Need a Schematic for: NEWCOMB Model: B-100A AM Radio

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Janitor Tzap
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Need a Schematic for: NEWCOMB Model: B-100A AM Radio

Post by Janitor Tzap » Wed Sep 28, 2016 8:03 pm

I just got this dropped into my lap.

Full of mouse turd's, seeds, and shredded paper.
Unfortunately for me, the paper was the schematic that had been pasted to the inside of the cabinet. :cry:
I've looked online for the schematic, but none of the ones I have found look exactly like it.

From what little information I could find.
These were made for the Government, and School Agencies.

In my bench checking of the power transformers, I found one with an open primary. :(
I have no idea where to even look for parts for this. :?

If the date codes on the components are right.
The parts are 50+ years old. :(

HELP!


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dyarker
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Re: Need a Schematic for: NEWCOMB Model: B-100A AM Radio

Post by dyarker » Thu Sep 29, 2016 4:45 am

Is this -
http://robert.guildig.org/2013/07/newco ... atics.html
one of the ones that don't look quite the same?

Even if case is a bit different, schematics are probably close.

If this is the one, I only see one power transformer. The other is the speaker impedence matching transformer. Which has the open coil?

Cheers,
Dale Y

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Re: Need a Schematic for: NEWCOMB Model: B-100A AM Radio

Post by haklesup » Thu Sep 29, 2016 10:43 am

Parts to restore it authentically will be hard to find but modern equivalent components in the values you need probably do exist if all you want to do is get it working.

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Re: Need a Schematic for: NEWCOMB Model: B-100A AM Radio

Post by Janitor Tzap » Thu Sep 29, 2016 12:41 pm

dyarker,

I looked at those two Radio's you linked too.
http://robert.guildig.org/2013/07/newco ... atics.html
Nope, the inner guts of this one are different.
haklesup wrote:Parts to restore it authentically will be hard to find but modern equivalent components in the values you need probably do exist if all you want to do is get it working.
Yeah,
Most of the components I can get newer replacements.
But that transformer with the open winding is going to be tough to replace. :(


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Re: Need a Schematic for: NEWCOMB Model: B-100A AM Radio

Post by haklesup » Fri Sep 30, 2016 11:58 am

if its the speaker matching xformer then its probably 15K to 8 ohms, they were common enough in tube sets so you have a decent chance of finding one. IN any case, the values were often stamped on the component. I see Digikey has a range of "Audio transformers" that will probably have a match.

Good luck finding a tube if you need one, these are getting expensive as they move into the antique restoration market

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Re: Need a Schematic for: NEWCOMB Model: B-100A AM Radio

Post by Janitor Tzap » Fri Sep 30, 2016 1:39 pm

haklesup wrote:if its the speaker matching xformer then its probably 15K to 8 ohms, they were common enough in tube sets so you have a decent chance of finding one. IN any case, the values were often stamped on the component. I see Digikey has a range of "Audio transformers" that will probably have a match.

Good luck finding a tube if you need one, these are getting expensive as they move into the antique restoration market
Actually, I can find the tubes rather easily.
One of the older ham's was selling out his tubes at fairly decent prices. :wink:
Only, I haven't got a Tube Tester.
All I can do is check the filament, or heater to see if it is open. :(

But as for that transformer.........
I think your right, that it is for the Speaker.
Replacing it still isn't going to easy.
There are no markings on it, except for {TR-134 and a in house number}.
Plus, I don't know who thought it was a good idea to spot weld it to the chassis,
but that is exactly what they did!
This picture has the transformer mounted the same way. :roll:
Image
It is all point-to-point wiring, and a lot of the wires have no insulation.

I had a talk with a friend at the Pavek Radio/TV Museum.
He couldn't find a schematic for it.
But he thought it was a waste of time to even mess with it.
Since it was just a junky AM Radio.

I'll have a talk with the customer, and see what he wants to do with it.


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Re: Need a Schematic for: NEWCOMB Model: B-100A AM Radio

Post by jwax » Thu Oct 06, 2016 6:59 am

If that is a 6V6 audio output tube, a 5,000:3.2 ohm output transformer will be fine.
Break out a drill to remove the spot welds, and insert screws/nuts to mount the new transformer.

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Re: Need a Schematic for: NEWCOMB Model: B-100A AM Radio

Post by Janitor Tzap » Thu Oct 06, 2016 9:06 am

UPDATE:

I found an exact replacement transformer {NOS}.
Only at about hundred dollars. :shock:

I couldn't find a Tube Tester I could borrow.
I contacted some of the local Ham's, but they had dumped their old Tube Testers years ago. :(
The Pavek Radio/TV Museum has a Tube Tester, only its 100 miles way from me. :(

I checked what the radio was worth if it was working.
It was appraised at $125.00 in excellent working condition, and cabinet.
{Here's a picture of a not so nice one.} :wink:
Image
I then had a long talk with the owner of this radio.
He decided it was going to cost more to get it running again, then what it was worth.

So, he took it back.


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Re: Need a Schematic for: NEWCOMB Model: B-100A AM Radio

Post by jwax » Thu Oct 06, 2016 1:00 pm

I'd go for the fix with this:
http://www.ebay.com/itm/OT8SE-Single-En ... 1625341933

Better than trashing it.

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Re: Need a Schematic for: NEWCOMB Model: B-100A AM Radio

Post by Edd » Mon Oct 17, 2016 11:56 pm

.


Sir Janitor Tzap . . . . . . .

( and frankly . . . . I think that YOU are noteworthy of more muuuuuuultiple T's Z's or A's . . .all being in accordance to how long the electrical arc is ! )

How long has it been . . . . .well long enough that I totally forgot my Four-rum password . . . . and then had to crawl in thru a rear window.

If that is the bottom chassis of that radio of the mans . . .and not another copied photo . . . .that is being one CLEAN chassis for its vintage
of circa 1956.
Considering that he can handle the units outwardly appearance aesthetics . . .the radio chassis should be an easy fix.

What I am a seein':


That is being a PREMIUM chassis for that time era with it including a frontal RF amplifier stage, provisions for phono input, a tone control and having
a bit larger speaker . . .cone and magnet . . . . than was then the norm.
( However, its showing a powdery cadmium oxide coating . . .and its shedding. . . . .cosmetically . . . . . . just like some of my OLD machine screws and nuts)

If you had the tube filaments all lighting up, I feel that its only need is that open primary audio output transformer being replaced.
The volume control cleaned , the large canned filter replaced with new tubular units IF it is presently causing any 120~ humming.
The one capacitor that is inherently bad is the coupling capacitor between the plate of the 6AV6 and the 6V6, which just happens
to have used a trouble free disc ceramic in this situation.
What you are basically now wanting is an output transformer installed . . .at no cost . . . to evaluate the set.
That is possible if you go thru all of your wall warts and find one of a 5, 6 or 9VAC output.
( In my area I can buy one of those for a buck a pop at thrift stores / flea markets.)
(Be sure that it is not a 95-240VAC input switchmode unit, which would all be DC output)
(If only finding transformered DC output models, that will involve getting in the case for AC winding access and diode /capacitor disconnects. )
The blades of the wall wart go to clip leads connected to the screen and plate of the 6V6, while its AC secondary feeds to the speaker, after one
lead of the old output transformer secondary is lifted.
I fully believe that you will then have a talking radio for evaluation purposes.
I know, and can tell you of several of that needed transformer, now available in the realistic $4-6-8 range.
It is a nominal 5K primary to 4 ohm secondary impedance.
FACTOID:
If you mismatch in using a slightly higher impedance . . . . its effect . . . the overall bass response will increase.
If you mismatch in using a slightly lower impedance . . . . its effect . . . the overall treble response will increase.

Sooooooooo . . . if you want to get in contact with that owner for repricing again, there won't need to be
anothers outrageous transformer scalping involved.
( Reminds me of E-bay where some ( multiple string of 12 diminutizing cursewords ) person had multi-paged ALL of his small COMPONENTS
at PER unit prices of either $9.95 - - - - - -$19.95 - - - - - -$29.95 . . . . . . .with FREE shipping.)

Thaassssit . . .

Le Schematique:


Image



FIO . . . .
The schemas abraded portion of the value of the plate load resistor of the 6AV6 is 270K and they have a 4.7 meg resistor used for its 1st grid
vice the ?18? listed on the sheet, with a 10 meg being another viable value, if being operated on up in its starved plate current mode.




73's de Edd



.

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Re: Need a Schematic for: NEWCOMB Model: B-100A AM Radio

Post by Janitor Tzap » Tue Oct 18, 2016 6:08 pm

Edd,

Nice too hear from you. :grin:

Well.......
The Chassis Picture is of a different model NEWCOMB.
But, it has most of the same components as the one I was working on.
Only........
The one I had on my bench, had a RCA jack on the back, and a External Speaker/Headphone jack.
The RCA Jack was for connecting to another Amplifier, or Tape Recorder.

This Picture is what it looked like.
Image
Though it wasn't missing the Vol/Tone Knobs, and wasn't missing chunks out of its cabinet.
And it had ugly yellow X's painted on it.
:roll:

Well, the owner decided it wasn't worth sinking a lot money in to it.

Because, besides the Audio Output Transformer that needed to be replaced.
The Speaker Cone was full of holes, thus it was in need of patching.
The AC Cord was completely shot, the plastic was crumbling off of it, exposing the bare wires.
The Large Can Filter Capacitor had one bad section in it.
Plus, all the bare wires on the underside of the chassis that needed to be insulated.
{Did I forget to mention the burnt mouse fur on some wires.} :roll:


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Re: Need a Schematic for: NEWCOMB Model: B-100A AM Radio

Post by haklesup » Fri Oct 28, 2016 4:39 pm

"The Chassis Picture is of a different model NEWCOMB."

The one in the picture looks like crap, restoring that cabinet would be just as tedious as the chassis. Owner should either sell it to another collector or treasure the arrested decay state it is in

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Re: Need a Schematic for: NEWCOMB Model: B-100A AM Radio

Post by Janitor Tzap » Tue Nov 01, 2016 6:06 pm

haklesup wrote:The one in the picture looks like crap, restoring that cabinet would be just as tedious as the chassis.
Yeah,
The cabinet is that first generation press board, with a combination of a glued on wood veneer and fabric on the outside.
I don't know how you could get the paint off it without ruining the veneer, fabric or the press board.
haklesup wrote:Owner should either sell it to another collector or treasure the arrested decay state it is in.
I suggested he should sell it.
But he said he was going to try and get the paint off of it himself, and if it turned out fairly good.
He'd just make it a shelf piece.


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Re: Need a Schematic for: NEWCOMB Model: B-100A AM Radio

Post by Lenp » Sun Nov 06, 2016 1:12 am

Do not junk it!
You can sell it as a prop if they ever remake 'Sanford and Son' or the British version, 'Steptoe and Son'! :idea:
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

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