Repairing a Faulty SRV-330

[cpsmusic]

Hi Folks,

About a year ago I picked up a Roland SRV-330. It was working well until a couple of weeks ago when I noticed that the LCD had started to flicker. I opened the unit up and of course the problem resolved itself. Now, after putting the unit back in a rack the LCD has gone blank. Note that it's still lighting up (i.e. there's a noticeable difference between when the unit is on and off) but there's no text visible.

I've opened the unit up again and had a look at the power supply, hoping to find a swollen cap or something obvious, however it all looks fine.

I've checked the output of the power supply and it's outputting the right voltages - +5V and +/-15V.

Next thing I checked was the voltage going to the LCD and it's 4.7V (it's supposed to be 5V). Would that be enough of a drop to cause the LCD to not work is the way described?

Any thoughts as to what else could be going on?

Cheers,

Chris

 

[synthiaks]

Impossible to guess without a schematic. Is the LCD connected with a flat cable? On the Ensoniqs the flat cables tend to fail.

Flicker kind of makes me think of some bad connection or a failing part (cap, IC) somewhere. Have you done a recap? If not I would start there as it will be to much "black magic" with old caps all over the unit.

S

 

[Bo Deadly]

The fact that it was flikering, stopped working, started working but with no data, etc makes me think synthiaks is right. That could definitely be a loose connector or a little oxidation on some of the contacts. Presumably it's driven through a press-fit fpc connector? Try disconnecting and reseating it. Maybe use a lens wipe with a toothpick and a dash of contact cleaner to clean up the contacts a little.

 

[pucho812]

my guess would be ribbon cable, if there is one, between screen and mother board.

 

[PRR]

> LCD has gone blank. Note that it's still lighting up

A naked LCD does not light-up. It is clear glass with grey ghosts.

The light is a separate thing. Some kinda lamp. Probably simple, and easy to fix. However yours does light-up so it's not the lamp.

LCD trouble-shooting is not always easy. The connectors are often lightweight and go bad with age, get worse when fiddled. The signal is very weak, and consists of conflicting voltages at high speed. Good luck.

 

[cpsmusic]

Thanks for all the replies - the LCD is connected by a ribbon cable so that's what I'll look at next.

Cheers!

 

[cpsmusic]

Service notes are available here:

https://archive.org/details/roland_SRV-330_SDE-330_SERVICE_NOTES

 

[cpsmusic]

Quick update - I removed the front panel and reseated the LCD's ribbon cable but no luck. The LCD is lighting up but no text is visible.

The flickering makes me think that it's a failing component, probably a capacitor?

So before I launch into a recap, any advice on where to start or how to approach this?

BTW, I've had a close look at the caps and "chopsticked" them but nothing is obviously wrong.

Cheers,

Chris

 

[cpsmusic]

Found this thread:

https://groupdiy.com/index.php?topic=36729.0

Think I'll recheck the PSU voltages.

 

[synthiaks]

Does it do anything? Does the LEDs light up? If you could test if it makes sound that would tell a bit about the state of things.

The LCD Card gets the signal directly from the Processor so if there isn't any caps on the LCD board I'm now thinking the LCD itself might be dead. Or the Processor doesn't work as it should.

It's not a leaky battery BTW? They can fry PCBs good if they want (yeah polysix... I'm talking about you)

But as said with old caps in there it could also be black magic going on somewhere.

S

 

[pucho812]

this maybe obvious but  are you sure don't have the contrast adjusted so you do not see any lettering?

 

[cpsmusic]

Got some time to have a look at this at last.

I've dismantled the case and checked the battery - all good there.

Next, I've removed the PSU as I think this is the most likely source of the problem. A close visual inspection doesn't reveal anything obviously wrong. However, I've noticed that one of the regulators (IC3 - 7815) is quite loose. It won't come out but it's much looser than IC2. Possibly a dry join? I've tried chopsticking the PSU  including IC3 but that didn't have any effect. But maybe pushing on the IC separated the connection even more.

Cheers,

Chris

 

[pucho812]

Would be much easier to measure the output of 7815, it's a voltage regulator.

 

[cpsmusic]

Had a momentary win - after resoldering the loose IC the unit fired up for about 30 seconds but then the screen went blank again. I've read elsewhere that the PSU caps are notorious for partially failing so I think I'll try replacing them and then see what happens.

 

[cpsmusic]

The PSU in the SRV-330 contains a PQ05RF21 2A voltage regulator. What would be the closest currently available equivalent?

 

[Khron]

Voltage-wise, the humble 7805 should do, but the Sharp part is rated for 2A, is in an isolated package, and has an "enable" input. Depending on how the regulator is used and how much of a load it has, a 7805 might suffice, but there's no guarantee.

But just about any 5V 2A regulator should do fine in that position, I'd reckon.

 

[cpsmusic]

A quick update on the SRV-330 - I'm pleased to report that after replacing the six PSU electrolytics the unit is now working  ;D

Cheers,

Chris