Hi. I have a 210-65 (2275-65 all solid state chassis) that was original a dumpster rescue. The US female power receptacle on the back and the model plate clearly mark this as a US market amp (it does not say "Export" as others do that I have seen in Europe). It also still had the ground flip switch (which was normally removed by EU distributers, I think). However, when I found it, it had a dead, but original MM 220V power transformer in it with a UK plug.
The most curious thing is that it was also completely missing the choke and only had the two larger filter capacitors - it was missing the two 20uf 450V caps that are normally alongside the two large Sprauge caps. On the paper card that holds these caps, there were no signs that anything had ever been soldered to the rivets normally used for this part of the circuit. Some rivets show no signs of ever having solder on them, and a couple are just coroded (see attached picture). And only one green wire (not three) goes through the entry hole into the chassis. And as far as I can tell, no resistor has been installed in place of the choke. I recapped it staying with the current set up (thinking it was some sort of mod) and my friend/tech helped me to put in a new US transformer.
The amp works and is fairly quiet...
But now I'm wondering if I should do something to try to restore the missing part of the circuit or whether this was a standard change seen in later versions of this amp.
Please advise.
Thanks - D
Adding some info... There is
Adding some info... There is an 2275-130 chassis on ebay that sold a month or so ago. It has the same layout as my amp (only two caps, no choke). AND it is marked 211 JJ 2-21 on the sides (mine is marked 211 JJ 2-15 on the sides). So, this is either someone who performed mods on these or someone at the factory working on these at the same time, which would mean that the layout is original. Any thoughts???
It's original
Hi D,
the choke and the 2 x 20uF filters disappeared along with the 12AX7 tube. Nothing special about it.
Cheers,
Lars Verholt
Hi Lars. Thanks very much.
Hi Lars. Thanks very much. What's weird is that my friend's Export 210-65 (originally from Germany) is all solid state but still has the Choke and extra caps. Perhaps his was a transition unit? Or, some of these were actually converted from the 12AX7 to solid state, correct? Perhaps his represents one of those cases.
I'd say conversion, yes
I much doubt any units were actually manufactured with both the choke, extra 2 x 20uF and the transistor driver board. The second 20uF capacitor is not needed at all if the 12AX7 tube is not there - and apparently the extra filtering for the screen supply (on the power tubes) was not needed in the later version of the amp.
Cheers,
Lars Verholt
Been meaning to do this for
Been meaning to do this for some time but if you are interested, there was a factory conversion instruction sheet that came FROM MM factory for those brave enough to convert from 12ax7 driver to SS. I had one of those(and still do) and DID convert one amp here locally. The factory supplied conversion process came with a SS driver board and all the fixin's. It does NOT involve removing the choke but honestly, if you track down WHAT was changed, it MIGHT have disconnected it. I honestly DON'T remember and I'm too lazy to take mine and track down WHAT was removed(it IS still here). IF you are interested, I finally scanned the entire document from them and added it here. Interesting reading. Mike.
PS-Converted it BACK some time ago and then dropped a pair of cutters in it while running and boom. What a dumb ass. Haven't fixed it from THAT yet and lost interest so it's my MODEL when I want photo's for the site!
thanks...
Thanks for all the info. Both amps are working perfectly right now, so we will leave them as is. Seems like my friend's 210 is a conversion though. - best
DT