Swan Mark II - SO-239 connectors

[Robb]

Just got this Swan amp. Began to go over it with a fine-toothed comb. But I didn't get very far before I found this.

Going to have to replace them with some silver plated nylon-insulated Amphenol connectors.

Just can't believe that someone running an amp like this w/~1.5KW output - would not notice both of these connectors in really AWFUL condition!

 

[n0zna]

some think

if it not broke dont fix it,and not check stuff out...i have a Cber dont the road that still has the same coax on his moonraker from back in 1977...he fusses when he can only get 300 out of a maco 750...hehe and splatters all over 10/11/12/15/17 anfd 20mtrs,hehe lids ya got love them...73

 

[Mudfoot]

At least that should be an easy fix.

 

[Robb]

Yeah, an easy fix. Kinda freaked me out when I saw it at first - is all. Ordered a couple of SO-239's with Delrin insulators and silver plating.

I know this is an old amp and it will need some renovating. All of the bypass and grid caps are next. Will be buying this amp back a piece at a time. Some things have already been replaced, especially in the power supply.

Will have to clean the band switch contacts and the drive pot too. Then buying a dummy load is next on the list before I can fire it up.

 

[BJ radionut]

Robb: Anything that "vintage" is a "work in-progress"
The good old hands-on is priceless....

Check the relay control RCA jack it looks to have a split in the insulator sleeve...you can change that also when you upgrade the SO239's....

While you have it open...
Check the tube sockets for sign of arching or overheating(black tarnish)....The big filament pins are most common.

With a tube inserted and seated check the pin contacts to make sure they are making good contact....(No gaps around the pins)...

Do not clean tarnish off the tank coil....You can disturb the finish and create "little" issues...
It may not be as pretty but that "plating" removes very easily...IMHO
My 2 cents
Be thinking about a "Fresh" set of 3-500z's...
K5SVC is your guy... again IMHO
All the Best
BJ

Clean the "gunk" off the fan blades,shafts and blow out the windings...couple drops of 3-in-1 oil around the bearings...."Preventive Maint."

 

[wavrider]

ROBB de oxit is great stuff, get it off ebay much less expensive than in Rat Shack.

Use regular notebook paper to clean the contacts on those old relays then de oxit to take the oxidation off, then back to paper again.

Tarn X works great on those old tank coils if they are silver plated.

DO NOT USE TARN X on any electrical contact. Don't ask me to explain just don't use it on anything electrical.

Deep Woods of removes stains like crazy. It even removes permanent marker.
Great for cleaning up inside the chassis case.

The band switch needs looked at with magnifying glass. Make sure all contacts clean and make a good physical connection.

Look at the tank coil soldered connections. Over time they can become brittle and make poor connections.

The SWAN has a pretty good dependable reputation but as BJ said start at the front and work your way through every circuit replacing repairing all you find wrong.

As far as tubes?: once you get to the point where you can turn the amp on, let those tubes sit and burn just the filament on for 10 hours or more, NO B+ you may have to unsolder some wires from the TR to the rectifier for this one but let it sit and burn in.

then reconnect the B+ and read how to getter 3-500Z tubes.
http://www.eham.net/ehamforum/smf/index.php/topic,72672.0.html

Fun project just no tuned input, not a problem if you have an old boat anchor for a rig.

 

[Robb]

Yeah, BJ - I saw that bad RCA plug as well. But that I can find; might even have one of those around here. When I replace the SO-239's, I will post up some close-up pics for them. There is a black ring on the outside of it; I suspect the amp output may have been arcing.

Thanks for the info too, wavrider and BJ. This is my very first tube amp and I most definitely appreciate these tips that come from experience from you guys and others.

The tubes are at 85%. I will make my learning mistakes with them. But I hope that I tune this thing correctly and keep them alive and viable for a long time to come. Dipping the current when the output is the highest. I plan to use this amp at/about the 5-600w range, as I would rather just let the thing loaf than push it.

I guess I will need to bring an even finer-tooth comb to this project than I originally thought . . .

 

[wavrider]

ROBB that old SWAN was built in the day where 1KW was the legal limit, input wise.

It should be a KW amplifier but not on 10 meters maybe on 20 meters and down.

Tubes at 85%? Put it on 80 meters with 85W drive and see if you do not get a KW out of it.

500 watts is great it will give you another 6DB + over a 100 watts and that is basically the most I use if I use an amplifier. ( well except for the 4X1 homebrew which I dont use anymore, I only have a 2kw meter and it keeps it all the way to the right so it now sits in the corner unused)

Enjoy the old SWAN and it is a great amp for learning on, just remember there are lethal voltages in thhe PS so be darn careful.

When you get ready for a SWAN rig I have a 700CX with stabilizer installed and it is a sweet rig. Might be able to talk me out of it.

Hope to work you on the air and hear how the SWAN is doing for you.

 

[Robb]

Wavrider, this Swan has a Peter Dahl xformer in it. The plate voltage is about 33-3400 volts, and the stock xformer put out about 2800. So, it should do the full enchilada . . .

Oh yeah . . . I will be using a Kenwood TS-2K and/or a FlexRadio SDR-1K with a manual antenna tuner between the amp and radio.

Read a lot of great things about the Swan 700CX; but not ready to go full boat anchor at this time. Perhaps in the future. Saw a nice Swan 350 for dirt cheap that needed some TLC just last week.

 

[wavrider]

Peter Dahl Iron?? Keep that old SWAN and yes,

If you have 3400VDC under load you might see 1.5KW with .75ma plate current.

Either way it is a keeper with that iron in it.

I know what you mean about the old tubers, That swan 700cx has enough output to bust through pileups by itself and nothing but unsolicited audio reports on the TX quality.

 

[WA8ZYT]

I would NOT clean the relay contacts. You could damage the coating on them, then you will have problems. However if you feel you must "clean" them, just run a business card through them, once.

 

[Robb]

Innards . . .

Here are some pics of the innards of the RF deck.

Still in the process of replacing the SO-239's; thought I would snap some pics while at it.

You can clearly see the black rings on the SO-239's.

Surprisingly as one can see, there has been a lot of parts replaced in the RF deck. Still going to clean the band switch and check all of the resistor values and replace any disc caps that are still in it and look old/original. Not many of those left that haven't already been replaced - BTW.

The last photo shows a close-up on the innards of the SO-239 connectors. The output connector (on the left) had almost 80% of the insulation material missing.

The right tube socket may need to be replaced if it doesn't clean up with some Deoxit.
The left tube socket looks nearly brand new.

 

[Captain Kilowatt]

Robb, those "black rings" on the SO-239 connectors looks simply like oxidization of the silver plating where it was exposed to air. Note the part that would be under the PL-259 is not black nor is the face of the connector that was against the inside of the panel. I see that all the time with silver plated connectors that are exposed to high humidity.That's my call unless I am not looking at the right place.

 

[Robb]

OK.
With sooo much of that insulation broken out of the connector, I was wondering if it wasn't arcing.

What do you think about the right tube socket (2nd picture from the bottom)?
Looks like it had gotten pretty hot; the tube pin clasps are oxidized and discolored.
Just hope they clean up. If not, going to replace it.

 

[WA8ZYT]

Looks very nice inside! I see they did an excellent job of grounding the grids. My SB-220 has a caps off some of the grid pins to ground and a .22 ohm resistor off one pin. That method of grounding the grids was supposed to improve IMD, but results in less power output. I am going to ground them directly.

Looks like a nice amp, I am going to be on the lookout for one of those!