This has been sitting in my basement for well over 20 years. I haven't been really interested in restoring it,
but I'm now thinking it would be a good winter project. 11 tubes, counting the 6G5 tuning eye.

The chassis is clean and complete (I bought a new set of tubes a while back). I'm wondering if anyone here
has worked on one. I've never worked on motorized tuning- seems like it could be a pain. The grill cloth looks
like thick drapery fabric. The only missing thing is the speaker. Unfortunately, it looks like it's 15 inches. Not sure
I have anything over 12" sitting around here. Here's a photo from the gallery:



I also need knobs and buttons, but I haven't found any clear closeup photos yet.

Any advice or information would be appreciated.

Thanks,
Dale

The set is one that works and sounds really well when everything is right.

Yes, the motor drive tuning is very problematic and often the fiber drive gear in the motor is stripped and has to be replaced.

Reproduction knobs and pushbuttons are available from Renovated Radios >>>>>> but Ed is currently unable to fill orders due to health issues.

The speaker is a 12" type with a metal ring that adapts it to fit a 15" cutout, it has a field coil and a P-P output transformer to match the 42 tubes in the output. It's not impossible to find, or you can adapt a modern PM speaker with a little work, or another brand of 12" field coil speaker IF the field coil is very close to the correct resistance.

Thanks for the info, Dennis. Hopefully the fiber drive gear doesn't have too many miles on it.
I have several 12" field coil speakers. How do I determine the correct resistance? I think at
least one came from a set with P-P 42s.

I hope things go well for Ed, as well as for Renovated Radios. It's an amazing resource.

Thanks again,

Dale

That model takes a Rola or Utah speaker with a 1000Ω field coil, which seems to be a pretty common value. There are actually 4 -42's in PP-parallel in the output stage, which would lead you to believe the primary of the output transformer needs to be about half the impedance you would see with P-P 42's. However, I have measured the original output transformers on a few Detrolas with 4 output tubes and they were actually rather high impedance, on the order of 10K to 14K plate to plate and sound fine. I don't think it's at all critical and probably any P-P output transformer would work if it's reasonably close. This set only runs about 275 volts B+ to the output tubes so they are not running anywhere near their max ratings. With an 80 rectifier tube, the total B+ current for the entire chassis has to be less than 125 ma anyway.

Schematic is here, that's the clearest one I know of: http://www.nostalgiaair.org/pagesbymode ... 003912.pdf

Performance is about that of a typical 7-tube set of the era, and plenty loud if you need volume.

The ones I have seen can be a bit quirky about parasitic oscillations in the output stage, which requires hand selecting a quad of 42 tubes or adding additional resistors and/or caps to stabilize it. It would have come from the factory with either Raytheon or Tung-Sol tubes. I haven't found the need to have 4 matched tubes as long as they all come from the same batch. You can even run it with two of the output tubes out, if you want to lighten the load on the power transformer.

I need to butt in here. I am not unable to fill orders. I can fill them, but I may fill them, with my wife's help, every few days instead of every day. And, I will probably be running out of some stock now and then. No new projects for some time.

Ed

Thanks for "butting in", Ed. I've just placed an order for the knobs and buttons. There is absolutely no hurry!!

And thanks for the additional information, Dennis. I've been looking at that schematic for quite a while. I can make
it all out OK, pretty much. It isn't the most impressive radio out there, but probably makes a pretty good amp for a
Bluetooth connection. I have a few of those Pilot FM tuners, and will probably use one with this, once it's been gone
through. I'm a bit jealous of the Detrola in another thread with a built-in microwave

Thanks,

Dale

Those are nice working radios even if you dont restore the electric tuning (which works well in most cases). The grille cloth looks like it could use my "gold paint dusting" trick, it pretty much removes stains and speaker rings. Shoot darker gold spray paint at a 45 degree angle from all 4 directions. The trick is to do it LIGHTLY and not have any spatters.
Mark Oppat

Mark,

The grille cloth is actually thick drapery material. It's gotta go. I should be able to find a big piece of
something pretty close to the original. Got the new knobs from Renovated Radios today. Amazing service!

Dale