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Old 26th August 2008, 05:15 AM   #21
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So your RH84 uses 100 ohm cathode bias? What OPT's?
I notice the original schematic I have for RH84 uses 130 ohm cathode resistor. First cap after rectifier was 47uF followed by 220uF after a large choke. You may be fine, but you could increase the cathode resistor to bring down the total current draw, I'm probably only stating the obvious. Some PT heat is normal.
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Old 26th August 2008, 02:59 PM   #22
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The RH84 shows 270 ohm on the cathodes. I am not sure if this is for one channel or for both though? I would assume it is a sound enough design that it doesn't use a shared cathode resistor. I am using 200 ohm resistors right now because it is all that I have.

The OPT's are the stock magnavox's, and this is the 86 chassis which is the little SE maggie. Mine came with magnavox branded Mullard EL84's. As for your concerns with power- I think that the original circuit had more power, or rather the assumption of more power, but it was notcibly a LOT dirtier. The distortion on this amp is so much lower, and the LF responce is a lot cleaner. The midrange is perfect and pops right out there and the Hf responce is as it was in the magnavox.

I think that the reson the magnavox circuit can be cranked more is because it is designed to limit LF extension to around 90hz or so, because I had to give it a lot of boost around 30hz to bring it up, and then it still didn't have the clean output that the RH84 does.
If I keep my EQ flat across the board I can get above 'average' listening levels with 84db speakers. When I cross them over at 90hz and run the rest to a sub I can get over 100db which is plenty for me.
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Old 26th August 2008, 09:49 PM   #23
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Don't forget to let us know when the web site is up.
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Old 27th August 2008, 01:48 AM   #24
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which one...?
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Old 27th August 2008, 02:27 AM   #25
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Sounds similar to my amp, other than RH mod. I use 270 ohm for each tube, shows 8v across that, B+ is 278 volts. That gives 29mA for each 6BQ5. yours is 6v across 200 which gives 30mA. I think you're fine. Tube amps are good at heating.
Enjoy the music!
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Old 27th August 2008, 02:29 AM   #26
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The one You are going to create....
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Old 27th August 2008, 04:37 AM   #27
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I should create one dedicated to maggie SE's, I have tons of pics that I have saved form ebay auctions and found online, as well as multiple circuits they can be built into. Unfortunatly, this might cause prices to climb even higher

I am hoping the receive the rest of my parts tomarrow so that I can convert my other chassis to an RH84. The chassis polished up nice and i clearcoated it. I ordered up some solen caps for the coupling caps because they were cheap. I am going to have a long period of time between classes tomarrow at college and I think I am going to take a box with the old amps in it and my two nova 6's to the student center. Should be fun for people to watch

http://www.audiokarma.org/forums/sho...d.php?t=134055 here is the maggie as it sits now before being modded from the reworked magnavox circuit.
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Old 27th August 2008, 02:02 PM   #28
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Young fella, you sure do nice work! Great attention to detail in everything you do! I'm envious! Everyone needs to click on the link to see your beautiful guitar amp. How did you learn so much so quick and find the time to do it all? (not really a question)
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Old 27th August 2008, 09:58 PM   #29
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Quote:
I'm gong to be creating a webpage as I go along for other DIY'ers to see how to restore/restomod these old amps as a budget Hi-fi system.
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Old 27th August 2008, 11:04 PM   #30
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OH yeah! That would be spelled going ... I got my parts today and am wiring everything up right now. So far its going smoothly. I also found more pictures of my last build on my school account so I will probably get them on my site as soon as I find time.

Thanks for the comment about the guitar amp!
Heres some photos of my workbench and some of my other amps:
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Click the image to open in full size. Click the image to open in full size.
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