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Spider Valve MkII HD100 switching channels randomly


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I had a recent problem with my Spider Valve MkII HD100 head - it would randomly switch channels for no reason.  I removed the shortboard and took all my effects out of the effects loop and the problem still occurred - about every10 seconds it would switch channels a couple times.


I spent some time searching/reading forums to see if anyone was reporting similar problems.  I saw two things

  1. Thermal problems with the HD100 MkI
  2. Someone suggested that if you play loud, sometimes the vibrations can cause the amp to think you are moving the knobs - suggested turning all the knobs to zero.

I decided to take the amp apart and inspect it.  Nothing seemed obviously wrong, but I hoped that disconnecting and reconnecting all the cables to the digital section might magically fix the problem.


No such luck.  Problem still existed.


I decided to turn all the knobs to their zero position - I wasn't playing loud, but had nothing else to try.


BINGO!  Turning all the knobs to zero and the problem went away.  I played for about 20 minutes with no phantom switching - previously it would switch every 10 seconds.


A little more investigation, and I noticed that when I moved the Drive or Bass knob, the channel would switch.  Looks like some cross talk between the first three knobs  (first 3 knobs are Channel, Drive, Bass - in that order).  None of the other knobs cause any problems.


So now the amp is usable - although I am a little hesitant to use it in a gig.  It still doesn't work right, but I don't actually use the Drive and Bass knobs much if  at all.


QUESTION #1 - anyone seen phantom channel switching like this?


QUESTION #2 - anyone got any suggestions for how to fix the problem I have with the Drive and Bass knobs causing channel switching?


Note: I bought another HD100 amp so I can play gigs.  I had to buy it used since they don't make new ones anymore.  Huge bummer because I think this is a fantastic sounding amp - and great for me since I play in a cover band and I need a versatile amp.


QUESTION #3 - if they don't make the HD100 anymore, what is the replacement in the Line6 product line?




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I've heard of the knobs getting the jitters before but not the physical switching like you describe.


As far as fixing the knob issue the cheapest easiest thing I can think of would be a small shot of Deoxit into the potentiometers themselves and then work them a bit by hand after. I should mention the old thing about tube amps packing enough wallop (electricity) even when unplugged, to kill a person so know what you're doing or take it to a pro.


I own the HD 100 mkii and as far as I know they made extra DSP chips for them so they are still somewhat "serviceable" should something go awry with them.


Conversely the HD 100 doesn't. Therefore I always thought it might be an okay idea to buy a plastic Marshall vent grill for the top and install it right over the 4 6L6's.


That way all the heat leaves the head quickly and dissipates upwards leaving everywhere else cool. Now people will say "Well tube amps are meant to get hot".


Well that is true but real full blown tube amps don't have finicky digital preamp chips in them that have proven time and time again to be extremely susceptible to excess heat.


They (the vent)  can be had online for about 15-20 bucks from what I recall. Then I'd say just take a drill and jigsaw to the top to cut the perfect slot.


I mentioned this a few years ago on here somewhere. Just my two cents, for an amp that basically is toast if that chip goes, so I thought an ounce of prevention might make it last many many years longer.

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  • 5 years later...

I have the exact same problem on the exact same amp. Anyone know what it is? I read it could be the tubes but the amp performs perfectly tube-wise... no weird noises or lack of power, anything like that, they sound great and are very quiet when not playing. I read that someone had this problem and changing the tubes, even the right ones properly biased had no effect on the issue so I am reluctant to try since it sounds great. I bought it used, and have no idea how old they are so they they might need changing anyways. I just don't want to throw good money after bad as I can still return the amp to the seller (they did not indicate any issues and listed it only as used). Any advice?

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Carefully, pull up the knobs and check that the nuts holding the potentiometers are snug and tight. 

It will maintain the chassis grounds for the controls.


If that doesn't do it, then it will need to be serviced by an authorized service center. There are four

other different things it could be,... and none of those are self repairable.


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I checked the knob nuts, they are tight. Do you have an idea of cost per each 4 possibilities? It is my 1st Line 6 product, and I absolutely love this amp.

I would like to fix it. I won it on eBay this week with the FBV2 footswitch for a steal at $259 shipped. They still bring $700 -$900 depending on condition.

Thank you for the quick response, I am anxious to hear your 4 possibilities and cost guesstimates. I live an hour and a half from Nashville Line 6 repair shop.



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I fix them here at Line 6, but cost is not something we techs deal with. We have people who set up the returns and deal with pricing.

As far as individual authorized service centers, pricing is determined by the individual service center.


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Internal things that need to be dealt with by an authorized service tech.

Do not try to service it yourself, the shock hazard in a tube amp is too great.

I know from decades of first hand experience, it hurts when you zapped.


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