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Couple 'O 700M Nudies

EchoWars

EchoWars

Hiding in Honduras
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700minternalparts5rj.jpg

This one belongs to Danamc...here for a rebuild. Thought I'd label a few parts and post a pic or two.

The 2.2µf 250V metal polyester caps on the large power supply filter caps are added, and you can see the 1.5µf 250V rust-colored metal polypropylene caps on the driver boards which replace the stock 1µf Mylar cap.

Unit also has new relays (blue-green colored cases) and tons of new electrolytics. The 700M has no offset adjust, so replacment Zetex transistors were carefully matched, and offset is less than 5mV on each channel.
 
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700minternalparts2.jpg

Another internal image. You can see the new Bourns bias trimpot, and behind the closest driver board you can see the .56µf film bypass for the bias diode string.
 
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700moutputtransistors.jpg

A shot of one channel's worth of outputs and heatsinks. One channel of the 700M has more heatsink area than most 200WPC amps have on both channels. No matter what you do to the 700M, it just never seems to get hot.

This amp got new On-Semi output transistors, as it arrived with the 2SB539 and 2SD287 NEC output devices, which seem to be easy to let the smoke out of. This amp looked great inside, and for a few minutes I thought I might be the first to work on it. However, upon examining the output devices I could see that several transistor screws were missing, and several others had #6-32 screws forced into the the transistor socket where a Metric M3 was supposed to go. Not much I could do except chase the threads with a #6-32 tap, and install the oversize screw in a few places.

The On-Semi transistors drop less voltage from collector to emitter at high power. Full output with the stock NEC devices was an even 200WPC, and with the On-Semi transistors that jumped to about 210. Small but measurable.

THD+N at the rated 170WPC was 0.012%. Lovely. :music:
 
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Thanks EW for the nudies of this impressive monster!

I added a link from TVK's 700M post to this thread.
 
EW,

The bypass capacitors on the filter caps I'm assumming you added. Can you elaborate on how this benefits the amp and how you select the size/type of capacitor for this function?

Thanks,

Gibsonian
 
Wow, that is impressive looking. Funny to see that today, as yesterday I saw the expensive basket case I posted on a few weeks back. Still in the same place for the same amount of money. Nice to see one brought back to perfect health and on its way to a great home.
BTW Glenn, how does it sound? :)
Erik
 
Impressive shots of the beast EchoWars. Thanks for taking the time to indicate each section. Mighty beast this unit is.


Wayne: what's wrong with Mexican transistors? I've seen RCA made Brazilian tubes and even some made in Argentina.
 
I love it EW! You just extinguished any thoughts I had about selling the 700M in favor of something else. Truly a beautiful amp :yes: One of these days I'll hafta send mine down to you for the special treatment :)

No matter what you do to the 700M, it just never seems to get hot.
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Agreed, even driving my 4 ohm subs at high volumes, this amp barely gets warm. Plenty of muscle and finesse :banana:
 
waynegreen said:
..........hmmm, first we have RUSSIAN vacuum tubes and now we have M-E-X-I-C-A-N transistors!!!!!
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Russians used vacuum tubes in their state-of-the-art MIG 29 radar because they are cheap and rugged. Are rad hardened without any extra work. They used them everywhere in their military. The west would not sell them the advanced processing gear needed for solid-state, so they improved tubes. As a result, their tube technology is the best in the world. Or, at least it was.

And, the huge hunks of silicon and large size dies and design-rules used in transistors like these are state-of-the-art from 25 years ago. That is why they are made in Mexico. One or two highly trained folks per shift and a bunch of folks who do as they are told and you have a 'sunset' fab. Cheap to run and very little in the way of pollution controls. Voila.....transistors made in Mexico.

As always, Glenn......beautiful work. :thmbsp:
Danamac - what speakers will you drive with this bad boy?
 
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Yamaha B-2 said:
As always, Glenn......beautiful work. :thmbsp:
Danamac - what speakers will you drive with this bad boy?
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I've been using a stacked pair of Large Advents over AR 2-Ax speakers with Audience AU-24 speaker wire. Awesome combination. :yes:

Dana
 
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Yamaha B-2 said:
Do you run them all off of the one 700M? Post a pic once you get everything back together.
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Absolutely. The 700M doesn't even breath hard pushing this combination. I've got the 700C and 700M as part of a tuner rack. Let's see if I got a photo of the rack. There you go. I'll post a pic of the speaker stack later.
 

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Oofta! I bet you had fun lifting that bad boy onto that rack shelf :no: I have mine on the bottom shelf and that's hard enough. Not a fun piece of gear to move around. Very nice looking rack, btw.
 
If I read correctly, you have three speakers per side (pair of LAs and a 2Ax). How do you have them wired to provide the best impedance match? Do you have the amp back and these are pic's from some time ago?
 
Yamaha B-2 said:
If I read correctly, you have three speakers per side (pair of LAs and a 2Ax). How do you have them wired to provide the best impedance match? Do you have the amp back and these are pic's from some time ago?
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Actually nothing quite that complicated. :scratch2: Just an AR-2Ax sitting on top of a Large Advent with Audience wire and spade connectors from the 700M to the AR-2Ax and a pair of jumpers down to the Large Advents. Repeat on the other side. As far as best impedance match I'm not all that critical. I just know the two speakers complement each other very well. :yes:

The 700M amp still sits in EWs lair undergoing beauty treatment. The rack pic is from last winter. Ain't this fun?

Dana
 
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