[sdiy] Tr-808 issue

[el macaco]

It powers on with no step Leds lit, just bank a and section 1 leds Lot with no change with toggles switched.

It’s the power protection circuit.  Sometimes switching it on and leaving it on for a while it will come to life with the step led blinking sudddenly.

One time I got it to live by plugging a Pedal into the start stop jack.  Sometimes with the din sync switch but only once or twice.  

Maybe a faulty trace on the clock circuit looks just like the protection circuit kicking in?

Thanks guys.  It’s been months of sometimes, then I thought I fixed it, it worked reliably for weeks, then when I put all the screws back in it didn’t work :/.

Giving me new fire to crack this problem.

> On Sep 13, 2018, at 3:51 PM, Richie Burnett <rburnett at richieburnett.co.uk> wrote:
> 
> 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?
> 
> -Richie,
> 
> -----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 transformer?
> 
>> 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.
>>>> 
>> 
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