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Post subject: Hot Rod Deluxe Problem (oh no!)
Posted: Fri Jun 04, 2010 6:56 pm
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I've been using a Hot Rod Deluxe for a couple months and I've been extremely happy with it. Earlier today I plugged into it and when i cranked up the drive on the "more drive" channel, the amp started to make a screeching, dinging sound. As i turned the drive up, the "ding" got louder, but it would slowly fade when I rolled it back and around the 7 mark it would stop completely.

I am pretty sure that the sound is related to the amount of drive that is set on the amp because of this, so I am hoping that it is just a problem with the tubes. Then again, I'm kind of new to tube amps.

Has anyone encountered the same problem? I hope that it's a simple fix, because up until now I've been very happy with it. Any suggestions would help.


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Post subject:
Posted: Sat Jun 05, 2010 5:09 am
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Hi,

1st, Make sure you have the same without input connected.

2nd, do you have technical skills?

Tissan


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Post subject:
Posted: Sat Jun 05, 2010 7:36 am
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Hey,


1. The same sound happens without an input.
2. Very minimal.


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Post subject:
Posted: Sat Jun 05, 2010 7:46 am
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Let the amp cool. First so you don't burn yourself and second that you break a tube while its warm. With the power off and disconnected from the wall rotate the 3 12AX7 tubes. Assign a imaginary number to them and change their order. Try something like this just make sure you let them cool in-between testing.

1 2 3
2 3 1
3 1 2
3 2 1

The problem should move when you change them - if so its a preamp tube.

If you haven't changed a tube before or the amps under warranty or you think your liable to break the tube legs yanking it out then leave it and get it serviced.


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Posted: Sat Jun 05, 2010 9:00 am
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When you say, "The problem should move when you change them," can you be more specific? Will the sound come from a different part of the amp or will it be caused by a different knob?


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Posted: Sat Jun 05, 2010 1:04 pm
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brad2 wrote:
When you say, "The problem should move when you change them," can you be more specific? Will the sound come from a different part of the amp or will it be caused by a different knob?


It will either get worse, better or go away.

If you swap them back to their original position and it comes back. Bad tube.


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Post subject:
Posted: Sat Jun 05, 2010 2:58 pm
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Hi

V1 and V2 are used in both drive and clean channels, the difference are the capacitors that short the kathode resistor for "AC" mode in order to have more gain.

V3 is the dephaser (a kind of differential amplifier) to supply 6L6GC power tubes AB style). I think V3 and 6L6GC are not concerned on first.

I don't think 12AX7 are the root cause, but a check is a fact.

I suspect relay, capacitor failure or soldering failure:
Down load the schematic and Check C8 and C9 (1µF 100V) , Q1 Q2 (Jfet), K2A and K2B (relay).

You can also test the power amp with another preamp if you have: line out in Power IN

Take care about HV (DC 450V) that can kill you. First unplug the ampl and secondly put a 100K 2W in // to B+/GND isolated wires with crocodile plugs, Third measure all decoupling capacitors (C31, 33, 35 and 36 close to 0V) before make any repairing.

Tissan


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Post subject:
Posted: Sun Jun 06, 2010 9:26 am
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Thanks for both of your help. I'm probably gonna let the guitar tech at a place that I go to check it out to be safe


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Post subject:
Posted: Mon Jun 07, 2010 5:00 pm
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brad2 wrote:
Thanks for both of your help. I'm probably gonna let the guitar tech at a place that I go to check it out to be safe


Make sure they can do tube amp repairs otherwise you might be wasting time (unless its just a tube swap problem).

I wouldn't leave an amp with anyone who isn't experienced with one they will either do more damage than good or just charge you and drop it off to someone else for repair in which case it will cost you more in the long run.


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