Synth Defects - Ticking Time Bombs

[krzeppa]

I didn't see this posted earlier, but I do believe the 100uF capacitor on the Virus B/Indigo 1 had a tendency to c**p out and need to be replaced. I know a couple of people who had it replaced by Access twice!

Didn't the Andromeda have problems with voice chips failing and loose ribbon cables?

[cornutt]

Didn't the Andromeda have problems with voice chips failing and loose ribbon cables?

I understand the early Andromedas had some voice chip issues. I'm not up on the details.

[pflosi]

Apparently... My A6 is running smooth though.

The loose ribbon cables can cause "ghost editing" (those and lots of dust). But you just have to reseat them properly.

[jxalex]

Roland JX8P --- some models wont boot correctly and the countdown stops or begins again. The problem is with its CPU reset circuit which design is somewhat funny with its capacitors and transistors.

[jxalex]

Aren't there some synths that have humming or buzzing backlit displays?

Korg M/T series
Roland D70/MV30
Kawai K5000

That's just in my arsenal.

Korg Wavestation A/D (it helps to reduce its buzz by reducing its transistor collector current with series resistor 50 ohms do fine, however somewhat the brightness is reduced)

AKAI S3200XL (same buzz. interesting that its contrast knob is with backlight switch off function)

[belltones]

Oberheim OB series - bridge rectifier on digital rail side of power supply is really inadequate for the current being drawn and gets so hot that it will scorch the board as well as itself. Even if it hasn't failed yet, it should be replaced with a much higher current-rated one (e.g. 6A instead of 2A) with maybe a nice heat sink for good measure (I add a heat sink and it still gets very hot!)

[DavidH]

Yamaha DX7 arc suppression capacitor meltdown.

Apologies if this has been covered already, I did try searching it.

Yesterday I added a MK1 DX7 to the stable. It came with a faulty on/off switch that wouldn't turn off. Within 10 minutes there was an awful smell and on opening the lid I found that the capacitor C10 on the incoming AC board was hot and smouldering. I removed it and the synth still works fine but I have ordered a replacement. It's purpose is to suppress sparks inside the power switch when turning the synth on and it is connected to the two hot wires that go to the switch.

I researched this and found that other MK1 DX7 owners had experienced the same problem. One guy only found out he had the problem when the smoke detector went off in his studio!

If you have a MK1 DX7 change capacitor C10 on the AC board (the furthest pcb to the right as you look at the synth as if you are playing it.

This is the replacement I have ordered http://www.conrad-electronic.co.uk/ce/e ... MSSD-1-pcs

It is X2 rated. The original caps specified by Yamaha were only 250 VAC rated so were already operating close to their limit.

[blueknob]

Just a brief note. I'd say be careful with the Ham XB2. I used mine for 1000 gigs, then put it away unused for about 6 months. Upon trying it again things were wrong, seriously wrong, CPU/Sound Engine wrong. There were a lot of custom chips and the best I could do was to suspect either one of the above, no schematics or chip data available and no chance of a replacement chip. I had to buy a whole replacement digital board.


BTW: Be careful when feeding the Geeks they usually spew up lectures to show only they know the most.

[DX21]

Sy77 belts turn to goo, backups leak

[AK79]

Yamaha DX7 arc suppression capacitor meltdown.

.

this appplies to any old PSU using that scheme. Those caps simply give up at some point.
My Solina String ensemble had this issue and that made me replacing those things on all synths I get my hands on.

on topic :
I recently found that trimpots become an issue on various synths. I had a number of broken ones in my Polysix and have seen it over the last year in numerous synths I get for repair.

Also a common problem I see regulary are busted contacts in rotary switches on Roland SH-Series and Korg MS-Series.

Did someone mention the shitty PSU in the OB 8 already ?

TB303 suffers from cracked PCB tracks especially in the area of the Tempo knob. This can diconnect the internal clock.

Another member of the Battery-Leakage-Club : Oberheim DMX.

br
Arne

[Mandala Music]

"Sy77 belts turn to goo, backups leak"

All floppy disk drives will eventually fail as their rubber drive belts dry out and lose their elasticity over time.

My first floppy drive to die was the one of my Yamaha V50 keyboard. My latest to die was the floppy drive on my Kawai K5000R rack synth. I am going to replace it with a USB floppy Disk Emulator Drive next week. I have already removed the floppy drive. I had to remove the motherboard, the faceplate, the phone jack and volume knob assemblies in order to access the four screws holding it in. Not a user friendly design.

[Yekuku]

Roland XP-50.
Surface mount electrolyte caps leak , corroding pcb tracks on their way.
Classic symptoms: No Display, no output, battery low 0V.
I have one in front of me, I have replaced all electrolytes, jumpered 2 pcb tracks and it still does not work.

[brianmccalla]

Here are some that I can't believe nobody mentioned:

Novation Supernova 2: d/a chips on different outputs eventually go bad requiring surface mount chip replacement.

Roland JP-8000: pots easily cold separate from board resulting in poor, erratic, and eventually no contacts. Open and re-solder.

Roland Juno-G: Dreaded display death. It seems that all G's without the replacement display Roland offered for like a month on these will eventually go bad rendering navigation impossible. Oh. And try finding a display NOW.

Novation X-Station: Bad pot and slider contacts possibly related to the case strain when tightened down uniformly... Even from the factory. Ugh!

Virus C KB: Known problem with MIDI comms which can, in rare cases, basically brick the C.

Tritons (and about all synths with disk drives): Drive belt goes bad or heads go. Need new drive or SD card conversion.


Roland MV-8x00: Plastic on buttons fatigues and breaks and buttons no longer pop back up. Same cold solder joint problem as so many other Roland products.

Yamaha CS6x; Similar solder joint problem on middle pots

Korg Microkorg: No reverse polarity protection on voltage regulator causes multiple chips to fry anytime a center positive ("normal") DC power supply is plugged into the Microkorg's (bizarre) center negative port. Many an owner missing their stock power supply has effectively destroyed their whole MK by just innocently trying to plug another same voltage power supply in to only be greeted with smoke.

Waldorf Blofeld: A bad internal resistor causes volume control havoc.

Roland SH-32: Cold solder problem. Especially on cutoff pot.

That's about all that I can think of at the moment. I'll add more later as they come to mind.

[WhinyLittleRunt]

Yamaha CP30 - hard to find or unobtainable custom ICs provided by Yamaha which control voicing on the individual boards.

Yamaha MR10 (drum machine) - same issue, but these are pretty trash-worthy honestly...

It makes me wonder how many other Yamaha synthesizers of the day have custom chips in them that are getting near impossible to find without a donor unit.

[ppg_wavecomputer]

[…] It makes me wonder how many other Yamaha synthesizers of the day have custom chips in them that are getting near impossible to find without a donor unit.

Essentially every Yamaha product of that era -- CS polyphonics are full of those dreaded things, and I suppose this is the reason why the count of playable CS50s has diminished considerably over the past 20 or so years.

It's the only way to keep a CS80 alive (unless you were lucky enough to find a huge box of original spares when a Yamaha repairer closed his shop, that is).

Stephen