Amerimex Consoles

[iomegaman]

So I'm picking up an older Amerimex StudioMixer II this week, I will have to build a psu for it...

I've done as much googling as I can and it seems they were a California based outfit in the 80's that started building modular studio consoles...but frankly except for a few ads in some recording mags I have not found anything about them...

This one is 24 channels and has 10 big VU meters(and a smaller cue Vu meter that is broken)...supposedly all these were handbuilt (per tapeop message board) which might explain the short life span and why no one has heard of them...

I figure for $100 the worst I end up with is 10 really nice VU meters and a bunch of scrap...on a good day it might be a decent opamp with EQ channel I can mod...

The one I am getting has 24 channels and a master bus...runs on -/+ 15/48 will need to get a tranx/psu...looks like a 7 pin amphenol

has unbal/bal output/ effect In/Out and Direct Out for each channel...

Anyone ever hear of them?

 

[rock soderstrom]

I don't know it but I like it! Beautiful console

 

[iomegaman]

Ok so I picked it up, weighs a ton, really solid build and pretty darn versatile...

From the looks of it (I am not sure will have to experiment), its 24 channels of 40 dB gain with 17kHz cut ot boost by 18dB, a mid at 400-10k (with +/- 18dB) and a bass at 20-400 Hz (same +/-)...effects send/return...
4 different channels of St.Mon

Each channel with a Hi Z/Pad-30 and Phantom pushbutton...

Big freaking slider but with push-button "cue" buttons beside the slider a Pre-EQ push button and Pan...

the 10 Vu Meters look like you plug them into whatever channel you want to monitor from the back since the back has a 'Direct Out/Meter" jack and the Meter bridge has 10 input jacks...

Each channel has 6 socketed TL071CP dual channel Texas Instrument chips and the pcb for each channel has each and every part labelled with its value (even the Transistors are labelled EBC)...

Holy Smoking Aces Batman this thing is very well made and quite pliable...insulated cable everywhere solid steel frame and chasis real wood sideboard and looks like real leather armrest...

VU's are Shinoara's

 

[fazer]

Build a channel  extender and get that baby working.  Usually the pots need cleaned on a routine basis.  Modular makes that board a keeper.    ???

 

[iomegaman]

Build a channel  extender and get that baby working.  Usually the pots need cleaned on a routine basis.  Modular makes that board a keeper.    ???

Yea definitely a keeper, the channel PCB's are all labelled with exact values for each component, even the transistors are marked with silkscreen showing "EBC", solid hand soldered each part...I will try and do a reverse engineering schematic to see what "genre" this board follows...reminds me of Trident stuff...the smaller square caps all look like they are made of metal, never seen these kind...

Apparently it is 26 channels, the two channels I thought were Master are actually "1" and "2" channels (exactly the same as the first two)...the "Cue" channels has a pink noise button and a "Lineup Osc" button...

 

[iomegaman]

Sooooo....

In trying to figure out the power supply (I went to the local electronics buffet and picked up a 3amp 15volt +/- psu)...I decided to forego the built in supply (which would have required locating 2 tranx for various voltage, I already have a 48vAC edcor soooo...I'm lazy)...

I look on the boards power strip(where you turn it on/etc)...it has 3 leds...15v...-15v...48v...

This thing runs about 6 TL071's per channel (X 26 channels)...but I could not get the psu to fire up just alligator-clipping the amphenol connectors to a tranx without an issue...so I decide to bypass the diode bridge/cap/dual supply and pull the voltage regulators  and just wire up my own psu...and use the existing strip indicator LED's...thing is...could not get the indicator leds to function correctly


So I decide to reverse engineer the ribbon connector to the psu...trace out the TL071's and use a MM in continuity mode when I discover the LED assigned to NEGATIVE voltage is actually the positive supply on the TL071 chip (pin#7)and NOT pin #4 (Vcc-)...thats when I go check the voltage regulator I pulled and discover that BOTH of them are positive (LM340T-7815/MC7815) neither one was a 7915...


This seems really odd to me, the TL071 needs both rails as far as I know...and one of the LED's is clearly labelled -15v...yet the psu did not have a negative regulator...typically I would count this up to someone modding the board and not knowing what they were doing, but the rest of the board is very solid, clear PCB labels and solid wiring, hand soldered, very quality components throughout...

What got me exploring was when I DID manage to fire up a tranX to the built in supply the -15v led always measure +15 and it was throwing me off...

Is there some simple way to check the existing TL071's to make sure they are not damaged/compromised?

Or would supplying positive only voltage on both Vcc of the chip just not work?

There's no way this console was working with the existing voltage regulators and that MIGHT explain why it is in such good condition...if someone tried to run it with the outboard psu (which from what I can tell was simply a few AC transformers for 48v/-15+15 and whatever the Vue Bridge requires (have not gotten that far) that get rectified inside the power strip with the indicators...

This is the exact psu strip like mine:

 

[iomegaman]

These are the LED's from left to right labelled 48/-15v/15

This guy at Tapeop had some psu issues as well...looks pretty hot on the board, mine did not look burned out...

I wonder if they simply shipped some consoles that failed to power up because they were not watching the regulators and this is why no one has heard of them?

Tapeop thread:

https://messageboard.tapeop.com/viewtopic.php?f=14&t=61619&p=531246&hilit=Amerimex#p531246

 

[rock soderstrom]

I wonder if they simply shipped some consoles that failed to power up because they were not watching the regulators and this is why no one has heard of them

I don't believe that, this is just the result of a repair attempt.

Solder in a new pair 7815/7915 and hook up a dual 15V transformer and this PSU will work again. Heads up, the labels on the second photo are wrong! Green/orange is 15V AC winding 1 and cream/white is 15V AC winding 2!

 

[rock soderstrom]

This thread would fit better into the "The Lab" now.

 

[analogguru]

These are the LED's from left to right labelled 48/-15v/15

This guy at Tapeop had some psu issues as well...looks pretty hot on the board, mine did not look burned out...

If you have this problem then the diodes get hot - replace them with higher current rating (1,5A, 2A, 3A) and lower dropout voltage and mount them 1cm above the pcb.

I wonder if they simply shipped some consoles that failed to power up because they were not watching the regulators and this is why no one has heard of them?

No, this is intended this way.  The Power supply consists of 2 independent 15V power supplies - therefore 8 diodes - where the output  of the second is connected to the ground of the first.  This results in that the ground of the second becomes the -15V.

Solder in a new pair 7815/7915 and hook up a dual 15V transformer and this PSU will work again.

No, it will not work again (see above).  DO NOT FOLLOW THIS UNPROFESSIONAL ADVICE !!!!

 

[rock soderstrom]

DO NOT FOLLOW THIS UNPROFESSIONAL ADVICE !!!!

There is no need to be offensive, even if you are right!

 

[mjrippe]

You can use a positive regulator for a negative rail.  Just ground the + and take V off the -.  Example attached.

What does the +15v LED measure?  Perhaps the LEDs are just wired backwards.  Wire up your supply to match the TL071 pinout and try it.

 

[iomegaman]

Thanks for all the helpful input...I had no idea you could simply invert the rails on a dual power supply and get that, don't know why it seems obvious...but this is a first for me...

I did manage to get it to light up correctly with my purchased psu, BUT (everyone has a big but)...I think I will put it back together and use two 16v AC tranx's instead...($8.00 each at local electronics cir +)

I'll use the other psu to run the bulbs in the 10 shinohara sd 830 vu meters.. connected my bench variable psu to the meter bridge "bulb" port and dialed it up to 15v and the bridge came to life...

Replace the psu Caps and see what happens...

 

[JohnRoberts]

Thanks for all the helpful input...I had no idea you could simply invert the rails on a dual power supply and get that, don't know why it seems obvious...but this is a first for me...

Think of it like stacking batteries, but transformer windings need to be floating.

JR

I did manage to get it to light up correctly with my purchased psu, BUT (everyone has a big but)...I think I will put it back together and use two 16v AC tranx's instead...($8.00 each at local electronics cir +)

I'll use the other psu to run the bulbs in the 10 shinohara sd 830 vu meters.. connected my bench variable psu to the meter bridge "bulb" port and dialed it up to 15v and the bridge came to life...

Replace the psu Caps and see what happens...

 

[iomegaman]

Quick update and a thank you to all who inspired:

Applied the two 16v AC tranx to alternate points 1/3 & 2/4 on built in power supply, replaced one of the voltage rectifiers that was bad...plugged in and had about three channels clipping with no input, so I pulled ribbon cable and am going to test one channel at a time...

Channel 1:

Bass for freaking days...EQ is VERY nice, cut/boost to satisfy weary ears...but the low end, man it is definitely present...

Plugged my Tele into Hi-Z channel 1 and BOOM louder than my Soundcraft it actually clips if I turn the trim all the way up, distorts like a broken speaker...

Overall the board is pretty quiet until you get to the last 10% of the gain...then it picks up some HF, but kinda expected from TL071's...no hum but its early and only one channel...25 to go.

I did flumox the phantom power side of the psu...and fried my edcor in the process (using AC pig-tails to test is ok until you trip on the damn  cords and pop a fuse) but I will rebuild it and get another tranx for it...

Also, the BIG VU Meters are really nice for these less than 20/20 eyes...and because of the soundcraft I have a bag full of bulbs for the lights...

 

[smb]

Quick update and a thank you to all who inspired:

Applied the two 16v AC tranx to alternate points 1/3 & 2/4 on built in power supply, replaced one of the voltage rectifiers that was bad...plugged in and had about three channels clipping with no input, so I pulled ribbon cable and am going to test one channel at a time...

Channel 1:

Bass for freaking days...EQ is VERY nice, cut/boost to satisfy weary ears...but the low end, man it is definitely present...

Plugged my Tele into Hi-Z channel 1 and BOOM louder than my Soundcraft it actually clips if I turn the trim all the way up, distorts like a broken speaker...

Overall the board is pretty quiet until you get to the last 10% of the gain...then it picks up some HF, but kinda expected from TL071's...no hum but its early and only one channel...25 to go.

I did flumox the phantom power side of the psu...and fried my edcor in the process (using AC pig-tails to test is ok until you trip on the damn cords and pop a fuse) but I will rebuild it and get another tranx for it...

Also, the BIG VU Meters are really nice for these less than 20/20 eyes...and because of the soundcraft I have a bag full of bulbs for the lights...

How do you get those VU meters apart to replace the bulbs? I have a series 1 with the same Shinohara SD-830 meters

Thx!

 

[Starshiptrooper2084]

These are the LED's from left to right labelled 48/-15v/15

This guy at Tapeop had some psu issues as well...looks pretty hot on the board, mine did not look burned out...

I wonder if they simply shipped some consoles that failed to power up because they were not watching the regulators and this is why no one has heard of them?

Tapeop thread:

https://messageboard.tapeop.com/viewtopic.php?f=14&t=61619&p=531246&hilit=Amerimex#p531246

Hello. Awhile back you sent me a manual for the studiomixer ll by amerimex. I've had mine for years but I recently found another one. This one is 19 channels plus 6 buses. I wanted to let you know that this one came with the real owners manual plus all the schematic. If you are interested I could email them 2 you.

 

[MidnightArrakis]

If you have this problem then the diodes get hot - replace them with higher current rating (1,5A, 2A, 3A) and lower dropout voltage and mount them 1cm above the pcb.

No, this is intended this way. The Power supply consists of 2 independent 15V power supplies - therefore 8 diodes - where the output of the second is connected to the ground of the first. This results in that the ground of the second becomes the -15V.

No, it will not work again (see above). DO NOT FOLLOW THIS UNPROFESSIONAL ADVICE !!!!

rock soderstrom said:
Solder in a new pair 7815/7915 and hook up a dual 15V transformer and this PSU will work again.

analogguru said:
No, it will not work again (see above). [DO NOT FOLLOW THIS UNPROFESSIONAL ADVICE!!!!] -- Wiser words than this have never been spoken before!!! Especially considering the source!!!

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