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  #31  
Old 09-18-2017, 10:55 PM
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Quote:
Originally Posted by bandersen View Post
Hmm. I don't see a 6BC5 in the schematic. I'm thinking it's in the tuner but that shows a 6AG5.
*scratches head* Dammit! And I already ordered a tube for it - the wrong tube, it is supposed to be a 6AG5. The vertical osc/amp tube was also wrong, a 12BH7 instead of 12AU7. According to my tube book, they're close approximations of each other, but meh. I'll just order another tube. I did put a 12AU7 in it, it didn't seem to make much difference.
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  #32  
Old 09-19-2017, 08:10 AM
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Tube substitution manuals: For the repair man who's tube caddy ain't big enough for two similar types with different numbers...

If the other type seems to work well in the stage then it may as well stay, but if it don't going for the original number is the wise choice.
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  #33  
Old 09-19-2017, 08:48 AM
kvflyer kvflyer is offline
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Truth be known, I store my tubes in tube caddies. Today,you can have a caddy for radio, another for audio, another for B/W sets etc.

That way, they ain't so heavy...
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  #34  
Old 09-19-2017, 09:01 AM
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Quote:
Originally Posted by kvflyer View Post
Truth be known, I store my tubes in tube caddies. Today,you can have a caddy for radio, another for audio, another for B/W sets etc.

That way, they ain't so heavy...
I sort of do the same thing....The stuff I've had the longest are in caddies sorted by number and tested. After that is is an unsorted mix of boxed NOS, and semi-sorted loose pulls (some stored in boxes after the caddys filled)...The pulls are sorted by type (HV diodes sweep power tubes, 7 pin, 9 pin octal/loctal signal, fat pin) A caddy FILLED with un-boxed loose pulls can get heavy fast.
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  #35  
Old 09-19-2017, 09:43 AM
dieseljeep dieseljeep is offline
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Quote:
Originally Posted by MadMan View Post
*scratches head* Dammit! And I already ordered a tube for it - the wrong tube, it is supposed to be a 6AG5. The vertical osc/amp tube was also wrong, a 12BH7 instead of 12AU7. According to my tube book, they're close approximations of each other, but meh. I'll just order another tube. I did put a 12AU7 in it, it didn't seem to make much difference.
A 6BC5 is the newer generation 6AG5. I seldom bought 6AG5's, always 6BC5's.
Way back then, I would try different variations of similar tubes, 12BH7 vs 12AU7 etc, to avoid having to troubleshoot the circuit.
That was in jobs where the set owner didn't want to spend too much money on an old set.
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  #36  
Old 09-19-2017, 12:22 PM
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Quote:
Originally Posted by Electronic M View Post
I sort of do the same thing....The stuff I've had the longest are in caddies sorted by number and tested. After that is is an unsorted mix of boxed NOS, and semi-sorted loose pulls (some stored in boxes after the caddys filled)...The pulls are sorted by type (HV diodes sweep power tubes, 7 pin, 9 pin octal/loctal signal, fat pin) A caddy FILLED with un-boxed loose pulls can get heavy fast.
Many of us could probably cull our loose/unboxed tube collection by:

1. testing all the HV rectifiers 1B3-1X2-1V2-3A3 etc weeds out the open filaments at least. Id hate to stick a bad one in a working set.

2. testing all the damper tubes for gas-shorts again where fails are obvious on a simple tester

3. Testing 5U4's and sweep tubes in a working set. emission testers miss often the bad ones

4. Run a quick shorts-gas test on all the common triodes and pentodes 6CG7, 12AU7, 6SN7, 6CB6....
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Last edited by DavGoodlin; 09-19-2017 at 12:25 PM.
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  #37  
Old 10-13-2017, 10:20 PM
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Ok, so. I recapped most of this set, but the picture didn't want to be right. So I ordered the rest of the caps, but then capacitorworld decided to screw up my order again, so I had to wait a while. I just got them today (from digikey) and put them in, but the picture is still crap. All the tubes test good, except the audio output (tested questionable), but the audio comes through clear (though with some buzz [a lot of buzz if the audio is silent]).

I've been fiddling with the adjustments. I noticed that the horizontal lock in range and horizontal drive trimmer caps were all the way screwed in, and the horizontal linearity coil thingy was very much screwed out. My main problem is with horizontal (although it looks like vertical has an issue too), as it seems the picture is overlapping itself several times horizontally. I'm a total noob at this, but judging by sound, it seems like the horizontal lock adjustment on the front speeds up or slows down the horizontal... um... 'drive'? But anyway, if I turn it up, the picture overlaps itself more, and down less. Unfortunately, it seems that the H lock in range is best set as far in as it can be. The H drive seems not to do much at all, but the picture is a bit clearer at just slightly less than all the way tight.

The other adjustments seem not to affect it much, which makes sense to me. The only thing I noticed while recapping is that one cap seems to have been replaced with a bumblebee. It was in a totally different place than in the Sams photo, and the leads of the snipped-out old one are still there. The stripes are discolored and I'm colorblind anyway, but my thingy measures it at .02 so I put a .022, but the diagram calls for .01. It's C32 for anyone with the Sams. It just goes to ground from a sort of... 'rail' that comes off of one side of the brightness pot, it goes to lots of things including a grid on the video amp and the audio output and all over the place. Actually now that I really look at it, it seems to have a lot to do with the horizontal stuff. Hmm.

The pic below is supposed to be an indian head test pattern.

Ideas?
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File Type: jpg 20171013_214921.jpg (71.7 KB, 30 views)
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  #38  
Old 10-13-2017, 11:17 PM
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Looks like the horizontal frequency is too low... there is a slug adjustment on the back of the chassis for horizontal frequency (it is protected by a metal bumper) turn that and observe the effect on the multiple overlapping images.

jr
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  #39  
Old 10-13-2017, 11:42 PM
EdKozk2 EdKozk2 is offline
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Hi,
I finished up a recap on an Admiral 20X1 chassis a few weeks ago. I was having trouble with horizontal AFC , just like your picture shows. I found the issue in my case, was the horizontal stabilizer coils' adjustment. It is on the underside of the chassis. I had to back (turn) the slug all the way out, to the end of its' travel. This adjustment is on the opposite side of the horizontal frequency control slug.
Make sure you follow the set up procedure in the Sams for the horizontal oscillator adjustments.
I posted a picture with an arrow pointing to the slug adjustment.
Ed
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File Type: jpg MVC-002S- Arrow to adj.JPG (52.2 KB, 29 views)
File Type: jpg MVC-017S.JPG (37.6 KB, 34 views)
File Type: jpg MVC-030S.JPG (37.4 KB, 34 views)
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  #40  
Old 10-14-2017, 12:26 AM
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Thanks guys. I had played with the H frequency before and it did nothing. I went back and unscrewed it nearly all the way, and the picture fell right into place. And I didn't even realize there was a thingy under the chassis. One little problem though...

I'll be following the Sam's instructions for an o-scope based alignment. But idk if that'll fix this. And before you go and mention the picture alignment device, it's already maxed out. Plus there's a clean straight end to the picture.

EDIT: apparently my input device is messed up. fml
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File Type: jpg 20171014_000445.jpg (51.3 KB, 32 views)

Last edited by MadMan; 10-14-2017 at 01:03 AM.
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  #41  
Old 10-25-2017, 11:13 PM
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OK. Update time.

I got a new thingy. I followed the whole big horizontal adjustment guide on sams to a tee. The picture is not bad, but it's not really any better than before I did the whole procedure. The only noteworthy thing about the procedure was that I was unable to get the picture to slowly scroll horizontally, in the one step that asked for that. The picture either flies by all skewed, or the closest I got was the picture far to one side with a bit of a ghost image next to it. Also, I think it asked to see the retrace as a bar on the side, and I couldn't find that either.

It's hard to tell from the photos, but the picture is pretty blurry. I could be mistaken, but it seems like it gets a bit worse as the set warms up. The focus is turned all the way up, and it does get worse if I turn it down. Maybe one of the resistors associated with the focus is bad? There was a capacitor I mentioned earlier on that was double value on the same circuit, I replaced it with the specified one, and it did jack.

There's also a shadow of everything, if you look closely, especially noticeable in the darker image.

Turning the brightness down improves the clarity of the image, but even with the lights off in the room, the image would be too dark (and have too poor a contrast) at a level of brightness that produces a clear enough image. On the other hand, with the brightness all the way up, though the image is blurry, the screen is pretty damn bright. So... the crt is good, I guess?

The thought occurred to me at one point that the ion trap might be out of whack. Before doing anything to this set, the FIRST thing I did was mark where it was, so that's where it stayed. But I decided to mess with it, and while I don't know ANYTHING about adjusting an ion trap, the picture is at its brightest where it was rotationally, but I found that backing it up about 1/4" made it even brighter. Is that... ok? The photo below shows where I moved it to.

Also, the horizontal linearity slug doesn't seem to do much at all. All the way in or out, it has VERY little effect. And no matter what I do, the left side of the image is a bit stretched out.
Attached Images
File Type: jpg blurrypic1.jpg (62.6 KB, 31 views)
File Type: jpg blurrypic2.jpg (61.3 KB, 34 views)
File Type: jpg iontrap.jpg (53.2 KB, 31 views)

Last edited by MadMan; 10-25-2017 at 11:23 PM.
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  #42  
Old 10-26-2017, 12:00 AM
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With Ion traps you adjust rotation then fore and aft for max brightness...If neck shadows or centering issues occur occur try to fix it with positional adjustment of the focus coil first and only try to fix them with the ion trap as a last resort.

Double magnet traps like yours only have one 'front' side (be sure not to reverse it). But single magnet traps can use either side as front and sometimes work best if you swap front and back (the rotational sweet spot will shift 180 degrees when you flip it). I mention single magnet as they are more common and if you own enough sets you will run into them eventually.
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Last edited by Electronic M; 10-26-2017 at 12:04 AM.
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  #43  
Old 10-26-2017, 12:59 AM
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...So what you're saying is... I did it right without even knowing what I was doing? Score!

Also I have no way of knowing which direction the magnet is supposed to be, other than the way that I found it. It has no arrow.
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  #44  
Old 10-26-2017, 02:05 AM
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"Maybe one of the resistors associated with the focus is bad? "

The resistors would be the first thing that I would check. Are you getting too much or not enough current to the focus coil?

jr
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  #45  
Old 10-26-2017, 09:07 AM
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bandersen bandersen is offline
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Quote:
Originally Posted by MadMan View Post
...So what you're saying is... I did it right without even knowing what I was doing? Score!

Also I have no way of knowing which direction the magnet is supposed to be, other than the way that I found it. It has no arrow.
Black to the base - it's on backwards. Also the linearity and width slugs have a very subtle effect and are meant for really fine tuning the picture.
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