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Messages - justinmroth81

#1
I'm ditching the suitcase cab for my 73 MK1 and am having issues with getting the VV sustain pedal to function. I recently had this piano bump modded and serviced and from what I can tell, the issue is that the dowel for the damper which has a felt pad on it is flush with the bottom of the piano. Essentially I tighten the wing nut on the sustain rod to make contact with the dowel but then the rod loosens with just one push and falls over. I'm guessing this dowel needs to move up to allow a bit of a recess to keep the sustain rod in place. This still wouldn't fix the issue of the wingnut not having enough strength to hold the telescoping rod in place.  Some years ago I used this without the suitcase cab. I took the sustain pedal and wooden rod from that, built a wooden frame to for the pedal to sit in and used a small block of wood screwed underneath with a hole drilled in it to stabilize the adjustable screw rod at the top of the suitcase pedals sustain rod.You cannot view this attachment.
#2
"Sudden loss in volume is suspicious.  Get a flashlight and magnifying glass and make sure you didn't put one of those transistors in "backwards" - meaning the collector and emitter are reversed.  At low voltages, the transistor will survive, but the gain (hFE) will be much lower.  Take are really good look at the schematic and make sure you are clear about exactly what solder pad should be the emitter, base, and collector.  (It would not be insane to mark them on the circuit board with a pencil or sharpie.)  Peterson preamp schematic:  http://www.fenderrhodes.com/org/ch11/fig11-8.jpg"

I switched around the base and collector as per the VV video here https://www.youtube.com/watch?v=ab7s0HMQpuo , the emitter remains in the same spot.

"On your hum issue, your complex setup may be creating ground loops, high-impedance paths, or simpy have dirty connectors that create high-impedance paths.
Have you isolated the hum down to the preamp itself?
Sort out the hum issue on the least-complex setup as possible.  No extra preamp, no effects loop, no external amplifier."
It hums with nothing in the loop (1/4" patch to complete path).  It also hums without the preamp 4 pin cable plugged in, I just noticed this but I guess this would point to the PS or power amps, though I don't think it's the amps...here's the thing, the hum is present in the external amp output and in my external cab, which would lead me to conclude that I have a dirty out-of-tolerance power supply, probably needs new filter caps at the very least.

"The distortion problem could be related to an overheating transistor.  The outputs in the suitcase bottom would be the primary suspects.  I think that also means checking the 1/2Ω resistors (and maybe the 820Ω and 2.7Ω resistors too).  You don't get distortion directly out of the Peterson preamp, do you?"
The distortion is present at both the suitcase cabinet and the external cabinet, my guess would be it would have to be coming from the preamp. (I tested with no effects, with and without external cab, and also straight from the harp board which of course, sounds fine)
#3
G'day all.  I have had problems with hum and buzz since I got my 73 suitcase.  I bought a preamp rebuild kit a few months ago with intentions of, well, rebuilding in hopes that it solved my buzz issue as well as I had a bulb out.  I kept putting it off and putting it off until, of course, a few days ago, a month before our record release show, I started experiencing some more issues.  It started sounding distorted for no reason.  I turned it off to check a few things, and after turning it back on it sounded ok for a few minutes.  Then it started distorting again.
  My set-up is harp board-out to pedal board, back to preamp input, 4 pin to power amp, 1/4" from ext. amp out to tube preamp, to external power amp, to 4X12" trapezoid cabinet.  I should mention I play pretty loud, but not pushing much through the suitcase cabinet, I let the external cab do most of the work.  I get the hum at any volume, as long as the power is on, even after the rebuild, but this is no longer my main concern.  I don't hear the distortion anymore, however the output is super low.  Before rebuild I usually maxed volume out around  9-11 o'clock (3-4 per Rhodes marking).  Now i have to crank it to almost all the way up, and it still is pretty quiet through the suitcase cab.  I can compensate with the external cab but I experience more noise issues.  I noticed in the VV kit there were NP caps replacing caps marked as polarized, I guess this is ok, maybe even mentioned somewhere.  I checked cap polarities and for loose connections and could find none.  I took care to switch the base and collector leads of the two transistors I replaced (shown below circled in yellow, these are what I saw to replace per the schematic).  I do not have a scope, however I have been an electronics tech. most of my life, with a degree.  Thanks for any help.
#4
I am experiencing some hum from my piano, grounding seems fine on the tone bar and what not, effects loop is fine.  The hum goes away when I unplug the preamp from the power, but when it's there it stays the same in amplitude no matter what the volume.  I have recently discovered I have one bulb out in the opto circuit, so I ordered replacements.  I am wondering if it's worth ordering preamp rebuild kit from VV?  I have somewhat extensive electronics knowledge so it won't be too bad, I just don't like throwing parts at something until it's fixed...unfortunately I don't own a scope :(
My first guess though was I needed to re-cap the power supply/power amp, though this may be the tube amp nerd in my thinking as that's where I would go first if this were tube'd. :o
#5
I figured mouser , digi key ect...wasn't sure if the average Chinese electrolytics were good enough.  I'm used to tube amps.
#6
Awesome.   I guess the ultimate purpose is to find parts.  I'm getting a decent hum at all volumes, figured a re-cap of the power supply may help.  Any advice on where to get suitable filter caps?
#7
And the amp?  4 pin peterson I think ?
#8
Hello all, new member here.  I hope I am posting this in the correct thread.  I am trying to identify what model I have, and have had a hard time finding something similar on the internet.