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Subject: Help diagnose Pianocorder problem 2

Author:
Dave Snowdy

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Date Posted: 10:16:07 07/12/04 Mon

I'm replying to an old message so I apologize if you see this topic twice. (see original text in lower part of message)

I've pretty much narrowed my problem down to the J6 output of the Player Board. I have a working upper and lower board and center board. It just looks like the bass driver isn't working. There's power at all boards.
There was a questionable resistor at R33 that I replaced but that didn't fix things.
I swapped upper and lower boards and each board works. Continuity on the J6 cable from the player board is fine.

Any input appreciated!

Dave

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I'm starting to look into a pianocorder system my girlfriend has. It's a model 100 on a Yamaha U7. She's got a repair manual with trouble shooting procedures. It at least let me trace the wires with some knowledge.

I knew that it sort of skipped some notes. I always thought it was the tape player (might be, a little bit. Most of the tapes also have the foam piece slipped out of place).

I finally sat down and watched it play. No notes below E near Middle C would play.

There's power to the bass section (as far as I can tell with a meter). I moved the control cables from the bass section to the mid section and I got playback (crazy as it was, just to see if there were signals there). So, as far as I can tell, it's at least a problem with the bass section itself. I think E-flat and a few others are in the mid section, though. There seem to be no stuck keys.

Any suggestions of simple things I might check?

Thanks

Dave Snowdy

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If I understand correctly, it sounds like the bass (first 32 notes) driver board may be blown. If the mid range (next 16 notes) is missing on just a few notes, it might just be burned out solenoids. Unplug those solenoid notes from the driver board and test them for continuinty for starters. If the solenoids seem, ok, then the mid driver board may also be defective.

If you determine that the driver boards need repairing or replacing, you can send them to Bob Baker for repair/replacement. Contact him at elecorch@aol.com and explain what you need, etc.

You also need to look around in there and see why this damage has occured. There may be a short somewhere. Make sure all wiring is in good shape, and properly secured. The boards should be free of debris, especially any metal shavings, spider webs, etc..

Cassette repair. Go to Tower records and buy a 15 count box of Maxell UR regular 90 minute tapes for ten bucks. Open the Pianocorder cassettes and replace the springs and pad using one from the Maxell cassette, check the two side rollers, replace if they are stuck. If the original Pianocorder cassettes are otherwise problematic, binding etc., just remove the the two reels with the tape and drop it into a Maxell shell.

Tom Lear
San Francisco, Ca.

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Check R33 (10 ohms, 1/2 watt)on the 32-note driver board and R17 (also 10 ohms, 1/2 watt) on the center driver board. These resistors provide a common connection for all emitters of the driver transistors.

A Superscope service bulletin from 1980 suggests a possible cause if you find that the resistor has blown--faulty cable connectors from the 170 volt power supply.

You will note that those connectors are not robust; they are quite wimpy in fact.

Power for the solenoids comes to the center driver board and is distributed to the other drivers from there. The symptoms might not show up until you try to play the piano.

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Replies:

Subject	Author	Date
Re: Help diagnose Pianocorder problem 2	Tom Lear	06:14:45 07/13/04 Tue