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Old 21st October 2010, 03:03 AM   #1
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Default Magnavox AMP-185

I may have found myself a decent tube amplifier to start myself out with here locally on the cheap!
I would like to get some info on the amp but so far I havent been able to find much

Does anyone have a schematic for a Magnavox AMP-185?
I havent got the amp yet so i dont have much more info than that and some tiny pictures:
Click the image to open in full size.
Click the image to open in full size.

Does anyone have any experience with these amps that can recommend from good mods for it, if it needs any?

Thanks!
Mack
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Old 21st October 2010, 03:55 AM   #2
pjanda1 is offline pjanda1  United States
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There is a great deal of info floating around about these. Were it me, I wouldn't spend much time modding the stock circuit. I'd either replace caps and resistors as needed (with decent but not tweaky parts) to get it working or strip it all out and build in some version of an El Cheapo. Nice Find!

Paul
Wild Burro Audio Labs - DIY Full Range Speakers
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Old 21st October 2010, 12:09 PM   #3
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There's a Magnavox board on Yahoo Groups that will have the schematic, or something very close. From the little pics, it looks like a standard late 50's 12ax7/6v6 push pull. Can't remember if the single tube with shielded circuitry is a phono stage or not.
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Old 21st October 2010, 12:39 PM   #4
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I've had really good luck with amps like that.
...once the can-caps acted up enough that I changed them, these days I use old caps like that only for pre-test, any ffffttt or gkk sound and out of the power supply section they're escorted off the platform if they're not gone already! Generally all the electrolytics have to leave at that time.
I had 1 bad OT not too long ago, the old tubes are in my amps.
Play 'em, they sound great !
When the sockets got loose, gut out time, especially when the solid core wires were knotted and then soldered to the lugs. Large [8pin] sockets seem to last longer.
Worth the trouble ?...Especially if you don't have one !
I pick a platform and play it these days. I used to repair and rebuild anything that got under the bright light...then decided pick the platform, build it strong like when it was new, then use it. Crusty brick resistors that drifted might matter, bigger=more heat dispersion, so the next Watt size up or double-watt if will fit.
I'd play it through the speakers before and after considering mods [generally the voicing of these amps is just 'wide frequency range'] unless there was some major difficulty in the performance...such as when used for guitar, tightening up the bass at the HP filters, usually the preamp provides sufficient control over this though.
Take care to have fun !

Last edited by petemoore; 21st October 2010 at 12:43 PM.
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Old 21st October 2010, 02:31 PM   #5
20to20 is offline 20to20  United States
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Quote:
Originally Posted by mackinthebox View Post
I may have found myself a decent tube amplifier to start myself out with here locally on the cheap!
I would like to get some info on the amp but so far I havent been able to find much

Does anyone have a schematic for a Magnavox AMP-185?
I havent got the amp yet so i dont have much more info than that and some tiny pictures:
Click the image to open in full size.
Click the image to open in full size.

Does anyone have any experience with these amps that can recommend from good mods for it, if it needs any?

Thanks!
Mack
One important thing to check on the schematic with this model is the location of the feedback components. I believe they were placed on the radio chassis instead of the amp chassis and the feedback signal was routed back to amp via cable. If so, you will want to plan on reinstalling them on the amp if you don't want the high distortion numbers (5% or more) you could get without the feedback.
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Old 21st October 2010, 02:33 PM   #6
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Im excited, I will be picking this amp up either tonight or tomorrow morning!
woot! ^_^
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Old 22nd October 2010, 02:10 AM   #7
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ugh, joining a yahoo group is tedious...
I hate yahoo
my membership is pending though
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Old 22nd October 2010, 02:57 AM   #8
20to20 is offline 20to20  United States
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Quote:
Originally Posted by mackinthebox View Post
ugh, joining a yahoo group is tedious...
I hate yahoo
my membership is pending though
There is a j-peg schematic of the 185 at the Yahoo Maggifriends forum. Looks like the feedback circuit is on that amp chassis. Have fun!
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Old 31st October 2010, 08:56 AM   #9
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I finally got the amp
it is a 185AA
I added 1/4" Jacks to the back
Installed a PC Power connector, the D shaped connector
Installed an inline fuse
Installed a power switch

Here are the pics

Click the image to open in full size.
Click the image to open in full size.


Added power connector:
Click the image to open in full size.

Added 1/4" Connectors:
(I also made my own speaker cables with 1/4" ends and Banana Plugs)
Click the image to open in full size.

Added power switch:
Click the image to open in full size.
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Old 31st October 2010, 08:59 AM   #10
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Next up im going to replace the RCA connectors, the ones on it now are rather worn and Ive got some gold replacements
I am also going to add 2 POTs, 1 for each side, to control input levels of each channel

Right now it sounds good but the highs are a little low, the low end is incredible though
Is there something I should check to get better highs out of it?

Its got 12ax7s for the preamp and Magnavox 6V6s for the power tubes
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