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32
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Website, Store / Support / Re: Possible Oscillation.....Squealing through speaker
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on: November 21, 2012, 09:35:45 PM
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Hey,
The squealing sound may be due to having the OT primaries at the power tubes swapped! When building an amp there is always a 50% chance to get that wrong and the outcome is a high pitch squealing sound on startup! In other words swap the blue and red wires at pin 3 on the EL34's then power up again!
Make sure not to power amp up without the speakers connected, will take out the OT!
Todd
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33
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Muchless / Lightning / Re: lightning test point voltages
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on: November 05, 2012, 09:05:14 PM
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Stuart,
Good find on the bad wire! Did you check all your voltages again on all the tubes? Hopefully they are all now in range.
No worries on the poor wiring job, we all start somewhere.
Sounds like you are getting pretty close to having a working amp
Todd
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34
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Muchless / Lightning / Re: lightning test point voltages
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on: October 30, 2012, 05:00:38 PM
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Hey Stuart
Is it possible to take some gut shots and post them here?
Also I would check all the dropping resistor values are correct. They are the large resistors mounted next to the larger electrolytic caps. Meter for continuity across the underboard jumper wires to make sure they are in correctly.
Todd
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35
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Muchless / Lightning / Re: lightning test point voltages
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on: October 24, 2012, 12:50:42 AM
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Hey Stuart Good find on the input jack. The wattage of the resistor will not be the problem. If it was underated the resistor will turn black and the smoke will come out  Maybe just double... triple.. check every connection and component value again. theres probably something off Todd |
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37
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Muchless / Lightning / Re: lightning test point voltages
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on: October 21, 2012, 04:25:35 AM
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The cap being wrong size should not be the cause of the readings but you should get the right size in there
Make sure and check all your ground connections are in place.
If possible post some gut shots
Todd
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38
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Ceriatone / Overtone / Re: Which Overtone?
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on: October 19, 2012, 11:12:18 PM
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No prob
The HRM, Bluesmaster and the MKII all have the HRM tonestack which is a separate treb, mid and bass for the overdrive channel. On the original dumbles and in the C-tone versions these potentiometers are located inside the chassis so they are pretty much set it and forget it. The purpose is to be able to EQ your OD separate from your clean. This could be seen as being more versatile than the standard OTS's by some. I prefer simple and have not once thought when playing my FM ( non-HRM ) that it would be better if it had separate TMB for the OD.
The OD trim is another potentiometer that in original Dumbles was mounted internally on the pre-amp board inside the chassis and was originally set by Dumble himself when tuning the amps he built before giving them to the original buyer. Nik at one point moved the potentiometer to the back of the amp for easy access which I think is great. It is just a drive knob really but it can set the OD section anywhere from just clean boost to serious crunchy drive. I set mine somewhere in between.
Hope this helps
Todd
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39
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Ceriatone / Overtone / Re: Which Overtone?
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on: October 19, 2012, 10:19:55 PM
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Can the MKII get close to RF tones = IMO Yes
Is the MKII more versatile than the FM = If you consider having the HRM tonestack more versatile yes. Other than that they are not much different animals.
The Marshally description you mention I believe is for the standard HRM not the MKII. I would not consider either the FM or MK even near Marshall territory when compared to my 2550. Could probably get close with pedals though through the clean channels.
Todd
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40
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Muchless / Lightning / Re: lightning test point voltages
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on: October 17, 2012, 04:32:58 PM
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How different?
The spreadsheet is kind of a ballpark comparison.
If there is only a 10-15% difference it may not be an issue depending on where the readings differ.
Post your readings if possible.
Todd
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41
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Ceriatone / Overtone / Re: Which Overtone?
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on: October 16, 2012, 07:51:03 PM
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The FM's clean channel is a little chimier than the MK
The FM's OD channel has a little more hair than the MK.
Both are great amps! The differences are subtle
If I had to sell one of them I would keep the FM
Hope this helps
Todd
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42
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Ceriatone / Overtone / Re: Which Overtone?
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on: October 15, 2012, 08:16:06 PM
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Hi
I have both the FM50 and MKII 50. I would say with the OD trim set the same on both amps the FM50 has more hair than the MKII. As you turn up the OD trim the FM seems to get a little fizzy quicker. I keep my OD trim on the FM at about 11:00 and on the MKII at about 3:00. I am running JJ 6cA7's in the MKII btw IMO they sound better than the EL34's I had in it.
I cant comment on whether that was a typo but in regards to the similarity between amps the MKII uses pretty much the same pre-amp board as the FM, just a totally different power section more like the 183, then add HRM. I have not played a 183
Todd
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to keep the forums alive.