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Samsung-Quad QSA30A servo amps

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So, adding to the long saga of keeping a Quad QSA30A P&P running for light duty, I ran some boards last month and the machine ran fine.  I fired it up last weekend, and had some PC hard drive boot-up issues, and then both of the XY servo amps failed to come up.  They get an error code on the single 7-segment LED of 3 horizontal bars.  Each of these amps failed with the same symptom about 5 months apart, about 2 years ago.  I got replacement used amps and got the machine running again.  I am guessing that the EPROM in the microcontroller has lost its contents, or at least failed the checksum.  When this last happened, at first the machine would not home properly, with jerky moves, but then after resetting the fault, it would run fine.  Later, it went completely dead with the 3 line symbol on the LED.  That does sound like a fading EPROM issue.

So, now the real issue:  Is it crazy to try to keep a 20+ year old machine running by replacing parts with 20+ year old used parts?
And, is it possible to replace just the Sanyo Denki servo amps with something newer?  I fear that new Sanyo Denki amps are going to cost more than I have invested in the whole machine.

I'm kind of disappointed with this whole mess.  This machine has been quite unreliable.  I first chalked that up to poor storage conditions after the machine was taken out of service.  But, now two more servo amps have died with the same symptom.  The outfits that sold me the spare servo amps don't seem to want to help, other than sell me two more at full (used) price.  I ran an even older Philips CSM84 (made by Yamaha) and it was insanely reliable (just not so accurate on placement).  I had one sensor die and an accumulation of commutator dust in one motor in 13+ years of use.  I don't know why this Samsung-built machine is just falling apart.
Suggestions welcome!

Ugh!  And it gets worse.  The spares from a broker are both defective.  One shows the same failure as my previous bad units, the other shows some different failure code.

how long has the spare been on the shelf 20 years, and where was that shelf - near the coastline in a humid area? Some ICs are specified for 10 years on my Mitsubishi Amplifier, they're 15 years overdue already. Certainly many parts exceed 10 years but if you want to build a business on it you need reliability of course...

When I recovered my CNC machine I also had to replace an amplifier, also one encoder and clean 2 encoders.
My fallback if more will break will be that I will rip out everything and replace it with Delta Servos.


--- Quote from: jmelson on June 10, 2024, 03:55:38 pm ---That does sound like a fading EPROM issue.

--- End quote ---

I don't know anything about these particular servo amps, but the fault you describe sounds more like an analog circuit failure which the microcontroller is detecting.
(Actually no - see below, this is just the idle state display - again meaning the micro is starting properly, but maybe with lost settings?)

Have you tried any reverse engineering of them?  What inputs and outputs do they have?  Model number?  I'm guessing these are not the modern Ethernet connected style.

Maybe you can retro fit a more modern servo driver like the Gecko G320X

Those take the common step pulse and direction logic inputs used by DIY CNCs.  You'd obviously need to check motor and encoder compatibility.
If the Sanyo Denki units have a proprietary communications protocol, you'd need to hack something like grbl to simulate the protocol and provide the step/dir outputs.
And you'd fake any other outputs, like fault or ready signals.

A quick search and I found a manual for the Sanyo Denki PE series, which has a 7-seg display and uses pulse inputs (one for CW, one for CCW).
The 3 horizontal bars means "The bus power (R, S, and, T) is present and the start ready complete (SRDY) signal is ON."
So this isn't an error state, more of a idle state.

See page 92 and onwards for troubleshooting info.  Even if yours are a different model, they might be similar.

can you take some photos of the servos (possibly motor and encoder part numbers) and amplifiers? So we know what you're writing about?


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