Something like an Astor JJ is reflexed.

If yours is reflexed I only see one can. JJ uses 6A8, IF, 6B8, IF 6V6 rectifier 5Y3. Reflexed sets often have a pF cap plate to grid.

Marc

Circuit diagram uploaded to Post 60.

Hey thanks Fred and Brad. I have some progress photos ready to send . I will try and send this afternoon

6K8 drawing is technically incorrect. it is a Triode Hexode.

6B7 Is a duo diode Pentode

6F6 is a Power pentode.

My attack on reverse engineering is to draw the layout of the set with the AutoCAD placing the tubes of type (these are pre drawn with pin numbers & all elements) in their place plus the coils & transformers predicted and then play joint the dots with the kids coloured pencils.

You draw it "as is" and it may take a couple of passes. Mistakes in wiring on the set are not fixed until the circuit is proofed.

That set looks like it was made for the cheaper side of the market, so I would not expect parts other than resonating caps in the cans.

Some, or all cathode resistors will be missing, as its back biased.

It was the running gag with Astor, that they made the prototype & then took parts out until it stopped: Put that one back & put it into production.

Hi Carl some more photos and confirmation of the number of IF's will help.

I did another roughie for 1 IFT and reflex with some pretend component values.

Will send to Brad to pin to this post.

Will be intriguing to see if I am any where near how it really is!


Fred.

Ok Fred.
That 32 Uf should by rights be a 8 μF as one of the cans on the chassis was a isolated (Earth) 8uf.

I wondered about that diagram. It shows the earth terminal not going directly to earth, but instead being connected to the volume? control.

If you're going by that one photo, yes it will be guesswork.

I've never used a CAD package, but I work in a similar fashion - I draw the tag strips, valve sockets and other large parts on a sheet of paper in their actual positions, then "join the dots" with the components and wires. After that, I make another diagram in the conventional fashion by following what I wrote in the first diagram.

I have always said, that irrespective of how you go about it, reverse engineering is a painful process. The first drawing is the layout diagram the second or lastly the wiring diagram.

I will as noted before use colour to separate primary & secondary wiring. I.e. Say reds for positive black & browns for negative; Blue screens especially in the RF; Green heaters.

There is an STC Chassis 59 on Kevin Chants site. That was one where a circuit could not be found, (AORSM's HRSA) so it got reverse engineered. There is a warning on it as to how it was acquired as it had been hacked and what was modified. However, should someone get into the poo. At least that circuit, as presented did work.

Time permitting (what time) It could be set with an AutoCAD to trial.

Yeh Rob, the first SCETCH got the volume control a bit wrong.
The second sketch has it worked so the aerial hooks to one end of the pot and the cathodes the other end.
It was a horrible arrangement that was used in heaps of early sets, including the first Little General..
As the rotor is connected to ground minimum volume shorts the aerial out and has maximum bias on the valves.
Maximum volume has the aerial above ground and the bias low.
Yes I know it sounds daft but does work on a non AGC simple set.

Carl put me out of my misery!
Does the set have one or two IFTs?

The idea of a SKETCH is to give a starting point to get ones head around the set or whatever the project is.
It is not a production engineering drawing.
Its a "concept" drawing and I did plenty of these in design to give production and engineering an idea of what can be done, before everybody goes off half cocked spending hours wasting time drawing a Giraffe when we were making a Gazelle..

When I'm scratch building I do concept drawings all the time and just change them on the fly
If I had the set on the bench I would then carefully go though the chassis and correct all the guesses.
Obviously cant do that but I'm busting to see how close any of it is.

Fred.

Yes, I've seen that arrangement in a few of my sets. It's ok-ish, until the control gets noisy. Then things turn nasty.

Really need to get hands on that actual set.

Fred it only has one IFT. I have sent Brad some more photos.

I am sending Brad & Carl an example of where the AutoCAD starts out. It will put in other caps & resistances and draw the wiring in colour.

Takes time to draw set in full.

Not on drawing pin one of 6K8 metal is grounded.

Photos uploaded to Posts 65, 71 & 72.

Guys, when e-mailing photos and documents, please do not assume I know where they need to be - please state the thread and post they need to go to every time.

Carl, that cabinet scrubbed up well!
The dial surround is perfect.
That is the correct finish, I've seen surrounds polished with brasso and do they look like crap!

Now you have a lovely cabinet next is the chassis.
It really needs to be stripped to bare metal and rebuilt using as much of the original parts as possible.
That is a long job and maybe what you don't want to do.
Perhaps just a good clean up with a buff up of the bits?

Marc's approach with the circuit drawing is the correct engineering procedure starting off with the knowns and adding the detail.
I use the free hand artistic approach and see the circuit as a holistic entity!
While a design engineer I used to throw a big sketch at the CAD operators and they translated scribble to production drawings.
Actually a lot of stuff got made and the drawing office came last and drew up what we fabricated from the sketch!
I even did CAD myself back in the 1990's got proficient to CAD13 and amazingly did many drawings for production.
I could even do the bills of material and link those to purchasing.
However there is nothing like grabbing a big sheet of paper and a 2B pencil and in 5 minutes showing a whole concept and what the project should look like.

When I think of it, designers like me are the horror of manufacturing, when the details of a project are mainly in my head, buts that's why the sketches were important, "that's how I see it, that's what I want".

Back to the set, its looking good.
Look forward to some more chassis photos so I can have a closer guess at the circuit!!
Fred.

The thing to note is that with the AutoCAD you can shift things if the space needs amending. That's why the oscillator coil is below the Frequency changer: Lots do that & it can get messy if you have a muti band Autodyne Colpitts oscillator as the exciter.

Marc