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Post subject: Major Problem, please someone, HELP ME!!
Posted: Mon Jun 09, 2008 10:32 am
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Rock Star
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Hey good people. I've had problems with my HRD 410 for ages now:

I play hard rock (Izzy Stradlin style) in a well known band here in Ireland and had been using a Marshall JCM in rehearsal/live while wanting to get my DeVille in the fold instead as when I use it at home it's more 'me'.

I read a lot of posts here about the problems with distortion, buzz etc and someone reccomended I change one of the 12ax7's and I replaced the 3rd one with an EH as after swapping around all day this seemed to have gotten the best results.

After being happy with it at home I decided to take it, finally, to my bands rehearsal room and pushed the JCM to the side and the other guys showed up and we rehearsed our set...........now the weird, bad part.....

The DeVille sounded awfully tinny up against our other guitarist, also a JCM user and even with the bass on the DeVille up full I wasn't getting any fat rhythm coming through. It was then I opted to use a Marshall Guv'nor pedal through the DeVille's clean channel and still it was awfully tinny sounding and not at all what I wanted.

Me and the guy's took the back off the amp to see if the valves were all connected properly and to my horror the seal (red blob) on the blue biassing dial had broken and was sitting at '10 past 12'.

I play a reissue Fender 72 Tele Custom through the DeVille.

Please note that the clean is still fat and beautiful.

I am confused and frustrated. Any advice on how to make my DeVille have full Marshall sounding dist while retaining my Fender clean would be greatly (and I mean that) appreciated.

Thank you very much!
K


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Posted: Mon Jun 09, 2008 10:40 am
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First thing I would do is have that biasing pot checked out by a tech.

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Posted: Mon Jun 16, 2008 1:34 pm
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Problem is I can't get it to a tech for while. Is there anyway I can fix this problem myself?

What tubes would you recommend to get a smoother distortion?

Am I harming my amp using it with the 'unknown setting'?
Thank you!
CC


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Post subject:
Posted: Mon Jul 21, 2008 12:45 pm
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Seriously though, am I harming the amp using it on the unknown setting?
CC


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Posted: Mon Jul 21, 2008 1:29 pm
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Celtic Cyclonus wrote:
Seriously though, am I harming the amp using it on the unknown setting?
CC


I don't think you would be harming the amp, but it will take a toll on your tubes.

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Post subject:
Posted: Tue Jul 22, 2008 7:29 pm
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CAFeathers wrote:
Celtic Cyclonus wrote:
Seriously though, am I harming the amp using it on the unknown setting?
CC


I don't think you would be harming the amp, but it will take a toll on your tubes.


Hello all,
With all due respect, I have to disagree. :) If the tubes are biased to high, there will be some considerable heat building up inside the cabinet where the pc board is. The heat will definatly cause a problem. Most probably to the two 5 watt resistors that are mounted to the board and possibly the solder joints where the tube sockets are soldered to the PCB. Those solder joints should be checked on these amps anyway as it is fairly common for them to develop small cracks with age and heat. :cry:

Adjusting the bias on an HRD is extremely easy. All you need is a multimeter. I found these instructions very easy to follow. http://studentweb.eku.edu/justin_holton/bias.html I have an HRD 410 myself and found the bias was very high and was getting very warm. I put it back to where it was supposed to be and while it still gets warm, it isn’t hot to the touch.

The bias should be checked when installing new tubes and every once in a while after as it can change as the tubes age.

Just be very careful poking around back there with the cover off. Even with the unit unplugged, there are some residual lethal voltages in the filter caps.....

Take care!
Keith


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Posted: Mon Jul 28, 2008 3:27 pm
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I've been knocked across the room before by the residial voltage of a TV picture tube to the tune of around 15KV static charge. The voltage is definately high but, since there is no amperage behind it, unless you have some sort of heart condition, it is highly unlikely you will be killed by the voltages in an "unplugged" unit.

Having said that, unless you like pain, you would do well to take an insulated screwdriver or some such and ground those capacitors before you begin working in there.

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Posted: Tue Jul 29, 2008 6:41 am
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You can be killed if you are part of the circuit. It is not like a static charge. The amp needs to be on to adjust the bias. Keep one hand in you pocket.
You need to measure the plate voltage and use the formula to get the proper mv for setting the bias at 70% dissapation. Otherwise the mv settings mean nothing. 68mv may be fine, 80mv may be fine it, it depends on the plate voltage.
If you don't know what your doing, let a tech handle it.
There are videos on www.eurotubes.com for biasing.


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