Zenith console SE tube amp schematic.

[BrokenHill]

I have been looking for a schematic for a stereo Zenith console SE tube amp, the code on the chassis is #S531518
It uses two 6BQ5 output tubes and one 12AX7 tube, the rectifier uses the 5Y3GT tube, the amp has three control
pots one for volume and the other two pots is for bass and treble control.

I checked at this web site > http://techpreservation.dyndns.org/schematics/Zenith.htm
and could not find the exact number on the chassis that I have, looks like I need the model number of the console
and that I do not have, I also noticed that most of the files at that web site I cannot see any info with the djvu
readers I have, I have tried the STDU Viewer and the WinDjView program to read the djvu files at that site and most
of the files I just get a white blank page with the viewers I use, has anyone else had problems at that web site
reading some of the djvu files there?

Maybe someone knows another source or web site to find a schematic for the Zenith tube amp I have, I have found the
schematic for the Zenith SE amp that uses the 12AU7 as well as the other tubes listed above but it's a different
circuit.

This little Zenith SE amp looks like it will be a fun project.

 

[century tek]

Although schematics are invaluable when searching out hard to diagnose problems, one is not really needed when doing basic troubleshooting.

Just curious, what is the problem with your zenith amplifier? I have one of those single ended stereo amps which uses a 12AX7, 6CG7, two 6BQ5's and a 5Y3.

 

[knockbill]

I rebuilt a little Zenith amp recently... Did you try HiFiEngine for your schematic? I never had luck with the djvu files either...

Post some pics of your amp, I'd like to follow your build...

Regards,
John

 

[BrokenHill]

The Zenith tube amp works fine and is indeed a very simple circuit although it has way to much bass, looking at the volume pot I see
it has the fourth tap that is usually used for a loudness switch in most amps, it looks like it's permanently connected to the circuit
and always on and that could be one reason why this little SE amp has to much bass.

If I had a schematic then I could post it here for others to see and possibly get some helpful suggestions on how to modify the circuit
to reduce the bass down to work better with modern speakers.

I will post some pics of the Zenith amp later.:thmbsp:

 

[Tom Bavis]

Try reinstalling the DjVu plug-in, or using a differnt browser like Chrome. Look for chassis numbers starting with "4" (Zenith chassis numbers start with # of tubes)

 

[BrokenHill]

Okay I will check that site again and try with a different browser.



Some pictures of the Zenith.

 

[century tek]

Mine's just a little different where I have a seperate bass control (contour) switch.

It looks like your bass (besides the bass control itself) contour is part of the loudness circuit. Just disconnect the loudness tap, or connect it to a seperate on/off switch so it acts like a seperate loudness control.

 

[BrokenHill]

Looking for the schematic on this 4 tube SE Zenith is not going so good, I keep finding the schematic for the 5 tube version with the 12AU7 tube,
I will just work on it without it.

The first thing I did was completely disconnect the loudness tap on the volume pot as century tek suggested and that did help a whole lot, the amp
still has a lot of bass but now it is more controllable with the bass control pot. :thmbsp:

Looking through my spare parts I found some film caps that are fairly new and replaced the white caps connected to the treble pot with a couple of
orange drops, I then tested the amp and did not notice any change in sound, I will change things out slowly so I can test and hear how much it will
change the sound that way it's easier to undue anything that may not sound so good.

I did find some Wima's that I had and replaced those .1 100 volt brown drops you see in the pics, the change in sound was a major improvement, the
sound is much cleaner, brighter with more detail, those brown drops were kind of muddy and dark sounding.

I will need to check the other components for their values and make a small list of parts and see if I can improve the performance of this amp some
more, step by step.

The little Zenith amp puts out a lot of sound for just 4 or 5 watts that it puts out and it hardly sucks any AC juice, maybe around 1/3 of a amp.