[Brad Winder]

Merry Christmas!

Today I pulled another long-time waiting project from my shelf...a Phonola cathedral, built by Grimes Radio Corporation, which later became Dominion Electrohome Industries. I bought it 16 years ago...where did time go? It is a model #161, built in 1931. 

It uses two 235s, two 224s, a 247, and a 280 tube. 

But...it is missing it's speaker. And the schematics I have don't give any specifications, other than it would have a 1800 ohm voice coil. Would anyone be able to "reverse engineer" from the schematic, and give me an idea of what I should be looking for?

[morzh]

It is 1800 ohm FIELD coil. Your voice coil is likely to be from 0.7 to 4 ohm.

Now that you don't have the speaker and probably missing your output xfmr too, just get a proper size speaker and match the transformer.

The sch is similar to Philco 20 but with A output stage so a speaker from 70 could do.

[Radioroslyn]

Or a Philco 90 w/single 47. I think I see one.

[morzh]

Yep. Thy are practically the same. Or are the same.

PS. Make sure if it is a 90 speaker it is from the one with a single 47 out, not a pushpull one.

[Brad Winder]

Ok! I'll just steal the one closest to the Phonola right now... ;)

[Brad Winder]

So, I did some measuring, and comparisons... and a Philco 70/90 speaker won't physically fit into the cabinet, between the decorative bolts. Actually, none of the multitude of speaker I have around here will fit the bolt pattern they used.

So, I did a bit of research, and using a picture of a similar set I found online, and a same-year battery set I have here...it seems that Grimes was using Utah speakers, made by their Canadian division.

[Brad Winder]

I have located a speaker that will fit. But, the field coil is 2600 ohms, which puts it 800 ohms higher than the original. I know that one can roughly go 300 ohms higher than the original value, without affecting the B+ voltage too much. But those calculations are also based on a +- 110 volt power source. Out here in rural Alberta, where I live, the line voltage is running 128 volts. Does anyone have experience using a speaker with a higher field coil value? Maybe the B+ will still be ok? Any issues in doing that, which might affect the power transformer?

[morzh]

Brad, you can put a power resistor in parallel to bring the value in line with requirements.
Yes you might want a bit higher value, maybe 2000 ohm as the resultant from the parallelling.

[Arran]

Brad;
  Try looking through some of the U.S Radio and TV schematics, some of the Phonola sets from that era are Kitchener built clones of those sets, I have one that is basically a gothic Gloritone in a slightly different cabinet, and says "Dictator" on the escutcheon rather then "Gloritone".
Regards
Arran