Author Topic: Passive Electronics Question...  (Read 261 times)

Offline groovemonkey73

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Passive Electronics Question...
« on: August 04, 2019, 08:00:51 AM »
My 79' Mk1 73 stage just keeps fightin' on me!

Ive now got all 73 notes working, 73 good pickups (at last)!
But now, my passive electronics have gone out. I tested my notes by bypassing that and going straight into the harp with a phono so I know its the rail board, plus there be a broken wire:


I'm pretty sure it should be attached to the pot its pointing at as it isn't long enough to attach to anything else really, and I quickly tried re-soldering it, but I didn't have a lot of time and was a struggle to get it to hold. I know I need to strip it back a bit, but am I thinking correctly in that it does live on that pot?

Thanks once again in advance!
1979 Mk1 Rhodes 73
Nord Stage 2 Compact
Hammond XK3c
1915 John Broadwood & Sons Upright

Offline sean

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Re: Passive Electronics Question...
« Reply #1 on: August 04, 2019, 12:10:50 PM »


That wire gets soldered back onto the other pot (the pot that is not in the photo).  It gets soldered to the first terminal on the C50K Bass Boost pot.
That terminal is the one that has a connection to the capacitor, but NOT a connection to the middle lug.

See the photos and diagrams at  https://ep-forum.com/smf/index.php?topic=4650.msg22605#msg22605

Sean

Offline groovemonkey73

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Re: Passive Electronics Question...
« Reply #2 on: August 04, 2019, 02:31:53 PM »
Hi Sean,

Thanks so much for such a swift reply, and your knowledge!

The diagrams are aberjillion percent helpful - Legend! Thanks so much!
1979 Mk1 Rhodes 73
Nord Stage 2 Compact
Hammond XK3c
1915 John Broadwood & Sons Upright

Offline groovemonkey73

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Re: Passive Electronics Question...
« Reply #3 on: August 05, 2019, 02:57:38 AM »
Also, just to update, I've re-soldered back as per the diagrams, and its now working again!

Not sure how long its going to last, but I've plans for either a new replacement passive set or potentially a tube pre-amp kit of some description.
1979 Mk1 Rhodes 73
Nord Stage 2 Compact
Hammond XK3c
1915 John Broadwood & Sons Upright

Offline pnoboy

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Re: Passive Electronics Question...
« Reply #4 on: August 08, 2019, 11:43:59 AM »
I have to say that IMO, and others may disagree, a tube preamp for a Rhodes is a waste of time and money.  I have played my Rhodes direct from the harp through both tube and solid-state amps, and I really hear no difference in sound except for that which is due to differences in frequency response.  Once the frequency responses are set to be the same, both SS and tube amps sound the same as long as they're played within their non-clipped range.  If you want to pretend to be a rock guitarist and play power chords and single-note leads on your Rhodes, get a distortion pedal, which is lots cheaper and lots less weight than lugging around a tube amp.

Offline groovemonkey73

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Re: Passive Electronics Question...
« Reply #5 on: August 11, 2019, 01:27:54 PM »
You must have been reading my mind, just picked up a 2nd hand Boss OD-3 to try through it!

1979 Mk1 Rhodes 73
Nord Stage 2 Compact
Hammond XK3c
1915 John Broadwood & Sons Upright

Offline shmuelyosef

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Re: Passive Electronics Question...
« Reply #6 on: August 12, 2019, 09:21:00 PM »
I use the circuit below for my Fender-Rhodes Stage 73 (1974 vintage). I went to higher impedance to keep the loads higher on the pickups...gives a much cleaner, stronger signal than the original if you are going into a high impedance amplifier (I use an FMR Audio RNP-8380).

The potentiometers are Emerson "Short Solid Shaft" Audio Taper; I bought them through Sweetwater.
The capacitor is a high quality polypropylene thin film.

I also had a natty old circuit like yours that I had just short-circuited and was going straight into the RNP for years, but decided I wanted on-board volume and tone control again, so just rebuilt the whole thing. The Emersons fit the vintage knobs perfectly.

The full output of the Rhodes pickups was a little much for some "Drive" boxes that I like, and this let's me dial down the power without introducing noise.
"When I read about the evils of drinking, I gave up reading" --- Henny Youngman

1973 Fender-Rhodes Stage 73 Dyno > 1912 Mason & Hamlin Model A > > Nord Electro 6HP 73 > DSI OB6 analog synth > Rondetti concert accordion > dozens of melodicas, saxophones, clarinets, flutes, drums, amps...help...I'm awash in GAS!!

Offline groovemonkey73

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Re: Passive Electronics Question...
« Reply #7 on: August 21, 2019, 02:21:52 AM »
Thanks for the info and insight shmuelyosef,

Once I've got everything actually working, and got it to sound how I want, I'm keeping my options open as to then passive electronics against wired pre-amps and things, and the options of re-wiring. I want something that sounds good, gives a good output without noise, and something reliable when humping it about. I don't plan on using for too many gigs/outings, but when I do I don't want to have to 'fettle' it before hand!
1979 Mk1 Rhodes 73
Nord Stage 2 Compact
Hammond XK3c
1915 John Broadwood & Sons Upright