1955 M3 Dumpster Intervention/Rescue, TG Calibration

[tpappano]

Hello All,
I observed this thing on CL for several days. I certainly didn't need it since I had recently obtained a really nice E183, which after oiling and a few simple mods really runs and sounds great! Before I got the E183 I was originally looking for an M3, and it was eating at me that this instrument could come to a sad end as it was really rough looking and missing the bench. I called the guy and sure enough he still had it and was going to junk it because he had no responses to his ad. This unit was in a church before being idled a couple years ago. I plugged it in and it started right up smooth and quiet. Amazingly most everything worked- switches, drawbars, vibrato, percussion, etc. Two tones were missing, it didn't take long to find a tg filter wire that broke loose from its ground lug, and amazingly, a bad factory solder connection between a harness wire and a tonewheel filter lug. "Bad" as in not soldered at all!

As many here have described, the organ sounded dull. I examined one of the tg filter caps and sure enough it was +60% out of tolerance. I replaced them all with polypropylene film caps that I use in my products. Great improvement! The tg output levels came up 6 to 12 db above what they were before. I also disconnected the vibrato and non-vibrato high frequency rolloff caps in the amp. This thing now sounds bright and crisp like the E183. I also replaced the caps in the delay line because the vibrato sounded 'not quite right'. They were way out of tolerance and causing excessive phase shift.

From the condition of the case and the 'working' condition of all the contacts I'm guessing this organ must have had the snot played out of it for the last 60+ years.

Since the tg filters are no longer optimally tuned, if I was to do anything else to the tg, is it fair to say the consensus of opinion is to simply adjust the magnets to calibrate the levels? I looked at some of the spreadsheet data on the forum but I was thinking perhaps use the E183 levels as a guide.

Thanks!

Also, how does one get an E183 up a flight of stairs 8)

[enor]

Don't use the E-100 series levels as a guide, those are built with lots of high frequency roll of further down the signal chain (in order to kill keyclick) and therefore are very brightly calibrated. There's plenty of M-series calibration data out there as well. Use that.

- - - Updated - - -

And re the stairs: you get hold of a set of organ dollies and 3 more people. It's straightforward from there on ;)

[tpappano]

You make a good point Enor, I will look for some M3 data. I have to study the moving situation, the organ may have to be turned up on end to make a right turn on the landing and get it pointed up the stairs 8)
Thanks!

[Sweet Pete]

Don't use the E-100 series levels as a guide, those are built with lots of high frequency roll of further down the signal chain (in order to kill keyclick) and therefore are very brightly calibrated. There's plenty of M-series calibration data out there as well. Use that.

- - - Updated - - -

And re the stairs: you get hold of a set of organ dollies and 3 more people. It's straightforward from there on ;)

And a set of stair skidders. ROK wheels like smooth surfaces.
A lot less lifting and a little more push/pull; but way easier.....

This R100 genny is really bright! It will need to be M specs to make the spinet I'm building (61/61/25).
The bass octave waveforms are different so I'll need to weigh that into the equation.
IIRC the lowest octaves of an E100/T100 are derived from a frequency divider?

[enor]

And a set of stair skidders. ROK wheels like smooth surfaces.
A lot less lifting and a little more push/pull; but way easier.....

This R100 genny is really bright! It will need to be M specs to make the spinet I'm building (61/61/25).
The bass octave waveforms are different so I'll need to weigh that into the equation.
IIRC the lowest octaves of an E100/T100 are derived from a frequency divider?

Yes, but only the very lowest octave (#1 thru #12)

[Jyvoipabo]

Hello,

Coil: I also had the problem of broken wire at the edge of the lug. Sometimes I was able to wrap a thin wire around the lug and join it to the broken wire.

Capacitor: How did you adjust the value that should be within the 5% maxi of a non-standard value ?

JP

[tpappano]

Capacitor: How did you adjust the value that should be within the 5% maxi of a non-standard value ?

JP

I simply installed 0.1 mfd 5% capacitors without attempting to select for signal peaking. Even this greatly improved the sound. When I get a chance I will sweep the filters with a function generator just to see where their center frequencies wound up. I did a quick check of the TG signal output levels after I replaced the capacitors and they were roughly +/- 3 db. Considering the mayhem that the speaker, enclosure and room acoustics wreaks upon overall frequency response, the variations might not be very noticeable 8)

[Jyvoipabo]

Thank you for the answer.
I think the value of these capacitors is not critical.
But it is not bad to sort them to keep only the most accurate.
That's what I did and everything was good.
It is clear than if we replace capas of + 640% value (36n measured for 5.6 marked) by ones better than +/- 5% it cannot go worse.
JP