Premier 88n

[Phil_S]

My head hurts.

[Andy Le Blanc]

How come?

[Andy Le Blanc]

Here's the inputs, lo- fi, nothing crazy. The mic vol. looks so far to be a simple
mix to the out, but the instr. vol. looks to do something else.

And one of the grids of one of the 12au7s looks to be grounded....
getting my hopes up to see something clever.

The plate V on the 6v6's in the lower unit is around 375v,
the bias on top of the series heaters is 23 to 24 v,
and is by-passed with two 10uF sections (parallel) of the 60-10-10-20
450v condenser cans, I think the plate V should come up a bit with fresh filter
caps, but the field magnet acts as a big dropping resistor.

The PS appears fairly typical and its safe to make assumptions for the number
of tubes on the fil. and 4x 6V6 on the power side. It uses two 5y3 to handle
the current for the B+, one for each leg off the mains AC.

I still want to get an Impedance ratio from the OPT.

[Phil_S]

How come?

Looking at those pictures....I wouldn't have the patience to follow that spaghetti. You're d'man, Andy!

[Andy Le Blanc]

here's the mess from the top of the switch box, the only surprise so far is
that the tremolo oscillator doesn't appear to use a 12ax7, I'd assumed it
would be for the gain.

The whole board is rivets and eyelets, hand fabricated, even the springs and switches.
Nothing you couldn't do on the kitchen table, a box and pan break would help.

Its funny that "push button convenience" was all the craze, and very modern.

[Structo]

That's not too bad of a birds nest considering the point to point and era of amp.
Interesting the use of the copper shielding.

Will you give it a three prong cord?

[Andy Le Blanc]

The way the tremolo is coupled into the signal path is just plain wacky.

The input is from the wiper of the 500k instrument volume, which receives the
signal from the instrument pre. The out is to the tone switching (1/2 12ax7),
I still have to draw up a scheme from the mess layout diagram there.
Except for the tremolo system its a relatively simple rig, it has a very soft
break up with the 12au7 inverter and buffer, nice.
The speaker presents well too, I'd love to find another just to build a combo around.

I've got to put back together and get it out the door, the owner doesn't want
to sink money into restoration. It needs to be recapped to get the trem going.
That would be a lot of time without return....

I tested the OPT and got a 1:27.3 turns ratio, that's around a 6K reflected
load on the primary with an 8ohm speaker. With the current loading,
the driver has a 6.8ohm voice coil and the tubes are seeing around a 5K load.

[Andy Le Blanc]

here's the thread.