Non-replicatable Issue

[trpullen]

I have a Rivera Venus 3 that I keep at church. A couple weeks ago, it made some loud static noises and then lost all signal. I shut it down and then powered it back up and noise again, no signal passing. I quick ran home and grabbed my Two Rock EXO, plugged it into the same cab with the same power cable and with the same pedal board etc. It ran great for the entire morning service.

I took the Rivera home to troubleshoot. Fired it up and it played fine. Played for a few hours, all fine. I thought maybe preamp tubes so, new 12AX7s all around and played again all the rest of the week. Took it back to church Thursday night and I fired it up, noise and very low signal. So CRAP!!! I grabbed my little Crate PowerBlock and finished rehearsal. Took the Rivera back home and guess what???? Yep, it plays just fine.

So....before I throw new power tubes in there (I bought a matched quad and used 2 and biased), Is there anything else I should check?

To summarize:
Church has a Port City 112 OS with a 16 ohm Celestion G12H30.

Home has a StageCraft Elite 212 with a 16 ohm Celestion G12H30 and a Eminence Cannabis Rex, also 16 ohm wired at 8 ohm.

I mention that in case it could be transformer related.

Any thoughts? Should I just swap the Power Tubes and take it back to church?

 

[Chrome Dinette]

Are you using the same cables when you test it at home and when you swap it out for the power block?

Also, does the amp have a loop? If so are you using it? If not, stick a patch cable in the loop and see if your problem goes away. Sometimes the nor malling contacts in the loop jacks can get intermittent.

 

[trpullen]

Are you using the same cables when you test it at home and when you swap it out for the power block? Also, does the amp have a loop? If so are you using it? If not, stick a patch cable in the loop and see if your problem goes away. Sometimes the nor malling contacts in the loop jacks can get intermittent.

Exact same cables at church with non working Rivera and the working two-rock and powerblock

Loop yes but not using it. And now that the amp works, I suppose I should haul it back to church to make it fail. ?

 

[Malcolm Irving]

It could be that the supply voltage is higher in the church, and this is triggering a marginal fault in the amp.

I think in the USA you have 120V +/- 5% ? That would allow the voltage to range from 114 (or can that go down to 110?) to 126 before the utility would have any concern.

 

[trpullen]

It could be that the supply voltage is higher in the church, and this is triggering a marginal fault in the amp.

I think in the USA you have 120V +/- 5% ? That would allow the voltage to range from 114 (or can that go down to 110?) to 126 before the utility would have any concern.

I will take my multimeter with me Thursday. Strange thing that it has not happened in 5 years before this and not messing with digital stuff, hammond organ, Blues Jr, Aguilar bass, etc. The building is very well built with modern electrical service...but worth a test.

 

[trpullen]

I have even tried bouncing the amp around a bit at home to see if the car ride may have "fixed" it on the way home. No avail.

Does the loud static and then low to no volume sound like a cold solder joint or you lean more towards the power tubes?

 

[Malcolm Irving]

It sounds more like a bad solder joint to me.

I don't know if you can see the power tubes while you are playing? When power tubes create big static noises in themselves, it is usually accompanied by blue light flashing (or similar) inside the tube. Also, this type of breakdown creates massively loud static.

(The 'light show' doesn't apply to an intermittent contact in the tube socket though.)

 

[TimmyP]

Put a cable in the loop (unless the loop has a bypass switch).

 

[Malcolm Irving]

Yes, if the amp uses switching jacks on 'send' and 'return' to bypass the loop, these contacts are the prime suspect for a bad contact (especially if they are seldom used).

Jumping from 'send' to 'return' with a guitar cable will check this out.

 

[trpullen]

I will give the loop a try.


I have the back off so i can see in it but can't get it to make the noise. GUH