Auditronics Grandson 110-8 Story

If you're dealing with 3mV of ripple I'd feel pretty good about that. At the end of the day, what really matters is signal to noise input to output and distortion. If that figure is unacceptable, then I would start probing deeper as to why, potentially leading to the power supply.

Spent much of the last day getting all of the knobs reattached, and replacing a few broken switches. I've got a couple pots that definitely need replaced (stops are broken), and a few knobs that were missing when I got it.

Getting really close to wiring up the patchbay, and really running things through their paces. I'll get the computer hooked up, and that will let me do some detailed measurements on noise, distortion, frequency response, etc... I use some software called ARTA for that stuff.

Thanks again for the encouragement. It's fun to share stuff like this with other folks who are into the same thing!
 

Attachments

  • 20161010_131948.jpg
    20161010_131948.jpg
    5.5 MB · Views: 58
No, they're just large knobs for the level. Each band has 2 selectable center frequencies via toggling a pushbutton. Plus a LPF and HPF. They're an inductor based design, and are supposed to be one of the cool parts of this console's sound.

Thanks again for the kind words. Enjoying reading through several of your threads here as well!
 
Oh now I see the frequency shift switches...! I was going to say I think push-pull pots are cool, but would be harder to identify the state of each band on each channel by sight or touch.

Inductor EQ is hard to do right and more costly to manufacture. I'm sure it was done well on your desk.

Thanks again for the interesting thread!
 
Made some decent headway the last few days. Got enough of the patchbay wiring done to pipe some signal through and get the computer hooked up.

Doing some rudimentary functional tests at this point. All of the busses appear to be working, which is a good sign. Had to replace one meter buffer opamp.

All of the meters have issues with intermittence. I had an identical issue with the auditronics 700 series I helped get up and running earlier in the year. You can literally tap on the meter bridge and some meters will randomly die, others come back.

It appears the root of the problem are the molex connectors that hook into the buffer boards mounted on the back of the meters. It's not actually the connectors themselves, but cold / microfractured solder joints where the headers are attached to the PCBs. I validated tonight, by resoldering all of these connections on the channel 8 meter. This issue is identical to what is commonly found in molex headers in MCI tape machines from the same era. After resoldering it's rock solid. Will continue to hit all of the meter buffer boards over the next few days. Fortunately, this is the only spot in the console these type of connectors are used.

Onward and upward!
 
Beautiful-looking console Bob! I'm really enjoying reading about your progress on it as well. Can't wait to hear how it sounds! :)
 
Good progress!

Yeah MCI tape machines and mixers as well. Those Molex connectors are a problem.

Onward indeed! :D
 
More work on the meters tonight. Turns out the molex solder joints were only part of the story. The meter buffer boards mount onto the meters' input terminals with a series of brass washers and nuts. It appears over the years oxidation has made electrical contact through these pieces intermittent at best. So... I removed all the nuts and washers, and took a small dremel wire wheel to them, the bolt post on the meter, and the pads on the buffer board. *Way* more reliable now. It's tedious. I'm through 4 of the 8 meters, but making progress, and calibrating the meters as I go.
 

Attachments

  • 20161013_222053.jpg
    20161013_222053.jpg
    2 MB · Views: 34
More progress this evening. Started doing some more in depth testing. As mentioned before, there is a hodge podge of input transformers on this thing, and I'd like to get them all standardized. I decided to give Ed Anderson's EA2622 a try, as it very closely matches the original specs of the Jensen iron that was original to the console.

I'm blown away by how this board, built in the 1970s, performs.

Frequency response is near ruler flat 20-20k. THD on 1kHz sine at reference level is .002%. The noise floor is slightly lower than original specs at 76dB below reference level.

Lots of functions to continue to test, but I'm 100% a believer in this board.
 

Attachments

  • 20161014_201318.jpg
    20161014_201318.jpg
    4.8 MB · Views: 37
  • 20161014_230922.jpg
    20161014_230922.jpg
    3.7 MB · Views: 13
  • 20161014_231653.jpg
    20161014_231653.jpg
    6.2 MB · Views: 12
Man! That looks pristine! And specs are that good without any re-capping??? Or did I miss that?
 
Cool. Very inspiring!

I have the same frame here, and a lot of the modules for it, but some were missing when i got it (eg. missing all input modules, unfortunately - as these were either racked up or sold off by the previous owner). Anyway, I decided to take what was left and try to bring it back to life one day. So it's always encouraging to see somebody working one up to a really nice state-of-play, and getting enthusiastic about the performance characteristics etc.

Shall be watching on for more updates .. . Is it in use by now?

Cheers!
Evan

---------- Update ----------

PS. If anybody has any spare parts (such as the back PCB boards which the modules slot into) My console is missing those boards . - keen to hear from you.
Cheers.
:-)
 
Hey Bob i just bought a 16 channel 110-8 from Rust College in Holly Springs,MS. No schematics were included with the console. Would you happen to have the schematics for the power supply?
 
This a mid-70s Auditronics "Grandson". Auditronics bought Spectrasonics I believe in the early 70s, and their first console was based on parts from a Spectrasonics board that listed for $36k, and was called "Son of a 36 Grand". This board, the 110 was the next set of consoles they came out with known as the "Grandson"...

Spectra Sonics was never owned by anyone other than Bill Dilley and later his son, until recently. The current owner,Bill Cheney, has renamed the company "Spectra 1964." Auditronics bought Spectra Sonics components for themselves and also built some Spectra Sonics boards under contract. That was the extent of their association.
 
Last edited:
Back
Top