69 Sunn 200s

[Soundmasterg]

This is the SDS he was talking about.

http://www.quadesl.com/

Sheldon makes replacement boards for Dynaco stuff in addition to other hi-fi stuff. Most of the Dynaco stuff works in Sunns too. You can buy most of his boards through Triode Electronics.

[djc]

The polarity switch is not needed with a 3 wire grounding system like modern electronics uses. I put mine to use as a ground lift switch, but as I said, the whole amp has to be rewired to make this work. You could just disconnect it if you change over to a proper 3 wire grounding system. If you need to know how to do this, there is info at other forums in the archives like the Hoffman amp forum for instance, or someone could type it here too. If you don't know what you're doing in regards to working on high voltage tube amps, you should learn before messing with it, or take the amp to a qualified tech as it is dangerous and can kill you.

Greg

this I would like to do.  any links for me?  as well I need a brief on how to discharge the capacitors.  any advice besides DO NOT TOUCH?

[Isaac]

This is the SDS he was talking about.

http://www.quadesl.com/

Sheldon makes replacement boards for Dynaco stuff in addition to other hi-fi stuff. Most of the Dynaco stuff works in Sunns too. You can buy most of his boards through Triode Electronics.

Yeah, but my answer was more fun!

[Soundmasterg]

Yah it was Isaac.

Working around AC wiring can be extremely dangerous so be very careful! To discharge the caps safely, go buy one of these:

https://amptechtools.powweb.com/stick.htm

or make yourself up something similar.
Also, I'd suggest to buy this book:

http://www.tubesandmore.com/scripts/foxweb.dll/moreinfo@d:/dfs/elevclients/cemirror/ELEVATOR.FXP?item=B-732

This book is rather basic for tube amps, but has great instructions in the basics that most can understand. It also has full page schematics and layouts of Fender amps which are very useful even if you don't own any Fender amps.

To change over to a 3 wire cord, there is a bit of work involved and its very important that you get it right so that it will be secure and not short to anything inside the amp. The 2 wire practice was to put the black (hot) line on one side of the AC, the white (neutral) on the other, and have the fuse and switch on either side of the AC, with a switch to switch the ground connection to whichever end is quieter. To change to a 3 wire setup, a green wire gets added and this goes directly to the chassis on it's own lug within an inch or two from the AC plug on the chassis. It's easiest to use the IEC plug but you can use the wire and grommet method too. The black gets wired from the wall plug to a fuse, and then to a switch and then to one leg of the power transformer. The white gets wired to the other leg of the transformer. You may have to add insulated and isolated terminal strips so you can solder the connections of wires together. If you have things wrong, then it can blow your power transformer btw. Best to do any testing after you think you are done with no tubes in the amp. Also best to draw up a layout of how it is now, and draw up another one of the changes you think it will need. If nothing else it will help you to visualize what is needed. If any of this sounds hard to you, then please do the safe thing and take it to a tech, or find someone who is knowledgeable locally who can help you, or learn the proper way to do it before you tackle this type of job. I read everything I could find, asked questions of friends who are electrical engineers and spent 4 years reading and reading and looking at amps until I was sure I knew what I was doing. This is because when I first started I shocked myself while messing around on something and knocked myself across the room. I was lucky I wasn't killed, and felt like I had beat up for weeks afterwards. Now I am extra safe any time I touch an amp.

Greg

[djc]

thanks greg, good to have you around still!  I install audio systems in churches and schools so I'm not a stranger to circuitry, tube circuitry however with a capacitor charged to 600v is new.  that snuffer stick looks pretty cool, I'm going to see if I can find one.  thanks for the run down on the ground plug as well.  did you end up useing the existing polarity switch as a ground lift?

[Soundmasterg]

Yes, in my Sonic 1 (200S) that I rebuilt, since I completely modified the grounding scheme and isolated all circuit grounds and jacks from the chassis, I was able to put the old ground switch to use as a ground lift switch. I hooked up the grounding scheme similar to Kevin O' Connor's galactic ground recommendations from his books. (www.londonpower.com) In order for that to work, all circuit grounds and input and output jacks have to be isolated from the chassis. If I hadn't done that, then I would have left the ground switch completely disconnected as it is not needed in a 3 wire power plug setup.

If you haven't yet, check out some of the other amp sites around, such as Ampage where this Sunn site is hosted. Also there is the bbs' at Webervst, Hoffman, AX84, 18 watt.com. This Sunn site is great for Sunns, but those other sites have info about amp work in general and there are many more people posting there to help than here who are knowledgeable about amp work. Also, I'd suggest to look in the archives here for my old posts regarding what I did to my 200S. It has all the info in there about what I did so I don't have to repeat things.

Greg