Altec 1270B Amplifier

[rghinton]

Where may I obtain an "Operating Instructions Manual" and a manual with a "Parts list and Schematic" for the 1270B. There are several listed on the internet for the 1270 but I can't find one for the 1270B. The Bias Adjustment shown for the 1270 is not complete. What is the procedure for setting the Bias on the 1270B? Is there a service manual for the 1270B?

[whitebroncoii]

The 1270B is the same as the 1270A with the addition of an input filter pcb. Output pcbs are exactly the same part.

Bias Adjustment:
1. With ac power off, remove the top cover (I recommend unplugging the amp)
2. Turn both channel controls fully counterclockwise.
3. Set bias potentiometer R16 fully clockwise (minimum). See figure 2 (seen through the large hole on the side of the frame)
4. Turn on ac power.
5. Set bias potentiometer R16 for an average voltage of 10 millivolte across output emitter resistors R25 through R38.

[rghinton]

Thank you so much for the information. I have never had one of these amps and now have one on the way to me. It should be here later this week. I think that I will be very happy with the sound of the amp with my A8 Altec speaker systems.

[rghinton]

I just found a picture of a 1270C amplifier. How is it different from the A or B Model? Are there later versions than the C?

[whitebroncoii]

The 1270C deleted the over-engineered input filter on the 1270B and used a simpler input filter.

The 1200 series power amplifiers (1268, 1269, 1270) all used a very beefy power supply and delivered incredible LF headroom. They also can draw a ton of current during turn-on. Do not panic when your 1270 briefly dims the lights when you flip the power on.