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

[Northwinds]

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

 

[George S.]

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.

 

[Northwinds]

Looks I will be ordering a couple fuse holders from Mouser to start

 

[Northwinds]

Here is the stack

 

[George S.]

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.

 

[Northwinds]

All screws

 

[Northwinds]

What is this thing on amp? Bias point checker??? It also looks like there was a plexi cover or something at one time???

 

[George S.]

Probably a cooling fan power plug, plexiglass was probably like a fan mount or bracket. No telling what you'll find inside.

 

[J!m]

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.

 

[Northwinds]

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!

 

[Gepetto]

All screws

View attachment 56004

Cad plated no less...

 

[Wheel-right]

Looks I will be ordering a couple fuse holders from Mouser to start

View attachment 55998

Came upon these guys on the Bay, might have something you need.

Vintage Electron | eBay Stores

 

[laatsch55]

That is a pretty stack...

 

[wattsabundant]

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.

 

[marcok]

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

 

[J!m]

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.

 

[pennysdad]

Dynaco Manuals >> Click me. [hifiengine]

You do have to join if you haven't already, but they're safe and manuals for just about EVERYTHING audio.....

 

[J!m]

I am a member (and vinyl engine of course).

great sites! I didn't think to look there for manuals...

 

[J!m]

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...

 

[laatsch55]

93's, 94's. And 95's and 96's should be a good teplacement....I THINK....what's in there now..