Regency Range Gain CB
 

ALL, unique problem.. radio recapped. working great with good rx and tx.. then after about 1/2 hour or so..channels of 4,8,12,16,20, and 23 kind of stopped working... but not really .. signal via signal generator went from s7 down to about s3.. also tx power went went down.. all other channels are ok.. only thing common to all those channels is a 8.533 mhz xtal.

can a xtal heat up and stop working somewhat?

very baffled with this one i can post a schematic if needed..

hope this is the right place to put this


Skip

Re: Regency Range Gain CB
 

Hello Skip,

From the sound of it broadly speaking there will be similar crystals doing the same job for other groups of channels like:-

2,5,9,13... etc
3,6,10,14...etc

Try swapping your suspect crystal with one of those others. Obviously the two blocks of frequencies will swap over, but the point is to see whether the fault moves with the crystal or stays where it is.

You must be using one signal generator as your test signal source - if you have a second (synthesised?) generator with rock steady output you could remove the suspect crystal temporarily and inject 8.533MHz from that alternative source to see if that 'fixes' the problem.

Edit: For the avoidance of doubt, this sounds like an interesting early multi-crystalled 23 channel AM set which is legal to use where Skip is, in the USA.

Re: Regency Range Gain CB
 

Ok thanks Xtals are soldered in place kind of hard to get to but not impossible..

I will fire it up this morning to see if it starts working again.. if so how long it does work..

And yes its a 23 channel older CB set used in the US Fixing for a friend

Thanks

Skip

Re: Regency Range Gain CB
 

Do you have some freezer spray available? Turn the set on, let it warm up until the fault comes on and then try cooling the crystal.

I would be interested in seeing a photo or two of the outside and inside of this set - by the time CB arrived in the UK the sets were typically only using three crystals or one crystal so we didn't see many sets like that over here. Also, if you have a link to an online copy of the schematic that would be interesting to see and would make it easier for us to follow your progress.

Re: Regency Range Gain CB
 

Sure I will take some pictures and post schematic.

Skip

Re: Regency Range Gain CB
 

Yes.

Cheap crystals usually were mounted in cans that were soldered together, and inside there would be a little solder on the wires connecting the electrodes on the quartz to the holder pins. I have in the past opened dud crystals and sometimes found dry joints inside. Re-touching them and cleaning worked, but there was a small shift in frequency. Excessive operating amplitude can also sometimes shatter crystals.

Once you've tried moving things around to verify it's the crystal which is iffy, then you have nothing to lose by opening it. I'm assuming it's a soldered HC6 series case. Look out for a plob of solder elsewhere on the case blocking a vent hole used during assembly. Open the hole before soldering the case back together, let the unit cool, then quickly blob over the hole to reseal the case.

David

Re: Regency Range Gain CB
 

I went on a pre-emptive search for information and wow, this is not only an early CB set but a valve (...tube) set, complete with a vibrator to enable the set to run from low voltage - if I'm looking at the right one.

http://www.oldtuberadio.com/data/Reg...5_p124-133.pdf

Re: Regency Range Gain CB
 

Just been looking at the diagram linked to above and the crystal associated with channels 4,8,12,16,20,23 has a frequency of 8.655MHz rather than 8.533MHz according to that information, so maybe I haven't got the right diagram?

Re: Regency Range Gain CB
 

Now that's a CB I've never seen! what a lovely valve set.
Would be good to see a proper picture of yours with the innards if possible.

Re: Regency Range Gain CB
 

Miss typed its 8.655 mhz

Re: Regency Range Gain CB
 

Taking some pictures Will post then soon

Skip

Re: Regency Range Gain CB
 

While waiting for those images I sat down and wrote a short program which shows how the combinations of crystals generate the (then) 23 channels of the USA CB system. The additional channels 24-40 weren't added until about 1977, or so I understand.

Each position on the channel select switch selects a pair of crystals whose frequencies are summed together for a frequency which is equal to the desired channel frequency minus 7.5Mhz. This summed frequency is used in receive mode as the input to the receiver first mixer (the receiver first I.F. is 7.5MHz).

In transmit mode the summed frequencies of the two crystals are further mixed with a 7.5MHz oscillator to produce the 27MHz TX frequencies.

This table shows how it normally looks - note the occasional 20Khz jumps and the large leap to the last frequency are correct - the jumps between channels 3-4, 7-8, 11-12, 15-16, and 19-20 were to step over already pre-existing radio control channel frequencies. The historic reason for the giant leap from 27.225 (Channel 22) to 27.255 (Channel 23) is less clear.

The next table shows how the channel frequencies come out if the 8655 and 8635 crystals are swapped over for diagnostic purposes.

It is possible that any heat applied to the suspect 8655 crystal while desoldering it could either make it fail altogether or 'fix' it, but the main aim of swapping over the 8655 crystal and the 8635 crystal is to see if the low RX sensitivity / low TX output problem moves from channels 4,8,12,16,20,23 to channels 3,7,11,15,19.

Re: Regency Range Gain CB
 

OK took apart the crystal section ( 4 wires) and resoldered the pins on the 8.655 xtal.. also re soldered the connections when i put back in

turned radio on it worked longer this time before the channels lost sensitivity..

signal went from s9 ( 50uv input) TO S3 .. TX also was about 2 watts less.. so not a complete loss..

Did not swap xtals.. so now looking for a xtal having a hard time finding one

Skip

Re: Regency Range Gain CB
 

You may have to have one made - there are several companies here in the UK who can make one-off crystals to order, I would think there are similar companies in the USA?

Re: Regency Range Gain CB
 

Just had a quick look around at USA crystal suppliers, here is one who says

http://www.bomarcrystal.com/index.html

I have not used this company myself and I am sure there are many other similar companies. Just an example of what to look for.

Re: Regency Range Gain CB
 

Thanks, I did email them a week ago.. no response..Will try again

Thanks

Skip

Re: Regency Range Gain CB
 

Might be worth a phone call just to find out if they are still trading - I didn't see a 'last updated' date stamp on the website.

Re: Regency Range Gain CB
 

Last update on their Facebook page was 2019.

https://www.facebook.com/bomarcrystal/

Unless they are just really bad at the internet / communications side of things, I fear they may have gone.

Re: Regency Range Gain CB
 

Yes, I'd like some more pictures. If you're taking photographs I'd like a back view which shows the maker's nameplate. We know it was made for Regency Electronics, Indianapolis not later than 1964, but that was the time when the American electronics manufacturers were starting to import products from the Far East, starting with Japan and Taiwan

Re: Regency Range Gain CB
 

Collecting pictures now..

PS I emailed Bomar and got a reply of very expensive.. plus they wanted to know specs.. I have none .. it sounded that they didnt want to be bothered..

So any places over there in UK that does Xtals??

Skip