Echophone model s3 no sound - Printable Version
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Echophone model s3 no sound - NostalgiaRadioTime - 06-10-2019
Working on the 5 tube version (three 24's, a 45 and 80) of the 1930 Echophone, this one is a model S3:
My chassis appears to be the "improved" schematic version on the bottom.
I replaced all of the caps, save for the two .02 mfd's (I wanted to replace the "tar boxes" and then see if I could coax some sound out of it). I also read a thread on ARF where Norm suggested changing c14 and c16 to 10 mfd electrolytics and eliminate c15 to improve sound and reduce hum, so that's what I did.
So, after trying several tubes, I'm still getting no sound. My voltages are quite erratic as well (See the chart below...I used the mouse to "color" in red the values I'm getting...hence the hen scratching that looks like a 4 year old wrote it
)Trying to inject a signal, I get noise that's controllable with the volume control across both the long and short antenna terminals. On the grid of the output tube I get noise, but no noise on the plate of the output tube. On the plate of the detector tube I get noise, but no noise on the grid of the detector tube. The resistors are a bit high (save for the 2 meg which is reading 5 meg) but none are open.
The choke measures about 400 ohms, so that's not open. Speaker field and output transformer are good.
Anyone (paging Terry) have any thoughts on where to zero in on first? It seems to be a relatively simple 5 tube radio but very ancient in design (it has a multi tap, open air transformer that looks pretty scary in itself but it still putting out voltage and not drawing any amps).
RE: Echophone model s3 no sound - Radioroslyn - 06-11-2019
Did you connect the - side of c-14 to the chassis?
Does it ave the original spkr that has a tap in the field coil winding?
RE: Echophone model s3 no sound - NostalgiaRadioTime - 06-11-2019
>>Did you connect the - side of c-14 to the chassis?
No, the neg side is going to the choke and transformer.
>>Does it ave the original spkr that has a tap in the field coil winding?
It's a Jensen speaker that looks to be a replacement, but it DOES have the tap in the field coil. That checks out good.
RE: Echophone model s3 no sound - Radioroslyn - 06-11-2019
How much - voltage do you have from the ct of the hv winding to the chassis? Need abt -50v. With -1.7v on the grid of the 45 the plate current is going to be pretty high. Disconnect one end of the C-5 and see with the - voltage increases. If C-5 is leaky that will apply + voltage to the grid of the 45, not good.
RE: Echophone model s3 no sound - NostalgiaRadioTime - 06-12-2019
I jumped the gun a bit and should've just went ahead and replace the two .02 caps and the resistor bank. That revealed an open 1 meg resistor, a bad solder joint at the non-grounded .02, and some bad solder joints around the speaker plug. Happy to report she is singing tonight and actually sounding pretty good for an 89 year old radio. Voltages are there where they should be now. What a strange power transformer, though. Just by moving the fuse between terminals 84 to 85 or 85 to 86 you can go from 110 volts to 125!
RE: Echophone model s3 no sound - Radioroslyn - 06-13-2019
The 2nd .02 (goes from from the output trans to gnd) could be reduced in value to brighten up the sound a bit, to .01 or .005 mfd.