Acoustic 470 cuts out.

[bowesj]

Hi,

about 30 years ago I bought an Acoustic 470 Solid State Amp. I stopped playing and had it packed away for 25 years. I just pulled it out to sell it figuring the pots would be dirty and they were so I started spinning them quick which always cleaned them up in the past. Instead the amp just faded out (no amplification). It is interesting that a similar thing happed today to my cheapo amp too (it too had been packed away with absolutely no use for about 25 years). So later in the day I come back and try the 470 again and it was fine (maybe it just had too cool down). I could turn the pots without any raspyness too which I guess was because of my prior fast turning of the pots. Okay so I am much happier but after about 10 to 15 minutes of tuning my guitar and playing the thing fades out again but this time without turning the pots. I am not sure if it is my amp or the guitar (an electric takamini classical) or what. I never had this problem with it when I was using it 30 years ago. Does anyone have any thoughts on what is wrong and how I can bring this really cool machine back to its original life.

By the way, it has been so long I can't remember what I am suppose to spray into the pots. Is it alcohol?

Gee, now I don't feel like selling it. This was such a cool amp.

Thanks so much,
John.

[52 Bill]

Does anyone have any thoughts on what is wrong and how I can bring this really cool machine back to its original life.

By the way, it has been so long I can't remember what I am suppose to spray into the pots. Is it alcohol?

Welcome to the board John.

The first thing that I'd check would be the accessory in/out jacks. Try plugging in a spare cord from the out to the in jack. If the signal returns, the jacks need to be cleaned.

As for the pots, you need to use a cleaner that is made for cleaning and lubricating pots and jacks, like Deoxit. Alcohol may damage the plastic parts in some pots.

[bowesj]

Hi Bill,

Thanks for the response. I found the cleaner at The Source "TUNER CLEANER SPRAY 6404315"

What you are suggesting sounds a little scary. How do I know the signal returns? Would that not cause a feedback loop like sticking the guitar directly in front of the amp and turning the volume up too high?

I am going to test the guitar tonight on a different amp to see if it is actually the guitar with the problem.

Thanks again,
John.

[52 Bill]

What you are suggesting sounds a little scary. How do I know the signal returns? Would that not cause a feedback loop like sticking the guitar directly in front of the amp and turning the volume up too high?

John:
The two accessory jacks on your amp are basically a break in the signal path. This is where you would plug in an effect unit like a delay unit or a parametric eq. Some amps call this an FX loop.

The jacks have a switch contact on them that automatically closes the signal path, so that when nothing is plugged into them the signal can flow straight through the amp. If the switch contact becomes dirty or oxidized the signal path is broken, causing the sound to cut or fade in and out.

By plugging in a cord from the out to the in jack, you bypass the internal switch contact, thereby testing the internal contact. If plugging in the cord restores the sound, you know that the jacks need to be cleaned.

[bowesj]

Hi Bill,

Okay, I get it now. I guess it has been a long time since I read the instructions (to say the least). I wonder if they are in the correct location?

I actually found the problem. It is the guitar after all. It is a Takamini Electrical Classical. It cuts out after about 15 minutes (or maybe when I play it a bit too loud in terms of how hard I hit the strings). I just put the pot cleaning stuff in a few minutes ago actually (a product from "The Source"). I did the same with the Guitar pots which are sliders and I will see what happens. Maybe it is the pot.

Thanks again,
John.