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Gear / Technical Help => Playback Forum => Topic started by: Tim on April 17, 2006, 08:24:17 PM
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Just noticed this the other day but I'm unable to bias the 2nd el34 on my ASL integrated. The meter just shows that it's running completely hot all of the time. I've switched tubes around and unfortunately it looks like it's that specific channel and not the tube itself.
anyone else ever had this problem? I'm wondering how long repair will take and where to send it. The dealer in town where I picked this up last year has since closed.
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Don't run it much until it's fixed !
LETHAL voltages are inside of tube equipment, such as the ASL AQ1003.
These can be present even after the device has been unplugged for quite a while.
When a tube device is not working properly, the probability of danger "under the hood" is increased.
Good luck and +T for troubles.
If you need a schematic to pass along to your tech, or if you're knowledgable in tube electronic safety and repair, I have the link.
PM me.
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Yeah I've run it very sparingly. I know all about the dangers of tube equipment so I've basically left it alone.
I was hoping to send it to a dealer but I may just take it to the local repair place that I've used a lot in the past.
PM coming Bob - thanks a lot!
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Tim:
There's a guy on South Broadway by the name of "lord valve" -- he's supposed to be a tube audio fanatic (builds/maintains derek trucks' vintage fender twin reverbs, etc.) -- you might want to see if he could give your asl a once-over.
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Just noticed this the other day but I'm unable to bias the 2nd el34 on my ASL integrated. The meter just shows that it's running completely hot all of the time. I've switched tubes around and unfortunately it looks like it's that specific channel and not the tube itself.
anyone else ever had this problem? I'm wondering how long repair will take and where to send it. The dealer in town where I picked this up last year has since closed.
Tim, I had the same/similar thing happening on my aq1001dt, originally I thought bias pot wasn't making good contact with the circuit board but after removing the pot and metering the circuit strip on the board it measured high resistance. The easiest and most reliable way to fix it was jumper the bad part of the circuit, when I went to do it I realized someone had already done that on one of the other output tubes on the other side. Two of the resistors also measured slightly out of spec so I replaced those too, but the problem with the pot seemed to be what was causing the bigger problem. Luckily a family friend worked on tube gear for over 30 years so he's been helping me learn what's what. I found a couple other mentions of a similar problem related to the same pot/board issues on random sites, it's a relatively simple fix and might save you a couple dollars in a repair shop if you can point out what needs to be done.
If you have a meter you might be able to see if you have the same problem, mine was jumpered to bypass the circuit board on the opposite side of the board so I didn't see it at first, so one of the other pots had already been addressed before.
Measure the resistance from the 2 points indicated with the arrows, you should get almost none. You can use the other 2 points as reference, or one of the other bias pots. Flip that baby over and pop off the bottom cover, but make sure you've have it powered down for a while before you go probing around.
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And wait, then test to be sure that the high-voltage power supply caps have bled off.
I had a failed bleeder resistor once that left nearly 1000 volts sitting on the plate of an 813 for days, even though the unit was unplugged !
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And wait, then test to be sure that the high-voltage power supply caps have bled off.
I had a failed bleeder resistor once that left nearly 1000 volts sitting on the plate of an 813 for days, even though the unit was unplugged !
Is there a correct or safe way to bleed off the voltage?
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Tim:
There's a guy on South Broadway by the name of "lord valve" -- he's supposed to be a tube audio fanatic (builds/maintains derek trucks' vintage fender twin reverbs, etc.) -- you might want to see if he could give your asl a once-over.
Thanks Darrin!
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I'm not touching anything :)
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I'm not touching anything :)
(http://lib.lbcc.edu/images/Religion/cisgod.gif)
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And wait, then test to be sure that the high-voltage power supply caps have bled off.
I had a failed bleeder resistor once that left nearly 1000 volts sitting on the plate of an 813 for days, even though the unit was unplugged !
Is there a correct or safe way to bleed off the voltage?
Jump in there with a screwdriver ;)
Actually, please don't. A good friend of mine shot himself half way across the room once because the guys at the studio he worked at thought it would be a fun prank. ::)