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Author Topic: AL-811H plate and load capacitors  (Read 7719 times)
K1ZJH
Member

Posts: 984




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« Reply #30 on: May 12, 2012, 10:51:37 AM »

Amen to removing the Al. filings!!! Been there, done that. It can make quite a light
show!

I know W8JI advises against filing and burnishing damaged plates, but I have had
good luck doing so on my SB-220. At the least, I'd clean up the plates and find the
cause of the arcing before risking the same damage to a new replacement. That
can get expensive, fast!

Pete
« Last Edit: May 16, 2012, 06:44:58 PM by K1ZJH » Logged
N0SQ
Member

Posts: 53




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« Reply #31 on: May 16, 2012, 05:06:56 PM »

The capacitor has been replaced with the original type from Ameritron. It's working great. No more arcs and sparks.

I guess I might have tuned incorrectly at least once to trigger the problem since the capacitor has worked fine since I bought the amp until now.
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KJ4WS
Member

Posts: 9




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« Reply #32 on: May 17, 2012, 03:02:33 AM »

IMHO, Just grounding the grids was the wrong thing to do. What if a tube flashes over? Now that could be some interesting Fireworks. If, I were really determined to make a Mod of that type, maybe a fast blow fuse rated at around 25-30% greater than the Maximum rated Plate Current? In my days I have seen lots of Blown Plate Chokes, Rectifier Bridges, and Power Transformers just because of the Mod described here. Also, what good is the extra 30 to 50 watts going to do for you anyway? Just turn the drive up a bit and be done with it. With 600 Watts, and it is the first 500 to 600 that really counts. Figure what the difference to a receiving station would be to add just that little bit extra. In quick summary, those resistors were placed there for a reason. The Al-811 is known for arcing Plate and Load Bread Slicers. And if I were going to do any kind of mod on one at all, it would be 2 things. 1. Better Plate and Load Caps in the Pi Network and 2. Replace those 811's with 572B's ......
                                                                                            73 de Wade/KJ4WS
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N0SQ
Member

Posts: 53




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« Reply #33 on: May 18, 2012, 09:53:58 AM »

IMHO, Just grounding the grids was the wrong thing to do. What if a tube flashes over? Now that could be some interesting Fireworks. If, I were really determined to make a Mod of that type, maybe a fast blow fuse rated at around 25-30% greater than the Maximum rated Plate Current? In my days I have seen lots of Blown Plate Chokes, Rectifier Bridges, and Power Transformers just because of the Mod described here. Also, what good is the extra 30 to 50 watts going to do for you anyway? Just turn the drive up a bit and be done with it. With 600 Watts, and it is the first 500 to 600 that really counts. Figure what the difference to a receiving station would be to add just that little bit extra. In quick summary, those resistors were placed there for a reason. The Al-811 is known for arcing Plate and Load Bread Slicers. And if I were going to do any kind of mod on one at all, it would be 2 things. 1. Better Plate and Load Caps in the Pi Network and 2. Replace those 811's with 572B's ......
                                                                                            73 de Wade/KJ4WS

Maybe you should take the time to read the details about the mod. This mod is recommended by the designer of the amp. http://www.w8ji.com/al811_important_modifications_changes.htm

What do you mean by better plate and load caps? Do you have a recommendation?

Next time I need to replace the tubes I'll consider buying the 572's.
« Last Edit: May 18, 2012, 09:57:21 AM by N0SQ » Logged
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