Any mods for SUNN 200S?

[doc10039]

Any mods that will improve design, sound, reliability,etc(caps are my first on my list)? I thought since I am kinda starting from scratch I would beef it up where I can. Any suggestions for a good PT? The one thats in it now looks sorta wimpy, its new but not very beefy. Any help will be appreciated.

[EdBass]

I think you are on the right track with the caps, other than that a 200S is an extremely stout amp, especially the iron. IMO the OEM power transformer will bring all you will need for a pair of KT88/6550 tubes.
If your "new" PT is the same spec as the OEM Dynaco or Schumacher I think it's actually pretty burly for a 60 watt amp.

[doc10039]

There are no markings on the PT so I don't know what its rated for or even who makes it probably chinese or something less. Thanks for you remarks.

[Soundmasterg]

Is your 200S a vintage one? Does it work? If so, then you can do some tests (if you know what you're doing) and determine which power transformer it is in the amp. Sometimes there are dates written in sharpie inside the chassis too, and we might be able to tell who made the transformer based on those dates. That is assuming of course that the transformer is original. The Schumacher transformer has a higher B+ voltage than the Dynaco, and personally I think the Dynaco set sounds better, though it makes a bit less power.

Greg

[doc10039]

No its not original. I took of the sides and no markings either. I figure its some cheap replacement.

[EdBass]

No its not original. I took of the sides and no markings either. I figure its some cheap replacement.

Post some pics, maybe somebody will recognize it.

[Soundmasterg]

Triode Electronics sells a clone of the old Dynacos that came in these originally and their copy is excellent. If you're looking to replace yours, you may want to check it out. Personaly I would wait until I had some voltage measurments on the one you have to see if it is appropriate or not.

You can see the Triode transformer here:  http://store.triodestore.com/mq782.html

Greg

[doc10039]

It is a new manufacture transformer with no markings, model number, manufacturer. I just don't feel comfortable using it. Before I took it out I tried to get some voltages at pin 5 on the output tubes and the meter would only give me a max of -33vdc. So I think this tells me the PT isn't rated correctly for this amp. Some one had switched it to run EL34's. I think I would feel more confident with a correct model made for this amp. I figure i got my self into this so I want to do it right just like when I built my Metro Plexi clone. Thanks


Doc

[Soundmasterg]

You should have been checking what pin 3 was, which is the plate voltage. Pin 5 is the control grid, and is where the negative supply from the bias comes in. The -33 v is probably not a max voltage but is just what the pot is set at. The PT could be perfectly fine, but some more measurments need to be done.

Greg

[doc10039]

By my info that I am absorbing the negative voltage at pin 5 should be higher. Like with Fender/Marshall amps by my experience the neg voltage should be higher.

[Soundmasterg]

It could perhaps be higher, but that is just where the bias pot is set right now. You need to backtrack the circuitry and see what the actual negative supply is right before the pot, or adjust the pot to full negative and see what you get. It may be ok. Since this amp used 6550/KT88's which need a higher negative voltage than the 6L6's typically used in Fenders, the supply should probably be somewhere around -75 max I would guess. I haven't measured mine lately to see what stock is and have no time to do so right now, but perhaps someone else knows offhand.

Greg

[Greg_M]

I just bought a new one from here

http://www.dynakitparts.com/store/product.aspx?id=247

[Soundmasterg]

That will work.

Greg