Accutronics What ohms?

Sonny Miller · Post by **Sonny Miller** » 10 Dec 2004 3:54 pm

I have a quad reverb that i need to put a reverb in , i think, because the reverb hums when i put any bass at all on the amp!

Maybe the reverb has the wrong ohms , or is that idea not possible.

When i bought it as a head the amp said, "no more than 4 ohms" ( the amp originally came with 4x12 " speakers ), before i bought it.)
Is it a 2 watt out put on the speakers? or do i need a new reverb unit? I use a 4 ohm cabinet! Is thewre a way to test the Reverv unit?

Ken Fox · Post by **Ken Fox** » 10 Dec 2004 6:11 pm

Your speaker load is not the problem. That would be an old Quad reverb right? Same head as a Twin Reverb. Many things could be wrong. The tank for those is an Accutronics part #4AB3C1B. It has an input impedance of 8 ohm and an output impedance of 2250 ohms (not to be confused with DC resistance, it is much lower).

Are you saying that it hums more as the bass is turned up? First I would clean the connectors at the tank and back of the amp. Reverb drive tube is a 12AT7, tube #3. Swap it with tube #6, the inverter 12AT7, just before the 6L6GC tubes. The reverb return tube is #4. Swap that with tube#1 (12AX&/7025)and see if that makes a difference.

Sonny Miller · Post by **Sonny Miller** » 11 Dec 2004 6:22 am

Thanks , i will try that today as i have more 12AT7 tubes around.

Yes, the hum increases when i turn any bass on!

I will let you know.

Donny Hinson · Post by **Donny Hinson** » 11 Dec 2004 6:45 pm

Sonny, unplug both reverb cables from amp, and then turn the bass up. If it still hums, it ain't the reverb unit that's causing the hum.

Sonny Miller · Post by **Sonny Miller** » 12 Dec 2004 9:51 pm

It turned out to be dirty connections on the reverb, a bad set of wires and weak tubes.
Without the reverb it was a quiet amp,
And thanks for the accutronics reverb number , i had the wrong reverb in it, and but had the right spare. I also made a correction on the 12AT7 tubes also to improve things some more. THanks every body. That what i love about the forum. GOOD INFORMATION AND HELPFUL ADVICE.

Sonny Miller · Post by **Sonny Miller** » 14 Dec 2004 3:23 pm

I now have a very quiet amp Quad 73, with the reverb.

With the right accutronics reverb unit in it, it has a hum in it.

I pulled on on of the scord on the reverb and it cut off. So i cleaned them up and the amp works better but,still hums. Any other ideas , such as clean the tubes imputs with steel wood or somwething else? Any ideas?

Sonny Miller · Post by **Sonny Miller** » 14 Dec 2004 4:22 pm

I finally took the new reverb wire off the amp i bought on Ebay, and replaced those wires with the old ones and that took care of the problem. Thanks everybody for your help!