UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > Components and Circuits

Notices

Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

Closed Thread
 
Thread Tools
Old 14th Oct 2015, 11:37 pm   #21
Biggles
Rest in Peace
 
Join Date: Feb 2004
Location: Hexham, Northumberland, UK.
Posts: 2,234
Default Re: What type connector?

Personally I would avoid trying to desolder the original socket from the board due to the risk of damaging it (for me anyway) particularly as there is a fair amount of metal to heat up and the board may be multi layer just to add further complications.
Alan.
Biggles is offline  
Old 15th Oct 2015, 8:39 am   #22
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,801
Default Re: What type connector?

I solder these sorts of connectors quite frequently, usually on multilayer boards. Both SMT and through-hole varieties. I use two soldering irons. One with a good blob of solder on the top of the body to heat the whole metal body and thence the four outer pins, the other iron on the underside of the board to get the centre pin.

Do this with the board inverted, so the 'underside' is on top and the thing just falls out.

Some of the boards are PTFE based dielectrics for GHz use, and copper adhesion is a lot less than on FR4... still no difficulty.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 15th Oct 2015, 1:43 pm   #23
greenstar
Octode
 
greenstar's Avatar
 
Join Date: Jul 2011
Location: Leicester, Leics. UK.
Posts: 1,681
Default Re: What type connector?

Well, fingers crossed. I have a massive old (electric) iron that will heat it up quickly.
Any thoughts as to suitable diodes would be helpful - I should think they would need a decent working voltage and not be the tiny glass ones.
Tony
greenstar is offline  
Old 15th Oct 2015, 2:07 pm   #24
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,801
Default Re: What type connector?

Low voltage diodes are fine. They're back to back in parallel, so the clamp the signal at +/- 0.7-ish volts. If one ever sees more than this, it or its partner has blown up.

1N914 or 1N4148 will do... the scope probe is going to add at least a megohm on the way from the valve stuff.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 15th Oct 2015, 2:40 pm   #25
Alistair D
Nonode
 
Alistair D's Avatar
 
Join Date: Jan 2010
Location: Edinburgh, UK.
Posts: 2,008
Default Re: What type of connector is this?

The only drawback of the back to back diodes is that if there is any DC on the signal you are measuring it will be shorted out. It would be worth connecting a 0.1uF 400V capacitor in series with the inner of your co-ax on the probe side of the diodes.

Al
__________________
I won't tell you how I discovered that.
Alistair D is offline  
Old 15th Oct 2015, 7:03 pm   #26
Techman
Dekatron
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 4,985
Default Re: What type of connector is this?

I’ve just been looking at the one that I have and have taken some pictures showing the unit and also a way of easily checking a ‘spot’ frequency to set its accuracy. It’s a shame the starter of the original thread linked to didn’t come back to let everyone know what connection he found to be the correct type, if he ever did.

A cheap CB radio is ideal. These can be had for a fiver and I’ve even seen them offered free in the ‘for sale’ section of this forum, although there were also some folk ‘fishing’ for these too in the ‘wanted section’ a while back.

An elderly neighbour, now sadly passed away, gave me an un-molested CB radio a few years back. He’d used it on his boat years before and although not mint, it has never had the covers off and, strangely, neither have I. If these sets are ‘un-touched’ they generally tend to be spot on frequency, even when well over 30 years old. I have checked this radio and it is in fact ‘on frequency’. There is no licence needed for these now in the UK, so it is quite legal for you to have and use one of these for testing purposes. I believe that it was a legal requirement for these radios that were produced from late 1981, defined by the ‘CB 27/81’ in the circle on the face plate of the radio, to have a ‘low power’ switch. So with the radio set to ‘low power’ ie, 0.5 watts, You could strip the end of a small piece of wire, inserting the stripped end into the small centre hole of the socket on the frequency counter, holding it in place with insulating tape, like the ‘bodge’ I’ve done, shown in the picture. Then bend the other end of the wire back on itself and insert it into the aerial socket of the radio, this is with the insulation still in place. You’re relying on RF capacitive coupling here and using very low transmitting power, so no harm will be done to the counter or the radio. In the picture it shows the connection made into a socket of a ‘watt/SWR meter that was connected via a short coax lead to the socket on the radio for convenience.

The highest frequency on the CB radio is just below 28 MHz and is 27.99125 exactly, and is designated channel 40 on the radio. I think this is quite a good way of checking the ‘spot frequency’ accuracy of the frequency counter and also some say that no radio collection is complete without at least one vintage CB radio, so you could use this as an excuse to have one – and even call it an item of test gear. You may find that a forum member has one in their junk box that they could let you have – they may even check it’s on frequency for you before sending it to you. You can reasonably check that it’s on frequency yourself by connecting it to your own domestic radio aerial and listen to a few ‘locals’ chatting to see if they sound on frequency. There will be the odd transmission that won’t be on frequency, but most will, so take the averages. Also, some radios, like the one shown in a picture below, have a ‘tune’ control on receive that will give you a ‘plus and minus’ setting to tell if the transmission you’re listening to is actually on frequency to your receiving set. Obviously, you shouldn’t try transmitting on your domestic listening aerial on the ‘normal’ 4 watt setting on your radio, as damage to the set could be caused.

As a last note – I probably don’t need to tell you that you should be ‘broad minded’ if you listen to some of the ‘chat’ on these radios, but it’s no different to what you will hear in any town centre pub, or city high street for that matter. The second point is that we need to keep in mind that discussion of actual CB radio, other than in the context of testing a frequency counter, is really ‘off topic’ for this particular thread. I suppose it could also be argued that even discussing the accuracy of the counter is a little ‘off topic’ seeing as the original question was just about the socket and it’s now drifted onto calibration of the counter, which is probably my fault, although certainly needed to be mentioned. One last thought is that it looks like you may have to dismantle the unit in as much as removing the rear circuit board from the front part of the counter to un-solder the socket, although it could be done if you’re very careful with a fine ‘bit’ without removing the rear board. You could just leave the socket in place and solder a ‘co-ax’ to the appropriate place. Be aware that the capacitance of the particular coax you use will have an effect at certain higher frequencies. If you had a radio transmitter working on normal power with a properly matched aerial, you could just wind a short length of the bodged on single piece of wire round the outgoing aerial coax and just use RF coupling for the signal to feed the counter. You could use this type of ‘search coil’ RF coupling method for a lot of the sort of tests you’re likely to do with the counter, anyway.
Attached Thumbnails
Click image for larger version

Name:	P1080349.JPG
Views:	64
Size:	167.7 KB
ID:	114296   Click image for larger version

Name:	P1080352.JPG
Views:	67
Size:	173.1 KB
ID:	114297   Click image for larger version

Name:	P1080353.JPG
Views:	68
Size:	162.8 KB
ID:	114298   Click image for larger version

Name:	P1080354.JPG
Views:	71
Size:	170.0 KB
ID:	114299   Click image for larger version

Name:	P1080356.JPG
Views:	70
Size:	154.9 KB
ID:	114300  

Techman is offline  
Old 16th Oct 2015, 1:38 pm   #27
greenstar
Octode
 
greenstar's Avatar
 
Join Date: Jul 2011
Location: Leicester, Leics. UK.
Posts: 1,681
Default Re: What type of connector is this?

Thanks for all the information. Techman's board is identical to my own so far as I can see. I'll probably leave the socket on as it looks a convenient way to attach to a case - there are no fixing holes - and solder on a bit of coax to connect it the BNC when it arrives. Callibration may come later. If it's off, can it be tweaked?
greenstar is offline  
Old 17th Oct 2015, 11:19 am   #28
turretslug
Dekatron
 
turretslug's Avatar
 
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,385
Default Re: What type of connector is this?

There's every chance that the little yellow trimmer next to the crystal can is for fine setting its frequency, but I'd leave it be unless I was very certain of what I was tweaking it against! At production, it might have been carefully set against an unimpeachable standard, or tweaked to something less good by someone who was expected to do 25 a minute all day, every day.... At the price, probably nearer the latter.

I've recently purchased an LED and a VFD frequency counter modules for money that made me think, I doubt that I could gather the components and PCB together for double that. Stunning. I'm afraid that all the years in the day job made me very averse to LCDs generally, I avoid spending my own money on them if at all possible Each to his own based on experience, I guess. These modules have a trimmer pot for setting a VCXO module but I've left them be as it's only "guidance" purposes that I got them for- workshop SG, receiver LO, that sort of thing, rather than critical usage.
turretslug is offline  
Old 18th Oct 2015, 12:03 am   #29
Techman
Dekatron
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 4,985
Default Re: What type of connector is this?

That’s correct, it is the little yellow trimmer.

It depends on how accurate you want the readings to be. On the one I have, the reading shown of 27.99125 MHz would probably have read something like 27.99113 MHz. As these are capable of reading correctly and as I need it to be spot on, I corrected it by adjustment of the trimmer shown.

The thing about these is that they’re just the ‘innards’ of a frequency counter sold for the ‘home builder’ to use in whatever they’re making, so it’s probably expected to be up to the person buying one of these to do the final calibration. It would be different if you were buying a complete frequency counter built into a case by a named manufacturer, as you would then expect it to be already calibrated.

These are very cheap starting at around £7.50 up to around £15 depending on where you buy them. It could be the actual supplier selling them to the public that does the calibration and the more you pay, the more time is spent on setting them up, but I’m probably wrong. At the price, the setting of the calibration is probably done in a matter of a few seconds set against some dodgy old frequency counter and signal generator and it could even be done by a child for all we know. One of the adverts actually showed one of the units displaying a readout (10 or 20 MHz, or something like that) against a ‘normal’ frequency counter, which didn’t look exactly modern, from what I remember.

It makes me wonder what these were originally made for. Are these made especially for the ‘home brewer’ to build into a case etc. if so, then why fit that socket, or were they made for something else that failed to be produced?

All in all, very good value, and for what most people want, the calibration as received will probably be near enough.

Let us know about the connector when you get it, although I’m not personally convinced that you’re getting the right one, but we’ll see.
Techman is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 1:08 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.