Fender Stage160 Reverb not working

[Rpasman]

The reverb on this amp is not working. If you turn it up you just get hum. No hum if set to 0. Found a schematic and checked TP20, did not vary with REV stetting it had a (-3.4mV) steady value, schematic said 2.45 VAC? TP21 read 18.9 mV schematic said >5mV? So the values are wrong. I'm a newbie so I'm looking for what I should do next. Reading other threads it appears soilder is a frequent problem with the STAGEnnn amps. Any advise is welcome. My next step is to get to the underside to examine but I'd like to know where to look. Rest of amp is working as designed. Year is 2000 amp is very lightly used. thx

[Twist]

Don't pull out the chassis yet. It sounds like the reverb tray is bad. Since it hums when you turn the reverb level up it's most likely the output of the tray is bad or possibly the cables going to it. In your case I would suggest ordering a new one or finding a good used one. Be careful when you order one because it's critical that it has the same input and output impedances as the original tray. If your familiar with an ohm meter you can measure each side of the tray to see if it's opened up and also look to see if there is a broken wire inside. If any springs are broken off then toss it. Ocassionaly the RCA connectors need a good cleaning.

[Rpasman]

Thanks for the feedback. I did inspect the tray during my first look at the problem and did not see anything opened up. The springs were in place. However each end of the tray did appear different where the coils wrap around the frame.

I turned the amp on set Rev @ 5 and touched the White RCA lead and definitley got a nice loud reaction. I think that is a good sign and your right about the signal being good. I had tested continuity of the RCA cables and they seemed OK, meaning I could get a audible signal when I held the tester on the leads.

I own and Ohm meter what should I be testing for? A complete break or a certain value of resistence? Please be specific where and how to test. Thanks for your help!

[Enzo]

There is an RCA jack near each end of the pan. Measure resistance between the center pin and the shell on each connector. The output end mught read in the 150-200 ohm range, and the input end might read anywhere from half an ohm to a few ohms.

Look at it this way though. The resistance won't be wrong. You either have continuity - and the right resistance - or you have an open. Open means the transducer has failed.

Yes, the drive transducer looks different from the pickup transducer.

Make sure one of the little black and green wires is not broken off.

[Rpasman]

Enzo thank you. I read 58 Ohms on the IN and 0 on the OUT. I do have the pan out at the moment, each wire has continuity from the RCA to the connector.

I removed the connector on the OUT and read Ohms accross the two transducer leads. Still 0. The reason I did this is the shell of the OUT RCA is grounded to the tray. Not certain if that should be the case or not? Definitely was assembled that way. The RCA leads on the IN are insulated from the tray.

Based on your earlier reply does this mean the transducer on the OUT is failed? Looking at the part It would appear I would need a full replacement. Any other test I could do? I have a Tech21 with a similar looking tray any harm in trying that to confirm?

The Fender Part is 8EB2C1B, Accutronics Cary, IL.

[Rpasman]

Enzo I found this link and answered my questions on grounding. It is correct. Looks like the OUT should have read 200 Ohms. IN should be 58 and it was 58.

http://members.tripod.com/~roymal/accutron.htm

[52 Bill]

Enzo thank you. I read 58 Ohms on the IN and 0 on the OUT.

By "0" do you mean "zero ohms" or do you mean "no reading"? If you touch the two leads of your meter together you should get a near zero reading. When the leads are separated you will get an infinity or wide open reading. If the output transducer is wide open, you have found your problem.

Based on your earlier reply does this mean the transducer on the OUT is failed?

Yes, but sometimes depending upon the type of tank construction, you may be able to find the broken connection. Does your tank have push on connectors on the transducers, or do the wires come directly out from under the yellow coil tape?

I have a Tech21 with a similar looking tray any harm in trying that to confirm?

If you know that the Tech 21 tank is working, try plugging it into the Fender amp. You can't hurt either the amp or the tank by trying it.

[Rpasman]

I had "no reading" for Ohms on my VOM it showed "0L", touching the leads together will eventually read 0. There are connectors but I removed them and tested directly to the leads. They read 0L as well. I also check the continuity to the connectors and that was good.

I've ordered a correctly sized replacement tank, hope to see it yet this week. Thanks to everyone who helped me on this! Visually everything looked fine.

[Enzo]

Are you clear now on the difference between 0 and open? Zero ohms is a dead short, like touching the probes together on your mater. No reading or OL means open. Yes, that means a bad pan. Unless the little green and black wires are broken off and can be repaired.

[Rpasman]

Yes, I now understand the difference. Thanks to you and Bill 52 for pointing that out. I'm looking forward to having this work again, replacement is on the way.

[Rpasman]

It's working again

Just thought I would give an update, the new tray fixed the problem. Thanks for all the help!