power switch for later suitcase

[jim]

hey ho,
can anyone give me info on they type of switch used in the later suitcase amps? the one that lights up.

i'd like to know the requirements of the LED in it..amps and such, as i have to replace one that is mysteriously missing.
the schematics don't seem to say.

rad.

[jim]

why can't this be like the rhodes tech forum?
my questions never get answers!

[Ben Bove]

im almost positive musicpartsguru.com has an original latemodel switch.

[jim]

argh bloody hell i bet they do.

i also bet it's broken.


surely the switch is a switch that is regularly used in other applications.

[Rob A]

Not speaking from first hand knowledge of that part here, but here goes.

Lighted switches usually draw power from the source they are switching. So it's almost certainly not an LED being that it switches mains power. It is likely a neon lamp. Neons can be wired directly across mains with no special circuitry to support them (which makes them ideal for this application).

Also, the lamps aren't usually replaceable in the lighted switches I've used. You drop the whole assembly in if the light fails. Get a catalog from a full line electronics house and you will find lighted rocker switches in a bewildering array of sizes--you just need one that a) fits your hole and b) is rated for mains voltages. Current draw won't be more than a couple amps (divide Watts by Volts to get Amps).

[Mark II]

hey, Rob A is right. in switches lamps dont use LEDs. I dont know the specific amps but the fuse in the US version power supply is stated by the schematic as a 3 Amps one. So, a switch with 3 amps should be fine.

Did you look at the back of the switch, Jim. On some switches are the specifications printed. But I dont know if that's the case with the Suitcase switches as I am only familiar with my stage model.

Kind regards

Mark II

[jim]

i love you guys,

the problem was that the original switch was totally gone!

i have found a replacement at my local electronics store that fits in perfectly and says 240V. 15A

we'll see how she goes eh?

[Rob A]

Should work a treat, having ratings in excess of what's required won't be a problem.

How do you guys power your Rhodes suitcases up when you live outside the 110VAC part of the world? Use a converter?

[jim]

oh we have export versions!!

BUT!!

it looks like the switch i have is wrong..i'm not sure if there's some nifty lateral thinking needed or if it's just not gonna work.

what the switch needs is..i think, the light can be constantly connected, and two other points to be switched.

what i have is two points going through the light..which sucks.. i need a cup of tea.

and i just got a shipment  from vintage vibe, and they have the switches! if only i'd ordered after i knew!!

[Mattia]

How do you guys power your Rhodes suitcases up when you live outside the 110VAC part of the world? Use a converter?

Well, usually the input transformer has a split primary stage: if you connect both halves in parallel you have a 110V input, but rewiring them in series it'll accept 220V. I still haven't done this modification on mine, so by now I'm using a 220-to-110 external transformer.

Luckily Rhodes don't depend on supply cycles (USA 60Hz against European 50Hz), as a Hammond does instead...

Jim, if you can post the schematic of the switch you have bought maybe we can find an idea to plug it correctly.

Byez!

[jim]

ok so i ended up calling a friend with the same amp, going over there and taking some pictures with my phone and running my umm, whatsitcalled to test the connections..it'l like 12.50am here..no brain. MULTIMETER!!! my multimeter.

and horrah it worked..but then..funny pre amp fizz out...i then used the forum and found the people who are awesome here telling me how to fix it and..horrah!, but now one channel doesn't work...and the fuse just blew again!! oh my.

also...I have done the 110 to 240 modd. easy as pie. just connect the two that want to come out and go round again..if you know what i'm saying.., which you do. cause ..bed time for me.

[Mattia]

Good, I'm glad you solved the switch problem, hope you'll find a solution for that blowin' fuse, too...

G'nite, mate! I envy you, on this side of the globe it's still work time...  :cry:

[Ben Bove]

Or, if you call  V V I'm sure they can get you one like on their site.

http://www.vintagevibe.com/p-407-rhodes-amplifier-power-switch.aspx

[jim]

i'm not sure but it seems as though the wires coming out of the rear end of the transformer may have been pinched several times..as they kinda want to hang out the side and get squashed when you put the amp back in the suitcase cab.

does anyone have a schematic near to see if what i think is right?
what i think:
should i be getting zero resistance between the green/yellow wire and the red/yellow wires? it appears that they should be connected inside the transformer? but i'm getting nothing and it makes me wonder if the yellow wire has suffered damage ...i think it's been squashed a gazzillion times.


hey mattia, now it's my work time! we are in an endless cycle of opposites!

[Mark II]

here is the schematic for the later suitcase power amp and power supply.

you are talking about the secondary winding of the transformer ?
yes, there should be a direct connection between red/yellow and green/yellow. both are common ground.

Mark II

[jim]

ok sorted, all is working now.

the problem was...wrong fuse! ha!  :oops:

so now that it's working, it turns out that two of the speakers are gone.
the owner just wants the thing to make sound, so i suggested i could wire it just going through the two speakers, so he'll still get the stereo vibrato.
i said this thinking i could just put an 8ohm resistor in place of speaker 2 on each channel. but when i went to my store to get some 8ohm resistors, the guy said "no it's an awful waste and it will cost you heaps to buy resistors of that wattage"

so..what's up there?
do i need 50W resistors? and apparently resistors' characteristics can change when they heat up?

and after all this, his strike line was off, it's amazing that i can improve the piano 80% by simply moving something over by 3/4 of an inch, compared to the drudgery of getting this amp going!!
also amazing that nobody got it right since 1979!! i guess there was ten years of the eighties in there. people probably LIKED a bad strike line back then. but i digress.

[Mark II]

oh my god, Jim, concerning the text of link below that's a jackpott:

http://www.fenderrhodes.com/service/speakers.php

the amp wants to see 16 ohm, as Steve Woodyard says.the 32 ohm speakers are wired in parallel. so you will need a at least 50 watt 32 ohm resistor. that's an awfull waste of power.
I would focus an getting 2 original speakers or replacing the 2 existing with 4 good alternatives (but dont ask me about this one).

Mark II

[jim]

it's not the peterson, it's the later, so they are 8ohm rather than 32. unless i am wrong?

red dot=8ohm.

but yeah...now i gotta tell this guy he needs to spend more money.

[jim]

but then, i am finding people on the net suggesting that i can just ignore the other speaker, and that perhaps an 8ohm load and a 4 ohm load are not that dissimilar...and that the amp wont mind..

i think someone suggested the same thing on this forum way back in that post about the neighbors complaining so they wanted to disconnect the speakers that faced the wall.

would the amp have to work harder i guess? that might be bad?  i'm not so savvy on these things.

and right now my stereo is just loosing volume every now and then..what's going on?

[Mark II]

OK, than I got the speakers impedance wrong. I am sorry about that. If you want to be sure, unplug the speaker and measure the DC resistance. the impedance is higher than the DC R. so, an 8 ohms impedance speaker would read somethin round 6 ohms.

when dealing with amps and speakers - no matter if tube or transistor - the best perfomance and most save setup is archieved when matching impedances.
you get the most power out of your speakers and let the units work at their designed operation point.
all other settings result in either increasing the danger of doing harm to your amp and/or speaker or decreasing the perfomance (less power = less volume).

So, if you are working on RHODES pianos on a professional basis - your new profile picture and reading between your posts seems as if - I would try to match impedances.

Dissenting votes, please !

Mark II

[Mark II]

Dissenting votes, please !

Mark II

Loudspeaker amplifiers

Modern solid state audio amplifiers do not use matched impedances, contrary to myth. The driver amplifier has a low output impedance, such as < 0.1 ohm, and the loudspeaker usually has an input impedance of 4, 8, or 16 ohms, which is many times larger than the former. This type of connection is impedance bridging, and it provides better damping of the loudspeaker cone to minimize distortion.

The myth comes from tube audio amplifiers, which required impedance matching for proper, reliable operation. Most of these had output transformer taps to approximately match the amplifier output to typical loudspeaker impedances.

mmh, it seams that my stating above is not uptodate anymore as long as modern solid state amps are concerned. But I think it is still true for a 20 years old suitcase amp. What do the electronic gurus here think about that ?

Mark II

[Rob A]

Amp wants 16 ohm load.

two 32ohm in parallel = 16 ohm
two 8 ohm in series = 16 ohm

I have tried to figure out what possessed them to use those esoteric 32 ohm drivers. I'm sure they had a reason. I've tried to analyze the amp schematic, but the reason doesn't make itself apparent to me.

In the "just want it to make sound" spirit, series-connected 8-ohm drivers should get him there and be safe to operate the amp into.

[Rob A]

would the amp have to work harder i guess? that might be bad?  i'm not so savvy on these things.

With one set disconnected, you have a 32 ohm load, which is safer to operate than a load that is rated less than 16 ohms.

[jim]

i gotta say again this is not the peterson, which uses 32 ohm speakers, it's the later model and contains 8 ohm speakers.

so two 8ohms parallel is 4 ohms

so what i would be doing is running what's usually 4ohms through 8 ohms.

i'm thinking the amp will just run on half the power, because it has double the speaker resistance.

[Mattia]

But... are we sure that later suitcases had 8ohm speakers installed in factory, and only Peterson design used 32ohm?

[Rob A]

Either way, it doesn't matter--removing one of a a parallel pair of speakers will increase the impedance, which is a smaller load on the amp, and as such should be generally safe.

[Mattia]

Of course, but if all amps (80W and 100W) were designed for 32ohm speakers wired in parallel, and jim's one has been modified with 8ohm speakers, it still has half the impedance needed... regardless of how the speakers were connected after substitution.
I mean, if you double one quarter, you get one half...  :wink:

[Ben Bove]

This guy is selling his Speakers from Haigler era 5pin cabinet.  speakers blatantly stamped 8ohms haha.  Never noticed that.  So I guess it is Peterson that used 32 only?

http://cgi.ebay.com/Four-4-Speakers-for-Rhodes-Suitcase-Electric-Piano_W0QQitemZ290220260279QQihZ019QQcategoryZ29552QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[Rob A]

Someone should update the "amp differences" page on the main site accordingly.

[jim]

yes and when i used to own a mk 2 suitcase it also had 8ohm speakers.

also, even the early satellites have 8ohm speakers.

very irritating when you're trying to steal speakers from one rhodes to bring the older cooler one back to life.

thanks guys, you've been very helpful. this guy just wants sound, so i'll wire each channel with one speaker for now but tell him he'd be good to replace or re-cone them as soon as he can.

[Mattia]

Very interesting... I wonder how many people re-wired replacement speakers in series to accomplish unnecessary 16 ohm load on 5pin amps...  :?

I took a look at both schematics and as I can see the output stage is very different between the two models: in 4pin we have a matching transformer with a simple push-pull stage, and it's clearly specified "to 16 ohms load"; on 5 pin the amplifier has no transformer and no specification about required load...

I'll ask an opinion from a friend of mine who's more skilled than me in audio amplifiers as soon as possible, but I starting to believe that later amps are less load-demanding than earlier ones...