Decent Junk Pile find! Need Advice suggestions etc.!

[athos56]

Then the captain drove it into an iceberg

I thought it was sunk by aliens?

 

[Wavebourn]

Wave, why do you say that?

Because for pentodes with high B+ would be needed totally different output transformers than for triodes with lower B+

Yes, they are "beefy". They have too much of too thin wire n primaries (cost saving? Huh? ) than is needed for what you have in mind.

 

[chrisb]

So,

I am looking for some suggestions as to the following

A: Strap them as "Triodes"?

B: Lower the B+ and G2 voltage? 300V / 300V ??

Either way I intend to put a 6SN7 Input stage in the chassis where the connector was located along with RCA inputs there.

I will also add a volume pot after the SN7'.

Aesthetically I think I will strip it down and paint the chassis and add some nice wood corners/legs. Replace the sockets with Teflon or Ceramic along with better caps & resistors.

Agreed she'd look nice tarted up with a new paint job, but since a proper job of that requires a complete stripping of the chassis, you could take the alternate route and highlight the vintage derivation, and just update the circuit and associated parts.

There's certainly tons of space on and under the skirt here for major parts upgrades, including the OPTs as already suggested. Aside from questionably reliable operating points, and the life span of cheaper EL caps, etc., these are generally the weakest link on this type of chassis. Edcor makes some pretty decent output transformers for budget projects.

Still considering TS or Pentode?

the partial schematic in your first post appears to suggest a separate supply for the screens on the output tubes (as opposed to U/L tap on the OPT) - if so, then Pentode would certainly give you more power, but if you don't need the grunt, the 6BQ5/EL84 can be one sweet sounding triode

are you sure you wouldn't want to put the volume pot at the front end of the input stage?

and as much as I like the sound of 6SN7 / 6SL7 on my George Wright 300B amps, it seems a bit lopsided to use an octal based input tube on this guy

I take it from your photos that the power supply is on a separate chassis, what type of rectification is used? if it's something like the 6CA4(EZ81) that we've seen on a lot of our organ donors (Nordmunde etc,) it would seem more visually consistent to use novals throughout.

 

[coldcathode]

OK, then engineers with a rich background designed the Eastland, of relevance here a) because the engineering problems leading to the disaster were likely due to "corrections" made after the Titanic sank, and b) because many passengers who lost their lives on the Eastland were employees and their families from Western Electric.

That was an extremely interesting tid-bit, it seems as though the ship lead a rather full life afterwards. Going on to "bigger and better things".

Not unlike the destiny of this Zenith amp!

 

[coldcathode]

Update!

Thanks to everyone for their input, (the main reason I enjoy this hobby/obsession so much is the help available) I am listing the suggestions that have influenced this project and how I plan to implement them.

Wave's suggestion of new OPT's is being heeded. I have a nicer set from my 6V6 push pull amp (I forget now where they originally came from, but they were from a higher end hifi piece) Eventually I will go with Hammond or Edcor but that is a whole other Thread/Debate.


Chris B brought up the most points to consider and mulling over those led me to the final decision.

The powersupply (if you want to call it that) IS on this chassis with 5U4GB rectification and CRC filtering. There is NO filtering other than the first "C" for the plate voltage. Then RC for the screens and another RC for the input/splitter/driver stage.

This HAS to be redone IMHO.

Input tube could be Octal or Noval (I really like the SN7's) since there is already the Octal Rectifier on the chassis.

The sockets used are some of the poorest quality I have seen. So stripping the chassis is not really an issue since it is more a "vintage" theme rather than some restoration etc.

My "listening room"/computer workstation area is rather small and I have a couple pairs of relatively efficient speakers so "Grunt" is not needed. This has me going in the direction of Triode strapping them. In playing with load lines and various data sheets/curves I am looking at something with about 320V on the plates, cathode bias of about -13V @ 32mA into a 10K P to P load.

I am guessing about 6watts with less than 2% distortion.

Since I am ripping it apart I plan revamp the entire circuit as far as operating point etc. I will post a reworked schematic soon.