Thanks for the video. To prove I visited I left a comment but I said I was from AK rather than DIY audio as I forgot where I was at the moment.
Hah and I thought the "from AK" bit meant you were from Arkansas! I made a goof in the video and said "film caps" when I read meant "wax caps". Either way those old capacitors were incredibly far gone.
Tonight I'll be testing the resistors and seeing if any of them are out of spec.
6BG6GA,thanks for that information. I'll just stick with the original schematic for the values and use the Chinese website sourced schematic for understanding the layout.
I went through all of the resistors last night and found that of the 14 or so that are used in the amplifier only three were outside of their 10% spec. Of these three none of them were out by very much with the worst of the bunch being 28% high. Not bad for something 60+ years old!
I'm curious,do you folks have any preferences for resistor brand?
I'm curious,do you folks have any preferences for resistor brand?
Request for schematics.
Hello cmfast! I would be interested in a copy of manuals for these. 3 years ago I saw the organ that was setting outside for several months. I finally contacted the owner and he gave the organ to me. To my suprise, he also gave me the speaker cab that had been kept inside. The cab had been cut down, but had all amps and speakers. The speakers were sold long ago. My bad
I am now in the process of gathering as much info as I can for my first attempt at HiFi. I believe I still have the amp from the organ but I am not sure yet. I was hoping the schematics would clarify some questions I have for my build and verify if I do still have the amp from the organ.
I am new to the forum and plan on keeping this thread going if there is enough interest in my project.
I appreciate your recent input!
Hello cmfast! I would be interested in a copy of manuals for these. 3 years ago I saw the organ that was setting outside for several months. I finally contacted the owner and he gave the organ to me. To my suprise, he also gave me the speaker cab that had been kept inside. The cab had been cut down, but had all amps and speakers. The speakers were sold long ago. My bad
I am now in the process of gathering as much info as I can for my first attempt at HiFi. I believe I still have the amp from the organ but I am not sure yet. I was hoping the schematics would clarify some questions I have for my build and verify if I do still have the amp from the organ.
I am new to the forum and plan on keeping this thread going if there is enough interest in my project.
I appreciate your recent input!
I like mills. dump the crossover. only thing I remember rehashing one of these is to make sure the B+ center tap is grounded properly if you plan to remove those speaker jacks. since its unnecessary, discontinue the field circuit too. 16 ohm speakers work the best on this amp.
Early stage completed. Have both 6420 amps running. Added 1/4" mono jack to both amps. Straight from MP3 player split left and right channel. Very nice sound as is thru my 70's Pioneer speakers. Not sure what next. 2 channel eq or possibly tone stack on each amp.
http://i1044.photobucket.com/albums/b444/tonekwest/Wurlitzer 6420 Monoblock/1.jpg
http://i1044.photobucket.com/albums/b444/tonekwest/Wurlitzer 6420 Monoblock/2.jpg
http://i1044.photobucket.com/albums/b444/tonekwest/Wurlitzer 6420 Monoblock/3.jpg
http://i1044.photobucket.com/albums/b444/tonekwest/Wurlitzer 6420 Monoblock/1.jpg
http://i1044.photobucket.com/albums/b444/tonekwest/Wurlitzer 6420 Monoblock/2.jpg
http://i1044.photobucket.com/albums/b444/tonekwest/Wurlitzer 6420 Monoblock/3.jpg
Decided to bring these back from the dead. Added a screen supply using 3) 100 volt zeniers, added a bias supply with individual output tube bias. Used a peavey power transformer out of a UM10 mixer amp with a voltage doubler circuit on a piece of turret board. Added a RCA input jack where the AC and input socket were an installed a plate there. Removed the speaker output jacks and installed a speaker jack.
Had originally set up the amp in triode mode but wasn't happy with the sound. Put out about 11 watts in triode mode. The amp really hammers now the bass is really firm and hits hard. I never imagined the amp could sound this good. The coupling caps were replaced with the "Orange" caps and the electrolytic caps have been replaced with the exception of the .047 from the plate of the voltage amp stage to the grid of the phase splitter. Removed the 50 pf cap (was leaking) and resistor that is across the plates of the output tubes. Running about 45mA-50mA per output tube.
Had run this amp in the past with a 6K resistor in place of the field coil. The amp never really sounded quite right for some reason and I shelfed the amps for a few years. Removed the 6K resistor and made the modification that I mentioned.
I have several questions... is the resistor and cap network really needed that was across the output of the amp where the output transformer is hooked up?
Second question is I have -24vdc where the bias circuit hooks up to the 92K grid resistors should it not be higher?
Had originally set up the amp in triode mode but wasn't happy with the sound. Put out about 11 watts in triode mode. The amp really hammers now the bass is really firm and hits hard. I never imagined the amp could sound this good. The coupling caps were replaced with the "Orange" caps and the electrolytic caps have been replaced with the exception of the .047 from the plate of the voltage amp stage to the grid of the phase splitter. Removed the 50 pf cap (was leaking) and resistor that is across the plates of the output tubes. Running about 45mA-50mA per output tube.
Had run this amp in the past with a 6K resistor in place of the field coil. The amp never really sounded quite right for some reason and I shelfed the amps for a few years. Removed the 6K resistor and made the modification that I mentioned.
I have several questions... is the resistor and cap network really needed that was across the output of the amp where the output transformer is hooked up?
Second question is I have -24vdc where the bias circuit hooks up to the 92K grid resistors should it not be higher?
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