Maestrovox Circuit Diagram (Schematic)

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Charles Hayward

Debbie Curtis

Maestrovox Consort
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Page 2 - 1950's Maestrovox Information Centre
These Pages are Copyright Protected - See Bottom of Page

Added February 2012 - Parts & Help  Regarding Restoration of Maestrovox - Supplied by JonDent in Australia who has recently fully restored a Consort:- http://www.flickr.com/photos/69117150@N02/sets/72157627989225366/

You can also view Technical Data Sheets from JonDent, Maestrovox Restorer at the following link:-

Technical Data Sheets for Maestrovox

Old Maestrovox Valves

To get this synth running much work was needed.
Below is a rundown on the repairs:
(hopefully it will help other restorers in the future).

1 Source and replace all Valves:
RAYTHEON 6SN7GT DUAL TRIODE VACUUM TUBE x 2
SYLVANIA 6V6GT/G BEAM POWER PENTODE VACUUM TUBE x 1
RCA 5Z4 FULL WAVE RECTIFIER VACUUM TUBE x 1
KEN RAD 6J5GT/G TRIODE VACUUM TUBE x 1

2 Source and replace all capacitors except main power supply filter -
this was still fine - these are all 600 volt and hard to obtain the original values.
Especially critical are the ones for tuning the Octave selector

3 Replace all resistors except the main high tension and the Keyboard array -
some resistors in the array did need replacing as they were causing mistuning.

4 Remove key assembly and clean and straighten all wafer switches, brass dip used:
Leuchtterm Brass Dip, then Caig Deoxit Red and Deoxit Gold

5 Remove short circuits from key switch assembly

6 Repair bent key spring wafers and realign all keys to be straight horizontally and spaced correctly.

7 Clean and repair all slider switches (tone switches) - some were shorting out and likely to blow valves!

8 Replace perished wiring

9 Repair vibrato section - faulty vibrato rate pot needed dismantling and cleaning

10 Repair Octal Plug used to connect Amp/Power Supply to Keyboard

11 Replace perished insulation sleeving with heatshrink in some dangerous areas!

12 Repair tears to top cabinet covering

13 Tune octaves, tune upper/lower key register

14 Repair vibrato section - faulty vibrato rate pot needed dismantling and cleaning

15 Replace missing cabinet screws - managed to find identical black brass ones

16 Reglue rubber piano pads

17 Clean case and all keys - remove stains from white keys

18-19 Receive electric shocks (2) good fun!

Cheers to my techo Keith for risking life & limb for music.

Link: JonDent Maestrovox Restoration Report on Flicker

New Maestrovox Consort Circuit Diagram added September 2011

Original circuit diagrams (schematic) and component lists for my Grandads Maestrovox Organ design from 1952. Also the patent, which gives a detailed description of the original Maestrovox's technical layout as well as a list of the components used in the diagrams.
It is likely that these circuit diagrams will relate only to the very first Maestrovox and not to later models. Please see the owner/engineer comments at the foot of this page.
As I know nothing about electronics, I would be grateful for any feedback, comments, corrections, observations etc. Also, if you have any diagrams, or have managed to create diagrams that will help others repairing or restoring a Maestrovox then please let me have copies for the pages. Thanks.
Do you own a Maestrovox or know someone who does? then please tell us.

Email Maestrovox

Click on a document to ENLARGE it

Maestrovox Consort Circuit
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Added September 2011

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This hand drawn circuit did not form part of the main documents, it was written on the back of circuit page 1 and may not be anything Maestrovox, if you work it out, please let me know.

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Maestrovox Home, History & Pictures

Comments from Owners & Engineers on the Circuit Diagrams & Patent

Owners Comment :- 16-01-2010 - Ownre of 1287 wrote :- I`ll be happy to answer any questions about this item for you (if I can).
something that may interest you is that mine also does not have the neons for the vibrato circuit (like the other guy that posted on your site), sadly the circuit diagrams you provided are a little hard to read for my eyes even with my glasses on.
but you can Still get the valves for these "organs" today and they don`t cost all that much either, so it`s safe to say that you could keep one of these going for another 50+ years without much trouble ;)

Owners Comment :- 31-07-2006 - Greg Middleton wrote :- I'm slowly working through the diagrams comparing them with my Maestrovox Consort De Luxe. My initial findings are that the circuits are for an earlier, more basic instrument, probably in support of the patent application. Mine has more refinement in the keyboard and envelope shaping circuits, and of course has a separate amplifier unit. Also, the circuit sketched on the back of the main diagrams is almost certainly much later, maybe 20 years later, as it is drawn in a more modern notation.

Owners Comment :- 30.07.2006 - Nigel Bailey wrote :-  "My consort model is definitely different from the diagram shown, not vastly, but I havent got any neons in the vibrato circuit of mine (which could explain why the vibrato doesn't work (!), or just that it's a different vibrato oscillator type). The patent document is really really useful, as it explains the circuit really well, and will probably help vastly in the decoding of what i've got".