[Antipodal]

Hello everyone,
 I realise this is a long shot and a few pictures will make it easier and I hope to do that soon,but I hoped someone may be able to point me in the right direction for a start. The radio I am working on is a 1930s vintage set almost certainly American.When I first saw it I thought it was a Philco.
It runs on 6 volts ,is roughly the same size as a Philco F1540 .It has no built in speaker. 

The valve lineup is 6D6 6C6 6D6 75 42 and an 84 rectifier. It is a superhet using the 6C6 as an autodyne.

So far, so "could be any brand ".However there are some "unique "characteristics.
It has none of the characteristics of the Hudson H6 built by  RCA which I have just finished .Nor does it share any characteristics with the Delco 632 which is the radio I hope to begin work on next.
The original valves were all Raytheon. The original capacitors were all Sprague .The original paint on the outside was a deep navy blue colour.
The chassis inside the "box" is very similar to a Philco but the chassis is "suspended" inside the box on four nuts and bolts riding in (now slightly perished) grommets.The vibrator is a Zenith  but of course this may be a replacement of the original.( Did Zenith make car radios of this type at this time?)The control cables  of the  set and the tuning head which might have given a clue are sadly long gone. The grid cap clips are also a bit unusual in that they grip the grid  terminal on the top of the valve  in the usual way but they also have a little cap on the top making them easy to remove by flicking up with a screwdriver.There are no schematics  or paper stickers inside either the top or bottom covers.The output transformer is "on board". The set  looks as though it was secured to the firewall with two bolts.
It is likely to be  a mainstream U.S.  brand as  in New Zealand it was mostly mainstream brands which were imported here.
Maybe some of the characteristics will ring a bell for some Phorum readers. I hope so .
Thanks everyone and all the best, David

[Joe Rossi]

Hello David,

On the Grillecloth.com website there are 21 radio’s with the same tube line-up. I have placed the link here:

https://grillecloth.com/sylvania/tubelis...ubmit&db=5

You’ll have to match your radio to the Riders schematics at NostalgiaAir.org

Sorry I can't assist an more! Happy restoration, Joe

[Antipodal]

Hi Joe, Thank you for your wonderful detective work. I have searched through Riders and found the set : it is a Model 680 Hudson radio built by Zenith dated 1934.So the vibrator , rather than being a "it works so we'll fit it " substitute may well be the original for this set.This is probably an especially rare set in N.Z. Here in N.Z.  in the 1930s few people could afford cars and ,as in the U.S. ,the Hudson was a rare luxury car especially coming out of the Depression.There were ,though, many Essexs,the cheaper Hudson offshoot on N.Z. roads .So thank you again Joe. I'm so impressed with how you have narrowed the search down. The set is nearly going,but a stray loose wire off the top of the volume control had me foxed. I will let you know how it all plays out. Thanks.

[mikethedruid]

Now, David, all you have to do is buy the 1934 Hudson in which to install it !

[Antipodal]

Hi everyone, 
Well good news! The 1934 Model 680 Hudson  set built by Zenith is now going.I would like to say that this was due to a rigorous and  disciplined working through of the various sections informed by a deep and instinctive grasp of radio theory until the set burst into life.I would like to say that. Certainly I discovered early on that the buffer cap across the 6Z4's anodes was a dead short. There was a smoothing cap missing off the H.T. line.The H.T. was only 89 volts until I reinstalled the original Zenith vibrator when the H.T. lifted to 158 volts.Lots of the caps have now  been replaced.Thanks to Joe's work pointing me toward the right Rider volume and then armed with the schematic I was able to reattach the loose wire from the top of the volume control with confidence.To be fair, when working blind I had a strong hunch as to which tag it should go to .The schematic confirmed this.But the set  still did not go.
So ,as you do , I fell to musing and pondering and poking , disconsolate , with the  prodding hook I use to trace wires.The signal tracer had shown that signal was appearing at the top cap (control grid) of the 6C6  mixer but not at the top cap of the 6D6 i.f. amp.So I was prodding around the 6C6 socket when , you guessed it. I'm still not sure  what short I had disturbed but I suspect something round the cap and resistor (grid leak ?) between the osc coil and the cathode of the 6C6 which would suggest the autodyne was not "dyning" so that no signal was appearing at the grid of the I.F. amp. Sound feasible? Any way it now goes.Time for rejoicing. Thanks especially to Joe for his help. So I now have two vintage  Hudson radios though neither has the flexible cables or tuning head ! Or indeed a Hudson to install them in!Thanks, Mike!
This raises a question though,  about oscillator testing. With a 6A7 or a 6K8  or similar  I usually look for a small negative voltage  on the grid of the oscillator triode to tell me if the oscillator is working.How do you test an autodyne  to see if the oscillator function is  operating? i have been offered a technique by a colleague here in N.Z. but I am not confident using it. Do Philco Phorum members have any suggestions about this. Thanks everyone and cheers

[Antipodal]

Hello everyone ,
In my last post there was rejoicing that the Hudson Zenith Model 680 was now going and some speculation about the oscillator function in this set.
Revisiting the set again the next day it again refused to go. 
This time I put the prod of my digital meter onto pin 2 of the 6C6 mixer to check that there was H.T. reaching the plate  there,  confirming that the i.f. transformer primary was still intact -no reason why it should go o.c. overnight but stranger things etc. Whereupon the set burst into life again.
 Which suggests that either the capacitance of the meter lead and prod or the high resistance of the meter to earth or both "flicked " the autodyne into oscillation. Or am I barking up the wrong tree entirely?I am interested to hear from others on this topic. Cheers everyone. Oh, by the way I have had success with a Philco C 1608 too , but I shall post separately about that.

[mikethedruid]

I think I'd retouch all the solder connections, especially the one you touched with the prod, and clean the contacts of the sockets and tubes. This symptom is often a result of an intermittent connection. I have found it best to eliminate the obvious before hunting down the esoteric.