[sdiy] Tr-808 issue

Richie Burnett rburnett at richieburnett.co.uk
Thu Sep 13 22:51:44 CEST 2018

If it's a cheap inverter that outputs a "squarusoidal" waveform, then it's 
more likely to make the transformer buzz loudly or to damage the smoothing 
capacitors and rectifier diodes.

Is your unit definitely configured for 120VAC, and not 240VAC?  Supplying 
the unit with the wrong voltage will obviously result in no operation or 
possible damage (if over-voltage.)

Is the TR-808 completely dead?  or does the sequencer (CPU) still function, 
LEDs flash, etc?  It sounds more like a problem with the CPU's power-on 
reset, or possibly the audio output muting?


-----Original Message----- 
From: el macaco
Sent: Thursday, September 13, 2018 9:33 PM
To: Kenny Balys
Cc: synth-diy at synth-diy.org
Subject: Re: [sdiy] Tr-808 issue

Am I on the right track thinking a squarish 120vac could bugger the 

> On Sep 13, 2018, at 3:26 PM, el macaco <elmacaco at hotmail.com> wrote:
> Yes.  Thanks!! I have a true sine wave inverter now and it’s solid and 
> even goes through line conditioners etc before the 808.  All the other 
> gear works fine on it.
> The earlier set up was before I had a proper solar set up.
>> On Sep 13, 2018, at 2:42 PM, Kenny Balys <kenny at beatkamp.com> wrote:
>> Are you certain of the AC power coming in to the 808?
>> I would suspect that as much as the power transformer.
>>> On 13.09.18 19:30 , el macaco wrote:
>>> Hello all,
>>> I’m asking for guidance to fix my Tr-808.  I usually fix my gear myself 
>>> but this has me stumped.
>>> I live in the amazon far from any reliable techs and have mostly 
>>> serviced my own stuff over the years with all I have learned from this 
>>> list since 1999.
>>> My TR-808 has an issue where the voltage protection circuit kicks in and 
>>> doesn’t let it run.  This happens when the power is unstable in the 808 
>>> and is by design.
>>> It first happened after running it from a solar power system with a 
>>> voltage inverter that wasn’t pure sine wave power.
>>> The power supply was giving uneven power, 15.6v and -14v.
>>> Replacing the parts in the power supply, rectifier diodes, capacitors, 
>>> regulators, resistors helped some but it doesn’t reliably work although 
>>> the voltages were even 15/-15.
>>> The only power supply part I haven’t replaced is the transformer, which 
>>> puts out static 26v AC voltage as required, but my oscilloscope is 
>>> busted so it’s with a DMM so I can’t see if there’s ripple or other 
>>> problems.
>>> That’s the next part I need to order, the transformer.
>>> Does anyone know how to test the transformer without a scope?
>>> Or is there something else that can cause this protection circuit to 
>>> engage?
>>> I also replaced capacitors and transistors in the protection circuit in 
>>> case that was the issue, it helped some initially but it still only 
>>> works occasionally.
>>> The service manual
>>> Mentions something about malfunctioning IC can cause this circuit to 
>>> engage.
>>> If the transformer doesn’t help next on the list is replacing the 
>>> electrolytic capacitors that filter the power at each circuit (25 total 
>>> I think).
>>> Any ideas greatly appreciated.
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy

Synth-diy mailing list
Synth-diy at synth-diy.org

This email has been checked for viruses by AVG.

More information about the Synth-diy mailing list