of the tube socket rotated. Another good reason for doing it is now I can see how poorly the solder job on pin 2 was done.
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That looks nasty!
Would you explain the nasty comment and I will try to fix anything I can. The little black marks on the wire sheathing was done 22 years ago. I know the PT worked so I am not going to replace it for some little burn marks I put on it 22 years ago. The egregious soldering on pin 2 is current and I apologize for such sloppiness.
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Cleaned up the solder on pin 2 and added yellow electricians tape over the wire to hide the burn marks. Solder on pin 2 would have worked okay but it looks much better now. Looks like pin 8 could use just a little more solder as well. Much easier to see with the camera than in person.
If you look in the picture for pin 8 you can see the stranded wiring going into the pin is not tight. It took quite a bit of effort to get the wire into the small hole in the tube socket. My question is, does it make sense to fill that loose wiring with solder. Could the loose stranded wiring cause arcing that could be rectified by filling it with solder?
Thanks
Mike
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Use heatshrink to tidy things up and avoid molten plastic in the solder. That's much cleaner and nicer to work on...
I am not the cleanest soldering guy.. but I always try to make it look nice.
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Use heatshrink to tidy things up and avoid molten plastic in the solder. That's much cleaner and nicer to work on...
I am not the cleanest soldering guy.. but I always try to make it look nice.
That does make it look much neater. I know what you mean about the molten plastic. One of the reasons I use Teflon as much as possible. Will start to use your heatshrink idea from now one. Just received on order of a lot of it in the mail yesterday.
Thanks
Mike
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Took a picture of the power end of the amp. The red wire from the rectifier pin 8 to the standby switch, not connected yet, will carry unfiltered DC. If you look at the 5f6a schematic and a picture of the original Bassman the red/yellow and green/yellow center taps were soldered to the left side wall of the chassis. I presume it is to keep the red wire carrying DC away from the center taps for AC wires. Otherwise the red wire running to the standby switch was run like I have it under the two twisted green heater supply wires with the bias supply wire lightly wrapped around the heater supply wires at a 90 degree angle. I am planning on running them under the end of the Hoffman style board and up through the board where the heater and bias wires are to be connected. Does anyone see a problem running them this way? The red DC wire is at least 3/4" away from the red/yellow center tap and crosses at an angle. The DC wire will be touching and crossing the twisted heater wires and bias supply wire at a 90 degree angle.
On the 5f6a schematic and the picture of the '59 Bassman the heater supply wires run first to the lamp holder. From there they go to pins 2 and 7 of the power tubes and then are daisy chained to the preamp tube heater connections. As previously mentioned the green and yellow heater center tap wire is grounded to the left side of the chassis. Using the Hoffman layout I presume I can run the heater wires under the end of the board along with the bias supply wire and bring them up through the board and wire them to the ungrounded ends of the turrets. I would use precision 100 ohm resistors to act as an artificial center tap and won't wire the green/yellow center wire to ground. It will be capped and moved to the left side of the PT. From there I would run 20AWG twisted wires to the lamp holder and 18AWG twisted wires to the tube heaters. The preamp wires are already wired with 20AWG twisted wire. Only needed 18AWG to V5 and to V4. The wire going from V3 to V4 is already 20AWG.
You can probably see I have the black and white AC supply wires run on the left and back sides of the PT. They go to either the fuse holder or power switch with the other ends connected to the PT primary wires. No big deal there.