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Posted: Wed Dec 15, 2010 9:19 pm
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Part of the beauty of using a 10 turn cermet is significantly less drift than a more traditional pot (accuracy). Add a set of GTs for even less drift than most other tubes, and your bias stays put longer. Sweet! :wink:

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Posted: Wed Dec 15, 2010 9:58 pm
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I thought you were soldering both components on the same side of the board Shimmilou, hence the jerry-rigged comment. :D

I am a little confused on your design though.

You must have soldered terms 1 and 2 together prior to inserting leg one into the first (top) hole for R87. Then you must have inserted term 3 into the opposite slot. Did you solder once side of the resistor to term 3 and then the other side onto the solder joint that you inserted term 3 originally? It just doesn't seem to be a good design to me for current levels as the new resistor is basically a safety precaution for the tubes.If it were soldered from term 3 of the pot then to the other side of where R87 used to be, that would make more sense. That is why I was thinking about them being on the same side of the card.

If I am looking at it the wrong way, let me know.


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Post subject: Re: Original Blues Deluxe Bias Problem
Posted: Sat Dec 18, 2010 8:03 pm
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Hey shimmilou, just looking at your amp pic and I have a question. Is that the power trans in the upper left ? It looks like bare windings or is it just the lighting ? Art

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Post subject: Re: Original Blues Deluxe Bias Problem
Posted: Sun Dec 19, 2010 8:04 am
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MrGreenGenes,

I drilled an extra hole in the circuit board between the two existing holes that R87 was in. And you are correct about the connections (I have my pot backwards). Terminals 2 and 3 of pot soldered together into the top hole where R87 was. Terminal 1 of pot into the new hole. On the back of the board, terminal 1 of pot connected to one side of new resistor, the other side of new resistor into second existing hole where R87 was removed. :)

aclempoppi,

That is copper foil on the transformer, maybe for shielding, I'm not sure. :)

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Post subject: Re: Original Blues Deluxe Bias Problem
Posted: Sun Dec 19, 2010 8:20 am
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Interesting how the chassis layout is different between your Hot Rod and my BDRI.

The biggest difference is the PCB that the tubes are mounted on. I now see why people complain about how the tubes are mounted to the PCB and the problems that that can cause. I don't have a photo, but on the BDRI, the tube PCB is mounted at about the same level as that small PCB to the left of the tube PCB, maybe a little deeper into the chassis. The power tube sockets then bolt to the chassis, and long metal "legs" run from the sockets to the traces on the PCB, a much better arrangement. The preamp tubes are still mounted directly to the PCB but I see that as less of a problem given their smaller size and lower heat output.

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Post subject: Re: Original Blues Deluxe Bias Problem
Posted: Sun Dec 19, 2010 9:15 am
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Oh, I'm sorry bluesky636, that is a picture of my BJr, not the HRDlx. I wasn't clear, I was just using my picture to show the pot installation, but I was referring to his amp and schematic R87. :oops: I think that the HRDlx and BDlx are pretty much identical as far as the layout and tube socket mounting. :) Here is the HRDlx (after installing new F&T power supply caps), and the second picture shows the heat sinks that I fashioned for the power supply resistors and zeners. I used binder clips with the handles removed, a little Dremel work to grind off the tabs, a little bending and they seem to work very well. :)

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Post subject: Re: Original Blues Deluxe Bias Problem
Posted: Sun Dec 19, 2010 10:06 am
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shimmilou wrote:
Oh, I'm sorry bluesky636, that is a picture of my BJr, not the HRDlx. I wasn't clear, I was just using my picture to show the pot installation, but I was referring to his amp and schematic R87. :oops: I think that the HRDlx and BDlx are pretty much identical as far as the layout and tube socket mounting. :) Here is the HRDlx (after installing new F&T power supply caps), and the second picture shows the heat sinks that I fashioned for the power supply resistors and zeners. I used binder clips with the handles removed, a little Dremel work to grind off the tabs, a little bending and they seem to work very well. :)

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Yeah, Ok. That does look more like my BDRI. So why do people complain about the tube mounting, particularly the power tubes? They seem pretty solid to me.

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Post subject: Re: Original Blues Deluxe Bias Problem
Posted: Sun Dec 19, 2010 11:06 am
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I think so too. Chassis mounted sockets, circuit board mounted on stand-offs, seems solid. :?:

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