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Old 11th Dec 2008, 2:37 pm   #1
georgesgiralt
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Default Could you help me finding the correct plug ?

Hi !
I own an IG102 Heathkit signal generator.
It was roiginally fitted with two chassis plugs one for the output signal the other one to feed a LF signal for modulation. The RF one has been replaced by a BNC plug.
I would like to get a couple of the original plugs, one for the chassis the other one for the cable in order to get my piece of kit a pristine look.
Do you have any clues of the make and model of these plugs ?
Thanks a lot in advance for your help !
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Old 11th Dec 2008, 3:14 pm   #2
Skywave
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Arrow Re: Could you help me finding the correct plug ?

Your picture shows a "UHF" / PL259 plug. There are various designs on this format - for example, yours shows a spring cable relief. The matching socket is called a SO239. These plugs / sockets were always popular with USA-designed equipment aimed at the Amateur market; Heathkit (= UK) being a subsidiary of the USA manufacturer (= Daystrom).

Original plug manufacturer could have been one of many: I suspect a Japanese source. 'Amphenol' is a remote possibility: would have too expensive for this product.

HTH

Al / Skywave

Last edited by Skywave; 11th Dec 2008 at 3:22 pm. Reason: General tidy to avoid confusion
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Old 11th Dec 2008, 3:15 pm   #3
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Default Re: Could you help me finding the correct plug ?

Would a TNC plug fit the original socket?

http://www.twenga.co.uk/offer/46111/...475742600.html
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Old 11th Dec 2008, 4:33 pm   #4
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Default Re: Could you help me finding the correct plug ?

I'm not so sure that this is a UHF plug. They talk about cutting off the excess of the centre conductor and the picture looks to me as if there is no pin on the centre conductor. I wonder if this is the sort of plug that Heathkit used for the microphone input on things like the HW30. The spring is also similar to that used on that connector. Probably get one from the USA. I have a feeling that mine is long gone and anyway I would only have the free mating part. The centre conductor of each part is not a pin or socket but the soldered centres touch when the two parts are mated. Pretty basic connector but fine for audio, not sure about RF though.


Ian
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Old 11th Dec 2008, 4:44 pm   #5
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Default Re: Could you help me finding the correct plug ?

Can you give us an idea of size please Georges? TNC is a threaded form of BNC.
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Old 11th Dec 2008, 4:50 pm   #6
georgesgiralt
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Default Re: Could you help me finding the correct plug ?

Hi !
I enclosed an image cut from the kit assembly manual to show that there is no center pin on the "male" connector.
The female plug has no pin. connection suppose that the solder on either is big enough to make contact.
I've no UHF male plug to see if it fit the socket remaining (as I will have to cut the centre pin vendors are reluctant to lend me one ....)
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Old 11th Dec 2008, 5:10 pm   #7
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Default Re: Could you help me finding the correct plug ?

These are US Microphone Connectors. Still available, but at a price:-

http://www.oaktreevintage.com/Vintag...one_Cables.htm

http://www.oaktreeent.com/web_photos..._cable_web.jpg

They certainly look like a PL259 minus the centre pin. With some (most?) PL259 plugs the outer internally threaded portion can be removed by screwing it towards the cable end. This would enable it to be tried on a socket without damaging the centre pin.
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Old 11th Dec 2008, 6:39 pm   #8
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Default Re: Could you help me finding the correct plug ?

Taking a look at the links, the correct connector would seem to be a 2501F for the connector on the cable and 2501MP for the panel mounting part. They are made by Switchcraft.

See: (It's quite a big file)

http://www.switchcraft.com/catalog/switchcraft_pab6.pdf

These can be purchased at Digikey for $3.07 for the 2501MP and $4.95 for the 2501F.

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Old 11th Dec 2008, 7:06 pm   #9
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Default Re: Could you help me finding the correct plug ?

These are, indeed, US microphone connectors, also known as Amphenol 75.
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They were commonly used on early Heathkit USA signal generators and other test equipment. However, Heathkit UK and, later, Heathkit USA, both used BNC connectors, almost certainly for reasons of reliability. The Amphenol 75 was, IMHO, never reliable, even as a mere microphone connector, relying as it did on an end-to-end, solder-blob to solder-blob interface. Any minute slackness in the retaining thread resulted in an intermittent connection. It must have been a great relief to roadies when the microphone manufacturers dropped it in favour of the immensely more reliable and noise immune (i.e. balanced) XLR connectors - but I digress.

All my Heathkit gear, including my IG-102, has been upgraded to BNC connectors, which fit very neatly in the same panel hole as the Amphenol 75 and are, IMO, authentic, as they were used by Heathkit themselves in the majority of later test gear products.

Edward
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Old 11th Dec 2008, 7:47 pm   #10
georgesgiralt
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Default Re: Could you help me finding the correct plug ?

Guys, you're amazing!
I get the answer, the comment and the cure on the same thread !
What a community !
Thanks !
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Old 11th Dec 2008, 9:09 pm   #11
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Red face Re: Could you help me finding the correct plug ?

Quote:
Originally Posted by Skywave View Post
Your picture shows a "UHF" / PL259 plug.

Al / Skywave
Ok - I was wrong!

I doff my hat to those more knowledgeable than I on this! I've never seen or heard of this connector, now accurately described & determined.

You learn something useful on every visit here!

Al.
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Old 17th Dec 2008, 4:21 pm   #12
georgesgiralt
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Default Re: Could you help me finding the correct plug ?

Hi !
I've just got an RCA SeniorVolthomyst (also known as Vizz SeniorVoltOhmyst) VTVM. It has the very same Amphenol 75 plug.
So it seems that they where pretty standard stuff in the US back in the late 60's early 70's...
When I searched for a VTVM with a large display, I saw pictures of the B&K 177 (which looks like a copy of the RCA) and it seems to have also the same plug.
This may serve others using Google or the like ;-)
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Old 21st Dec 2008, 3:07 pm   #13
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Default Re: Could you help me finding the correct plug ?

Yes this forum is a great source of knowledge. This particular topic did actually come up some time as I'd had the same problem with a heathkit IG-37. I did fit BNC connectors in place of the originals. I am clearly in good company.

I have fitted BNC connectors in place of the tv type coax connectors on a couple of British Heathkit signal generators. This is an easily reversible modification which is convenient as most of my other test kit has bnc connectors.

https://www.vintage-radio.net/forum/...light=heathkit

Edward
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