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Couple 'O 700M Nudies

Gibsonian said:
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?
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Power supplies are supposed to act as a dead short to AC signals, but large electrolytics often have rising impedence vs frequency simply due to their wound construction. Bypassing with a good quality non-inductive film cap helps keep the power supply rails looking like a dead short to all frequencies. The size of the cap isn't usually very critical...anywhere from 1µf to 4.7µf is fine, with 2.2µf being a common size...but it does need to be a good quality non-inductive cap.
 
EchoWars said:
Power supplies are supposed to act as a dead short to AC signals, but large electrolytics often have rising impedence vs frequency simply due to their wound construction.
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I am curious how this helps as the frequency doesn't change. I also thought bypass capacitors were to reduce voltage spikes. Just wondering.
 
Put simply, high frequencies will be riding on the supply rails unless they also have a low impedence path to common. That's what the cap prevents.
 
Hi frequencies from where? The A/C line? What do you define as high frequency?

EchoWars said:
Put simply, high frequencies will be riding on the supply rails unless they also have a low impedence path to common. That's what the cap prevents.
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EchoWars said:
.... The 700M has no offset adjust, so replacment Zetex transistors were carefully matched, and offset is less than 5mV on each channel.[/QUOTE]

Very nice work!

I'm surprised the 700M doesn't have the DC offset adjustment, as I think even the 600 integrated does.

Ever consider selling matched transistors to us folks who want to lower the DC offset of amps that can't have it adjusted? Or is it something that must be done in the amp?

Also, nice to know that the output devices can still be replaced!

As always, it's amazing to see the insides of these beasts and a treat to see you getting them back up to spec. :thmbsp:
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Been a while since I was inside mine but I don't recall the bias diode string bypass caps on mine. Is that another "EW exclusive" to add to the list of your 700m mods (servo mod, rumble filter comp feedback pair upgrade and the various cap improvements)?

Or was it factory on later units? What's the ser#?
 
Does Aaron have two 700Cs?
(Crying)Momma!Aaron's got TWO 700Cs!I want three!:tears:
Axel,I'll register my second 700C(Pokes tongue out at Aaron),as soon as I recieve it from EW.
No EW that's not a cheap shot from a very patient Aussie.:thmbsp:
Aaron,glad to hear you're not thinking of selling the 700M..:yes:
 
Just out of interest's sake, may I ask what system Echowars listens to for enjoyment? When you are working on these vintage classics do you have the AM tranny on the workbench going with talkback?
 
My main system is a 700C, 700M, and a KT-8007 tuner feeding a couple of homemade Dynaudio 20W75's and Heil AMT's, bi-amped with a TDM 24CX-4 analog crossover and a much-modified Kenwood KA-3500 driving the Heil AMT's.

The system is on the other side of the room and around a corner, so most of the time I'm listening to the last piece I've worked on driving some Dynaco A25's.
 
EW, I was curious if as you work on a piece of gear, the 700M for example. do you have a list of parts you change each and every time you rebuild one or do you check and replace only whats necessary on each one you see?
 
Depends on the unit, and how well I know it. On the 700M, what needs to be replaced is pretty consistant nowadays.
 
This 700M amp, and its matching 700C preamp is available to an interested party. See the AK classified section. Drop me an email if interested.
 
Typical pile 'O parts replaced in a 700M restoration...

700mpartsreplacementex9.jpg


31 electrolytic caps
10 resistors
6 transistors
4 zener diodes
3 relays
2 Mylar film caps
2 trimpots
 
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Damn, I shouldn't have read this post with all my OCD tendencies... now I want to rip apart the denon.... Why replace zeners and transistors? those values fade with time too? what actually holds up to the test of time in an amp? It seems not much. I bet some repair guys go even further, like replacing wiring and other goods..

Good job Glenn, as always...
 
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