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Author Topic: Yo................ Vincenzo.......................  (Read 129306 times)
N4NYY
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« Reply #30 on: December 25, 2011, 02:30:07 PM »

Super sweet! FYI, when I get the occasional CB to service that a friend brings over, something these channel selector or SSB switched seem annoyingly dirty. The problem is that they are usually sealed. The Deoxit does not travel well thru sealed containers.

What size filter caps do you need?
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AC5UP
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« Reply #31 on: December 25, 2011, 02:55:05 PM »

Being installed in a car is rough duty. I never saw a crystal go bad before I started tinkering with CB's and the symptoms are so vague that it's not easily diagnosed. Typically the problem on AM is distorted RX audio or with SSB an inability to find any spot on the clarifier that sounds right. Voice pitch and tone might be good but otherwise something is obviously wrong, like the local oscillator is trying to FM. I'll 'scope the three crystals in a PLL rig and typically the 10.240 rock will have low or distorted output. Haven't tinkered with a CB in a while so I'm going on memory for that...........

As for an electrolytic for the Emud, it's dual section Valvo twist-lok type in a long thin can that I know can't be matched with a current part. 50 / 50 @ 350 vdc and I have plenty of pieces in the junque pile that should be close enough. Funny thing about the Emud, it's a nice little radio that I like but a real PITA to work on. Chassis layout is tight and it was built in layers. Someday I should give it a full rebuild as the tube sockets are about as crappy as any I've seen.
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N4NYY
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« Reply #32 on: December 25, 2011, 03:01:02 PM »

I got 47uf/350 if you need them. And yes, I have seen long dormant CBs here that the 10.240 was way off. I have a stash of scrap chassis for no other reason than the 10.240 crystal.
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AC5UP
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« Reply #33 on: December 28, 2011, 05:40:25 PM »

Who needs a Heathshkit when you could have one of these !!!!!!!!!!!

http://www.shopgoodwill.com/viewItem.asp?ItemID=9151795

http://www.shopgoodwill.com/viewItem.asp?ItemID=9151484

Looks like an original Vintrola to me............  Tongue
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N4NYY
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« Reply #34 on: December 28, 2011, 06:25:57 PM »

Nelson,

A friend of mine was asking for a 12BY7 driver. I have 12BY7A. Google shows that the A has a filament saver. But I would rather as you. Are they interchangeable? I have a few and will just give it to him.

BTW, those radios were fugly !
« Last Edit: December 28, 2011, 06:28:34 PM by N4NYY » Logged
AC5UP
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« Reply #35 on: December 29, 2011, 02:34:56 PM »

Google shows that the A has a filament saver.

The Google is telling you stories... Never heard of a filament saver version of a tube but maybe that means I need to get out more. (?)

Some tubes have precision heaters that are supposed to come up in 10-15 seconds, but according to http://www.nj7p.org/Tube4.php?tube=12BY7A the 'BY7 and 'BY7A versions are identical in terms of 6.3 volts @ .6 maps or 12.6 volts @ .3 amps. Both show a center tapped filament and both use the same pins for the filament.

I see no reason why a 12BY7A can't sub for a non-A. Plus, if it's going into anything Heathshkit a new tube is way too good for the radio anyway.......... Grin
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N4NYY
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« Reply #36 on: December 29, 2011, 02:45:32 PM »

Quote
I see no reason why a 12BY7A can't sub for a non-A. Plus, if it's going into anything Heathshkit a new tube is way too good for the radio anyway.......... Grin

I think it is a driver tube for a Tram D201A. My friend got a hold of one. I told him they were a piece of junk and to sell it. I have never seen a consumer grade piece of electronics, that after normal usage, looks like it was thrown into a fireplace (no joke). But the tube is not doing anything here, so I might as well let him have it.

BTW, I am working on a Philco B-570. This was on one leg of the volume pot, with the other leg going to chassis ground. The schematic only shows a .1uf cap. However, this does not jive with color codes. It does not measure resistance. The cap meter only measure a hint of capacitance.

Bands are left to right: black, brown, black, brown, white. Any ideas?

http://i224.photobucket.com/albums/dd78/yankees_1996/IMG_2195.jpg

BTW, I had a productive week off. I finished my IM-13 VTVM, my E-200D RF generator (Iggy is on ebay as we speak), and I am working on the Philco B-570 and F-817 Edsel. I am actually making progress now. I also am going to install an antenna grounding panel outside my house, since I never did this.
« Last Edit: December 29, 2011, 02:56:41 PM by N4NYY » Logged
AC5UP
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« Reply #37 on: December 29, 2011, 07:19:19 PM »

http://www.tpub.com/neets/book2/32NE0179.GIF

The way I read it you're looking at an axial lead ceramic marked as "10" with a multiplier of 1. Like...... 10 mmf........ And if it was installed from the volume control hot side to ground the intent was to take the edge off high pitched noise by reducing the treble response. Tolerance of black = 20%, white temperature coefficient = +120 to -750. It's a cheap ceramic that's more than adequate for the intended purpose.
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N4NYY
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« Reply #38 on: December 29, 2011, 07:27:54 PM »

Quote
The way I read it you're looking at an axial lead ceramic marked as "10" with a multiplier of 1. Like...... 10 mmf........ And if it was installed from the volume control hot side to ground the intent was to take the edge off high pitched noise by reducing the treble response. Tolerance of black = 20%, white temperature coefficient = +120 to -750. It's a cheap ceramic that's more than adequate for the intended purpose.

Dammit. I replaced it. Still, it did not measure .1uf on the Extech. It barely measure about the capacitance of the leads.
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AC5UP
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« Reply #39 on: December 29, 2011, 07:40:12 PM »

If it's what I think it is............ A .1 mf condenser as a substitute will make the audio very, very muffled. Like, nothing above 1kc or less.

If you don't have a 10 mmf part on hand, any small value ceramic or silver mica will be close enough, like a 68 or 100 mike-mike.
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N4NYY
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« Reply #40 on: December 29, 2011, 08:04:59 PM »

I put a .1uf polypropylene. Seems to sound great with it. Anyway, I need to find a small orbital buffer/polisher, to use the Novus 2 and 3 and get these scratches out. Something that has like a 2" pad.
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AC5UP
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« Reply #41 on: December 30, 2011, 05:57:55 AM »

We could be talking about two different condensers that both connect to the hot side of the volume control, or effectively so with one on the potentiometer itself while the other is on the AF output of the detector... Same circuit, but the larger of the two is a DC block from the detector to the 1st audio grid and typically .01 mf or .022 mf. A larger value like a .1 will improve the bass response but IMHO that's overkill. Not that much deep bass on an AM radio to begin with and a 4" to 5" speaker won't reproduce it well.

The second condenser, as mentioned previously, would be in parallel with the detector AF output and is a small value intended to reduce noise. On high end and Hi-Fi AM tuners like a Fisher or Scott from the day you might see a 10 kc whistle filter in the 1st audio section. A stagger-tuned wide IF sounds better than a narrow one, but at night when there's a signal on every allocation a 10 kc heterodyne whistle might be heard on some stations. The fix for that was a 10 kc tuned LC notch filter (at best) or a small value condenser across the AF line.

Seems like I recall .001 mf was popular as the whistle / noise filter condenser.................. (?)
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N4NYY
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« Reply #42 on: December 30, 2011, 08:24:42 AM »

http://www.nostalgiaair.org/PagesByModel/933/M0013933.pdf

I think the problem is that I may have a slightly newer rev radio. My radio is slightly different in PCB layout and version. I think my version is a 124, while this version is a 121. I cannot see any other component that is connected to both chassis and the leg of the pot.

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AC5UP
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« Reply #43 on: December 30, 2011, 10:40:38 AM »

Just for grins I pulled up the 1954 edition of Beitman's Most Often Needed and found the exact same schematic on page 80. Beitman mentions the known variants on the radio and how they are essentially similar, but the published schematic covers only the root version of that model. Apparently mutant models did not merit a schematic addendum until Philco declared a new model and then re-started the process on the new set.

From what you're describing the schematic does not match your radio. The closest thing on the paper to a 10-mike-mike tubular ceramic is the 7.5 mmf drift compensation condenser across the oscillator coil and not even you could confuse a coil with a volume control....... Even though I know you'd try. If the ceramic condenser you photographed was in fact a 10% 10 meg resistor it was way too large and it's unlikely the blue or green band would fade to brown, so I don't see that as an answer.

If the radio plays the radio plays and that's the goal of this exercise, but it makes no sense to me how you could swap a 10 mmf part with .1 mf condenser and hear NO difference at all. Even if the condenser was simply (RF) grounding an IF coil winding something like that should detune the crap out of something....
« Last Edit: December 30, 2011, 10:50:12 AM by AC5UP » Logged

Never change a password on a Friday                
N4NYY
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Posts: 4742




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« Reply #44 on: December 30, 2011, 02:04:01 PM »

Well, there is only one thing to do. Try the 10 mmf and see if there is a difference. I have to see if I have anything close to that in 400V. The parts list says it is a B- to chassis. I saw the drift compensation cap, and it is definitely a cap, and looks like a Mica.
« Last Edit: December 30, 2011, 02:09:20 PM by N4NYY » Logged
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