Leslie 145 Problem - No Sound

[carndawg]

Howdy,

Glad to be joining the forum. I bought a Leslie 145 w combo preamp pedal yesterday that has stopped producing sound. I plugged a guitar in to test it yesterday and it sounded great. It did take switching the speed once or twice to produce sound, but maybe that was just the tubes warming up.

I sprayed the tube sockets/reseated tubes this morning, and cleaned out the dust/assorted small items that somehow ended up inside of the cab. Upon powering it back up, there's no sound. The tubes all light up and speed can still be switched. The only audible sound i can get from it is when I put my thumb directly on the tip of my patch cable, and even then the preamp has to be cranked for it to be audible. It seems to cut out abruptly if I turn the preamp below 2-3 oclock.

The 6 pin cable seems a little finicky. If wiggled at the female end it occasionally turns the amp off for a split second. I've checked it for continuity and it seems fine. I checked the joints on that end of the connector and they seem good. The movement issue makes me think there's a break further back in the cable.

I'm wondering if this is a case of a break in the cable that's showing up fine when I test, or maybe something got bumped while I was cleaning. Is this a common issue? Just looking for ideas before I hack up the cable.

Thanks!

[clem]

I'd check the connector on the other end next. For one of those wires to be broken inside a person would think there would be some visible damage to the exterior of the cable. The audio signal wires should be the black and red ones.
Also...maybe spray some contact cleaner into the jacks on the preamp pedal....or take a peek inside it and see if you see a problem.

[David Anderson]

With the Combo Preamp and 145, you've got two separate audio circuits with two separate power supplies, one inside the preamp and one in the Leslie.

The motor switching will continue to work because it's just 120VAC not tied to either audio circuit.

First step is to figure out where the problem is. Are the preamp audio circuits getting power? Is there a bad transistor in there? Bottom line is that there are a number of points where the signal can be interrupted, and we can't guess where that is. I have seen one Combo Preamp with a bad power transformer.

It's easy enough to do a continuity/short test on a cable with a digital multimeter. It's not uncommon to have connector issues with the female end of the cable at the amp, but if you move it around, you should hear the signal cut in and out. Unless the cable is very old or looks abused, it's unusual to have a problem inside the cable. Some very old Hammond cables can suffer shorts between conductors 1 and 6, but those are cables from the 40s and early 50s.

[carndawg]

Thanks for the responses. Problem is solved.

I re-soldered the female end of the cable despite it testing fine, re-seated the tubes once more and the sound was back right away. Had a look inside the pedal before that and it seems to be in great condition.

I'm thinking it was the preamp tube not making great contact.

Thanks again. Glad i didn't start chopping the cable.

[David Anderson]

It's not uncommon to have problems with the 12AU7 pin/socket connection in the 147 amp. The sockets Leslie used have a small contact area, so if there is any oxidation on the 12AU7 pins, you may end up with intermittent contact. If you try to re-tension the socket contacts, be very gentle, because they can break off. It's best to clean the 12AU7 pins thoroughly, which can take more than a spray with contact cleaner.

[NittyRanks]

Wes is on here and he isn't that far from you in Kingston if you need any help.