Recapped a CTC 7AH..still have a problem
 

:scratch2:got a '58 RCA CTC7AH color console"Grenoble"
completely replaced all of the E-caps;including a old Bumblebee on the A/C
safety [email protected] the variac on the first power up it shows a huge current draw:scratch2:on 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:scratch2:

check resistance at the plug

I am assuming you are starting at zero with the variac, should be zero volts and zero amps.

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.

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

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.

that's correct:thmbsp:..on the set having a thermal switch; one side goes to the single section 160uf@250 is on the positive side of the caps center leg; going too the thermal switch,and on to the filter choke..the negative is to the safety fuse holder,and one leg on thermal sw is going to the power switch:scratch2:the single cap is not grounded...this must be a simple fix..i hope i've not damaged this 53 year old set..it has a beautiful cabinet

you lost me on the power switch. it goes plug, saftey cap, on off switch, thermal switch (the heater part), primary of transformer.

was it working before the recap?

Dave
I installed a new 160uF@250 that's on a fiber wafer....the other 2 E-cans,2 and 3
were junk; i used 2 new terminal strips that were long in length mounted them
on the empty space rear of the tuner soldered all of my new radial E-caps
to the new strips making sure to only ground the one side that was required
too...place the leeds to each correct value one at a time..double checking as went according to the schematic:yes::scratch2: no the set
hasn't been on for over 35 years

pm sent

the color picture tube is mint:yes::thmbsp:; tested with my Sencore CR-161 tube tester

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:

http://antiqueradio.org/art/RCACTC-7FirstImage.jpg

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

http://antiqueradio.org/art/RCACTC-7Recapped.jpg

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, can you pls confirm the resistance of the primary of the power transformer.

my 3-4 ohms is on a CTC-16

Sorry, mine is stuck behind a pile of stuff right now.

Phil Nelson

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.

hmmm well the sams says DC resistance under one ohm not shown so maybe thats right.

Phil, Is that CRT a 21CY?

found the power tranny in the primary a dead short:thumbsdn:,probably left plugged in during a thunderstorm.."Lighting Hit!"years ago;:scratch2: anyone have a good replacement:scratch2:....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???

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 drop:thmbsp:all of the E-caps i had already replaced in the cans...probably a dead short in the primary:thumbsdn: it read 00.6 ohms,on my Sperry 5300 autorange DVM across the safety interlock

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!

Phil Nelson

.6 ohms is bad, mine had like 3 or 4 if I remember right. If you can disassemble the transformer, it might be possible to repair. Sometimes the windings will be shorted near the top, where you can still get to them. If it's the type that's potted in wax or whatever, good luck. I wouldn't want to even think about the mess that would make...

If anyone can cross the numbers I have a transformer #300251-1. If memory serves me correct, I think it came from a RCA upright chassis color.
The lead colors are black, black/white, green, green, beige, beige/green, red/black, red/green, and what looks like orange. If it'll work it's yours the shipping.

Thanks Zenith;
waiting on what,Mr.Bill of Moyers Electronics has to say about the old RCA number crosses too...I'll compare it to what you have..if they gave me sticker shock! I'll need what you have...be so kind in looking @ the Sam's for mine...its in folder 459 or 495... I forgot what - number after that:scratch2:...Its a CTC 7AH Grenoble style with ultrasonic wireless remote!...please pm me with you're phone number let's talk:yes::thmbsp:

Zenith'and Phil'
it is a potted tranny on mine..about the size of a small loaf of bread
and heavy...i take it that yours is the same:scratch2::yes:

Zenith'
please look and see what chassis number you got that from?..according to an original RCA shop manual dated '1957 the early production power trannies had the two 5U4's tube sockets mounted in the top of the transformer case like an old Philco 37-60 radio's tranny..what's listed in
Steve McVoy's website link..mine's is the later version that didn't have that twin Tube rectifier setup in the case,..mine uses 2 "Top-Hat"style diodes on terminal strip..with one solid red on the bottom end of the strip and the Red/Green tracer soldered in between the 2 diode top end with a 0.1uF@ kilo-volt ceramic cap to ground,..both are still tested good :thmbsp:is your's like mine:scratch2:

Mine is an unpotted transformer and rather large. I'm pretty sure it was used with a doubler from the way it is wired. I looked for a schematic but so far I can only find the CTC7 with the 5U4's on the transformer.

Sams 433-2 covers the CTC-7AH. It says the power transformer is number "106358" with specs as follows:

primary - 117v 3.8a
sec 1 --- 150v 0.880a
sec 2 --- 6.3v 2a
sec 3 --- 6.3v 13a

thanks Rich'
looking forward to hopefully replacing this dud Power tranny!
it may work if the one you have is the same setup...enjoyed our phone chat awhile ago and too more in the future:thmbsp::banana:

remove the caps at the interlock.

I did..
completely unhooked the tranny from TV set,and still got the same results:thumbsdn:DEAD SHORT:thumbsdn:in the primary..Mr.Bill @ Moyers electronics called me last night..informed he had a NIB power transformer in the box
for my model 7 AH..sent him a money order off today..and I'll still obtain one as a spare out of Louisana...that should cure the problem will have the original rebuilt later when possible$$:thmbsp:

Awesome, you found a NIB transformer! Very lucky.

Yes folks;
:banana: from Moyers for the amazing price of $87 bucks! I'm sorry peoples:tears:
that was the last one they had...even if its been in they're stock inventory
for the past 45 years on the self:yes::D:thmbsp:

New one is now mounted and working up the rewire hookup
got one that's the longest wire,.its a white/black tracer.heavy gauge
can't remember where it goes..its over a foot long..i matched up
the rest and one left hanging...haven't powered up it yet..just want make sure
for correct reinstall...can you power up on the bench without any of the
tubes in?:scratch2: to check the voltages are correct:scratch2: after we figure out where that single power lead goes...will it fry anything without all of the tubes not installed??:scratch2:

yes you can try it with the tube out, just monitor the AC line current going in, and the AC voltage coming out on the secondary. slowly ramp up the voltage, with no filaments to heat up and no plate loads on the B+ the current should be very low, near 0 amps at low voltage, and only a few milliamps at full line voltage. with Tubes in but B+ disconnected (like a popped fuse or circuit breaker on the B+) it should be about 1 amp at full line voltage to power all the filaments. This is where a variac and AC amp meter really pay for themselves.

Did you ever get around to taking the transformer apart? A direct short is very suspicious and may appear to be fixable.

Ok I found where the last wire goes to terminal strip near the E-cap #2
to the rear of #1..double checked my connections by doing one wire at a time by color code and tracer...I
Did clip back a 1/4"inch from the solder terminal.:scratch2: leaving a tiny bit of original insulation with the color code removing the old tranny..:yes:
one Brn/Blk to ground:yes:Red/Grn to CRT and other filaments.:yes:one Grn/REd to the "TOPHAT"diodes;one REd to the bottom of fuseholder
Brown to one side of the fusible link #26 wire;Black to terminal lug..solid green
to filaments..trying too remember the connection of the White/Black tracer goes too:scratch2:?..

sorry Penthode
have gotten too the old tranny yet it appears to be spotwelded together case wise on the bottom half:scratch2:

AHHH! that wht/black tracer goes to chassis ground...tried a few minutes ago to power up after double check of my reinstall:scratch2:and still got a signifigate hard current draw on the Amp meter on the variac...it wants to
and has tripped the circut breaker in my living room twice:sigh::scratch2:
I redouble check my solder connections it appears to be the same as the factory had built it...i did do one wire at a time as stated before...now i just tried it again it doesn't tripp the breaker which is weird:scratch2:...keeping in mind this is a brand new transformer..the field choke is still good reading 17 ohms...and yes I've been doing this with variac:yes:Superior "Powerstat 116"
all of the E-caps are new:yes:and still have a current draw @no voltage:thumbsdn:what gives?:sigh: that's with no tubes in