Author Topic: General Electric E-61  (Read 311 times)

TC Chris

  • Hero Member
  • *****
  • Posts: 2118
    • View Profile
Re: General Electric E-61
« Reply #15 on: August 06, 2019, 08:16:31 PM »
One of the jobs I need to do on this radio is to restring the dial.  What a PITA this is going to be.  There is no spring tension on the cord.  It passes thru two holes, and, I assume, you tie the knot tighter and tighter until it doesn't slip.  The cord is still on, but hanging by a thread.  This model is not listed in the dial stringing CD I have.  i'll make a diagram and hope for the best.   ::) ::)

I have been known to improvise dial cord arrangements by adding a spring, as became standard practice later.  This isn't going to be a museum-quality resto anyway, and function is a high priority....

Chris Campbell

electra225

  • Hero Member
  • *****
  • Posts: 3333
    • View Profile
Re: General Electric E-61
« Reply #16 on: August 06, 2019, 08:51:03 PM »
No way I can see to add a spring.  The shaft for the tuner runs in a slot thru the pulley that runs the dial cord.  Damnedest setup I have EVER seen.  What I'll have to do (after I fix my magnifying light that I just broke  >:( :( :o) is to remove the brittle, 85-year-old plastic dial so it survives.  Radio Daze does not repop it.  Then take the string out and measure it.  Then cut a hunk of string so I can eventually end up with the correct length.  Then string the dial and hope I get it right.  It is self-tensioned, if that makes any sense.  The messes I get myself into..... ::) ;) :)

Edit........Chris you may have caused the light to come on.  What if I drill a hole in the drive pulley on one side of that slot?  Then I could kluge a loop with a spring to fit in the hole......That might actually work........ :) :)
I don't need Google.  My wife says she knows everything.

Motorola Minion

  • Hero Member
  • *****
  • Posts: 1056
  • Southern Pennsylvania
    • View Profile
Re: General Electric E-61
« Reply #17 on: August 07, 2019, 12:31:45 PM »
Dial strings are a PITA but to eventually make them work, we get creative because failure is not an option. This E-61 sounds like its worth the effort, at least from the owner's perspective.

Round dials usually are easy to string drives, but the one on a 1938 Crosley Dynatrol I am working on has a standard tuning drive shaft with a slotted outer shaft that operates a switch to tune up or down the dial using two electro magnets vibrating drive belts.  Pulling two turns through the slots was not hard but then I cut the string and tied it to the spring before I allowed for the turns around the tuner wheel.

Took a break after I realized what I did>:(, it was about time ..
Tubes - Magical - Tubes

Dave

electra225

  • Hero Member
  • *****
  • Posts: 3333
    • View Profile
Re: General Electric E-61
« Reply #18 on: August 07, 2019, 05:31:39 PM »
This thing has a hum...... >:( >:(

Remember when I started this project?  Remember when I found out it had an "odd" arrangement for the filter caps?  RCA, GE and Westinghouse were always considered something like "cousins" when it came to their business.  RCA and GE enjoyed a love/hate relationship for years.  Apparently when this radio was built, they were in the "hate" mode.  The power supply is one of those goofy ones that was designed to circumvent the RCA patents.  This radio has the choke for the power supply, the speaker field coil, connected to the center tap of the power transformer.  More commonly, this component is in the B+ circuit, right off the cathode of the rectifier.  I was REAL careful when I wired the replacement filter caps.  I did a careful resistance check to make sure the rectifier was "seeing" the proper amount of resistance in B+.  All that checked good.  I had good B+ when I applied power and had no shorts. 

I had a hum when I was working with it yesterday.  I was using my signal tracer as the audio output section after I found the output transformer primary open.  I was using an unshielded test lead to feed the input of the signal tracer and had wires dangling over power cords and other sources of hum, so I didn't give it much thought.  I wanted to hear the radio talk, it did, and rather well, so I was not worried about the hum.  Until today....

I wired in a different output transformer and used a PM speaker.  I wired a 1000 ohm, 10 watt sand resistor in place of the original field coil.  I powered up, the radio still worked well, but it had a fairly noticeable hum.  Not affected by the volume control.  Typical of a power supply problem.  So I got to checking voltages.  Remember I had good B+ in the radio.  I don't remember checking B+ at the filter caps, per se.  No need to if I had good B+ beyond the filter caps, right?  The 22uf cap that I had wired as the primary filter cap, measured about 300 volts on the positive.  The 10uf cap that I had wired as the secondary filter cap not only measured zero volts, it actually measured NEGATIVE voltage.  How in the H-E-double hockey sticks does one end up with negative voltage on a filter cap, yet have a working radio with good B+?

The original can for the filter caps was cardboard.  There were three wires exiting the can, tan, brown, and yellow in color.  The can gave the values of the two filter caps, but made no mention of negative.  One would commonly think of two positives, a 10uf and a 16uf and a common negative for the three wires.  Not on this one...... ::) ;) :)

Oh, no.....

This one had two negatives and a common positive.  To make a long story short, I have no primary filter cap at all.  I wired the 10uf across the center tap to chassis ground, why I had the negative voltage.  I have the 22uf that should have been the primary as the secondary at twice the listed value.  I believe what I'll do is to leave the 22uf alone and put another 22uf in as the primary by moving a negative wire.  I'll replace the 5W4 rectifier with a 5Y3.  Jeez....

I am very careful before I start a project to print the diagram and study it before I begin.  I sure missed this one.  It plainly shows the two positives connected.  Plain as day.  After I messed up then used BOTH eyes, I see that now.  The good news is I learned something, no damage was done, and I may have an avenue of investigation for my Zenith 5-S-56 that has a hum and squeal for 30 years since I restored it.  It  ran fine in dad's milk parlor for 30 years, but has never worked right since I "fixed" it.  I'd be willing to bet one of the filter caps in it does not have B+ on it.  It has the same power supply setup at this thing does. 
I don't need Google.  My wife says she knows everything.

Bill

  • Hero Member
  • *****
  • Posts: 1283
    • View Profile
Re: General Electric E-61
« Reply #19 on: August 07, 2019, 07:20:02 PM »
I guess with time everything works its self out.  I'm glad you are over this bump in the road and now can proceed with the next bump.  ;) :) ::)   Any news on the cabinet?

Bill


electra225

  • Hero Member
  • *****
  • Posts: 3333
    • View Profile
Re: General Electric E-61
« Reply #20 on: August 07, 2019, 08:00:56 PM »
Not yet.   :)
I don't need Google.  My wife says she knows everything.

electra225

  • Hero Member
  • *****
  • Posts: 3333
    • View Profile
Re: General Electric E-61
« Reply #21 on: August 10, 2019, 05:34:14 PM »
The filter caps are wired correctly now.  I have B+ on both positives, since they are connected together.  I have good B+ in the rest of the radio and it works really pretty good, all things considered.  My next step is to restring the dial.  It is really delicate.  There is no spring on the dial cord.  You just run the string around the big pulley, over two smaller pulleys then back thru a hole in the big pulley.  If it is too loose, you just add a knot.  All the dial string does it run the pointer, it does not drive the tuning cap.  Rather a different setup than is commonly seen.  Apparently, okay is good enough.  It is not very tight now, so we'll see. 
I don't need Google.  My wife says she knows everything.

Motorola Minion

  • Hero Member
  • *****
  • Posts: 1056
  • Southern Pennsylvania
    • View Profile
Re: General Electric E-61
« Reply #22 on: August 12, 2019, 09:23:54 AM »
I repaired 2 GE cathedral sets (not the cabinets) , made a few years before Greg's E61 and it was a GE K-52, THEN identical to RCA R28P. While the power supply was textbook simple, IF and detector circuits were very odd, especially if you're used to Philco as a basis of experience.

Working on the "early" AC and TRF radios (pre-1934) is more of a challenge, trying to deal with non-standard circuits.

Tubes - Magical - Tubes

Dave

electra225

  • Hero Member
  • *****
  • Posts: 3333
    • View Profile
Re: General Electric E-61
« Reply #23 on: August 12, 2019, 01:41:10 PM »
The filter resistor (formerly the field coil) is in the center tap of the PT circuit.  It gets warm, but not hot like they do when they are in the positive end of B+.  I'm still not sure I understand how the resistors that separate B+ circuits work.  There is negative voltage on the filter resistor.  The negative voltage is used for bias, but also for the AVC circuit somehow.  I'm rather surprised to see an "alternative" circuit used in a GE, given their typically close relationship to RCA.
I don't need Google.  My wife says she knows everything.

electra225

  • Hero Member
  • *****
  • Posts: 3333
    • View Profile
Re: General Electric E-61
« Reply #24 on: August 13, 2019, 04:47:50 PM »
This is a "hot" little radio.  It can bring in a couple stations I can't get on my Hallicrafters SX-110.   ;) ;)

This is basically an AA5 with no RF amplifier.  How it works so well when it has wonky wiring, drifted resistors and has not been aligned, is beyond me.  I may not do much in the way of an alignment.  I may touch up the antenna trimmer after I get it to the customer's house, but that may be about all I do.  I have found that the wiring that carries B+ is cloth-covered.  The rubber wiring carries low-voltage, signal type current.  There are a few wires that will absolutely be replaced.  The rest I believe I'll leave alone.  If one of them would happen to short, it might kill the radio, but is not likely to burn anything up.  Perhaps my best avenue would be to do the minimum I need to do to ensure it is safe to use.  I may be at a point of diminishing return.

I got the dial re-strung.  I'll have to say it was not too bad.  I cut the first piece of string a little too short and had to start over.  The two small pulleys on each end of the dial just fall off when the string is loosened or removed.  All that holds them is the tension of the string.  The left end of the dial is kind of like a spring.  It keeps tension on the string to a certain degree.  I took some pictures if anybody is interested.  A magnifying glass with a  light works real well for this procedure. 
I don't need Google.  My wife says she knows everything.

electra225

  • Hero Member
  • *****
  • Posts: 3333
    • View Profile
Re: General Electric E-61
« Reply #25 on: August 14, 2019, 05:39:30 PM »
I'm done with this chassis.  It works well, so I'm not going to mess with alignment.  I finished a couple of little chores on it this afternoon then moved on to the old Stromberg-Carlson I've been working on.  Ron is working with the cabinet as we speak for the GE.  The owner wants it painted, so that is the plan right now.
I don't need Google.  My wife says she knows everything.

TC Chris

  • Hero Member
  • *****
  • Posts: 2118
    • View Profile
Re: General Electric E-61
« Reply #26 on: August 14, 2019, 09:27:55 PM »
Good job, saving one more old radio for the future.  Even ordinary ones have some value as survivors, and as you noticed, they often perform much better than their modest designs might suggest.  Tonight I was working on a Detrola AA5 table radio (talk about modest) that a friend asked me to fix for her.  It seems to need filter caps at least and so I went to ARF to ask about that, since I don;t have a model no. to work from.  Nostalgia Air has a bunch of Detrola schematics so I can make a guess, but figured it was worth asking about values.  It has a field coil as a choke.  Nothing spectacular, but if I can make t work, one more person will interact with vintage, glowing-filament electronics.

Chris Campbell