Admiral T102 scored
 

I've wanted one of these little two-tone portables for a while and one finally showed up just a few miles away. The seller has a nice collection of vintage furniture, paintings and nicknacks. He's moving to Maui so it all has to go.

There are a few chips and some worn areas, but not bad for a 55 year old set I think. All the knobs are there too.

I'm a little surprised it draws 135 watts. Seems like a lot for a little 10" set.

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Very nice. One of those are on my list of 'want to haves'.

I recently picked up a pile of Riders and Sams, but am missing this model :rolleyes:
Does anyone have a scan of the Sams or Riders for this model ?

Thanks!

I spent a few hours going over this set tonight. The front came off easily enough, but the back was stuck.
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The knobs were especially stubborn. I'll let them soak a while to clean off the gunk.
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I ended up pulling the whole chassis. It's a little dirty, but looks OK.
http://farm5.static.flickr.com/4079/...9567b7d6_z.jpg http://farm6.static.flickr.com/5058/...fd01fe66_z.jpg

National Video Corp picture tube. I hope it's good.
http://farm6.static.flickr.com/5260/...b9d50f4d_z.jpg

Yes it is :D
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The speaker has a little patch. Could that be asbestos around that tube ?
http://farm5.static.flickr.com/4098/...b6bd773b_z.jpg

The bottom is nice and clean.
http://farm6.static.flickr.com/5252/...1c022a96_z.jpg

Curiosity got the better of me and I slowly powered it up on a variac and isolation transformer over the course of an hour or so.
I kept my fingers crossed that the seleniums and electrolytics had some life left. None of the cans got hot.

Eventually, I was treated to a raster :)
http://farm6.static.flickr.com/5138/...ae5540f8_z.jpg

I flipped the clunker around until I hit 6 where we still have a low power NTSC signal.
The horizontal, brightness and contrast are all very touch, but I do get video and sound :thmbsp:
http://farm6.static.flickr.com/5299/...1ff1e361_z.jpg

You bet that's asbestos! I've wanted one of these portables for awhile, just of the same generic 8pt, hotpoint variety. Everyone I've found has been too overpriced. It's cool you get that copper plated chassis with that package, too.

I paid $65 for it. Dunno if that's a good price, but it was so close to home I couldn't pass on it.

I tweaked it a bit more and hooked up a converter box. Here's some Untouchables action.

Yes, I know - the seleniums and caps are likely to fail any time. I'll do a proper resto. soon.
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I wonder why only one tube has asbestos :scratch2: It's on the tuner and the other two tubes have metal shields.

Probably because it's right next to the metal cabinet and they didn't want a hot spot on the side of it.

Here's the turquoise version for sale in Kingston, WA. http://cgi.ebay.com/VERY-NICE-1957-1...-/260737501535

http://i.ebayimg.com/02/!CFzGRRQEGk~...or7hl!~~_3.JPG

I wonder if that antenna is stock ? Perhaps I'm missing mine ?

I have a couple of these, one Turquoise and White and one Two Tone Green.

The Turquoise one is the first thing I ever bought on eBay around 1998 and it was a mess, got it working and repainted it but it's still not all back together.

the Green one just needed a Damper tube and it worked, it still came on a couple months ago when I tried it last. I bought it pig in a poke from some woman who contacted me through my site I think. It's in good shape with just a little peeling paint.

Cool :thmbsp: Do they have an antenna on the back ?

I popped the CRT out and found where all the caps were hiding :)
It's much easier to work on now :yes: I used a sharpie to mark where the ion trap magnet and other bits were positioned. I hope that'll make it easier to put back together properly.
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You definitely need to do the hot chassis fix. these were notorious for the cabinets being hot despite all insulators being in place.

What's the fix ? better insulators ?

Speaker of hot chassis, there's a big 54 ohm 20W resistor running down one side to drop the filament voltage.

Here's the series wired tube lineup:

3.15 - 3BC5
4.70 - 5J6
3.15 - 3CB6
3.15 - 3CB6
6.30 - 6BA8A
4.70 - 5U8
3.15 - 3DT6
12.6 - 12CU5
6.30 - 6CM7
6.30 - 6CG7
12.6 - 12DQ6
12.6 - 12AX4GTA
6.30 - 10ABP4
----
85 @ 600mA

I plugged that into this website Reece tipped me off to and got this.

note: I used 120 for the supply voltage. If I use 117, I get 53 ohms @ 19.2 W.

* Dropper resistor = 60 ohms @ 21.6 W

* Dropper resistor with diode = 1 ohms @ 0.3 W

* Dropper capacitor = 22 uF + 17 ohms @ 6W

I like the idea of shaving off most of that wasted 20W. Has anyone tried the diode or capacitor method in a series string TV set ?

Assuming the heater amperage is the same I wonder if you could change some of those tubes for the higher voltage versions?
6CB6
6U8
6DT6
6J6
25DQ6 I think there was one of these?

Yes, there was 25DQ6. Good idea, but, unfortunately, those are all 300mA.

The hot chassis fix here is to rewire the switch to switch the power supply instead of the chassis. I have the fix in more detail on my website. You want the chassis wired directly to the interlock, and the switch to the power supply. Polarize the plug so the wide blade is to the chassis.

Because never, ever, is any AC outlet ever miswired....

No, pretty sure that is an aftermarket item.

Just checked, my Green one has a couple holes where an antenna may have been mounted, it also has some factory untapped holes that may have been for a factory antenna.

Thanks for the info. The anodized green set is really cool :yes:

Here's the original schematic and my proposed modifications to replace the seleniums and eliminate that 20W filament dropping resistor.

http://www.bobandersen.com/images/Ad...102/sch-01.jpg


I figure I can replace the 10 ohm fusistor with a plain fuse and 100-200 ohms to drop the voltage down when the seleniums are replaced with silicon.
Seems easier than using two separate resistors - one for each diode.

My hope is that the CL-90 will provide a soft start but not restrict the current too much. I have a CL80 and CL-130 I can experiment with too.
Perhaps I should use a diode that can handle more current ? The surge might be too much for a 1A 1N4007.
http://www.bobandersen.com/images/Ad...102/mod-01.jpg

The 1N4007 will be fine. Silicon diodes can take a brief surge higher than their average current rating. You'll have to look at the brightness of the heaters in the tubes to see if they look to be the right level, as a voltmeter won't give a meaningful number (though a true RMS meter might).

As for the hot chassis fix, relocate the switch to the filament circuit and your low voltage fuse. Connect the now empty lug on the interlock to the chassis. Polarize that side of the line cord, and hope your outlets are wired correctly. As noted earlier, these sets were notorious for hot cabinets.

I finished recapping the set over the weekend. I unmounted and restuffed all the eletrolytics and replaced all the paper caps with some nice Cornell Dubilier, Mallory and Orange Drops.

I uncrimped the ends on the two electroytics cans that are exposed.
The rest I just cut open because the seam will be covered by a cardboard tube.
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New caps installled
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I also cleaned things up a bit while I had it all exposed.
http://farm6.static.flickr.com/5096/...56d40506_b.jpg

I left the big 20W dropper and seleniums in place. I'll tackle those next.

The picture seems a litle crisper and the sound is much better :)
The horizontal hold is still very touchy though.

Perhaps I should replace the dual selenium AFC rectifier ? It's the green thingy on the circuit board in the picture above.
What type of modern diode would be appropriate ?

http://farm6.static.flickr.com/5057/...71177926_b.jpg

I tacked in a 1N4007 and CL-90. I also disconnected the CRT and stuck a 5 ohm resistor in it's place just in case I got something wrong.
I turned the set on and the filaments slowly lit up to the normal brightness :)
I reconnected the CRT and it works just fine. The CL-90 getts a little hot - maybe 2-3 watts. Certainly better than 20W :yes:

I also tried a CL-80 (slightly lower 'ON' resistance) but didn't notice much difference.

Now, on to the selenium rectifiers. I checked B+ with them still in the set and it's only 213 volts :no: It should be 255!
I'm really curious to see what effect getting B+ up to the proper level will have.

http://farm6.static.flickr.com/5055/...eda11499_z.jpg

Here are the final modifications I went with. I rewired the power switch as Big Dave suggested.
It runs cooler now and B+ is dead on.
http://farm6.static.flickr.com/5060/...94242629_b.jpg

I mounted the new components on a terminal strip near the AC interlock.
http://farm6.static.flickr.com/5218/...8eff2b09_b.jpg

Do you mean that the set as a whole runs cooler? Also, what do you think was keeping the B+ below specs and did bringing it up provide any noticable performance improvement?:scratch2:

Well at least one corner of it is cooler. That's where I've replaced the 20W filament dropper with a diode.

The old seleniums were keeping the voltage down. They got noticeably warm during operation. I suspect their resistance has increased over time.

As for performance - it's a mixed bag. I can get a brighter picture now, but the contrast isn't as good. Also the vertical retrace lines are more visible. The horizontal sync is still flaky like it has been since I first powered up the set. I suspect I need to replace the dual selenium AFC rectifier. The important thing is that i can stop worrying about the seleniums go up in smoke while I continue tweaking the set. I've had it happen once before and don't ever want to experience that again :yuck:

I'm also checking the resistors more thoroughly than I did first time around. I'm considering replacing the germanium video detector diode while I have the set open too.

I take it that the diode has a similar forward resistance as the old wire-wound resistor had in order to maintain the proper voltage. I am sort of new to the whole concept of replacing one component with a totally different, more modern component. I have read up a bit on eliminating 5U4s or other tube diodes used in a rectifier configuration, and replacing them with silicon diodes and a resistor to drop the same voltage as the tube filament. I have seen a few sets with the selenium rectifier disconnected and some older (germanium?) solid state diode(s) wired in its place. I thought that selenium rectifiers tended to run a bit hot, hence the cooling fins. I KNOW that they smell terrible when the finally do burn up, but the few that I have seen burn up were caused by bad electrolytics.

The silicon diodes have a lower resistance than the seleniums. That's why I have to increase the 10 ohm resistor to 22 ohms. I actually used a 32 and 75 in parallel each rated at something like 25 watts because that's all I had on hand. Really I think a 5-10 W would be fine.

As for using a diode in the filament string, that's a new concept to me as well. I first heard about it a while back as a potential replacement for the nasty VT71 ballast. I didn't actually try it until a few weeks ago in a Philco 37-611 radio. So cool that one little bitty device can replace a big 20W resistor and generate virtually no heat.

There is nothing wrong with the huge, original resistor and I could have left it alone. However, this little set uses around 130 watts and I figure any heat savings are a good idea.

I pulled the dual selenium AFC diode and tried to check it on a DMM and a VTVM. I got infinity on every range. I'd read these were tough to test. There seems to be some debate on what to replace them with as well: http://www.antiqueradios.com/forums/...c.php?t=110903

I just went with a couple 1N4007 because I have a bunch on hand. The horizontal sync is definitely more stable now. I'll poke around for some 1N914s too. I'm curioius to see if there's any difference.

The contrast and retrace lines seem better now as well.

Although the earlier screenshots I posted look good, the set and a tendency to either lose sync or drift off center like this.
http://farm6.static.flickr.com/5057/...bb34b784_z.jpg http://farm6.static.flickr.com/5096/...d446ece9_z.jpg

Here it is with the new diodes installed :thmbsp: Now, you have to really crank the hor. lock control way off center to lose sync.
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I'd use any diode that is suitable to use as a AM radio detector diode. Rectifier diodes may be too slow (in time) to "recover" (start or stop conducting) and have too much stray capacitance. The set may have better sync stability even more, with the detector diodes.

I thought I posted last night about the domino shaped capacitors, some are mica (usually good) and some are paper caps (usually bad). Maybe I hit "cancel" or maybe my linking to another site's images was bad or wrong. :scratch2: Anyway, large uF class caps are usually paper, the pF class are usually mica. But horizontal circuits more likely use micas. Papers should be bad by now, so if the set works, they are probably micas.

There's about 20 volts p-p across the diodes so a 1N34A or 1N914 should be OK. I'll give both a try.

I also picked up a replacement 1N270 for the video detector. I haven't installed it yet though because it's a bit hard to get at.

I poked around my local Menards for matching orange paint. This is what i came up with - Rust-oleum Engine Enamel Chevy Orange Red rated for 500F.
I hardly need paint rated for that temp, but it was the best color match.

Here's a test I did with a big iced tea can. Pretty good match I think.
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My first tube TV was a GE 14T1- green and white two tone that someone replaced everything except the filters on. I paid 5$ for it and an EICO fly tester. It has great audio, but no HV. Once I dig it out of storage I'll debug the HV and possibly sell it, if I can't get HV I'll definitly sell it. In my bassackwards mind something has to work before it qualifies to sit on a shelf and go unused for months!

Tom C.

LOL - That's what happens with most of my sets too.

I polished the chrome carrying handle with Simichrome. It turned out well but now I can't touch it or I leave fingerprints ;)
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I noticed that this CRT like many of my others has some air bubbles in it. Not really noticeable unless you sit really close.
http://farm6.static.flickr.com/5017/...c203a5e3_b.jpg

The original is working fine, I'd leave it. You'd get no picture if it were bad. They don't go bad like seleniums do.

Sure that those air bubbles in the CRT screen glass are not vacuum bubbles? :D

LOL - could be. OK, I'll leave the detector diode alone.
BTW I did put small signal diodes in the AFC instead of 1N4007s and it's working even better now :yes:

:scratch2:That is exactly the way I am! I (along with most of the women I have dated) have often wondered if it was some kind of mental condition that caused a person to have a drive to repair something just so it can sit on a shelf and get used once or twice a year in order to keep the capacitors in working order. Also, if I get stumped on something I seem to not want it around and the way things are now I am forced to go back in time and scrap it. I used to at least be able to give a TV set to someone, or better yet make a few bucks to make back some of the cost of replacement parts and the value of tubes.:thmbsp: After NOT being able to find a loving home for my 1958 24" Zenith Space Command console set, neither for money or for FREE, I am just going to scrap anything that is not simply extremely rare.:no: I had high hopes for the Zenith due to what seems to be a VERY low use chassis and crt and the fact that the 24" tube is not exactly common, nor was remote control at the time. :scratch2: