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Topics - sopranojam85

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Hi everyone,

I'm working on a Wurlitzer 206A with a subtle, but somewhat nagging issue. There are audio artifacts (high frequency) that sound a bit like a crackle, or static. At other times, the sound is periodic, about 3 or 4 "clicks" per second. I know that the sound isn't coming from the reed bar. The reed bar is completely disconnected from the amp board. I have traced the source of the signal to the 15V rail of the power supply. This is the only rail of power that I can pick up this sound occurring.

The board has had all electrolytic caps replaced, and this made no change in the issue. All resistors are well within tolerance.

I can see that the 15V supply is coming from a Motorola 142349 IC. Since I didn't have one of these handy, I disconnected the 15V leg of R28 and R23, and connected these to a separate 15V DC power supply. Sound disappeared.

The 22.5V and -22.5V rails are looking very good. I've replaced the 4 power supply diodes, and this smoothed out what little AC ripple it had by even less. There appears to be only 2 or 3 MV of AC ripple on these rails, and no other anomalies.

So this leads me to wonder if I can replace that voltage regulator. What's an equivalent replacement for the chip? It's got a big M on it (I assume a Motorola logo), and has part number 142349 silk screened on it. So far the most likely candidate is this one, but I'm not sure if it's all correct or not. http://www.weisd.com/test/GenericParts_WEISD_view.php?editid1=142349

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Hello,

I'm about to get cracking on a Rhodes Janus I 50W Amp. This is the vertical free-standing ones that Rhodes intended you to buy either one or two of them together. Anyway, there's only one, and it's developed a fairly horrendous crackling sound.

I'm not 1,000% certain, but am mostly certain that this is the proper schematic for this little beastie: http://www.fenderrhodes.com/org/ch11/fig11-3.jpg

It's been interesting trying to differentiate between the suitcase built-in amps, and the stand-alone amps. If this is not the right schematic, I'd appreciate a gentle shove in the right direction.

This is coming back to the shop for a re-work. The original problem was a crackle, and I noticed that the Power transformer was dangling off the chassis by one nut. The hardware mounting it was all stripped out. I replaced all the hardware, and the crackle went away. While the amp was out, I put a dummy load on it, powered it on, and measured 38 V on the 30 V rail. So that's an area of concern. Something is probably not drawing enough current, or the voltage regulators are not doing their job, or both.

Does anyone know what the expected AC voltage is on the power transformer secondary windings for these things? (Power on, and secondary windings disconnected, freely measured?) I have a notoriously bad time with power transformers failing, and before I start chasing IC problems, I'd like to make sure the power transformer is doing its job.

Also a recap is in order, and replacing any off-spec resistors... Any advice is much appreciated. I'm more a tube guy.. this solid state stuff is easier to work on, but harder for me to understand.

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Parts, Service, Maintenance & Repairs / Some reeds too dang quiet
« on: July 27, 2015, 11:22:51 AM »
Hello folks,

I'm working on a Wurlitzer 206A which has notes #36 and #37 that are entirely too quiet. I've done all I can think of to fix the issue, including:
-- Sanding all sides of the reed with emory paper, then 0000 steel wool (These reeds are shiny enough to shave with now.)
-- Sanding the harp surface contact point of the reed.
-- Removing all solder and starting over. (It now has a perfectly-shaped flattened pyramid of solder that is fit for a diorama.)
-- Setting proper let-off and check-off
-- Adjusting hammer striking point and gently filing hammer tip to be a bit more pointed.

No luck.

I've even tried swapping reed #37 with reed #38 and the issue follows the reed - not the key. (Admittedly, I probably should have done THAT before messing with the hammers, but what's done is done.)

It's seeming clear to me that I need new reeds. But I've read (here, and elsewhere) that reeds don't go quiet. They go flat and brittle, and then they break. Yet, the Wurlitzer 200 series service manual states "Any foreign material on the head of the reed will dampen the oscillation. If this does not cure the ring time, the reed should be replaced."

Am I missing something? Meanwhile, both Vintage Vibe and Retro Linear seem to be out of stock of their reeds, and even everyone's favorite auction site has some reeds, but not these ones. I'm kind of high and dry on reed supply unless someone knows of another source.

Thanks for any help!

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Hello everyone! First post here, and I hope I am putting this in the correct location. I have a Rhodes Mark I Suitcase piano which suffered a fall on stage. Everything was fixable, except that the vibrato speed and depth pots were damaged - their lugs sheared in half right where the lugs meet the pot's body, making them completely trashed.

I'm looking for replacements, and am having a heck of a time finding ones of the same size.

These are 25k and 100k reverse pots. The body of the pot is 24mm in diameter, and it has a 6mm-diameter shaft. The total shaft length is 25mm, but the tricky thing is that the threaded portion of the shaft is about 16mm long.

I understand why the threaded portion of the shaft is so long; it is used to structurally support the preamp chassis behind the nameboard. The threaded portion must protrude through the preamp chassis, AND through the nameboard.

I managed to find a few pots with a 25mm shaft, but none which had a threaded length even close to 16mm. (8mm was as long as I could find.) Reverse pots are the most limiting factor here, I think. They just are not as plentiful as standard pots. I've lost track of the number of suppliers I have checked with. I remember for sure that I've checked with Mouser, Digikey, Newark, Vintage Vibe, a few eBay sellers, and also Alpha. Alpha can make this pot if I provide them specs, but a minimum order size of 1,000 is required...  :-\

I'd love to find an identical replacement without actually buying a junk preamp or Rhodes to do it. Any ideas?

If worse comes to worse, I will have to make a few mods to the preamp chassis (NOT the nameboard.. just the chassis behind it) to accommodate the body of a shorter-length-shaft pot, and come up with a way to support the chassis elsewhere.

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