ARC SP-6 Warmup time

I enjoyed my SP-6b for 14 years. The power light stopped blinking after about 3 minutes. I normally let it warm up for an hour before listening. I suggest checking the bias voltage of V2 and V5 (The two middle tubes in each series of three). Unless your preamp has been modified, the bias voltage must be adjusted manually. If it is too far off, the unit will go into automatic mute mode (blinking light)at times.
If you are not handy with an electronics screwdriver and a voltmeter, have someone do it for you. It has been a few years, but as I recall, I set V2 at 155 Volts and V5 at 150 Volts. There are adjustment potentiometers next to each of those tubes. Check voltage from the capactitor next to each of those tubes to ground. It is shown in the schematics. Be careful. Don't go poking around in there too much. Voltages are very high. One time I put my voltmeter lead on a transistor case and measureed 550 Volts! I still have an old analog voltmeter that I used for calibrating bias voltage. A digital DMM should be fine as well. Just that I prefer analog :)

One other thing... The tubes could be worn, which would also cause the bias voltage to be off. Try some new tubes- especially if you do not want to poke around in there with a voltmeter. I recommend trying some NOS tubes. Search the web for some ideas and places to buy and which brand/vintage to get. I bought some on the bay for a very reasonable price and was blown away at how good they sound.

My backup SP-6B preamp takes about a minute to stop blinking. A call to ARC service will give you good information. ARC has a great service crew with quick turn
around. Keep in mind your preamp is over thirty years old. The 6B I bought in the mid eighties has been serviced 3 times by ARC...All the best..

I owned a couple different versions of this preamp. The 6B and later did have a "timer mute" circuit, but I remember it only took a minute or two at most to unmute. It was a long time ago,so maybe I've forgotten.

Here is an excerpt from a 6B owner's manual:

http://www.arcdb.ws/SP6/ARC_SP6B_flyer4.jpg

The SP-6C-1 was my favorite, followed by the 6E.

Nope, it's not normal. I would recommend calling Audio Research. It sounds like you will be sending it in for repair. I hope you didn't pay too much for it. This is why a 9/10 rating on these older units is not accurate. The faceplate may be free of scratches, however, the electronics is 30 years old and failing. Also, if you want your preamp restored to original and sound the way it's supposed do not send it to anyone except Audio Research. It may cost a little more, but it is well worth it.