[sdiy] Tr-808 issue

[Tom Wiltshire]

Could "squarish 120vac " instead have messed with the protection circuit so that now it kicks in when it shouldn’t?

To re-phrase that another way;

Do you know that the protection circuit is behaving correctly and that the problem is with the input voltage?


> On 13 Sep 2018, at 21:33, el macaco <elmacaco at hotmail.com> wrote:
> 
> 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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