Specifications

In Fig.6, Letter "A" points to the 28Vdc regulator, which was an LM-317T, good for about
1.5A. @ 32Vdc. The schematic calls for an LM-350T, rated 3.0A. @ 32Vdc. Since this
regulator provides all the DC current for all the controls, displays, and relays, the circuit
could easily exceed 1.5A.
I replaced it with the proper LM-350T.
There is another pair of LM-317T on the control board which reduces the voltage to + & -
5Vdc for the digital IC's on that board. It is fed from the LVPS 28Vdc regulator.
Fig.7
Fan & blower
Letter "A" in Fig.7 points to the "auxiliary" fan mounting port, and main air intake opening on
the back panel of the 86. Fig.5 letter "D" shows a new "Aux" fan installed.
The fan I installed is a Radio Shack® cat.# 273-241C Ball-bearing, 65CFM, 115Vac "muffin"
type fan, about $23 and change. These are very quiet, and I have used them in several
amps before.
The fan fits perfectly in the port, and the factory mounting holes are perfect, even the grill
can be reused on the intake of the new fan. Rather than use the grill, I installed a plastic
foam fan filter, Jameco
part # 196816CF, $1.95 + shipping. It fits perfectly on the intake side
of the fan via the standard mounting holes in the fan body. The new filter is washable and
should be cleaned at least once per year, twice if the environment is extra dusty.
In case you were wondering, Alpha/Crosslink charges up to $300 for the "aux" fan upgrade
kit.
This "aux" fan mod adds much more cooling air to the system, and pressurizes the cabinet,
"force-feeding" the squirrel-cage blower that pressurizes the tube plenum. I have used this
mod on the old 76 series of Alpha amps with great success.