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60s / 70s Admiral 'Instant Play' Portable
Hi guys. Long story short, my grandpa passed away and I got the honor of cleaning his attic. I found my mom's childhood TV set. A POS Admiral portable that she gives no craps about. He was a top electrical engineer back at Simpson Electric, but I have a sneaking suspicion that this tv was retired because grandpa either couldn't or didn't want to fix it.
I thought it might be a nice set for me to practice my tv-repairing skills on. So first thing, I tested the picture tube. Huzzah! It tested good! Second, I took out the circuit board and resoldered all the (many) broken joints. Big Mac disapproves of this filthy circuit board. Next, I powered it up on a variac, using my new (grandpa's old) Simpson watt/voltage meter to monitor it. It... started smoking. But hey! I fixed that, I think. One of the metal shields around one of the transformer thingies was... improperly installed, and therefore touching (grounding) one leg of a capacitor. I unsoldered it and positioned it the right way and then I resoldered even more joints. The holes in the board are too big for the pins, so it's easy for components to rock around I guess. Also, the grounding spring that touches the aquadag was hooked to that shield thingy, which seems awfully flimsy to hold that spring. Then again, this set is a POS, so... Anyway, this time, it didn't smoke, and I got some good high pitch tv-working noises. And actually some kind of display: The yoke is crooked. I didn't let it run too long, but it seemed liked the horizontal was getting weaker and weaker. Best I can guess is the horizontal circuit has a problem. (I'm so smart.) Now, the horizontal output tube (33GY7A) is made in Korea, and this youtube guy says they suck, so I'm guessing this one's gotta go. However, this tube got super hot, as well as the sync. sep(arator?)/vertical oscillator & output tube (23Z9) and the sound det(ection?) & output tube (17BF11). Which are all original Admiral tubes. Ironically, every other tube is another brand, even the HV rectifier tube, which... do those ever go bad? It's just two pieces of metal and some mercury, right? As far as I understand, a hot tube implies a short or other circuit problem. Most of the caps on this thing are ceramic, with a few that are clear plastic ones I've never seen before, a couple film caps, a couple mylar(?) caps, and then that giant worrysome filter can cap thing, which is made of cardboard painted silver, pretending to be metal. I guess replacing all the not-ceramic caps on this thing wouldn't be too hard. It's probably only 10 or so. But could this be a resistor problem? And uh, I can't test most of the tubes in this thing because they're 12 pin compactrons, and my Hickok 533A doesn't have this new-fangled socket! /cry I did a little looking into this, and I suppose it wouldn't be too hard to make a direct-wired adapter from a 12-pin socket, but then... how would I know the settings to use on the tester to test them? Well I'm not in a hurry on this one, and who knows? Maybe grandpa has the fancy-shmancy adapter device hidden away in his garage somewhere. Or maybe not, and that's why this set was retired. Can anyone give me an idea of what the model number might be? The sticker on the bottom is completely obliterated. I tried some searching and came up emtpy handed. I'd kinda like to get a Sam's for this thing, especially if I'm gonna have to start poking circuits. Big Mac is wearing a yoke and standing on a yoke. Any advice would be appreciated. Thanks! Last edited by MadMan; 01-09-2017 at 12:57 AM. |
#2
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HV rects are not mercury arc tubes...They are normal filament type vacuum tube rectifiers, and can go bad.
Power tubes like horizontal, vertical, and audio output often DO get very hot by design...If the plate starts to glow a dull red/orange in a dark or (worse a) light room then the tube is being run well beyond it's plate current rating indicative of major circuit issues...Start by verifying grid bias voltage relative to schematic in those conditions, and avoid running a tube that is 'red plating' for more than needed to warm up and get a reading....You will shorten tube life, or ruin a tube by letting it red plate for more than 1 min on end.
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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 |
#3
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Used to fix & sell tons of these. Not everyone can afford
a Zenith ! And if you think this is cheap you should see a GE ! This will run much better & last longer....... First thing I see is the horz hold shaft is missing. It goes in the coil behind the horz osc tube ( 8LT8 ??). What will happen is some one will adjust it too far & not be able to get it back to the right spot. The pix will usually be narrow, have lines & multiple pictures side by side. It will often make a loud high pitched sound. It can overheat the 33GY7 also. Best thing is to get a source on it like an old VCR to see if thats whats going on first. 73 Zeno LFOD ! |
#4
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See if the slug is still in the H.osc/hold coil. Somebody mighta screwed it all the way out and lost it. I've seen that happen before.
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#5
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On the horizontal osc. coil, the slug is there, and it turns easily with an allen wrench. It doesn't appear to be too far in or out. I'm pretty sure the extension shaft thing just broke off at some point. But I didn't even think of messing with its adjustment while the set is running. I'll try that later, I have the whole set apart so I could scrub off the rat piss. Horizontal hold thingy. Last edited by MadMan; 01-09-2017 at 10:04 PM. |
Audiokarma |
#6
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Be really careful turning that slug with an allen wrench as it's very fragile powdered iron and cracks easily. There are special tools called alignment tools ('diddle sticks') made for that.
The 33GY7 obviously has grid drive since you have a raster. Taking voltage measurements on the tube wouldn't really gain you anything. |
#7
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The numbers & letters stamped on top of the flyback box will be your chassis number. You can look up the service data that way. Number will be something like this"4H-1A". All the best,Tom.J
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#8
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The one with the 8LT8 seemed to be a GE design. The Admiral designed sets were great. Those used the 8FQ7 and a different design, altogether. |
#9
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Yeah I initially thought the set was a GE (I have a ~16" that looks similar) and was going to see what the model was on mine thinking it might be the same set as his.
__________________
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 |
#10
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on often. Also not all of them are in Sams. Looking up on line is not the best way. You cant drill down through a list but I have the paper index. IIRC the old Sams index on disc will do MUCH better searches. Last resort is to find a similar chassis. Any Admiral with the same tubes will be almost identical. I can help with that. 73 Zeno LFOD ! |
Audiokarma |
#11
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Many of those GEs had a problem with the Hor. oscillator not starting because it's supplied from B Boost. The fix was to put a diode between the Boost source to the B+ line. That way, the H.osc starts on B+, then when the Boost comes up, the diode becomes reverse-biased and the osc. then runs on Boost.
I don't remember seeing this particular problem in the Admiral clones, though. Another frequent problem in both GEs and Admirals was- someone would jam the back on without lining up the H.hold shaft with the hole, thus ripping the coil partway out of the circuit board. Never seen the 33GY7 actually red-plate though, even under sustained absence of grid drive. Figgered this was due to the low B+ design. |
#12
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Zeno re: post 10 what you say is quite true, but knowing about this chassis series as in having 6 of them sized 15" to 21" gave a good stab at it(H4-1A). Also these are AOC made not GE. All the best,Tom.J
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#13
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Ok guys, so today I hooked everything up outside of the cabinet (a little easier for me), and fired it up. First off, in my research I found that 'Instant Play' meant that the tube filaments were always on at a low voltage to give a quick startup... but it looks like they're on 100% filament voltage with the set off, that seems so stupid to me O_o. ANYway. I turned off the lights and watched the tubes for any red-plating, of which I could see none. So I let it run for a bit. Still I think those tubes are getting abnormally hot. I'm aware that tubes are by nature warm, but this set could double as a space heater.
Oh, also, how important is the grounding spring that touches the aquadag on the screen? Could I test-run the set without it? Because it's a pain in the ass to keep the spring in place without the cabinet assembled. Um, at first power on, I had about 3/4 of the horizontal going. after about 2 minutes, the horizontal was getting weaker noticably, and at about 4 mins, it lost horizontal altogether, leaving just a flat line on the screen, at which point I turned it off. There's no way this could be caused by a tuner tube, is there? Cuz the VHF RF amp (3HA5) tests very weak. Doubt it, anyway. I let it rest and turned it on again, it started sparking. I resoldered one joint and that took care of it. This time it again started with about 3/4 of the vertical and slowly lost it. Now I didn't see any red plating, but I did see some blue... plasma arcing whatever, inside the AGC video amp & sound IF amp (14BR11). I'm assuming that means it's gassy? I wasn't able to capture it on camera, but I'm pretty sure I wasn't hallucinating. Quote:
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Help? Please? :3 It says T7H2-1A on the flyback box. There are also lots of numbers on the PCB. I do have the serial number, but I doubt that'll help. |
#14
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MadMan, yes the chassis number is T7H2-1A basic chassis is H2-1A. Sams folder #1062-1. Now there will be minor differences between basic chassis as Admiral built these for a few years. All the best, Tom.J
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#15
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MadMan!
Look at the back of the power switch. The Instant Play function was a diode across the power switch. Clip it out, as it must be shorted. Then the tubes will not be lit, when the switch is in the off position. Probably, just as well. I used to see those small sets, where the owner would install an in-line cord switch, as it bothered them, that the set was using power all the time. Also, many thought it was a fire hazard. |
Audiokarma |
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