Hi. I recently bought a 2nd-hand Roland HP-860 electronic piano (88-key, analogue). It has a louder hum than the piano notes.
I'd like to fix it myself. I have been learning electronics most of my life & I'm in the 3rd year of Electronics Trades at TAFE NSW (Australia).
I've removed the plug from the final stage PCB (Revo board), and the amplifier is quiet. This makes me think that somewhere before the amp, there is hum being made. I could poke around with my CRO, but I wouldn't know what to look for.
This piano has heaps of boards, for which I've worked out most of the features.
I could try replacing all the aluminum electrolytic caps, but that could just be a waste of time. It was made some where between the late 70's and early 80's.
I looked for date codes, and only found 1, I think.
This piano uses a wiring loom design, with some PCBs using plugs, but most are wired up (soldered).
To see pics of it, search Google images for "roland hp-860" use quotes and thaisecondhand.com has the pictures. NOTE: I have the 240VAC version.
> Hi. > I recently bought a 2nd-hand Roland HP-860 electronic piano (88-key, > analogue). > It has a louder hum than the piano notes.
> I'd like to fix it myself. I have been learning electronics most of my > life & I'm in the 3rd year of Electronics Trades at TAFE NSW > (Australia).
> I've removed the plug from the final stage PCB (Revo board), and the > amplifier is quiet. This makes me think that somewhere before the amp, > there is hum being made. > I could poke around with my CRO, but I wouldn't know what to look for.
> This piano has heaps of boards, for which I've worked out most of the > features.
> I could try replacing all the aluminum electrolytic caps, but that > could just be a waste of time. > It was made some where between the late 70's and early 80's.
> I looked for date codes, and only found 1, I think.
> This piano uses a wiring loom design, with some PCBs using plugs, but > most are wired up (soldered).
> To see pics of it, search Google images for > "roland hp-860" > use quotes and thaisecondhand.com has the pictures. > NOTE: I have the 240VAC version.
> Please help! :) > TIA
Have you looked at the power supplies with your scope? Here's your chance to put those 3 years of education to good use.
No I haven't! Thanks for the tip, and thanks for the quick reply! I'll go and try it now. It has a bunch of different voltages out, and they're labelled on the PCB! I guess I should look for ripple on what should be DC, right?? Then trace it back to the offending cap(s). Then go buy some new ones of those only.
BTW: It has a main voltage going to all the keys of 46V which measures 43V.
> No I haven't! > Thanks for the tip, and thanks for the quick reply! > I'll go and try it now. > It has a bunch of different voltages out, and they're labelled on the > PCB! > I guess I should look for ripple on what should be DC, right?? > Then trace it back to the offending cap(s). > Then go buy some new ones of those only.
> BTW: It has a main voltage going to all the keys of 46V which measures > 43V.
You seem to be jumping to lots of conclusions for no apparent reason. This is not going to help you.
What's with this "offending caps" businsess? You seem to have decided there is a cap problem and replacing them will be the solution. Stop guessing, it will get you nowhere.
You need to investigate and gather information. You start with the power supplies, If they are OK then you look elsewhere.
On Sat, 6 Sep 2008 14:36:12 -0700 (PDT), "Josh9.0"
<squalene...@hotmail.com> wrote: >No I haven't! >Thanks for the tip, and thanks for the quick reply! >I'll go and try it now. >It has a bunch of different voltages out, and they're labelled on the >PCB! >I guess I should look for ripple on what should be DC, right??
Sounds good.
>Then trace it back to the offending cap(s). >Then go buy some new ones of those only.
>BTW: It has a main voltage going to all the keys of 46V which measures >43V.
Ba-ding... Now I wonder why that voltage is low? Could it be, oh, maybe... A bad filter cap?
Gareth Magennis wrote: > "Josh9.0" <squalene...@hotmail.com> wrote in message > news:b5bb74fd-fccb-4579-a414-fa7ac9e673cd@c58g2000hsc.googlegroups.com... >> No I haven't! >> Thanks for the tip, and thanks for the quick reply! >> I'll go and try it now. >> It has a bunch of different voltages out, and they're labelled on the >> PCB! >> I guess I should look for ripple on what should be DC, right?? >> Then trace it back to the offending cap(s). >> Then go buy some new ones of those only.
>> BTW: It has a main voltage going to all the keys of 46V which measures >> 43V.
> You seem to be jumping to lots of conclusions for no apparent reason. > This is not going to help you.
> What's with this "offending caps" businsess? You seem to have decided there > is a cap problem and replacing them will be the solution. > Stop guessing, it will get you nowhere.
> You need to investigate and gather information. You start with the power > supplies, If they are OK then you look elsewhere.
> Gareth.
Thats because searching for any electronics problem on google comes up with "check all the electrolytics", ESR is the new religion. I get so many people bringing stuff to me saying, hey its probably a cap, you got an ESR meter?, can't be more than 10 bucks to fix. Yeah right. A little bit of knowledge can be dangerous. Good luck to the OP, with a scope should be an easy fix.
>>No I haven't! >>Thanks for the tip, and thanks for the quick reply! >>I'll go and try it now. >>It has a bunch of different voltages out, and they're labelled on the >>PCB! >>I guess I should look for ripple on what should be DC, right??
> Sounds good.
>>Then trace it back to the offending cap(s). >>Then go buy some new ones of those only.
>>BTW: It has a main voltage going to all the keys of 46V which measures >>43V.
> Ba-ding... Now I wonder why that voltage is low? Could it be, oh, > maybe... A bad filter cap?
Er, what exactly is this 46 volts supposed to be doing? I doubt there is anything like 46 volts anywhere near the keyboard.
> Er, what exactly is this 46 volts supposed to be doing? I doubt there is > anything like 46 volts anywhere near the keyboard.
> Please try again.
> Gareth.
Yes... I checked it again. it's a common to all keys. No... there's little chance of electric shock, as there is a lot of plastic between the user and the switches.
Sorry for jumping to conclusions. It's what I do, sometimes. And... as you will know, aluminum electrolytics are prone to going dry given a few decades (or less) !
>> Er, what exactly is this 46 volts supposed to be doing? I doubt there is >> anything like 46 volts anywhere near the keyboard.
>> Please try again.
>> Gareth.
> Yes... I checked it again. it's a common to all keys. No... there's > little chance of electric shock, as there is a lot of plastic between > the user and the switches.
> Sorry for jumping to conclusions. It's what I do, sometimes. > And... as you will know, aluminum electrolytics are prone to going dry > given a few decades (or less) !
Your measurement is incorrect. No way is there 46 volts around the keyboard. Possibly 4.6 volts, a slight but possibly acceptable drop from the 5 volt supply.
You are still wanting to find the answer in dry aluminium electrolytics or something else. Stop trying to make the symptoms fit your conjoured up answer. This is not the best way to fault find. You need to establish some facts. So far you have virtually none at all. Go get some and stop guessing. Really.
