Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

Retrofitting speaker for Philco 84
#9

I think you are correct Ron and Terry. It is not as bad the other way (8 Ohm speaker on a transformer with a 1 Ohm secondary), at least for fidelity. However, empirically, they say it is better to run a tube style amp with a shorted output transformer secondary than with an open one. It is very important not to run a Pentode tube with a transformer with an open primary, the screen grid will melt and short. For solid state amps, the exact opposite is the case; one should never short the output of a solid state amp. As a kid, I replaced a slew or transistors for friends who hooked up 3 or 4 8 Ohm speakers in parallel.

Remember, resistance and impedance are 2 different things. I am not a radio engineer (Ask me questions about clinical chemistry, I'm your guy) but do understand a lot of it. I think that the members who are General or Extra Class HAMs could explain impedance better. It has to do with reactance, inductance and capacitance as well as resistance. There is an "Impedance ratio", however, if you try to run a transformer from a 6L6 (impedance of 2500 Ohm, 6W output) output transformer on a 50L6 Output stage in an AA5 (2500 Ohm impedance, 1 W output), the 50L6 will be drawing more current then with the correct speaker due to the resistance of the 6L6 transformer being lower than the one designed for an AA5 using a 50L6 even though the impedances are the same.

I think that if the schematic lists a value of 400 Ohm for a primary and 0.89 Ohm as a secondary, they are describing the DC resistance and not impedance. After all, they give the Field coil resistance in Ohms, not the inductance in Henries. (Is that the plural of Henry?)
By the mid 1930s, speaker voice coils were either 3.2 Ohm, 4 Ohm or 8 Ohm impedance (at 400 Hz or 1KHz). I don't know what the original Philco "Pie Plate" or G E "Kellogg Rice" speakers as used in the Victor early RCA, Majestic, etc. units used.

HAMs, jump in here (and save me).

"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards, 

MrFixr55


Messages In This Thread
Retrofitting speaker for Philco 84 - by Ctkid - 09-25-2022, 06:39 PM
RE: Retrofitting speaker for Philco 84 - by Ctkid - 09-26-2022, 09:57 PM
462ron - by 462ron - 09-29-2022, 08:29 AM
RE: Retrofitting speaker for Philco 84 - by MrFixr55 - 09-29-2022, 05:34 PM



Users browsing this thread: 6 Guest(s)
[-]
Recent Posts
trying to identify this wire type
The red wire is rubber covered wire. The others are cotton braid over rubber often in colors or a tracer, also strand...Chas — 02:43 PM
trying to identify this wire type
Greetings Phorum members, Hope you can help me identify this type of wire in the photo I have attached.  I am not sure ...georgetownjohn — 01:53 PM
Philco 60 Squealing
All correct shields must be in place, all tubes correct no subs of any kind. Check any soldered, riveted ground conne...Chas — 01:24 PM
Philco 60 Squealing
I have recapped and replaced out of tolerance resistors and so on. Radio plays nicely on fairly strong stations. The pro...dconant — 10:55 AM
Philco 46-420 Code 121 Reception issues
Welcome Eric, I agree with Bob and far as the two main electrolytic filter capacitors did you change them yourself or w...radiorich — 11:43 PM
Philco 46-420 Code 121 Reception issues
You mentioned the Philco manual and going through the check points...just to be sure we're on the same page here's the m...klondike98 — 08:13 PM
Philco 42-1008 conversion kit
Interesting. I haven't seen that before.klondike98 — 07:02 PM
12' Philco
Yes I had looked for it on the web as well some time back and could not find it. I was glad to see it turned up in Ron'...klondike98 — 06:59 PM
Shadow Meter Bulb
Now if you had a set with a tuning light then the bulb type is important to the circuit, some sets used those prior to t...Arran — 04:58 PM
Shadow Meter Bulb
Ok. Thanks for the correction.RossH — 03:09 PM

[-]
Who's Online
There are currently 7182 online users. [Complete List]
» 4 Member(s) | 7178 Guest(s)
AvatarAvatarAvatarAvatar

>