Who is the Dynaco guru here? Just found a gorgeous Dynaco stack

Northwinds

Northwinds

Veteran and General Yakker
Joined
Mar 18, 2013
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Coventry, CT
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Fondler errrr... fan of all Nav's avatars
Only one yellow light came in for channel A, not B but I also have a bad fuse holder. Otherwise, these 3 pieces (400 amp, PAT4 preamp and FM tuner) are immaculate but obviously need to be gone over. The PAT4 preamp turns on but make a bad noise with CD player hooked up

I will post pics as soon as Jer gets me set up so I can visit this forum with my phone. I have no clue what my password or email I used to register here so computer logged in but I got locked out with my phone trying passwords

I have acquired a lot of stuff this summer for next to nothing. I don't know why I have to stop this shit
 
Don "Watts Abundant" was a "tech" I think for them in some form. He's your "go to guy". Just do search here on the forum for posts of Dynaco by him and you'll get more info.
 
Looks I will be ordering a couple fuse holders from Mouser to start

20211027_120505.jpg
 
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I built that model tuner and preamp from kits back in the early 70s. Couldn't afford that big amp so built a I think 120 watt Solid State amp. Rumor is if the phono jacks are mounted with screws then kit built, factory built used rivets.
 
What is this thing on amp? Bias point checker??? It also looks like there was a plexi cover or something at one time???

20211027_210122.jpg
 
Probably a cooling fan power plug, plexiglass was probably like a fan mount or bracket. No telling what you'll find inside.
 
Fan plug. The front power knob rocks in two directions- with the fan one way, and without the fan the other way.

I just picked up a stereo 400 (free) myself. Former owner says it has distortion on one channel. So I’m tuned in to see what I need to do, when I eventually get to it.
 
Thanks for explaining Jim! I had a 400M also a few years ago. Thanks for explaining the pigtail and I always wondered why the two On positions!
 
I bought a 400, PAT5, and a FM6 at an estate sale last year. The assembly had to be factory as it was so neat. The amp and preamp had a few bad coupling caps. Barely made 200 watts at 8 ohms. Otherwise it was fine. Sold the set on EBAY.

In the early 90's I did sub contract work for Sound Values who later became Sound Valves. I tested hundreds of driver boards for 4XX's. I last saw John Peterson about 8 months ago.
 
I have a Dynaco system : Pat 4 , Fm 5 and ST 120 .
They drive a pair of AR 6 great .
In Pat 4 I had to replace the the power suppy cap due to hum .
Use small diameter RCA plugs in Pat 4 due to the small clearance .
I added a dual 8A relay on switched outlet to save power switch .
Furthermore ( optional ) I modified Tape Head and Special inputs to have
two other aux inputs .
Here you'll find spares and suggestions
https://www.ebay.com/str/QUA-CO-AUDIO?_pgn=5&rt=nc
https://www.updatemydynaco.com/
Ciao
Marco
 
I think once my phono pre is done ima gonna fillet this Dynaco I have, and replace everything. Every small component will be replaced with higher wattage/temp and tighter tolerance (where reasonable). I will need the biasing procedure and having a BOM and (most important) a schematic, would be most appreciated if someone has a copy they are willing to share.

The old metal can, butterfly heat-sinked transistors may have to stay, but they are probably most responsible for the “sound signature” anyway. If any are blown, I’ll need a lot of help there.

But mine may not start until Christmas. Once I’m done restoring it I’ll probably sell it off to finance another project.

And if someone wants a project, knowing shipping will be national-deficit level high, (or wants to collect in person) shoot me a PM.
 
I am a member (and vinyl engine of course).

great sites! I didn't think to look there for manuals...
 
Downloaded! Thanks for the reminder.

In the replies to the post there, there is a reply:
"Jim Bongiorno had a hand in the design of the Stereo 400, as well. he was Dynaco's chief engineer at that time. I have had a Stereo 400 for 40 years and replaced the output transistors with, I believe the ON Semiconductor MJ21194/MJ21196 or MJ21193/MJ21194 family of linear power transistors. That seemed to be a significant sound improvement. "

Any thoughts on this? I don't know that any outputs are "bad" but if any are...
 
93's, 94's. And 95's and 96's should be a good teplacement....I THINK....what's in there now..
 
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