Hello Duncan!
On 20 Dec 97, Duncan Markley wrote to Bill Riley:
 DM> catalogs, the 800 and earlier transformers are substantially more money.
 DM> The 900's are considerable less.
Which is a good thing if they blow a lot ~8-)
 DM> I also looked at the Guitar Center "NOS" 800's.  One was sitting on top
 DM> of a 900 and you could compare the transformers.
You visited the Brea store?
 DM> As far as beefing it up, I don't know if that could be done or not. I
 DM> know that voltages must be met and maybe Rich or Jeff V could tell you
 DM> better than I could.
Given the fact that the 800 and 900 are both 100 watt amps using the same 
output tubes, the B+ levels and currents will be comparable. The tubes want 
to see the same primary impedance on the output tranny, and of course, the 
speakers want to see the same secondary impedance.
Unless there's a difference in how the output impedance change is wired, the 
800 transformer should be an electrical, if not mechanical, drop-in 
replacement.  Of course, I would only do this to a "working" amp that is not 
being kept original for investment purposes.
There may be a change in tone, as the difference in the size of the iron core 
and wire gauge used will affect the frequency response and efficiency.  It 
may be something that only Eric Johnson could hear, or it may turn a 900 into 
an 800... I don't know, but Marshall had to have a reason for the change 
other than cost or they probably would have implemented the smaller tranny on 
later 800 series heads.
C-ya! Rich
--- GoldED 2.40
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