VH4S cracks : Repared, but can't change channels anymore...

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billy_lost

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Hello !

I've bought a VH4S 2 years ago, never had any problem.

A few das ago I've bought a Mesa Boogie Recto recording preamp to have a different sound. I've connected the "live outs" of this preamp in the serial returns of my VH4S. The general master of the mesa preamp was set on 12h, the volume of second channel (overdrive) set on 9h...

I've played 90 minutes, then re-plugged my guitar in the VH4S preamp, and disconnected the Mesa preamp of the serial effect loop return.

When I play now, the VH4S males "cracks" in the sound, and sound cut very fast, cuting the sustain of my guitar, like a high cut noise gate...

DOes anyone know what is the problem? Help ! :aww:
 
You could have cooked a preamp tube. Try a new one in each spot one at a time.
 
Sorry but.. It can't be a preamp tube, the problem happened without using the VH4S preamp...
 
The loop uses preamp tubes !!! They can die even though you are not using them too at full operating voltage.
V1 to V4 are all before the loop so at least try the V1 and V4.

VH4:
V1 Used by all channels
V2 Used by channel 4
V3 Used by channel 2/3/4
V4 Used by all channels
V5 Mixer and Send buffer
V6 Return driver
V7 Phase Inverter
 
Yo Mark2C....

Are you DEAD certain these are the mappings for the V...?? Not arguing, just wanting to know fo'shizzle if this is 100% accurate. And also, a point that may be confusing, there are 9 preamps in the VH4S.

V.
 
The S has two PI's and two loops but anything before V4 would still effect the preamp just the same.
You can have the loop work fine since it's past Ch. 1-4 in the signal chain. If V1, V3 or V4 go bad
if effects the preamp signal as they are before the loops.
 
Ventura":182jrbg3 said:
Yo Mark2C....

Are you DEAD certain these are the mappings for the V...?? Not arguing, just wanting to know fo'shizzle if this is 100% accurate. And also, a point that may be confusing, there are 9 preamps in the VH4S.

V.
Click to expand...

To the best of my knowledge since I don't or never have owned an S, the layout is the same as the VH4
plus the added second loop and second PI. From looking at a photo of the PCB It should be like this:

VH4S:
V1 Used by all channels
V2 Used by channel 4
V3 Used by channel 2/3/4
V4 Used by all channels
V5 Mixer and Send buffer
V6 Return driver 1
V7 Return driver 2
V8 Phase Inverter 1
V9 Phase Inverter 2

Peter or Olaf can correct me if I am wrong, but this is what makes sense to my brain and eyes.
 
Well, thanks ! :thumbsup:

I will try to change all one by one to see if the problem comes from tese tubes, I hope it is the case !

Which preamp tubes do you preconise, Peter's original choice or others?
 
Well, I've took a few time to try to eliminate these annoying cracks... This is how I've proceed :

_change both V1 and V4 (Used by all channels) : still cracks, so re-install original preamp tubes
_then change V2 (Used by channel 4, even if cracks can be heard on every channel) : still cracks, so re-install original preamp tube
_so change V3 (Used by channel 2/3/4) : still cracks, so re-install original preamp tube
_change V5 (Mixer and Send buffer) : still cracks, so re-install original preamp tubes
_ V6 and V7 (Return driver 1 and 2) : still cracks, so re-install original preamp tubes
_endly change V8 and V9 (Phase Inverter 1 and 2), and...still cracks, so re-install original preamp tubes !!! :thumbsdown:

So... Disappointed. :cry:

When I play clean sound (channel 1), even with my SG (so powerfull humbuckers), I hear cracks and if I play smoothly, the sound cuts as if I have a noise gate... :confused:

So... If you can help me... ;)
 
That I wanted to say.

Thanks Mark2C, You are always helpfull :thumbsup:

@ Billy: Please check the tube fault fuses also when
the LED´s are not indicating.
 
Well... I've changed all the 12ax7, sound keeps on cutting and cracking...

Without volume on poweramp's channel left and volume on poweramp's channel right, cuts and cracks...
Without volume on poweramp's channel right and volume on poweramp's channel left, cuts and cracks...
:doh:

Tell me, there are 4 EL34, 2 for channel left and 2 for channel right, am I right?

I've changed all the tubes a few time ago, I rarely play my rig. Pay 200€ one more time without any assurance to endly eliminate the cuts and cracks... :cry:

I'm so disappointed..............
 
try plugging and unplugging in the loop sockets of your vh4s again several times. correct me if i'm wrong but if you unplug from the serial loops, the internal circuit lactches close in the plug socket. if it's not been used for some time the latch contact can be corroded and not close again right after unplugging a device.

to try out if the powertubes are broken plug the mesa back to the loop-returns and play for some time.... if there still is some crackin you know it's gereated behind the loop-return.

if you have another poweramp try plugging the vh4-loop's send to the other poweramp. if it still cracks then somethings's wrong before the loop. don't forget: the preamp on the vh4s only gives sound when not beeing in standby...so don't forget the load to the vh4s either...

ps: and check the guitar cable first...and the speaker cable.
 
Thanks elfredoo !

elfredoo":1rxciz0b said:
try plugging and unplugging in the loop sockets of your vh4s again several times. correct me if i'm wrong but if you unplug from the serial loops, the internal circuit lactches close in the plug socket. if it's not been used for some time the latch contact can be corroded and not close again right after unplugging a device.

to try out if the powertubes are broken plug the mesa back to the loop-returns and play for some time.... if there still is some crackin you know it's gereated behind the loop-return.

if you have another poweramp try plugging the vh4-loop's send to the other poweramp. if it still cracks then somethings's wrong before the loop. don't forget: the preamp on the vh4s only gives sound when not beeing in standby...so don't forget the load to the vh4s either...

ps: and check the guitar cable first...and the speaker cable.
Click to expand...

I've done all these steps one again... Still cracks... and yes, cracks come from the preamp section (send direct in VHT 2502 poweramp, cracks are still here...). Well, so... :gethim:
 
:doh: Incredible loss of volume on channel 1.......... I can hear the guitar as if it was a mile away... And still cracks on other channels...

This is really frustrating, I've change preamp 12AX7 n°1 and n°4 one more time, nothing...

Does anyone here knows how a VH4S work? Peter???
 
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