M3 A029 substitution

[221mac03]

Can an H-A029-7 be substituted for an H-A029-13?

[enor]

The only real issue when substituting one AO-29 for another is making sure they're both for the same type of speaker... earlier ones are for field coil speakers, and later ones for permanent magnet speakers. Other than that, swap away.

[221mac03]

Thankyou enor. I do recall that their was a technical service bulletin from Hammond which discussed a modification to the speaker (maybe a shunt resistor).

[Jaim]

M3 or M1xx? In the M1xx series, the -13 used 2 of the pins on the speaker plug to route heater voltage to the pilot light. I have 2 AO29-7's and both are PM types. Check the speaker plug in the amp. 2 wires - PM type, 4 wires (2 brown) PM type with pilot, 5 wires - FC type.

Jim

[221mac03]

Thanks Jim. I have a spare amp with two wires at the speaker socket. Would you be able to suggest a suitable pm replacement speaker? What should I be looking for in terms of impedance?

[Jaim]

M3 Schematic says 8 ohms.

Jim