damage to VH4 if running while not connected to cabinet

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insomniac

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hey all

a few weeks ago i loaned my vh4 amp to a band for their album recording,

they have used several amps which were all located at the control room.
also, they used a patch panel to connect the amps to various cabinets on another room.
all the cabinets were recorded simultaneously to multiple tracks.

at the end of the recording day, they have noticed that although the vh4 cable was connected to the cabinet at the other room -
there was no sound coming out of it, hinting there was a problem either with the cable or the patch panel port.

its been running like that the whole recording day without them noticing it.

since then, it seems to me that the vh4 sound has degraded significantly.
the amp sounds somewhat compressed, with lots of treble and less bottom.
plainly put, it just sounds thin.

before every time i lend the amp i stress the importance of making sure the amp
is connected to a cabinet before even turning it on, as stated in the manual.
the manual also says it might cause great damage to the amp - with no clear troubleshooting help.

i'm not sure if its just a psychological thing or has the vh4 sound really degraded that much.

could anyone shed some light on that matter and how i should proceed?

if it has any relevance, just a couple of weeks before the aforementioned incident - the amp got its tubes freshened up (4 ruby 6l6's, V1-V2 TAD 7205 S, V3 - V7 TAD 12AX7-C) and was biased properly - it sounded awesome after that.

thanks!
ron.
 
First check the 4 power tube fuses.
Then check the power tubes. Replace them
and bias them.
If all is replaced and the issue don´t disappear
we will send You a new output transformer.
Sending the amp to Germany is possible but
maybe expensive.

Stay cool :thumbsup:
Peter
 
thank you, i'll order a quad from ebay right away.

so it is possible the sound quality was damaged because it was left open that way?

ron.
 
Sorry to hear that, good luck with the amp, I hope you can sort it out with the power tubes!
 
hey all

UPDATE - i did as peter suggested and checked the tubes fuses, it actually turned out that the ch3 and ch4 fuses were blown.
after i replaced the fuses the sound got awesome again :) thank you peter!

i already ordered new 6l6's, should i replace them just in case?

two more questions come to mind -
1. why weren't the red LEDs saying "tube fault" lit? aren't blown fuses considered somewhat of a tube fault?
2. just wondering, how does blown fuses for ch3 and ch4 affect the overall sound of the amp? including the other channels?

ron.
 
Glad to hear your amp is working again.

2. If you mean the fuses in back panel, these are not for the channels but one of each tube.
 
Exactly, because of the two blown fuses you were operating the amp with only two active tubes, which, as you found out, greatly affects the sound and performance of the amp. I think you were very lucky that this was the only damage, and goes to show that the amp is very well built and the safety circuits worked as they should.
 
thank you all for replying!

what i dont understand is how the two tubes were still lighting up although their fuses were blown.

ron.
 
Just have to chime in here...this thread is a great example of Peter's stellar customer service!
 
insomniac":kjwbwn2u said:
thank you all for replying!

what i dont understand is how the two tubes were still lighting up although their fuses were blown.

ron.
Click to expand...

What Peter said. The heater is still drawing current despite damage to the rest of the tube. They were probably blown fairly quickly and once they did, they took the fuses with them to save the output transformer from suffering the same fate. It's a very good design practice that for some reason isn't followed on many high end amps (Diezel obviously excluded).
 
glassjaw7":v4qjyoee said:
Just have to chime in here...this thread is a great example of Peter's stellar customer service!
Click to expand...

:thumbsup: :thumbsup:

That's exactly what I thought :D
 
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