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Philco F-1801
Philco F-1801
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Old 8th February 2012, 01:56 AM   #1
TexasAudio is offline TexasAudio  United States
diyAudio Member
Join Date: Nov 2009
Location: Texas
Default Philco F-1801

I have been a member for awhile now. Iíve not posted much I mostly read and gain info from the other post. I have decide to do my first real tube project. I have recapped radios, amps and the such. I replace the caps and other parts with the same parts and donít change much. I do understand some about tube theory and ohms law but have lots to learn. So the project I choose to learn on is an amp out of a 1958 Philco console. I want to use it to play my guitar through and a line input for CD, MP3 player etc.. Its tube compliment is a 12AX7 AF amp, 6C4 Phase inverter, 2 6CZ5 output configured in a push pull arrangement and 5Y3GT for a rectifier. I have included a schematic from a Sams photofact for reference (if any needs a higher resolution copy let me know). The second schematic is what I have done to the amp already. I replaced all the electrolytic capacitors and C17 & C18 the filter caps. I cleaned the pots and tube sockets and tube pins. I also removed the multi-gang switch that selected the input and added a 2A fuse. I have measured the voltages they all read about 12% low, which is within spec but I would like to get them tighter. I put a 1Khz square wave through. Distorts on the leading edge, not sure what that means though. I will post photos when I get batteries for my camera. Here is where I ask for opinions and help on what next. Let first state what I would like to do and some questions.

1. I would like to add a standby switch. Where should I put it?
2. Add line input and convert it from stereo to mono. Do I just combine the two signals after they come in?
3. Should I replace all the components with better tolerances?
4. Should I replace the tube sockets and potentiometers with better quality ones?
5. What can I experiment with to change the tone quality?
6. Any other suggestions and opinions.

These should get me started. I will post photos of the amp and o-scope waveforms when I can. I want to go on the cheap however I am open to all suggestions. To my surprise the speakers that got with it sound good. I am going to try and use them. My primary goals are learning more about tube amps and have some fun with it. And hopefully have something to brag about when Iím done.

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