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Remember the Alamo

5/26/2000 3:04 PM
Remember the Alamo
I'm woking on a freinds old Alamo "Electra"amp that he found in a pawnshop. Does anyone have a schematic? It has very low output. Someone has already been in and they appear to have done some strange stuff to it. For one thing the first preamp (not the vibrato tube) 12ax7 has the plates and grids soldered together, and there is no B+ voltage going to this tube. I've never seen anything like this, I am missing something or is this just screwed up as I suspect?  
5/26/2000 3:19 PM

Thanks for remiding me. Are you in Texas?  
a 12AX7 that truly has plates & grids connected would act as a diode if it was done right. This could be intentional to provide diode clipping on the input instead of gain ?  
this could have been set up by someone who was very smart or either somewhat questionable :-/  
*Left home this morning, and was almost to the lab when it struck me, darn, I had forgotten the Alamo, and this wasn't the first time!*
5/27/2000 7:29 AM

Of course I'm from Texas, the greatest state in the union! BTW there is no basement in the Alamo.  
This amp has me stumped, I'm tempted to just wire it like a princeton, but first I'd like to know why it was wired this way.  
5/29/2000 1:13 PM

Am too lazy to pull the tube manual but are you sure that the amp is wired for 12A_7s? Many of these amps used tubes like 6AU6 (yeah, 7 pin socket, I know) and other tubes that were currently available for cheap (a large manufacturer would change a product line and tens of thousands of tubes would hit the market really cheap and small manufacturers would retool their line to use the available tubes - not hard to do with hand assembly). You might want to pull out a tube manual and check the socket wiring for some other possible candidates - remember the 12AX7 fixation is a recent phenonemae.  

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