Hum in 400 LTD

[mtulbert]

Hi Everyone,

Another day another hum probelm

I got a session 400 LTD on a trade without a speaker in it. Yesterday I finally got the 1501 BW for it and put it in. What a nice sound but the reverb has a terrible hum. I went through the posts here on the board and checked things out but there a couple of oddities with this.

The molex connector is indeed very tempermental as Carl D. has stated. Here is what I did. I checked for a short across pins 1 & 2. There is a short according to my ohm meter. It is not a dead open however.
Pins 4&5 check out fine.

Here is the kicker; if I disconnect the output from the reverb tank and shake the spring I still get reverb!!!!

Also, the amount of reverb seems to be weak. While this is not a critical issue with me (the reverb that is) I would like to have the amp working properly.

Any thoughts that any of you might have would sure be appreciated.

Regards,

Mark T.

[Bill Crook]

I test this on my 400, using the same options you stated, and got the same results !!

I believe its due to:

1) Eventho the spring input coil is suppose to be just that, it also can be modulated by the spring action. This in turn is sent along to the next ampifier stage because the signal for the spring unit is picked off the previous stage amp thru a R/C network.

2) The R/C network is bi-directional, so it dosen't make any difference hoe the next stage gets it signal, it acts upon it (ampifi's it).

Now, if you disconnect the input cable along with the output cable, This apparent problem will go away !! (I did the test)

Also check to see if the cables may have been reverse connected to the spring unit. Based upon your last comment, I think this is what is happening to your system.<FONT SIZE=1 COLOR="#8e236b"><p align=CENTER>[This message was edited by Bill Crook on 23 August 2000 at 06:49 AM.]</p></FONT>

[Mike Brown]

I spoke with one our techs here at the factory who repairs single units amps like the Session. He states that the reverb input and outputs are reversed. That's the reason that you are hearing a 'return' signal. Try reversing the connections at the pan.

Let me know if this was the problem. If not, please call me at 1-877-732-8391 and I'll assist in getting a solution for you. Thanks.

[mtulbert]

Thank you Bill and Mike for your help. That was a major part of the problem along with a cold solder joint on the input cable.

All is well in reverb land.

Thanks again,

Best Regards,

Mark T.