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 Post subject: GE E-91 Colorama display problems
PostPosted: Oct Tue 29, 2019 9:15 pm 
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Joined: Sep Mon 24, 2012 10:14 pm
Posts: 1096
Location: Topeka KS
When I got this radio it had been “worked on”. Someone had done the following:
1. Cut the metal strip between the red wire and the first green bulb and soldered it to the strip between the black wire and the first red bulb.
Attachment:
4245BA52-2B7E-485B-ABCB-ED6B62C156F9.jpeg
4245BA52-2B7E-485B-ABCB-ED6B62C156F9.jpeg [ 48.3 KiB | Viewed 870 times ]

2. Soldered the strips between the second red bulb and second green bulb together.
Attachment:
EFD2F10D-AE86-4FAD-9FCD-5C3AEDA94A8A.jpeg
EFD2F10D-AE86-4FAD-9FCD-5C3AEDA94A8A.jpeg [ 42.33 KiB | Viewed 870 times ]

3. Connected the green wire from the reactor to chassis ground and then to the display.
4. Connected the red wire from the display to pin 2 (heater) of the 6C5 tube instead of pin 6 which is a tie point.
When I put everything back as shown on the wiring diagram I get no lights on the display.
The reactor checks out close with 1931 ohms compared with 2150 ohms specified between the red and blue wires and called for 30 ohms between the black and green wires.
The transformer is supplying 3 volts.
Any ideas?


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Oct Tue 29, 2019 9:29 pm 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 3267
Location: Lexington, KY USA
Did the display work to some extent before you changed the wiring?

Can you provide a sketch of the wiring as-found?

Can you provide a link to the schematic for this radio that you are using?

Ted


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Oct Tue 29, 2019 10:29 pm 
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Joined: Sep Mon 24, 2012 10:14 pm
Posts: 1096
Location: Topeka KS
It didn’t work correctly. The first three or four lamps all lit as if they were a dial lights.
Here is a link.
www.angelfire.com/electronic2/radiosean ... -25_28.pdf.


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Oct Tue 29, 2019 10:51 pm 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 3267
Location: Lexington, KY USA
Thanks for the schematic!

The transformer is supplying 3 volts.

The display requires far more than 3 volts to work at all.

Does the radio work otherwise? The voltage for the display comes from the same winding as the heater voltage, so perhaps the heaters are getting only something like one volt?

How was this 3V voltage measured?

Perhaps someone can chime-in with the correct voltage for this transformer winding. Otherwise, a search of the forum should turn up some more information.

Ted

PS

This may help:

http://vrps.org/ColoramaTuning.html

Looks as if you want 25V. 3V isn't going to get it.

Note that all of the light bulbs need to be the correct type, and matched-up fairly well. And all must be in the circuit for correct operation.

Image

https://mcclellans.com/GEColoramaE-101.htm

Image


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Oct Tue 29, 2019 11:26 pm 
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Joined: Sep Mon 24, 2012 10:14 pm
Posts: 1096
Location: Topeka KS
The radio does work. The transformer is a replacement. Looks like when it was replaced they “modified” the circuit and display to use three volts.
Things are starting to make sense.
I’ve got an E-101 that needed the correct transformer, looks like I’m looking for another one.
Does anyone know what chassis have the correct transformer?
Thanks


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Oct Wed 30, 2019 12:32 am 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 3267
Location: Lexington, KY USA
The replacement power transformer explains why the lamps were re-wired. I guess they at least provided a normal dial light.

You might consider hiding a small 25V transformer under the chassis. The extra 25V tap on the heater winding had pretty narrow application.

This could be a reversible, temporary, solution until the correct transformer comes along.

24V or 25.2V at 1/2 amp would be good, and pretty small.

Ted


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Oct Wed 30, 2019 3:52 am 
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Joined: Sep Mon 24, 2012 10:14 pm
Posts: 1096
Location: Topeka KS
Would something like a furnace control transformer work? There are 100’s of them on eBay.


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Oct Wed 30, 2019 6:14 am 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 3267
Location: Lexington, KY USA
I expect that one of those 24V furnace transformers would work OK.


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Tue 05, 2019 10:18 pm 
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Joined: Sep Mon 24, 2012 10:14 pm
Posts: 1096
Location: Topeka KS
I got one of the 24 volt furnace transformers and patched it in. The display does work.
Two new questions.
1. It will look best if I put the transformer under the chassis. Might that cause problems like introduce hum? The only place above the chassis would be right above the oscillator and. RF coils. Could that cause similar problems?
2. When aligning the set is it necessary to follow the instructions starting with I.F. alignment or can I just skip to R.F. alignment? I think I know the answer but just want to be sure.
Thanks again.


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Mon 11, 2019 3:37 am 
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Joined: Sep Mon 24, 2012 10:14 pm
Posts: 1096
Location: Topeka KS
Here’s what I came up with to mount the transformer.
Attachment:
E7981E7D-B414-4CB1-B898-3C79CA9CB995.jpeg
E7981E7D-B414-4CB1-B898-3C79CA9CB995.jpeg [ 63.02 KiB | Viewed 680 times ]


First question. I put a 50 watt 25 ohm resistor in the line in. With the two transformers it runs at about 200 degrees. Is this anywhere close to normal?
Second question. The display was mostly red all the time on broadcast band and the radio wasn’t very sensitive. I went through the alignment procedure for the broadcast band (that’s the only alignment I did) and the radio is much more sensitive BUT the display is mostly green all the time now.
Any ideas?


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Mon 11, 2019 12:41 pm 
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Joined: Jun Sun 03, 2012 12:40 am
Posts: 1326
Location: Cromwell, Connecticut
Hi Kirbyc,

I believe there is a sensitivity switch (S4) for the lights. It existed on my E-101. It makes a difference to how responsive the lights are. I had to put mine on low with an outside antenna.

To be sure the lights are working ok, short the antenna and ground terminals. The lights should be red. If strong noise is present on the antenna you are using, it could saturate the receiver giving the green lights.

As far as the the transformer temperature, I would calculate the power dissipated by the radio. Since you are installing a dropping resistor, it will provide you with the current flowing through the transformer primary. So take the voltage drop across the resistor and divide it by the resistor value. Now take the current and multiply it by the voltage across the transformer primary. You will have an idea of how many watts the transformer is dissipating. Your radio is rated 105 watts. Since the 25 volt transformer is separate, your main transformer should be lower than 105 watts.

Also, your light transformer may be rated at 120V input, so it may not need to go through the dropping resistor keeping it cooler.

Hope this helps.

Edit: Your 25 ohm dropping resistor might be too much. I’d like to see 108-110 volts at the transformer primary. Give that a check. Also, it looks like your transformer is the original. Is that true? If it was a replacement, we may not know it’s ratings. Just another thought.

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Tony

People may not remember how fast you did a job, but they will remember how well you did it.


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Mon 11, 2019 3:45 pm 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 3267
Location: Lexington, KY USA
The extra transformer looks plenty large for the job. Of course, it is OK to go with what you have.

The second transformer is required because the replacement power transformer had no 25V winding for the Colorama feature.

200 degrees F is OK for most sorts of power resistors. Go look at the data sheet for the part you are using. You do want to keep that heat away from other parts in or on the chassis, though.

While checking voltages with the line dropping resistor in place, do look at the heater voltage on the tubes. You want that to be pretty close to 6.3V. Perhaps 6.1 or 6.2 VRMS.

If the sensitivity switch for the display does not solve the problem, you can fiddle resistor values to get the response you want. You might also try different tubes in the Colorama socket.

Ted


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Mon 11, 2019 7:58 pm 
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Joined: Sep Mon 24, 2012 10:14 pm
Posts: 1096
Location: Topeka KS
Here’s where we are now. I shorted the antenna terminal to the ground terminal. Lights stay the same, green bright, red dim. Local distant switch doesn’t seem to matter. At about 121 volts input I’m getting 5.7 volts on the heater string. However if I crank up the input so I get 6.1 on the heaters nothing changes on the display. With the antenna shorted I’m not getting any sound out of the speaker unless I turn the volume way up and then I get motor boating.


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Tue 12, 2019 2:40 am 
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Joined: Jun Wed 14, 2006 11:49 pm
Posts: 7669
Location: Leo, IN or Zellwood, FL
Ignore the resistor temperature. You need to read the power transformer temperatures. Main power transformer should stay
at or below 130F if you expect it to survive.

JOhn k9uwa

_________________
http://www.JohnJeanAntiqueRadio.com


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Tue 12, 2019 6:34 am 
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Joined: Sep Mon 24, 2012 10:14 pm
Posts: 1096
Location: Topeka KS
Both transformers stay at close to room temperature.


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Tue 12, 2019 7:13 am 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 3267
Location: Lexington, KY USA
5.7V is kinda low for the heaters in 6.3V tubes. How accurate is your AC meter?

Does the power transformer run hot when full line voltage is applied?

What sort of high impedance DC meter do you have for measuring the grid voltage on the colorama tube?

Ted


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Tue 12, 2019 12:36 pm 
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Joined: Jun Wed 14, 2006 11:49 pm
Posts: 7669
Location: Leo, IN or Zellwood, FL
Usually Lurking wrote:
5.7V is kinda low for the heaters in 6.3V tubes. How accurate is your AC meter?

Does the power transformer run hot when full line voltage is applied?

What sort of high impedance DC meter do you have for measuring the grid voltage on the colorama tube?

Ted


So at full line voltage maybe your filament comes close to 6.1v? Curious since it is a replacement transformer with full line voltage
to the chassis what plate and screen voltages do you have? Chart shows 240 250 and 290 on 6L6 and screen grids mostly 100 volts.
And for sure the 6C5 shows 180 in the chart. Plus yes you should complete the alignment.
John k9uwa

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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Tue 12, 2019 1:19 pm 
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Joined: Jun Sun 03, 2012 12:40 am
Posts: 1326
Location: Cromwell, Connecticut
Kirbyc wrote:
Here’s where we are now. I shorted the antenna terminal to the ground terminal. Lights stay the same, green bright, red dim. Local distant switch doesn’t seem to matter. At about 121 volts input I’m getting 5.7 volts on the heater string. However if I crank up the input so I get 6.1 on the heaters nothing changes on the display. With the antenna shorted I’m not getting any sound out of the speaker unless I turn the volume way up and then I get motor boating.


One thing that stands out is Motorboating. If the radio has any oscillation in the RF sections, the AVC voltage could be high negative just like a strong signal. Thus constant green lights.

Be sure that all tubes are metal types and test good. This radio requires metal tubes.

Also, early on, it was mentioned that the lights were wired just to light up since the 25 Volt transformer winding was bad. Is it possible the previous repair tech re-wired the lamp sockets? They need to be in a specific order in series, so wired just like the schematic, with the red and green lamps in specific positions. You likely know this already, since you've recently worked on another Colorama set.

Just a thought.

_________________
Tony

People may not remember how fast you did a job, but they will remember how well you did it.


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Tue 12, 2019 7:55 pm 
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Joined: Sep Mon 24, 2012 10:14 pm
Posts: 1096
Location: Topeka KS
The display is wired correctly. Before I messed with the alignment by adjusting C12, C7, and C2 the display seemed to work a little on broadcast and correctly on a couple of stations on one of the shortwave bands.
The tubes are all metal. When I rechecked all of the tubes today I found that the 6C5 tube checks out at the top end of ‘REPLACE’ on my I-177 tube tester. I’ll swap the 6C5 with the one in my E-105 tomorrow and report back.
Thanks


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Wed 13, 2019 10:45 pm 
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Joined: Sep Mon 24, 2012 10:14 pm
Posts: 1096
Location: Topeka KS
Switching the 6C5 from the E-91 to the E-105 made no difference in the working of the E-105.
Guess the easy fix won’t work this time.
What else do I need to check?


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