200S date/ power,/and # of tubes?

[MarkG]

I found a 200S in very good shape,and sounds great,but it's tube configuration is a little differant than what I would have expected,at least compared to the documentation I have seen on this site. It only has 3 tubes. 1 6AN8 and 2 6550s .There is no rectifier tube, or even a socket hole where one ever existed.Would this be a factory solid state ,or diode rectifier? Also there is no 12AX7. Where did that go?? Or was that only in earlier models also ?? Other differances I see are a circuit breaker instead of a fuse.and a 4ohm external jack rather than a 16 ohm external. My overall assumption from all this is that this is one of the later 200S units made. Can anyone verify what year(s)this version  might have been manufactured? There is no serial# I can find.Would this version have had more power output than the ones with tube rectifiers?? Comments from the experts please on all this? Thanks!

[mike]

This is probably from late '69/early '70 onwards as that seems to be the period when the switch to a solid state rectifier was made. As far as the 12ax7 is concerned, it's hiding from you! As you face the BACK of the amp, with the tube protector strip taken off, feel around in front of the transformer on the right--it should be there, but very difficult to get to. Its location is in close proximity to the input jacks.

[MarkG]

Mike,thanks for the tip on location of 12AX7. I found it! Hey,any idea why my #2 input might sound weak compared to #1 ? Looking at the 1967 schematic ,they both use 68K resisters in series. Did they change this later? Its the only component unique to the 2 inputs. I have not opened this up yet to see if values are actually the same.Not a big deal for me.Seems to be the only thing wrong with the amp.

[Tom Loizeaux]

When they changed from a GZ34 to a silicon diode, they change the name of the amp to 190B. The earlier versions used stickers with 190B on them that covered the engraved 200S name.

Tom

[MarkG]

Tom ,this one says 200S engraved,and not even a hole where the GZ34 would have been. Where do I find the serial number? can I tell from that? There is no evidence that a 190B label would have been peeled or scraped off. It all seems original,including the name plate  riveted on from "Continental Music" in Chicago,which was the big Sunn dealer here during late 60s early 70s. I still have my Concert Bass that I bought from them in 1975 with the same plate. Wished I would have bought the Mod-T instead of the Concert. I would still have it I'm sure.