Neve 5316 Diagrams

Posted in Uncategorized with tags , , , , , , , , , , , on July 21, 2013 by AnalogAudioRepair

I have been working on some modifications to the Studio G Neve 5316.  The board came from BBC Scotland and did not have any schematics.  While it is certainly possible to figure out a lot of the signal flow without block diagrams, it is sort of like driving across country without a map – you know where you start and end, but you have to find signs in between.

I posted on Geoff Tanner’s vintage Neve forum at http://auroraaudio.net/forums/ and frequent contributor Mr. Blake Devitt was able to provide some helpful documents.  The forum did not handle large images well, so I volunteered to host them here for anyone who needs them in the future.

Block Diagram

Block Diagram

Circuit page 1

Circuit page 1

System Diagram

System Diagram

Advertisements

Telefunken ELA V624 Discrete Preamp & EQ

Posted in Repaired, Restored with tags , , , , , , , , , , , on June 29, 2013 by AnalogAudioRepair

Bad packing, or should I say NO packing, is to blame for the damage this preamp suffered.  It was shipped to me in a small flat rate Priority Mail box with nothing to protect it.  As you can see, the frame was bent and one of the circuit boards was broken into six pieces!  The frame was easy enough to bend back, but the PCB was like a little jigsaw puzzle that required epoxy and jumper wires to make it structurally and electrically sound again.  While I had it open, I replaced the electrolytic caps and added XLR ins and outs as well as a power jack with regulation.

The ELA V624 is a nice little module from later Telefunken mixers.  It has a mic pre with 60dB of gain, high and low EQ (I believe at 60Hz and 10kHz), and a line input as well.  Both the mic and line have transformer balanced inputs and I wired the unit with an impedance balanced output.  The circuit is fully discrete transistor and runs on +24v DC.  They are not as huge sounding as the earlier discrete modules (V672 Pre, W695 EQ, etc.) but very useable on a variety of sources.  Certainly worth the time spent repairing such unnecessary damage!

Bent Frame

Bent Frame

Broken PCB

Broken PCB

Broken PCB 2

Broken PCB 2

Before

Before

Fixed Frame

Fixed Frame

Fixed PCB

Fixed PCB

Recapped

Recapped

XLR Box

XLR Box

Completed, Front

Completed, Front

Completed, Back

Completed, Back

Transformer Saturation Box w/UTC & Davens

Posted in New Build with tags , , , , , , , , on June 29, 2013 by AnalogAudioRepair

This is a neat box I built for Joel Hamilton at Studio G Brooklyn.  It is a simple circuit consisting of UTC transformers and Daven attenuators.  The idea is that a hot audio signal can be sent in, saturating the input transformer.  It is then attenuated by the Daven and sent back out through a second transformer.  Joel likes to use it on inserts of the SSL so he can pump a track through a high output compressor like a Sta-Level or Collins 26U and then get some extra transformer tone before returning it at a reasonable level to the board.  Since it is built into a 3 space rack case, we decided to get extra large knobs and dial plates for the Davens for a great vintage “black box” look!

Chassis drilled full of holes.

Chassis drilled full of holes.

Inside

Inside

Close Up

Close Up

Front panel

Front panel

Zim-Gar Vintage Transistor Amp

Posted in Modded, Repaired, Restored with tags , , , , , , , on May 4, 2013 by AnalogAudioRepair

This is a funny little solid state amp I bought from a fellow on Craig’s List.  I bought it “as-is” and it hummed and made noise but passed no signal.  At first I thought it was Japanese, but when I took off the back panel there was a tiny schematic marked “Paris Corp. Salina, Kansas”!  I replaced the first transistor which took care of the noise and lack of signal, but the tremolo wasn’t working.  I rebuilt that section with some new caps and a resistor and dug up a vintage footswitch to turn it on and off.  The power supply filter cap had already been replaced so I can only think that the amp has always had some hum (it was certainly not high-end when new).  Adding a second stage of filtering killed the hum and made this into something that could actually be used.  Honestly it was more work than the amp is probably worth, but a fun project nonetheless!

Zim Gar Front

Zim Gar Front

Zim Gar Panel

Zim Gar Panel

Zim Gar Panel

Zim Gar Panel

Zim Gar Schematic

Zim Gar Schematic

Zim-Gar Guts

Zim-Gar Guts

Sphere 1014 and 910 Equalizers

Posted in Racked Modules with tags , , , , , , , on May 3, 2013 by AnalogAudioRepair

This is a rack full of vintage Sphere equalizers.  My client made the wooden case from zebra wood and walnut.  I wired and mounted the EQs and transformers and built the power supply.  The 1014s are IC based parametric EQs with high and low cut filters.  The 910s are fully discrete graphic EQs with inductors for each band.  We used transformers from Orphan Audio – Quad Eight inputs and Reichenbach outputs.  Unfortunately the Reichenbachs were PC mount so I had to attach them to some perfboard.  The Quad Eights mounted right below the input jacks on the back panel.  Power requirements were +/- 24VDC for audio and +5VDC for logic.  It was a lot of wiring to fit in the box, leaving length for servicing.  They are pretty fantastic EQs, especially the graphics!

Sphere On

Sphere Back

Sphere Back

Sphere Wiring

Sphere Wiring

Sphere Xfmr Board

Sphere Xfmr Board

Sphere PSU

Sphere PSU

AKG BX20 Spring Reverb

Posted in Restored with tags , , , , , on May 3, 2013 by AnalogAudioRepair

So a client brought me a BX-20 – the largest of the AKG BX series spring reverbs.  I have always loved the BX-10 and was interested to work on the big daddy.  The amplifier cards were partially recapped, so I completed the job.  I even replaced the tantalum caps on the preamp daughterboards because they were getting leaky.  With a little adjustment the boards now sounded good but one side of the reverb was spitting out random noises.  After chasing ghosts for a while, I determined that the problem was in the spring assembly and proceeded to take it out and open it up.  It was measuring like there was a broken wire or burned out coil.  I was hoping for the wire, but unfortunately one of the tiny red coil windings that hangs in the magnet gap had gone open.  There are no replacements for these so for now it will be a mono reverb!

AKG BX20 Panel

AKG BX20 Panel

AKG Daughterboard

AKG Daughterboard

AKG Inside

AKG Inside

AKG Spring Tower

AKG Spring Tower

AKG Spring Base

AKG Spring Base

AKG Coils

AKG Coils

Suzuki Omnichord OM-84

Posted in Repaired with tags , , , on April 28, 2013 by AnalogAudioRepair

I recently serviced two vintage Omnichords, both model OM-84. One had been attached to the wrong power supply, the other cut out intermittently and had to be turned off and on to reset.

The first one had an obvious problem – the power amp chip had literally blown! The power supply circuit has some regulation for the digital logic and other circuits, but the power amp gets the full supply. The part is obsolete but I sourced a genuine replacement to get it playing again.

The second unit had some intermittent issues. I found that pushing on the front panel or tapping the side would cause a playing rhythm/chord to freeze and require re-booting. Opening the unit it became obvious that the connectors between the two PCBs were at fault. Cleaning and reseating did not solve the issue so I touched up all of the connector solder joints on both boards – problem solved!

20130428-162220.jpg

20130428-162230.jpg

20130428-162239.jpg