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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Thu 14, 2019 2:22 am 
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By any chance, have you checked the grid voltage on the Colorama 6C5? It should change based on the strength of the station. It is tied into the AVC. If it stays high negative, no swing, the problem is in the receiver section. If not, then the issue is in the Colorama section.

I’ve never tried this, but I suppose you could use a 9 volt battery and a high resistance pot to make a variable grid supply. Separate the AVC feed to the grid, and use the supply with the + to ground. Then you could test the Colorama response.

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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Thu 14, 2019 5:02 am 
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Tbone wrote:
By any chance, have you checked the grid voltage on the Colorama 6C5? It should change based on the strength of the station. It is tied into the AVC. If it stays high negative, no swing, the problem is in the receiver section. If not, then the issue is in the Colorama section.

I’ve never tried this, but I suppose you could use a 9 volt battery and a high resistance pot to make a variable grid supply. Separate the AVC feed to the grid, and use the supply with the + to ground. Then you could test the Colorama response.


Plus completing the alignment of the IF and redoing the RF alignment might also make a difference.
John k9uwa

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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Thu 14, 2019 6:04 am 
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Joined: Sep Mon 24, 2012 10:14 pm
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Location: Topeka KS
I have disconnected the display and connected it to a DC power supply through a pot. It does change from red to green. I’ll let you know about the voltages tomorrow.
Thanks again


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Fri 15, 2019 6:27 pm 
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Location: Topeka KS
I checked between pin 1 and pin 5 of the 6C5 tube. With the sensitivity switch on sensitive I’m getting around-3 volts between stations and -8 volts when a station is tuned in with no change in the display.
I’ve traced out the wires from the reactor and the display. I’ve replaced the R29 and R30 resistors and The C52 capacitor. Earlier I checked the reactor and got 1931 ohms instead of 2150 ohms for L27 and 30 ohms for L28 as it should be.
Now what?


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Fri 15, 2019 7:18 pm 
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Kirbyc wrote:
I checked between pin 1 and pin 5 of the 6C5 tube. With the sensitivity switch on sensitive I’m getting around-3 volts between stations and -8 volts when a station is tuned in with no change in the display.
I’ve traced out the wires from the reactor and the display. I’ve replaced the R29 and R30 resistors and The C52 capacitor. Earlier I checked the reactor and got 1931 ohms instead of 2150 ohms for L27 and 30 ohms for L28 as it should be.
Now what?


what is the DC voltage to pin3 of 6C5 tube? What is DC voltage to pin4 of 6L6 tube? What is the DC Voltage to pin3 of the 6L6? The voltage chart calls for 180 on the 6C5 and 250 on the Screen grid of the 6L6 and 290 volts on the plate.

Your -3 to -8 on the grid of the 6C5 sounds somewhat reasonable. When you had the DC supply only hooked up to the 6C5 what voltages were needed to turn the bulbs red and what voltage to turn the bulbs green?

John k9uwa

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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Fri 15, 2019 7:49 pm 
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Location: Topeka KS
Pin 3 of the 6L6 tube is 296 volts. Pin 4 is 273. This tube is running VERY hot by the way.
Pin 3 of the 6C5 is -.05 volts between pin 3 and pin 1.
The red lights start to come on at around 2 volts and the greens at about 5 volts.


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Fri 15, 2019 10:01 pm 
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Kirbyc wrote:
Pin 3 of the 6L6 tube is 296 volts. Pin 4 is 273. This tube is running VERY hot by the way.
Pin 3 of the 6C5 is -.05 volts between pin 3 and pin 1.
The red lights start to come on at around 2 volts and the greens at about 5 volts.


If you follow the 273 volt wire from pin4 of the 6L6 you will come to resistor R-28 a 4700 ohm resistor. Following from the other side of R-28 you arrive at the primary of L-27 the primary of the saturable reactor transformer. Previously you stated that the primary of it was around 1950 ohms. And following from the saturable reactor onto pin3 of the 6J5 tube you should have around 180 volts rather than -.05 volts. That is a DC voltage reading. So either a miswire or else R-28 is open or else the primary of L-27 is open preventing the 6C5 tube from working correctly.

John k9uwa

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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Fri 15, 2019 10:10 pm 
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Location: Topeka KS
The John. I’m at work now but as soon as I can I’ll check this out and let you know.
Thanks again.


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Sat 16, 2019 2:14 am 
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That should have said ‘Thanks John’


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Sat 16, 2019 6:38 am 
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Joined: Sep Mon 24, 2012 10:14 pm
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Location: Topeka KS
Reason for this problem found. There was a bad connection at one end of R-28. The display works!!
Now for the alignment.
Thanks again John and the others.


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Sat 16, 2019 1:03 pm 
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Kirbyc wrote:
Reason for this problem found. There was a bad connection at one end of R-28. The display works!!
Now for the alignment.
Thanks again John and the others.


EXCELLENT.
John k9uwa

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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Sat 16, 2019 1:27 pm 
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This is great news! I’ve been on and off the forum last few days dealing with my sick cat. John’s the man and got you going.

You are lucky to have 2 Colorama sets. Most are lucky to have just 1.

On to the next radio!

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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Sat 16, 2019 2:10 pm 
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Location: Leo, IN or Zellwood, FL
Tbone wrote:
This is great news! I’ve been on and off the forum last few days dealing with my sick cat. John’s the man and got you going.

You are lucky to have 2 Colorama sets. Most are lucky to have just 1.

On to the next radio!


I have the 15 toober E-155 Colorama GE console that one will rock the windows and the walls.

Agree onto the next one!!
John k9uwa

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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Sat 16, 2019 2:12 pm 
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Joined: Sep Mon 24, 2012 10:14 pm
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Location: Topeka KS
I’ve still got to align this one. I think I’ll have one or two questions about that.
Thanks
Hope your cat is better.


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Sun 17, 2019 8:30 pm 
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Joined: Sep Mon 24, 2012 10:14 pm
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Location: Topeka KS
I’m ready to try the complete alignment and I’m afraid I’m overthinking it.
Is the following correct?
Short the antenna to ground.
Set band switch to band D.
Set tuning condenser to the low end of the scale.
Set the signal generator to 465k
Connect the signal generator to a .047 capacitor and the capacitor to the grid cap of the 6K7 2nd IF tube after removing the lead to the 2nd IF transformer.
Connect a 10,000 ohm resistor from the grid cap of the tube to the lead from the 2nd IF transformer.
If this is correct I thing I’ve got it.
Thanks.


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Sun 17, 2019 8:59 pm 
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Location: Leo, IN or Zellwood, FL
Kirbyc wrote:
I’m ready to try the complete alignment and I’m afraid I’m overthinking it.
Is the following correct?
Short the antenna to ground.
Set band switch to band D.
Set tuning condenser to the low end of the scale.
Set the signal generator to 465k
Connect the signal generator to a .047 capacitor and the capacitor to the grid cap of the 6K7 2nd IF tube after removing the lead to the 2nd IF transformer.
Connect a 10,000 ohm resistor from the grid cap of the tube to the lead from the 2nd IF transformer.
If this is correct I thing I’ve got it.
Thanks.


Yes you have it. Just follow through with each step. Always keeping the RF gain control of the signal generator to a minimum needed to hear the audio in the radio speaker with the volume control UP on the radio.
John

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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Sun 17, 2019 9:12 pm 
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Joined: Sep Mon 24, 2012 10:14 pm
Posts: 1095
Location: Topeka KS
Thanks again. I’ll let you know what happens


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Mon 18, 2019 8:08 pm 
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Joined: Sep Mon 24, 2012 10:14 pm
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Location: Topeka KS
I think I have the wave trap set correctly so now I’m into the ‘B’ band alignment. I’m through the C-12, C-7 and C-2 adjustments. I’m not clear on the 580Kc adjustments. Am I turning the tuning condenser and padding capacitor at the same time? Or turning the padder a little then turning the tuner back and forth?
Thanks


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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Mon 18, 2019 8:41 pm 
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Kirbyc wrote:
I think I have the wave trap set correctly so now I’m into the ‘B’ band alignment. I’m through the C-12, C-7 and C-2 adjustments. I’m not clear on the 580Kc adjustments. Am I turning the tuning condenser and padding capacitor at the same time? Or turning the padder a little then turning the tuner back and forth?
Thanks


The Padder adjustment requires turning both the dial and the adjustment trimmer. The idea here is to tune both for max signal level which may or maynot coincide with 580 on the dial. It should not be more than 5 to 10 khz away from 580 on the dial. Once you peak up this padder then it is back to the upper oscillator and other adjustments 1500 khz or whatever is listed in the instructions as the Padder adjustment will also effect the adjustments at 1500 khz. If the padder happens to be off by a considerable difference from 580 then you may have to go back and forth between 580 and 1500 settings a couple times before you get both reasonably close to match the dial settings. Just be sure that you end this with the final adjustments being the 1500 ones.
John k9uwa

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 Post subject: Re: GE E-91 Colorama display problems
PostPosted: Nov Tue 19, 2019 11:49 pm 
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Joined: Sep Mon 24, 2012 10:14 pm
Posts: 1095
Location: Topeka KS
I don’t know if I’ve messed something up with the alignment or if I have some other problem. My local 580 station doesn’t tune in clearly at around 580 on the dial however it showed up clearly at about 810. I should be getting a Kansas City station there. I also am getting 1490 at 800. I pick up several stations between this area and the 1440-1490 area on the dial. 1440 comes in about where it should but I’m getting 1490 in the background. 1490 comes in pretty well about 1510 but not perfectly. The display stays red all the time. On band D however the display works as it should.
I’m wondering if part of my problem might be the sensitivity switch but I’m sure that isn’t the major problem.
Thoughts?


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