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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Jan Wed 06, 2021 9:50 pm 
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Joined: Jul Mon 01, 2019 4:42 pm
Posts: 994
Location: St. Louis, MO
Huh. I tried that 50 ohm terminator straight into channel 1, but I noticed there was no difference between having that 50 ohm terminator plugged in or not. The waveform was noisy either way.

So I tried something. Here's all 4 channels with nothing plugged in, all channels on 1X, vertical zoomed in as far as it will go, horizontal stretched as wide as possible, stats for channel 1 since it looks BARELY worse.

So what's the verdict?


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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Jan Thu 07, 2021 2:21 am 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 3509
Location: Dallas, TX
Well seems like the noise is internal and since it is the nearly the same for all the channels.
I've used digital scopes in the past at work but I don't remember whether they acted like this.
I don't want to disrespect your scope but it doesn't seem to me that it should do this.
You would need to talk to other owners of this scope to see if this one is not working right or all
those models work this way.
I have heard somewhere that digital scopes designers didn't always do a good job with the analog
input circuits.

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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Mar Wed 24, 2021 1:07 am 
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Joined: Jul Mon 01, 2019 4:42 pm
Posts: 994
Location: St. Louis, MO
Well, I finally got around to installing that 39.75 MHz NOS crystal and it's DOA. I tried it in both the 39.75 marker circuit and an neighboring circuit that I was sure worked and I get no output from it.

So what are my options? I'm looking at this very old card that it came on and it does have a lifetime warranty, and CTS Knights Inc is still in business...

https://worldradiohistory.com/hd2/IDX-C ... e-0080.pdf
https://www.ctscorp.com/products/freque ... -products/


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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Mar Wed 24, 2021 1:46 am 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 3509
Location: Dallas, TX
Well you don't know for sure it is not meant to oscillate at 50.45 MHz. Maybe the circuit can't run that fast.

You could try contacting them, but I don't think they will honor that guarantee. You didn't buy it from one of there distributors and the company may have gone through some changes, they probably sold it to someone many years ago. Also if you soldered it in that would probably void the guarantee.

You don't know if it is your oscillator circuit that failed. Is the oscillator getting power?

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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Mar Wed 24, 2021 2:50 am 
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Joined: Jul Mon 01, 2019 4:42 pm
Posts: 994
Location: St. Louis, MO
It is. The transistor for this marker passes the voltage tests for both of the two settings in the manual. I can also borrow a crystal from a known-working marker circuit and the 39.75 marker will come alive again. Likewise, putting this DOA crystal in a known working marker circuit will kill it.


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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Sep Sat 04, 2021 7:35 pm 
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Joined: Jul Mon 01, 2019 4:42 pm
Posts: 994
Location: St. Louis, MO
Another 39.75 MHz crystal turned up. It's completely the wrong package, but it has been tested to work, unlike my DOA NOS one. Would this work with soldering some pins to the legs?

https://www.ebay.com/itm/274793247417


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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Sep Sat 04, 2021 8:56 pm 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 3509
Location: Dallas, TX
ZombieElvis wrote:
Another 39.75 MHz crystal turned up. It's completely the wrong package, but it has been tested to work, unlike my DOA NOS one. Would this work with soldering some pins to the legs?

https://www.ebay.com/itm/274793247417

I would not risk melting the solder internally by soldering to the pins.
Salvage some pin receptacles from a tube socket, looks like an octal may work. Solder short wires to the receptacles first.

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It's not the Destination, It's the Journey.


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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Sep Sun 05, 2021 2:12 am 
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Posts: 2116
Location: SW, MI
to me looks like surrounding noise I get with my dig scope. Could be from many sources, lights, pwr supplies everywhere.

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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Oct Thu 21, 2021 9:32 pm 
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Joined: Jul Mon 01, 2019 4:42 pm
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Location: St. Louis, MO
I'm still getting hung up on aligning this thing. According to the Section 12.4.1 in the manual listed in the OP.

I have hooked this thing up to XY mode on my old Eico 470 tube scope like the manual specified. I can see all of the markers now, even 39.75 MHz (that eBay crystal works!) like I'm supposed to. I'm STILL hung up on not getting any voltage output from the output jack. I'm talking about the last 2 paragraphs of section 12.4.1. I built the probe from page 2. The problem I'm having is that when I try to use this probe with my VTVM on its lowest range (1.5V), I get zero voltage from my VTVM. The way I see it, either my probe doesn't work or there's no output from this B&K 415.

So how do I test if this probe works?


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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Oct Thu 21, 2021 11:44 pm 
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Joined: May Thu 14, 2015 4:15 pm
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Location: Dallas, TX
Do you have another generator that puts out a signal in that range with a decent amount of amplitude?

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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Oct Fri 22, 2021 2:54 am 
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Joined: Jul Mon 01, 2019 4:42 pm
Posts: 994
Location: St. Louis, MO
I've got an old Accurate 153 that I restored, the older 4 tube model.


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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Oct Fri 22, 2021 4:41 pm 
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Joined: May Thu 14, 2015 4:15 pm
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Location: Dallas, TX
I don't know much about that generator but it would be worth a try to see if the detector will react to the generator output. Probably will need to set the generator to maximum output. An un-modulated RF signal will show as a DC voltage from the detector. A modulated RF signal should have some audio AC as an output.

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It's not the Destination, It's the Journey.


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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Oct Sat 23, 2021 7:15 am 
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Joined: Jul Mon 01, 2019 4:42 pm
Posts: 994
Location: St. Louis, MO
Notimetolooz wrote:
I don't know much about that generator


The Accurate 153 was rebadged as the Lafayette KT-208 and the Olsen KB-141 if that helps.


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 Post subject: Re: B&K 415 Sweep/Marker Generator
PostPosted: Oct Sat 23, 2021 1:31 pm 
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Joined: May Sat 20, 2017 10:16 pm
Posts: 90
Location: Magnolia Texas
ZombieElvis wrote:
I've got an old Accurate 153 that I restored, the older 4 tube model.

Mr. Carlson's lab just posted a video on youtube about the Accurate 153 signal generator.


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