From a post I did a while back on the Forum:
Amp came in with great reverb, just a lot of hum in it. A close inspection revealed the factory reverb cable was assembled incorrectly. The shield and signal wires were reversed causing signal to be carried on the shields.
The connector is a 5 pin Molex and should be as follows (note pin 1 is near the end of the connector with the wedge shape:
pin 1, white wire (to reverb tank input, longer of the two reverb cables
pin 2, shield/ground from the longer cable
pin 3, no connection
pin 4, white wire (to reverb tank output, shorter of the two reverb cables)
pin 5, shield/ground from the shorter cable
It should be noted that the reverb tank used has the input ground isolated from the body of the reverb tank. The output of the tank has the jacks shield connected to the tanks body. With the configuration I found the output signal was attached to the body of the tank. Just touching the tank caused in increase or different sound in the reverb return circuit!
I substituted a cable assembly from a second Nashville 400 I had to resolve the issue. Perfectly quiet reverb now!
I have ordered a Molex pin extractor tool to correct the pin arrangement on the old cable assembly.
Considering the number of complaints about reverb hum in the Nashville 112 makes me wonder if a wrong reversal could have occurred on some of the Panduit connects they are using. Easy to do! I have already seen a N-112 with the Panduit cable plugged in backwards, resulting in reverb tank input to amp reverb input and reverb tank output to amp reverb output. Amp still had reverb, just a lot of hum.
Human error is easy when making up a Molex or Panduit style connector. I made up thousands of the Amp (red) and Panduit(white) style connectors when installing Rauland Borg and Dukane school intercom systems (in my working days)! Made a few errors myself, easy to do.
It is also very important to check for spiking on the top, leading edge of the sawtooth wave form at the filter caps(looks like a sharp church steeple). If it is there, replace the caps. Keep in minds there are 6 filter caps there for the different voltage rails! All are located next to each other. There are 2 at 4700uf, 2 at 1000uf and two at 22uf or 25 uf.
Make sure the reverb connections are clean and tight at both the reverb tank and especially at the Molex connector to the amp.
[This message was edited by Ken Fox on 20 October 2006 at 12:00 PM.]
[This message was edited by Ken Fox on 20 October 2006 at 12:01 PM.]
[This message was edited by Ken Fox on 20 October 2006 at 12:05 PM.]
[This message was edited by Ken Fox on 23 October 2006 at 08:50 AM.]
[This message was edited by Ken Fox on 23 October 2006 at 09:29 AM.]
[This message was edited by Ken Fox on 01 November 2006 at 03:29 PM.]
