Author Topic: Nasty Hum on 1974 Suitcase 88. Help please!!!  (Read 3030 times)

Offline Nitrofunk

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Nasty Hum on 1974 Suitcase 88. Help please!!!
« on: May 23, 2010, 04:57:13 PM »
Hi!
I got a nasty Hum-Problem with my Suitcase 88 (made in 1974): When the Piano is turned on, there is a very annoying Hum as well as some other background noises (the Vibrato makes a "Thud-Thud-Thud"-Sound when activated, for example). The Volume-Level of the Hum doesn't change when the Volume on the Preamp is turned up or down (its Sound, however, changes when I turn the Rhodes' Treble and Bass-Controls). However: When I disconnect the grey 4-Pin-Cable from the Bottom, the Hum is gone and the noise level is absolutely ok.
Since I want to get rid of this issue: What could be the Cause of the Hum? Is it a Power Supply-/Preamp/Power Amp Problem? Is it a difficult issue to fix that costs a fortune?
Hope you can help.
Thanks!
Peter
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Offline Tim Hodges

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Nasty Hum on 1974 Suitcase 88. Help please!!!
« Reply #1 on: May 23, 2010, 07:08:53 PM »
Peter this video should help you on the thud issue:

Fender Rhodes 4 Pin Suitcase Pre Amp Vibrato Thump Mod

They say it's usually a problem with the resistors which have gone out of tolerance. But the video will clarify the issue.

T
Bristol Electric Piano
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Offline Nitrofunk

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Nasty Hum on 1974 Suitcase 88. Help please!!!
« Reply #2 on: July 05, 2010, 08:57:20 AM »
Hmm - when the Piano (the Preamp) isn't connected to the Bottom, the Bottom is relatively silent. So it seems to me that the Problem is somewhere inside the Preamp, right?
Vintage Vibe 64 Tine Piano - Strymon Mobius - TC Electronics Hall of Fame - Podium MXVS Amp
Fender Rhodes Suitcase 88 ('74) - MXR Micro Amp - Small Stone Phaser
Moog Prodigy
Nord Piano
Suzuki Pro 38 Melodica

Offline Nitrofunk

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Nasty Hum on 1974 Suitcase 88. Help please!!!
« Reply #3 on: July 06, 2010, 08:37:07 AM »
Anybody?
Vintage Vibe 64 Tine Piano - Strymon Mobius - TC Electronics Hall of Fame - Podium MXVS Amp
Fender Rhodes Suitcase 88 ('74) - MXR Micro Amp - Small Stone Phaser
Moog Prodigy
Nord Piano
Suzuki Pro 38 Melodica

Offline Spaceduck

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Nasty Hum on 1974 Suitcase 88. Help please!!!
« Reply #4 on: July 06, 2010, 02:06:05 PM »
Quote from: "Nitrofunk"
Hmm - when the Piano (the Preamp) isn't connected to the Bottom, the Bottom is relatively silent. So it seems to me that the Problem is somewhere inside the Preamp, right?


I'm no amp expert, but I think that's a good assumption. In fact, the problem could even be originating before the preamp. Whenever I hear Rhodes & hum used in the same sentence I immediately think of the grounding wire on the harp. That's usually been the culprit in my experience (and an easy fix!). Try messing with the ground wire at the RCA harp jack as well as on the other side of the harp. Could just need a quick re-solder.

Offline Tim Hodges

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Nasty Hum on 1974 Suitcase 88. Help please!!!
« Reply #5 on: July 06, 2010, 02:29:40 PM »
My 3 thoughts:

1. Possible ground problem from the damper
2. RCA socket issue on harp (as mentioned above)
3.  Pre-amp

The first two should be easy to troubleshoot and if the problem persists then you could assume that it might be the preamp, if so VV 4 pin preamp repair kit should do the trick.
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Offline Mark II

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Nasty Hum on 1974 Suitcase 88. Help please!!!
« Reply #6 on: July 06, 2010, 05:21:05 PM »
well, difficult issue.
I am no suitcase expert, but a suitcase bottom without preamp connected is without any input signal, so it could be quiet even if something is wrong there ?!?

Do you have a preamp outputs on your suitcase. some of the later suitcase cabinets have preamp output jacks where you could feed the preamp's signal to another amp in order to check if the preamp signal is clean.

I would blaim the suitcase amp for humming. bad/ old elcos in the power regulation, something like that.

good luck
Mark II
Rhodes Stage 73 Mark II 1980 / modified Peterson Suitcase Preamp

Offline Jenzz

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Nasty Hum on 1974 Suitcase 88. Help please!!!
« Reply #7 on: July 12, 2010, 01:06:30 PM »
Hi Peter .-)

Seems that there are defective coupling caps, so the LDRs modulate the DC voltage instead of the audio only...

Jenzz
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