[sdiy] Tr-808 issue

[el macaco]

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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