Synth Defects - Ticking Time Bombs

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Re: Synth Defects - Ticking Time Bombs

Postby krzeppa » Sat Apr 01, 2017 8:43 pm

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?
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Re: Synth Defects - Ticking Time Bombs

Postby cornutt » Mon Apr 03, 2017 9:57 pm

krzeppa wrote:
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.
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Re: Synth Defects - Ticking Time Bombs

Postby pflosi » Tue Apr 04, 2017 9:45 am

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.
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Re: Synth Defects - Ticking Time Bombs

Postby jxalex » Sat Apr 08, 2017 12:17 am

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.
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Re: Synth Defects - Ticking Time Bombs

Postby jxalex » Sat Apr 08, 2017 12:21 am

max badwan wrote:
coastalscrub wrote: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)
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Re: Synth Defects - Ticking Time Bombs

Postby belltones » Mon Aug 07, 2017 11:14 pm

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!)
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Re: Synth Defects - Ticking Time Bombs

Postby DavidH » Fri Aug 11, 2017 9:11 pm

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.
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Re: Synth Defects - Ticking Time Bombs

Postby blueknob » Wed Sep 27, 2017 8:01 am

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 :geek: they usually spew up lectures to show only they know the most. ;)
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Re: Synth Defects - Ticking Time Bombs

Postby DX21 » Thu Sep 28, 2017 6:17 am

Sy77 belts turn to goo, backups leak
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Yamaha DX7 > Yamaha SY77 > Kawai K3 > PC via Roland UM-ONE Rev 1.
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Re: Synth Defects - Ticking Time Bombs

Postby AK79 » Fri Oct 06, 2017 1:47 pm

DavidH wrote: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.

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