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  #1  
Old 10-26-2011, 11:44 AM
47'Plymouth 47'Plymouth is offline
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Recapped a CTC 7AH..still have a problem

got a '58 RCA CTC7AH color console"Grenoble"
completely replaced all of the E-caps;including a old Bumblebee on the A/C
safety interlock...047@600volts..on the variac on the first power up it shows a huge current drawon the Amp gauge..I then use my 3way Dim-bulb tester with all of the tubes pulled and the CRT unplugged also..bulb does'nt light...while on the variac brush starts to arc..i shut her down instantly.i tested the set on the Dim-bulb alone to test for a short in the Primary...no problem there...double checked all connections with the schematic to make sure i didn't mess up on that end...what gives
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Old 10-26-2011, 11:46 AM
DaveWM DaveWM is offline
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Quote:
Originally Posted by 47'Plymouth View Post
got a '58 RCA CTC7AH color console"Grenoble"
completely replaced all of the E-caps;including a old Bumblebee on the A/C
safety interlock...047@600volts..on the variac on the first power up it shows a huge current drawon the Amp gauge..I then use my 3way Dim-bulb tester with all of the tubes pulled and the CRT unplugged also..bulb does'nt light...while on the variac brush starts to arc..i shut her down instantly.i tested the set on the Dim-bulb alone to test for a short in the Primary...no problem there...double checked all connections with the schematic to make sure i didn't mess up on that end...what gives
check resistance at the plug
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Old 10-26-2011, 11:47 AM
DaveWM DaveWM is offline
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I am assuming you are starting at zero with the variac, should be zero volts and zero amps.
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Old 10-26-2011, 11:52 AM
DaveWM DaveWM is offline
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should be about 3-4 ohms on the plug. with the power switch on.

if that checks then check resistance at B+ (right after the choke), should be around 10k AFTER the filter caps charge up from the voltage of the VOM, do this with the set unpluged of course. If the B+ resistance is a lot lower then you have a short somewhere or a filter cap installed backwards. If it uses a doubler cap in the power supply make sure you have it wired up with the correct polarity, check it to the schematic, doublers can be tricky.

Last edited by DaveWM; 10-26-2011 at 11:56 AM.
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Old 10-26-2011, 11:56 AM
47'Plymouth 47'Plymouth is offline
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ok with power sw on with no power of course..you stated that to test for 3 to 4 ohms @ the safety interlock..trace over to the filter choke.correct?@10K ohms
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Old 10-26-2011, 11:58 AM
DaveWM DaveWM is offline
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I trust nothing so I would check the actual plug for the 3-4 ohms.

so if that clears yes look for the filter choke I think there is a thermal breaker there.

again triple check those 160uf caps C1 should be a single section or a single cap the neg does NOT go to the chassis ground.
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Old 10-26-2011, 01:34 PM
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If you haven't replaced the papers/or paper-milars those can some times cause troubles in early roundys.
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  #8  
Old 10-26-2011, 02:35 PM
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Phil Nelson Phil Nelson is offline
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Quote:
Originally Posted by Electronic M View Post
If you haven't replaced the papers/or paper-milars those can some times cause troubles in early roundys.
Here is my CTC-7 after I had replaced only electrolytics. Bad horizontal, lousy vertical, colors all hosed:



Here it is after I replaced the old "maroon drop" mylar caps:



Still need to do the usual setup (convergence, etc.), but you get the basic idea.

Phil Nelson
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Old 10-26-2011, 02:51 PM
DaveWM DaveWM is offline
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Phil, can you pls confirm the resistance of the primary of the power transformer.

my 3-4 ohms is on a CTC-16
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Old 10-26-2011, 02:56 PM
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Sorry, mine is stuck behind a pile of stuff right now.

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Old 10-26-2011, 03:04 PM
DaveWM DaveWM is offline
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I discussed it with the OP, he has 0.6 ohms, which seems WAY low to me but not sure, the sams does not specify. Hope someone out there with a 7 can chime in.
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  #12  
Old 10-27-2011, 02:56 PM
47'Plymouth 47'Plymouth is offline
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found the power tranny in the primary a dead short,probably left plugged in during a thunderstorm.."Lighting Hit!"years ago; anyone have a good replacement....tried again; unhooked the power tranny.disconnected from the set..and my Variac sparked up again with huge current drain on the Amp meter...resulting in no volts obtained when trying to turn the knob on the variac...stopped immediately to prevent damage to my variac...calling Moyers asap..any suggestions model 7 owners???
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Old 10-27-2011, 03:04 PM
47'Plymouth 47'Plymouth is offline
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to answer the question Phil;
on did i replace the other caps..all are original "Sprauge"..maroon drops..the good kind..had only one "Bumble Bee"
at the plug in socket; it was a .047@600 between A/C the power pins..i replace with Orange dropall of the E-caps i had already replaced in the cans...probably a dead short in the primary it read 00.6 ohms,on my Sperry 5300 autorange DVM across the safety interlock

Last edited by 47'Plymouth; 10-27-2011 at 03:07 PM.
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Old 10-26-2011, 05:12 PM
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stromberg6 stromberg6 is offline
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Question

Quote:
Originally Posted by Phil Nelson View Post
Here is my CTC-7 after I had replaced only electrolytics. Bad horizontal, lousy vertical, colors all hosed:



Here it is after I replaced the old "maroon drop" mylar caps:



Still need to do the usual setup (convergence, etc.), but you get the basic idea.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html
Phil, Is that CRT a 21CY?
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Last edited by stromberg6; 10-26-2011 at 05:13 PM. Reason: spelling error
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  #15  
Old 10-27-2011, 04:02 PM
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Phil Nelson Phil Nelson is offline
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Quote:
Originally Posted by stromberg6 View Post
Phil, Is that CRT a 21CY?
Yes, 21CYP22.

Regarding the old "maroon drop" caps, I used to assume they should be as good as new orange drops, but I guess 50+ years can take a toll on this kind, too. I didn't get a reasonable picture until I replaced them. The CTC-7 boards are easy to work on, fortunately.

Too bad about that power transformer -- ouch!

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