Swan 500CX

[kc4umo]

Last week end a friend of mine gave me a 500 and a 500CX.
Long story short these 2 radios used to belong to Charlie K4SKI. He had gotten rid of them 20 years ago. He regretted it since. Later I found the radios, bought them and gave them back to Charlie.  He fell ill over the years and was getting up in age. Wife passed and he became dependent on others. He now resides in a nursing home.  Charlie gave the radios to his grandson which is also a ham. He had them a number of years.

When he got the radios his grandfather told him the story how he gotten the radios back. So when the grandson decided he was not going to do anything with them he contacted me and asked if I wanted them.  Well you know I said yes. He said he rather give them to someone that would appreciate them and he knew I would.
Well yes.....

Both radios receive a treat. Only took a little cleaning to get them going.  Also came with 2 power supplies. One in the speaker cabinet and the other without the speaker.  Which I had to replace the filter caps and rectifiers.

Here is what I did find though. The CX had both 150pf caps on the course load switch blown.  So they took the switch out of the plain 500 and installed in the CX. I removed the switch and replaced it back in its original spot in the 500. It also loads up and transmits fine.
Now I do have the parts in stock to rebuild the blown switch. I have a decent assortment of wafers from that era. The question is, Have you ever seen anyone replace the load switch with a variable air gap capacitor?  Would this not do the same thing and relieve stress on mica caps?
I been looking at the schematic over the week and I think that would work.
Thaoughts?

[W2VW]

That will work but it may not be possible to fit an air variable with that much range into the rig.

[KA2DZT]

With the circuit you posted you could replace the loading caps with a variable cap.  Problem is, do you have room for another tuning cap.  Multi-section caps can become large in size.  I use a 4 section 550pfd (each section) tuning cap in my HB rig.  You only need broadcast style caps for loading.  No need for wide plate spacing for loading caps.

Fred

[kc4umo]

Thanks for the replies guys. I am going to have to do a bit of measuring in there. The current switch has 4 330 pc and 2 150 pc silver dip caps on it. I have not yet added the values together to see what I would need.

[W2VW]

If you want to keep the guts intact an external box could be fitted with a large loading cap inside. The antenna connector would be plumbed to the box and another. Both connectors in parallel with the cap.

[kc4umo]

Well, after coming back out to the shop I see fitting a var cap is impossible. As you can see in the attached pic the fine tune cap is only about and inch long.
So guess I will just rebuild the blown switch.  A section of the bakelight is missing from where the last cap flamed out.  The last contact is right on the edge and it will not be long before it breaks free.  Other than that the switch works perfectly fine.

W2VW,
That is a possibillity.

[KA2DZT]

You need a ceramic switch or at least a ceramic waffer.  Which tuning cap is the loading cap??  I see three tuning caps, two in the final box and one other.  You do have room in front of the final enclosure, but it would take some mechanical work.  The loading cap doesn't have to be in the enclosure.

Fred

[KA2DZT]

OK, I took a look at the front panel.  It seems that the small one section cap is the loading cap and the switch is over it directly and you have it removed.

With the right tuning cap you could mount it between the front panel and the enclosure.  A three section cap might fit and you could still use it as a course loading cap and fine tune loading with the original cap.  Usually three sections could add up to about 1300pfd maybe more.

This would take some mechanical work.

Fred

[K4RT]

Was the damage caused by hot switching?

[kc4umo]

Fred,
I thought about  putting one just behind the front panel. may play with that idea a bit.

Was the damage caused by hot switching?

Wish I knew.
But that would be my first guess.
Was like this when I received it.

[K4RT]

Good luck on the repairs.

I have a 500CX and 117 PS I bought at a hamfest. After minor work and replacement of the 6LQ6 tubes it has turned out to be a nice SSB transceiver from that era. I enjoy using it on SSB and CW.

Every once in a while I check into the Swan Tech Net on 40 meters. I think the net meets Saturdays on 7235 KHz at 2 p.m. eastern. NCS Stu K4BOV used to work for Swan.

Brad

[kc4umo]

Good luck on the repairs.

I have a 500CX and 117 PS I bought at a hamfest. After minor work and replacement of the 6LQ6 tubes it has turned out to be a nice SSB transceiver from that era. I enjoy using it on SSB and CW.

Every once in a while I check into the Swan Tech Net on 40 meters. I think the net meets Saturdays on 7235 KHz at 2 p.m. eastern. NCS Stu K4BOV used to work for Swan.

Brad

Thanks, it should be a fun project.  Since both radios work (as long as there is a load switch installed) most of the issues are cosmetic.
This morning I plan on giving the shop/shack a good cleaning. Spent an hour last night looking for my box of wafers. I also do not seem to have any 150pf SD at 1000 volts. So going to make a few calls later today to some local friends here.

After I finsh cleaning the shop I plan on seeing what caps need replacing in both units.  I have most of the caps in stock or the other supply. Then I think I will tackle the cosmetic issues. Lots of grime built up over the years. All the speakers are intact and have no holes in them. So I may try and coat them to preserve them a bit longer.

Made a contact on 20 the other day with the 500 and got a great report back. Looking forward to playing with these rigs and will check out the Swan net.

[kc4umo]

Transmit power is up and running on the CX now.
I cleaned all the burnt backlight away, then cut a new piece and glued it in place. Works fine.
Seems there is anothing issue with this one I need to tackle before I start the clean and replace parts process.

After about 25 to 30 minutes of run time the receive becomes distored, volume drops off a bit, and the S-meter starts hanging around S6 or so. May be something in the AGC heating up or a tube gassey.

[kc4umo]

I scanned the dial incase someone needs an image. The dial does not look too bad.

[K4RT]

The green stripe on the dial is what caught my eye at the hamfest where I bought my 500CX and got me to take a second look at the transceiver.

In regard to your receive distortion and S-meter issues, in addition to checking the AGC circuit and tube, check the components connected to the RF gain pot. If I recall correctly there are several resistors there one or more of which might need to be replaced.

[kc4umo]

The green stripe on the dial is what caught my eye at the hamfest where I bought my 500CX and got me to take a second look at the transceiver.

I have to agree. That green stripe really sets the dial off.  In fact, I am thinking of a way to put a green stripe on my Siltonix 1011C and 1011D.

In regard to your receive distortion and S-meter issues, in addition to checking the AGC circuit and tube, check the components connected to the RF gain pot. If I recall correctly there are several resistors there one or more of which might need to be replaced.

I will give that a look.  Cant be to much causing the problem. Radio sounds good until about 30 minutes into warm up then the receive issue starts.
Thanks