#46
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Just curious as o the reason to replace the 5U4.s
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#47
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Perhaps the power trans runs hot or is a common failure point...That is the only reason I ever switch from tube to SS rectification (except for 6X5s which I have no faith in).
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#48
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I’m the owner of this set, but Mike who is far more experienced then myself is doing the chassis restoration.
Quoting Mike: “By doing these modifications it not only eliminates vacuum tube heat, it also eliminates a lot of unnecessary wiring that has the potential to cause arcing which of course is very undesirable.” He said the wiring in the area is in poor shape.
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Personal website dedicated to Vintage Television https://visions4netjournal.com |
#49
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Quote:
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#50
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We need two more.
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Personal website dedicated to Vintage Television https://visions4netjournal.com |
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#51
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As long as the chassis is out, would you mind measuring the depth of the white screen mask, as in how deep it extends?
The one on my H840CK15 is missing, and I'm going to try to construct a duplicate.
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"Restoring a tube TV is like going to war. A color one is like a land war in Asia." |
#52
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Quote:
UPDATE, SEPTEMBER 24, 2018, Day 55 Greetings Marshall. I have recapped the main power supply and verified the design voltages as they are at this time. They will likely be lower during later tests since I have the sweep circuits disabled for the preliminary testing. For the foreseeable future, and maybe permanently, I will be leaving the original design in place with the 5U4 tubes. We will see how that goes later. OK, now for the pictures. Picture #1 shows a couple of caps replaced but except for that, the chassis is as I received it. Mostly "untouched" which is how I like to get them. These caps were actually broken off at the terminals so I went ahead and replaced them. They can be seen as orange and brown components at the lower left. Picture #2 is the main power supply chassis before re-capping. Picture #3 is the main power supply chassis after re-capping. Picture #4 shows my oscilloscope screen showing the waveform of the grid drive to the Horizontal Output Tubes (6BG6's). This tells me that the horizontal oscillator is running and the drive signal to those tubes is good even before recapping. This signal on the scope is about 200V P-P and the Photofact refers it to be 150 V P-P. Given the fact that most of the running voltages are a bit high right now because I have the main power to the sweep circuits disabled, it is expected that the signal would be a bit high. This is good at this point. This step is important because it means now, that I can do some testing of the flyback transformer. It won't tell me everything about it, but I will tell me a lot. Mike. Link for full size images: https://visions4netjournal.com/westi...-carousel-6116
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Personal website dedicated to Vintage Television https://visions4netjournal.com Last edited by etype2; 09-24-2018 at 02:58 PM. |
#53
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The flybacks on the 15 inchers don't seem to be terribly failure prone. I would reinstall the jug at this point and try to get HV, horizontal deflection, vertical deflection, even in a brief test, and a quick check of the convergence circuitry and CRT itself before going any further. My 2 cents...
There's little sense in continued restoration efforts if critical parts are dead. I don't like the test results of the 15GP22 at all... |
#54
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The dynamic convergence transformer is T-701. It needs to be replaced with a Folsom reproduction ASAP, before you damage pots in the focus circuit.
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#55
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Thanks. Mike wanted to know if it was the T-701. I think I have John’s email.
__________________
Personal website dedicated to Vintage Television https://visions4netjournal.com |
Audiokarma |
#56
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I'd be surprised if John has any left; I think my friend Ed got the last one about a year and a half ago as a precautionary measure.
My cabinet is home now and miniman82 is doing the complete restoration on my chassis. I don't have a good 15GP22, but at this point I'm thinking out a plan
__________________
"Restoring a tube TV is like going to war. A color one is like a land war in Asia." |
#57
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Good luck with it. Maybe we can compare notes. Nice Marantz. I have a Model 20.
The mask is so large, it could accommodate a larger CRT.
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Personal website dedicated to Vintage Television https://visions4netjournal.com |
#58
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The 21AXP22 in our 21CT55 tested like this.
These figures are about the same as the test on 15GP22. As we have posted on another thread, the 21AXP22 puts out a decent image despite the tired CRT. I wonder what criteria was used by the ETF. The CRT was described “good” and “excellent” prior to the auction. Fingers crossed.
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Personal website dedicated to Vintage Television https://visions4netjournal.com Last edited by etype2; 09-25-2018 at 11:01 PM. |
#59
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Also keep in mind that for sufficient brightness, you'll have to draw more cathode current from the 15GP22 cathode as it runs a lower ultor voltage than the 21AXP22 does (or should) in the 21-CT-55. 19.5 kV for the CT-100 versus 25 kV for the 21-CT-55. The difference in apparent brightness with the two different ultor voltages will be not be negligible. At the very least I would expect poor tracking, and quite possibly insufficient green. I suppose your saving grace here is that the weakest gun is the green gun. If it were red, you'd be in worse shape... I too am curious as to what happened here as far as testing goes. Your results certainly don't look "excellent". I don't doubt Steve's integrity. Perhaps your tester needs looking at? Do you have an extremely strong like new tube to compare with? |
#60
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Quote:
I'm at the point where I rather test it myself before bidding my top dollar than trust the accuracy of the posted info. My guess they either have an iffy tester, an iffy operator, are taking consigner's word for CRT health or some combination thereof.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
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