Magnavox 169 BB Schematic needed

Hello Group,

I need some help in locating a Schematic for an old Magnavox 169 BB amp. I just acquired 2 of these old gems....and I'd like to get an 'electrical look' at them before I tackle the project of doing some up-dates or mods. I've not even plugged them in.....but I believe they can be a good building-block for some nice performance. However, I'd like to change the driver stage a bit, and find a suitable way to replace the 6AN8 with a 12AX7 tube. So, if anyone has any suggestions, please let me know. I'm a "Rookie" at this....I have some building experience, but no real 'design' knowledge, and no technical background. This is all 'learn as I solder' stuff......and sometime the fumes fill my head (as I'm sure you are all aware). But, if you have the base schematic and can email a copy to me, I'd really appreciate it. My address is Wharf_Creek@Hotmail.com. Many thanks, Tom D.

Try this thread .
http://www.audiokarma.org/forums/showthread.php?t=211157
belive you will find what you need .

This will work for 12AX7 mod Schematic by Gordon W ,just use the ps in you amp and the 6V6's

This is a HUGE help!! Now, if I could ask just one more favor: Can you either send this to me as a PDF that I can print off (Wharf_Creek@Hotmail.com) or tell me if there's a way to print-off what you've copied on to this thread? Perhaps you can tell I'm NOT very savvy with this type of forum ....but I'm trying to learn! (old dog...new trick). MANY thanks for the help!! Regards, Tom D!!

Hey Batt..... just a quick F/U..... I've managed to not only print your schematic (w/ 12AX7 conversion) but also found the thread with the link to a PDF of the original schematic, and got some good prints from that as well. RE your schematic w/ 12AX7, is that a 2.2K feedback resistor? I can't really read it on my print-out, nor on my screen. I think all the other values are pretty clear. I did find it interesting in reading the threads that someone actually had 2 of these, one with the 6AN8 and the other with a 12AX7....and they converted the 12AX to a 6AN8 to match the other. I wonder why they didn't go the other way? Any thoughts on that? Is the 6AN8 actually a better driver tube than the 12AX7? I would not have thought so! I have a very nice little PP EL84 Pilot console amp here w/ 12AX7 drivers....and it sounds about as good as any amp I've ever listened to.....bar none! I've go 6AN8s in my Mark IIIs and in my old Heathkit amps....and I've often wondered why the more available and seemingly better sounding 12AX7 wasn't used more often back in the day........???

Hi the feed back resistor is 2.2 K ohm . I like 12AX7 drivers beter than the 6AN8 , The reason the the 6AN8 was used it becaue the pentode in it provides greater voltage gain .

magnavox 169bb

i have one of these ... amps - need the schematic - and was just wondering what wires on the pre amp input do i need to solder together to get the thing to come on when i plug it in... you see i don't have pre-amp but its true that that has the on/off switch for the amp ... i see one black wire one gtreen and one yellow and i am sure i have to join two of them ... hey maybe all three .. not sure any insight appreciated..

I have a scan of the Sams folder - email for a copy. tbavis(at)rochester(dot)rr(dot)com

In essence, you need to connect the power cord to the two ends of the transformer primary (black wires). You REALLY should add a fuse - 1/2A slow or 1A fast-blow should do. You'll find one of the transformer is connected to power cord already - the other connection is made through the switch on the record changer. You can add a switch and fuse, or just a fuse. In the old days, the transformer was the fuse - so it smoked a bit when a cap or tube shorted - no big deal!