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 Post subject: Re: Heathkit FM4
PostPosted: Mar Wed 28, 2018 1:25 am 
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Pbpix wrote:
john8750 wrote:


Easy answers to your questions.
I was $1 short of the minimum order of 20 bucks. The higher voltage has a bigger size. All caps on the FM4 are radial. Axials would look weird in a place where radials were meant to be.

I only saw axials under there with a bunch of ceramic discs... no radial e-caps.
I don't think radial e-caps were even invented back then.

"look funny" to whom?
Is it going into a museum where the visitors get to unscrew the bottom. And are these people old enough to realize that only axial caps were available back then?... and would these museum visitors really care?
Even if it stays in your home, who's going to tear off the bottom and tell you your caps are not period-correct? lol



Just in case the Smithsonian wants it in the museum, we're good to go.

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Wed 28, 2018 10:17 pm 
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john8750 wrote:
Pbpix wrote:
john8750 wrote:


Easy answers to your questions.
I was $1 short of the minimum order of 20 bucks. The higher voltage has a bigger size. All caps on the FM4 are radial. Axials would look weird in a place where radials were meant to be.

I only saw axials under there with a bunch of ceramic discs... no radial e-caps.
I don't think radial e-caps were even invented back then.

"look funny" to whom?
Is it going into a museum where the visitors get to unscrew the bottom. And are these people old enough to realize that only axial caps were available back then?... and would these museum visitors really care?
Even if it stays in your home, who's going to tear off the bottom and tell you your caps are not period-correct? lol



Just in case the Smithsonian wants it in the museum, we're good to go.


Plus, it's yours to do with however it makes you happy.

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Wed 28, 2018 10:22 pm 
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Don Cavey wrote:

Plus, it's yours to do with however it makes you happy.

Careful... John likes those hillbilly capacitors too... :-)

Image

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Wed 28, 2018 10:36 pm 
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Yeah, what Don said-----------------------Peter the teaser :lol:

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Wed 28, 2018 10:56 pm 
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john8750 wrote:
Yeah, what Don said-----------------------Peter the teaser :lol:

Oh, you hit the nail straight on the head. I get it too...

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Wed 28, 2018 10:58 pm 
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Pbpix wrote:
Don Cavey wrote:

Plus, it's yours to do with however it makes you happy.

Careful... John likes those hillbilly capacitors too... :-)

Image

Shotgun method??? :mrgreen:

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Thu 29, 2018 1:12 am 
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Got the caps changed.
Attachment:
20180328_154653.jpg
20180328_154653.jpg [ 137.78 KiB | Viewed 1508 times ]

Here are the old ones.
Attachment:
20180328_160346.jpg
20180328_160346.jpg [ 130.01 KiB | Viewed 1508 times ]

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Thu 29, 2018 5:49 am 
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I'll bet you forgot to measure all those carbon resistors.

They tend to drift high over the years.
You'll have to lift one end to get the accurate measurements.
If they drifted more than 10 or 20 % they are going to drift further with time.
Probably just as good to replace them with the nice new metal film type.

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Thu 29, 2018 6:10 am 
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I would rather go on with other things first. Like a good cleaning, oil and adjust the dial mechanism, tighten up all the hardware, check the solder joints. After a powered test, if I have a problem, then look further into the tubes, resistors.
The wiring looks good so far. Just dirty.

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Thu 29, 2018 9:32 am 
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john8750 wrote:
I would rather go on with other things first. Like a good cleaning, oil and adjust the dial mechanism, tighten up all the hardware, check the solder joints. After a powered test, if I have a problem, then look further into the tubes, resistors.
The wiring looks good so far. Just dirty.

Well... if nothing else.... at least lift one or two and measure them. If they are close then it's ok to not worry maybe. Remember this is a radio receiver and the oscillator and RF amp section are very sensitive to proper resistor values!
And to not even measure them isn't what most hillbillies call SCHMART.
Trust me... most carbon comp resistors do drift high.. a lot.

A few brands do hold up... but most don't.

Replacing caps because you know they aren't good after all these years... is no different for carbon resistors.

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Thu 29, 2018 4:40 pm 
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I measured several resistors in the FM4 I recently refurbished, all I could without
desoldering one or opening up the tuner.

The only ones that really matter are the cathode resistors R1 and R8,
the balance of R13 versus R14, the two filter-dropper resistors R27 and R28,
and R18 the de-emphasis network resistor.
Dropper, decoupling, or grid return resistors could be 25% off in a thing like this and not matter.
But in fact every single one was well in tolerance.

I was going to restuff the huge cap on top of the chassis, for cosmetics, but realized that
I could leave it there, solder the + end under the chassis to ground just to hold it on, and
replace it with a nice small modern radial one under the chassis.


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 Post subject: Re: Heathkit FM4
PostPosted: Mar Thu 29, 2018 9:53 pm 
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I will check the cathode resistors and the power supply resistors. I want to preserve as much 'vintage' as possible.
I like the idea of the fake 100uf on top. What about the 10uf on top? I am a gonna replace them and install the new ones like you did, great idea......

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Thu 29, 2018 10:18 pm 
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john8750 wrote:
I want to preserve as much 'vintage' as possible.

Sure... that's nice... as long as yer "vintage stuff" is still in spec... lol right?

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Thu 29, 2018 11:39 pm 
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Pbpix wrote:
john8750 wrote:
I want to preserve as much 'vintage' as possible.

Sure... that's nice... as long as yer "vintage stuff" is still in spec... lol right?




Of course. I like the idea of showin off the old stuff on top. No one needs to see the bottom anyway, except'n my.

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Fri 30, 2018 11:07 pm 
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Looks like someone broke the dial string, and tied a knot in the middle of it. Now it makes a bump as the dial is turned. The tuner, knob, and indicator is all out of whack. I will look for some dial string. I had some, but where is it now?

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Fri 30, 2018 11:21 pm 
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john8750 wrote:
Looks like someone broke the dial string, and tied a knot in the middle of it. Now it makes a bump as the dial is turned. The tuner, knob, and indicator is all out of whack. I will look for some dial string. I had some, but where is it now?

Here John:
http://www.radiodaze.com/dial-cord/
Radio Daze has lots of everything for antique radios
you can also use black nylon fishing line... and other places sell this stuff.

https://antiqueradiosandparts.com/Dial%20Cord

https://www.ebay.com/itm/12-Ft-Radio-Di ... 1296438162

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Sat 31, 2018 12:01 am 
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Thanks Peter. The next thing I was gonna do, look for the dial strange.
https://www.ebay.com/itm/12-Ft-Radio-Di ... 1296438162

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Sat 31, 2018 12:54 am 
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john8750 wrote:
Thanks Peter. The next thing I was gonna do, look for the dial strange.
https://www.ebay.com/itm/12-Ft-Radio-Di ... 1296438162

strange string? :mrgreen:

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Sat 31, 2018 6:35 am 
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Pbpix wrote:
john8750 wrote:
Thanks Peter. The next thing I was gonna do, look for the dial strange.
https://www.ebay.com/itm/12-Ft-Radio-Di ... 1296438162

strange string? :mrgreen:




Well, make up your mind :lol:

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 Post subject: Re: Heathkit FM4
PostPosted: Mar Sat 31, 2018 6:44 am 
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I tightened up a lot of screws and nuts. The chassis is already kinda clean for being so old. Just dust. Some rust in the tuner area, especially the tube shield. But I see that on all the FM4's. The wiring looked like some insulation was old and brittle. But it was just some dust coating and cleaned off easily. After I establish a good B+ and filaments, I will change to the FW rectifier. Will that increase the B+ voltage much?

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