Brad...what a memory!! Yes same escutcheon as the one on your thread and U tube. Unfortunately , I could not see the printing clearly on the dial glass but certainly the same manufacturer of both dial assemblies, even though my dial drive has not got dial lights both sides.

If we assume this is a small manufacturer, we may also assume he did not build his own cabinets. So they could vary from batch to batch. The hole for the escutcheon on mine was cut out after the cabinet was finished and painted inside.

I did not want to overload you with photos, but will post one more, a clear shot of the underside.

It has rheostat volume control that appears to have about 100v applied to it. Prior to my vintage. Not something I ever worked on just a vague memory.

Marc, I don't have access to a valve tester , so it's power up and measure voltages and hope! I have recapped the 6D6 (IF) and it seems ok.??? If I can file a bit of glass back I may revive the 6A7 (RF) but not holding my breath , also you will note that it's plate resistor (from memory) has been cooking at some stage so don't hold much hope for it.

Off to my shed with camera. Thanks all, Gary

I've just found a 1938 ad for a "Velco" battery kit-set. Apart from being a battery set, the chassis and the dial/escutcheon look the same as the one in this thread.

"Velco" is the brand name for Arthur J. Veall, who was a large radio and electrical retailer in Melbourne. Veall's was represented in Queensland by a B. Martin of Charlotte St., Brisbane.

I still wont call this radio as being a "Velco" as I believe this style of dial/escutcheon was used in many generic radios made around 1938.

As for a road map, I'd first look at the 1938 Weldon 3/38D that was mentioned by GTC. The other radios mentioned seem a bit too early.

There is a faded ARTS&P label on the bottom right hand corner of the chassis. Are you able to make out any large letters such as a D, E or F.? This will indicate year of manufacture - for example E = 1938.

The chassis above has all the hallmarks of mine, Same factory, but different component layout.

The ARTS&P label is # E 11905.
On the top left corner of the label is "No. 4". If that is the production run, it would fit Miller's signature dated 4 July 1938.

I'll look for data on the Velco and especially the 1938 Weldon 3/38D and see what I come up with.

Brilliant folks, thankyou. Gary

Bearing in mind I do the odd commercial repair. I would get rid of every wax paper cap in it and I will not use electrolytics below 500V on an 80 / 5Y3 and similar filament rectifiers.

You will find (eg early STC 50 series) that it was common for the volume control to be in a divider network, or sharing with the first two valves in the cathode circuit. That shifted the bias on the grid (self bias) as the cathode became more positive the grid became more negative & desensitised the valve (shut it off).

100V sounds too high on the pot. Check the earth side. Need to know electrically where it is, as a dud coupling cap leaking like sieve, can also wipe out the grid bias on a valve and cause it to be damaged.

Those pots have a notorious habit of going open, and there is one sitting on my shelf, that has done that. If it has to be replaced, there may need to be an adjustment. Eg. In an STC 59 chassis here (no circuit ever found). The pot was 6K, in the divider, & missing. The best I could do was an RS 5K wire wound.

This one controls the bias of a 6D6 (elec same as 6U7). I had to make a slight adjustment for the 1K and to stop 6D6 from overloading the plate detector (spotted with Oscilloscope when calibrating).


Marc

Thanks to the leads from Brad, Monochrome, et al. , I now have a blurry thumbnail circuit of the Weldon 3/38D. (found on Radiomuseum)

Compared to a schematic I drew up using my mystery chassis, they appear to be the same.

Unfortunately, the component values are obliterated on the thumb nail and the Radiomuseum site is not as user-friendly as you guys, so cant immediately get a clear image.

Marc, thanks for the heads up re the volume control. As per "notorious habit" this one has a tangled mass of wire within. So much so, Ive no way of measuring its resistance.

The paper cap change was mandatory back in the good old days. Frustratingly, for many years, the NZ industry could only get Ducon caps and pots. Philips could not import their own components due to Oz/NZ trade arrangements, I seem to remember the local manufacturers eventually threated to close their factories unless the NZ govt. changed its position. Caused Immediate change and there were parties in all workshops.

Cheers Gary

Here is a better quality pdf circuit of the Weldon 3/38D.

Weldon 3-38 and 3-38D Circuit Diagram.

Its pretty obvious why there is 100V on the pot. If there is a tangle Its cactus & a 5K WW from RS is on the list. Buy 630V Axial caps, I do not like the length, but use in places the red Greencaps.

If you serviced radio's you know the trap with top trimmer IFT's & their live primaries. Pay attention to that new polyester from the 70's, I have seen several split the jacket at the end like some Muds.

I would not go below 500V as before & I note it is back biased & that & the field coil in negative on sets, gets many into strife.

Once you have parts, the electrics look like a wet afternoon job, do not forget resistors. You may need an extension shaft for the pot, RS do have with a long shaft but $, as are extensions. Depending on what's lying about, I will make either a socket & salvage a bit of the old shaft, or make a one piece job. Lathes are handy... just used it to make a replacement odd ball bolt for the chair I am sitting on.

I note no polarity on the 10μF cathode bypass? Surely if they used electrolytics in the PSU that was as well?

Marc

Monochrome, In your debt again ! Thanks mate.

Marc, while I did service many radios, I've forgotten more than I ever knew, as they say!!!

I appreciate your comments, great revision notes for those wet days. Thanks.

Gary

I am indicating that I think this one should be easy.

For clarity re the 100V for others. The volume pot, wired rheostat, is the cathode resistor (refer previous) the set is back biased & that will set a bias of perhaps -3V on that valve even when the cathode is brought to chassis potential.

If the cathode looses contact with the chassis, or its self bias resistor (where used) goes open then the cathode (and grids) will go positive and may actually reach B+. The only cathodes that commonly get to that voltage are rectifiers and "plate detectors" that can be in the order of 40V and will normally have high resistance cathode resistors e.g. 6K - 10K+. This set is one that uses a plate detector. Distortion is common with this setup especially if things are out of spec.

Marc

Back again!!
I have a question about the oscillator.

But, first with plenty of rainy days up here in previously sunny QLD, I got into cap changes etc. Found a full set of valves in the USA = to local price of the 6A7.
After 10 mins the power tranny cooked (not surprised due to past weather exposure). Liberated the transformer from a Philips 3552 and did a 'Hail Mary' over the existing IF cans. So far so good.

Waiting on Mr Wong to send me the 5K ww pot so have a fixed 1K2 in its place.
Broadcast Band is working fine.

Question:
What voltages do you expect to find on the 6A7? More specifically, the Oscillator? As I tune across the BC band the g2 fluctuates madly going from -40v to + 300v. SW band; g2 remains about -40v. Optimum seems to be about 100 to150v when on a BC station.
I'm assuming the pentagrid configuration is self exciting the g2 anode ??????? therefore I'm reading the high voltage. Using an old analogue meter so I find it surprising.
( B+ = 200v , 6A7: plate; 200v. g3&5; 100v. g1; 5-10v. cathode; 15v.)

Await your wisdoms,
Cheers Gary

http://tubedata.milbert.com/sheets/049/6/6A7S.pdf.

This is a link to 6A7 data. 15V for cathode is high but it was used as the volume control. Most Australian sets ran 250V B+ (not all).

One of the most popular methods for frying transformers, is to turn it on to see if it works, after it has been sitting for years. Aside from the fault that was probably in it to cause it to be abandoned. Electrolytics (where fitted) loose their polarity and often present as a short circuit.

Marc

Hi Marcc, Understand precautionary principle. Nothing I could do for shorted turns in the transformer. By the look of the chassis (now repainted) I suspect it was exposed to salty air or similar.
I have the 6A7/8 data. From it I deduced possible g2 instability. Just thought someone might have had the same experience.
Thanks again for your help. Gary

Whilst I test what valves I can, to avoid putting in shorted ones into new work, If there is 6A7 / 6A8 instability, all of the caps & resistors around it should be checked. Those valves are voltage sensitive.

Marc