[Paul Philco322]

It feels good don't it? Good luck on the rest.

[Stormlord5500]

Thank you sir. Yes I feel good and also relieved because this one's been weighing on me a bit.

[Arran]

I use a pair of Mastercraft brand DMMs from Canadian Tire, from what I read most of those DMMs use the same main chip regardless of the name, it's the peripheral stuff like switches, sockets, test leads, and the case itself that differ, and they can cheapen out on. It's true that they are not as rugged, but I think that the previous two DMMs I bought from Canadian Tire were on sale for under $30, with tax, so if one blows up or breaks it's not a huge loss. Before that I was using a VTVM from EICO, till I blew up one of the resistors.
Regards
Arran

[Stormlord5500]

I need to get a vtvm. I think that little component tester is just more accurate. Plus it shows the inductance which is nice. It's like and ohm meter, RCL meter, and a component Identifier all in one. I highly recommend them. The TinySA also.

[morzh]

A DMM is good enough.
One rarely has to measure indictance, but if you do, short of getting a serious LCR meter (I have one, but rarely use it) there are DMMs available with L measurements.

[Stormlord5500]

That's true. Of course If I were to get a vtvm I'd probably have to sink money in to it to get it working right. Probably just stay with what I have.

[Stormlord5500]

So one last question before I finish this radio. Regarding the speaker and output transformer. I salvaged the original opt from the speaker and noticed from the get-go that my code 123 model 38 has the opt mounted to the chassis. On the 121 chassis it's mounted to the speaker. Where it's mounted on the 123 (1A6 pentagrid tube) is between the converter tube and 19 output amp tube. This is the only spot on my 121 chassis I can mount it, between the 15 and 19. Since the 123 uses a more standard converter circuit I am wandering if the autodyne circuit that the 121 uses would be susceptible to magnetic interference from the opt and that's why they mount it to the speaker. My replacement does not have a mounting for the opt. The only other spot is on the cabinet arch support in the back. What do you think is best?      
Code 121
   
Code 123

[MrFixr55]

Congrats on your success Stormlord. My rough guess is that since both the 15 and the 1A6 are supposed to be shielded, I don't think that it will be an issue mounting the transformer on the chassis. If you are worried or don't have the shields. bend a 3X3 metal sheet into an L shape and mount it under the transformer so that a "wall" is formed between the transformer and the tube. This should provide sufficient shielding.

[Stormlord5500]

Thank you sir. I thought about it and decided to put it up in the arch support. I was looking at the chassis and didn't want to drill it because there is alot of circuitry in the area and I got the radio somewhat working and didn't think moving anything out of the way would be a good idea.

[Arran]

So what was wrong with the original speaker? Was the cone damaged? Unless it's totally hopeless I would put it aside as they can be reconed.
Regards
Arran

[Stormlord5500]

The cone unfortunately got damaged when I removed it. The glue that held the cone to the basket was sloppily applied and the cone got glued to the speaker board. I didn't notice and when I pulled the speaker the cone wasn't ripped but it did almost like an inside-out umbrella.

 The voice coil is still ok. The spider is destroyed. I tried to straighten the cone out but it has creases and bellies in it.

[MrFixr55]

Do make sure that you twist the 3 wires from the chassis to the transformer, and dress away from tubes, especially audio tubes. Dressing toward the speaker, then along the underside of the peak, and finally to the arch. Rotate the speaker till the terminals are toward the top to keep the secondary connections short. Using #8 fender washers, 8-32 screws and nuts, you can possibly mount the transformer on the speaker without having to drill. Use 2 fender washers and a nut to sandwich the screw onto the frame at one of the slots. Repeat for the other screw and bend the transformer tabs to follow the curvature of the frame.


BTW, check out the magnet on that original speaker. This is one reason for most pre-war sets having electromagnets, as AlNiCo was expensive until after the war. (The other was the use of the field coil as a filter choke.) Of course, battery sets of this type required a permanent magnet.

[Stormlord5500]

I will definitely check my lead length and wire dressing. Thanks for the ideas.