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Post by johnnygodfrey on Apr 20, 2016 18:21:36 GMT -7
Hi there,
I have had a couple issues using the Brake Lite with another amp. I have a Blues Jr. modded with several of the Bill Machrone mods, including output transformer, tone caps, power caps, and bias trimpot. When I run the BL with the Jr., the amp will experience a sudden precipitous drop in volume, swell back to full volume, and then drop again. It doesn't sound healthy when this happens; there seems to be a slight spittiness when the volume drops off. It has happened with the BL on 2 or 4, but has only happened after the amp has been warmed up and is fully opened up.
I am using speaker cables to make the connection from amp to BL to speaker. Also, I know the BL is not the issue, because when I run it with my Remedy I have no problems. Any suggestions/ideas as to what's going on with the Jr? Has anyone else had problems using the BL with other amps?
*I'm waiting for the comment: "yeah, the problem is you're using a Blues Jr. instead of the remedy!" Touché, sir, touché.
Thanks for your help!
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Post by purpletele on Apr 20, 2016 23:26:53 GMT -7
It could be that the BrakeLite is creating an additional load and creating a heat overload or there may be a weak tube that is failing under the load.
Most likely the latter.
That's my late night logic.
I hope Bill Machrone is doing ok. He had been battling
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Post by dergit (Markus) on Apr 21, 2016 3:23:30 GMT -7
damn, that sounds scary. purpletele 's hypothesis makes sense to me but I don't know enough to give you any advice with confidence other than giving the Doctor a ring. After you tried different power tubes, that is.
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Post by zpilot on Apr 21, 2016 3:49:21 GMT -7
I'll bet that you are running the BL at full attenuation and cranking the BJ way up. That is after all one of the main reasons people use an attenuator. If so, you may be stressing the output transformer to the point where it is shorting somewhere between windings. That would be my first guess. When things are intermittent like that it usually is because of heat.
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Post by purpletele on Apr 21, 2016 8:12:19 GMT -7
Just checked for info on Bill Machrone.
No updates are available that I can find.
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Post by johnnygodfrey on Apr 21, 2016 14:05:40 GMT -7
It could be that the BrakeLite is creating an additional load and creating a heat overload or there may be a weak tube that is failing under the load. Most likely the latter. That's my late night logic. I hope Bill Machrone is doing ok. He had been battling Thanks for the tip. This happened once during the middle of a gig - I eyeballed the tubes quickly and didn't see anything obvious, but I'll do a full swap-out and see if that takes care of the problem. Right around the time I placed an order with him was when he left the shop to undergo chemo. My order was delayed and he said as much in an email to me. It seems he is up and running again.
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Post by johnnygodfrey on Apr 21, 2016 14:09:21 GMT -7
I'll bet that you are running the BL at full attenuation and cranking the BJ way up. That is after all one of the main reasons people use an attenuator. If so, you may be stressing the output transformer to the point where it is shorting somewhere between windings. That would be my first guess. When things are intermittent like that it usually is because of heat. The BL gave me this same issue on two occasions; one time when it was set to 4 and one time (during a gig!) when it was set to 2. And yes, the BJ was hitting its ceiling. I hate to think that the output transformer was shorting - I swapped the stock transformer with the David Allen-designed TO20B, purchased from Bill's website.
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Post by purpletele on Apr 21, 2016 17:33:09 GMT -7
Johnny,
I was thinking about your symptoms.
If you performed the power mod the you reduced the value of your power resistor from 5k ohm to 3k ohms if memory serves correctly.
That should be considered with your perfect storm of a totally cranked blues Jr. with an attenuator.
It makes sense that you are allowing a significant amount of voltage through that wasn't necessarily designed to handle, then you might have a potential overload on one the components
I bet that if you changed that resistor back to higher value and installed new power tubes you would resolve the issue. However, you loose the mojo of that mod.
Just trying to think like an electron
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