Herbert post-shipping troubleshooting - Help! solved

[narad]

So I bought a Herbert here on the forums, and I've been waiting almost two months to return home and try it out, of course when I finally do it doesn't work! On first inspection three of the power tubes were tilted to the right, when looking at the back of the amp, one so far it was barely in the socket at all, so it clearly took *quite* a fall. The packing was really good - original box, original packaging and then some more on top of that, and the box didn't show signs of damage but it was packed so tight on the sides we figure it didn't have much room to dent in. Anyway, the seller's a good guy - RoidRage - and we chatted for a while, and figure the tubes are messed up and I'll have to call in an order for new 6550s.

But since I actually turned it on and know the symptoms, I wanted to run it by here, maybe someone had similar symptoms or maybe, Peter, you could tell me if this is definitely the tubes or something more. The amp does standby/power on fine, in that the lights are all working. I can change channels, but there's no sound. On channel 3 when I adjust the channel-specific volume a humming will start and get louder as the volume is increased, but again, no sound based on the signal going into the amp. Before I go buying tubes, is that symptomatic of anything more?

The transformer screws/screw plates are bent up the tiniest amount, just small enough to notice. I've had transformers with much larger bends from shipping and still be fully functional, but I thought I'd mention it.

Thanks!
Jason

 

[MARK2C]

Try replacing the V1 or V6 preamp tube. If the power tubes were bad the fuses would blow.

 

[Peter Diezel]

Check out if the preamp tubes are tight in the sockets.
If yes, replace them. If the amp don´t work again please
contact a tech.

 

[narad]

Great - thanks for the info! I have the preamp tubes out, but
unlike 12ax7s I've taken out of other amps, these were more
depressed in their sockets. Anyone know if this is normal or
if the circuit board that the preamp sockets are on has been
dislocated further from the chassis?

About 1 1/8th an inch or .... 3 centimeters?

One was tilted a fair amount, not sure if it could have still been
seated properly. Still hoping it's just tubes, if the circuit board
looks normal I'll try reseating and firing up again:

 

[steve_k]

The preamp tubes seat deep, but the one that's crooked isn't right. The power end should be fine.

Pull the chassis and have a look. Maybe a preamp tube socket and a solder worked its way loose.

There's a lot of things happening on the Herbie. Guess you have made sure the mute and loop is not engaged? Haven't messed with mine for a while and trying to remember.

Tony's a good guy though and would totally trust him.


Steve

 

[narad]

Phew - I think your advice was good and the preamp tubes appear to be the problem - I swapped the loop preamp tubes with v1/v2 and I have sound on channel 2 and channel 3!

I'm about to order new preamp tubes, but I still no sound on channel 1, which seems odd to me - I didn't see any preamp tube that only affects channel 1. Is this a sure sign of problem larger than just preamp tubes?

 

[King Crimson]

I didn't see any preamp tube that only affects channel 1.

V1 - All Channels
V3 - All Channels

 

[narad]

I didn't see any preamp tube that only affects channel 1.

V1 - All Channels
V3 - All Channels

Sure, but if V1 or V3 is bad, shouldn't I also have no sound on channels 2 and 3?

 

[MARK2C]

The 12AX7 is a twin triode. There are two separate tubes in one bottle. It is very possible that one side of the
V1 is bad and the other is functioning.

 

[narad]

I did enough swapping and found that my NOS v4 was the culprit of the missing clean channel. Thanks for all the help - that was scary stuff!