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#1
07-05-2014, 10:34 AM
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Recent CL find - Admiral color console
I happened to check CL recently, and came across a posting giving away two old TV's - this Admiral, and a solid state Sylvania console. I called, and met up with him, and had a great time talking to him - definitely a fellow hobbyist, with a long history of TV repair and electronic tinkerings. He even had the Photofact for the Admiral, from having repaired it previously. This set had been his daily watcher for years, until it was replaced with the Sylvania in the 80's, then, that got replaced by a flatscreen within the last couple of years. He had, years back, put a new flyback in it, so it has the Thordarson replacement fitted. It was working when stored in the 80's, but, he said the last time he powered it up, a year or so back, he got a zapping noise and shut it off again.
This is an Admiral G13 chassis set from 1967. Photofact 915-1. This one has the 25" tube. The cabinet is pretty good, with a fair bit of wear, but not bad. The legs are coming unglued, and one dropped off while I was carrying it into the house, so I've temporarily got that corner of the set supported by an old external SCSI disk and a stack of paper. I need to flip the set upside down and reglue/clamp them. The chassis is dirty, but not overly so - about average for a television that's several decades old. First tests, I took the chassis out and inspected for any obvious burn marks, and metered the power supply filter caps to see if there was anything horribly shorted. A large electrolytic had been soldered in previously in parallel with one of the main filter sections, but neither tested shorted. Overall, looked OK, so I brought it up slowly. Tube filaments lit up, dial lights, and then some humming static from the speaker. No high voltage, but, after a minute, there was a pop and a flash from under the chassis and the humming got a lot louder, so I shut it off. I pulled the chassis and checked it out, and saw that the replacement electrolytic had vented out the side. Checking again, one of the cap sections was partially shorted. Time to get replacing. I fortunately had a fair stock of parts on hand, enough to replace the main filter cans with new components of fairly close values, always erring on the side of larger value caps. I first replaced the tall can containing the primary filters and the one that had been bypassed. I cut the can off at the base, and mounted one of the new caps by drilling holes through the old base and mounting it on top - the other two were snap-type electrolytics that I was able to zip-tie to the chassis underneath and wire up. With the larger can replaced, I tried it again, this time I was rewarded with high voltage and a sickly purple picture with insufficient height and a hum in the speaker. Progress! I proceeded to cut off the other can, and replace it with new components as well. I re-purposed one of the lugs as a negative terminal and mounted the smallest cap under the chassis, allowing me to attach the other three above and wire them neatly. Cutting the cans open like this, you can really see just how crummy these old electrolytics get after all these years. The tallest can had very obviously leaked internally and the electrolyte paste was staining the base disc in places. The other, smaller can, the paste had badly dried up, and the whole thing had shrunken internally, so when I cut it off, it fell out of the can. After that replacement, I got a much more stable screen full of purple static, and no hum. I reassembled it and checked it out with an input source, and was able to dial in the color and the picture somewhat OK. It still has a long way to go, but it's alive and running. The tube is weak, and has a bad case of cataracts. There is a a fair bit of horizontal smearing and fringing. The audio is pretty good though, and all the controls are smooth. The convergence is pretty good as well. Overall, it's in good shape - and it'll take some more work to make it perfect, but, getting this good of a picture out of it this early is very encouraging. -Ian 
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#2
07-05-2014, 01:31 PM
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Another one with the same face as my grandmother's old set, which was the family's first color set. French Provincial couldn't have been a very popular style, I've never seen another one.
Good way to install the new 'lytics. I wouldn't want to fully rebuild a four-section can, too hard to get at the new ones if anything goes wrong, and in this case it looks like that big one may have made a full rebuild impossible anyway.
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#4
07-05-2014, 06:45 PM
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This set doesn't use a 6EW6. Probably just a production change though. The chassis has two holes for horizontal output tubes, but only one has a socket. It uses a 6KN6. According to the Sam's, some sets used a pair of 6JM6's - hence the second socket cutout.
This set also can use a 23EGP22, but this particular one has a 25" tube in it (and a little "25" badge in the lower right corner of the bezel). I'm not sure which 25" tube it has, but it's likely the original, it has an Admiral stamp on the 'dag coating. I'm going to have to do cataracts surgery on it at some point if I ever want a watchable picture. I'm not sure who made the tube, but the PVA is breaking down like an RCA. Glad it's not the 23EGP22, especially after reading another's account about one evaporating into a puff of glass shrapnel during a cataracts removal. I do have the HV cage, I just removed it to inspect the flyback for any evidence of arcing. -Ian
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#5
07-05-2014, 07:10 PM
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Running the set some more to do some testing, and I'm hearing a HV hissing from somewhere. I've already cleaned the HV rectifier connections, focus rectifier pins, and the anode cap on the picture tube, but I'm wondering if the anode cup itself is breaking down. It's a clearish plastic, but it's developed discolored spots inside it, much like the CRT cataracts, and it's very stiff and not pliable at all. I'm going to have to wait until it gets really dark out to check for corona discharge, since the room I'm currently using as a work space has large windows in it.
Interesting enough, I hear the hissing of HV mostly when the tube is nearly dark - for instance, if I turn the brightness down all the way - or if I get to the second level on Super Mario Bros, with the dark background. The darker the picture on the CRT, the more hissing I hear. Interesting. -Ian
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#6
07-05-2014, 07:26 PM
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Quote:
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#7
07-07-2014, 10:39 AM
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Your HV may not be regulating. Dark pix puts less load ( beam current)
on the HV so if its not regulating it can go up. Usually the pix will also bloom ( expand & contract ) as you run the brightness up & down. Origional G-13 did have 2 h outs. When the flyback went it came as a kit with lots of mods for the different runs. We had an old goat that did them all but it took him two mornings. Maybe cause he was in the can nipping vodka a lot..... 73 Zeno 
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#8
07-07-2014, 01:12 PM
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Quote:
The H12 was a better chassis, that was very similar, but used the shunt regulator. The G13, used some kind of a feedback or pulse regulator and was hard on flybacks. 
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#9
07-07-2014, 04:16 PM
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My very first thought looking at the rear view of the chassis was "Where's the regulator tube?", hoping it wasn't the dreaded pulse-feedback imbroglio. But it looks like it is.
  Admiral was not our house brand, and we used to dread having one of those come in. Invariably, the flyback and H output tube were fried. Upon replacing the fly and doing the required circuit mods, the HO cathode current would sometimes still soar to over 400 ma as the brightness was turned up(!). When this happened, we had to do some creative stuff to bring the current down to reason. A 'width cap' across the damper* would lower the current while boosting the width. Then drop the HO screen grid voltage a bit to bring the width back in. All the while, HV regulation had to hold steady thru the full brightness range. So juggling those values was quite a challenge. Hopefully your set will not run into this level of difficulty. ------------- *A disc ceramic of either 68, 82, or 100 pf @6KV, between cathode and plate of the damper
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#11
07-07-2014, 07:03 PM
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This is exactly how I've replaced can caps. Using the old cap terminals as a terminal strip, with the bigger caps on top, leads passing thru small holes I drilled next to the respective terminal. If I don't have the new caps on top, I'll use some sheet insulation to cover the terminal stubs, so my fingers don't find B+. Using one of the repurposed terminals for the common negative allows me to connect that negative to a point in the circuit to avoid cap recharge ripple current from circulating in the chassis, thus avoiding any ground loops. Quote:
__________________
Last edited by wa2ise; 07-07-2014 at 07:08 PM.
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#12
07-07-2014, 08:33 PM
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Ian's set looks like any HV regulation issues were probably addressed when the fly was replaced. But it still wouldn't hurt to monitor the HO cathode current across the entire range of the brightness control.
Last edited by old_coot88; 07-07-2014 at 09:53 PM.
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#13
07-08-2014, 05:14 PM
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Yeah, I'll definitely have to check that - I haven't tried measuring the cathode current yet, but I'll probably do that next. I need to remember to check tonight when it gets dark out to see if I can determine where the hissing is coming from.
There is some blooming and changing of size with screen content, but it's not excessive. A lot of old sets don't have great HV regulation. I do like the idea of modifying it with a regulator tube, has anyone done this? Is it even possible with this flyback? Seems like it would be more stable then. I mean, there's already an extra chassis cutout for a tube socket... The thing I really, really need to do is the cataracts surgery though. It's kind of difficult to judge picture quality with the tube clouded up as much as it is. Annoying, because there isn't really a way to remove the tube while leaving the yoke on it, so I'll have to reconverge everything when I put it back together - shame, because the convergence seems really good as it is. -Ian
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#14
07-08-2014, 09:01 PM
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Quote:
BTW, the H12, used a housing on top of the HV cage. 
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