Dudley and Pete, The absolute maximum differential input voltage for OPA2674 is +/-1.2V. For that reason I used clamping diodes for protection in one instrumentation application of SDR-1000 when I was not sure the operators remember to keep the sound card output at reasonable level. Be careful though not to distort the signal.
73, Ahti OH2RZ On 10/12/2008, Dudley Hurry <[EMAIL PROTECTED]> wrote: > Pete, > > You did not mention what sound card you are using, but if the sound > card output is too high you can easily overdrive the low level driver, > particularly the PreSonus can drive more than 4 volts peak to peak.. > > > 73, > Dudley > > WA5QPZ > > > > Pete Ferrand wrote: >> Ahti: >> >> Thank you for taking the time to reply. My radio has the OPA2674 and that >> is what it had originally. The issue is not one of a short circuit, but >> most probably one of dealing with a high impedance load which would send >> the voltage up beyond what the part can handle. At least that's what I'm >> guessing; I'm not sure of the correct troubleshooting procedure for this >> kind of fault. >> >> My hope was that someone has figured out how to make the circuit more >> robust but since yours was the only reply and there's no mention of it in >> the archives I suppose that hasn't happened. >> >> 73, >> -Pete >> WB2QLL >> Somers, WI >> >> >> >> >> >> >> >> >> >> -----Original Message----- >> >>> From: Ahti Aintila <[EMAIL PROTECTED]> >>> Sent: Dec 9, 2008 4:54 AM >>> To: Pete Ferrand <[EMAIL PROTECTED]> >>> Cc: flexradio@flex-radio.biz >>> Subject: Re: [Flexradio] blown SDR-1000 final opamp >>> >>> Pete, >>> The very old SDR-1000 units have OPA2677 as the final amplifier and >>> cannot stand short circuit. The newer radios use OPA2674 that has >>> internal short circuit protection. Anyhow, ask Flex people directly, >>> they know better the difficulties with some of the first production >>> units. >>> >>> 73, Ahti OH2RZ >>> >>> On 09/12/2008, Pete Ferrand <[EMAIL PROTECTED]> wrote: >>> >>>> Some months ago I blew the final opamp in my 1W SDR-1000 whilst matching >>>> it >>>> to a linear. Wasn't happy about that but since I accidentally hooked up >>>> the >>>> attenuator resistors wrong I wasn't too surprised since the rig saw a >>>> very >>>> high impedance. Worked fine ever since. >>>> >>>> Unfortunately I'm less happy about blowing the amp this morning, about a >>>> half year after that first incident, whilst trying it on six meters for >>>> the >>>> first time. Without the linear which doesn't cover six. Just wanted to >>>> see >>>> if I could work a couple locals. As far as the MFJ-269 showed there was >>>> a >>>> perfect match into the ATU but when I increased the power beyond about a >>>> tenth of a watt output the opamp popped again. >>>> >>>> Besides the time and money aspect, the circuit board clearly can't take >>>> a >>>> lot of parts replacements. >>>> >>>> Has anyone figured out how better to protect this part? Or some better >>>> solution. This is a four stack including the rfe board, older version >>>> with >>>> nylon spacers. >>>> >>>> Thanks. >>>> >>>> -Pete >>>> WB2QLL >>>> Somers, WI >>>> >>>> >>>> >>>> >>>> _______________________________________________ >>>> FlexRadio Systems Mailing List >>>> FlexRadio@flex-radio.biz >>>> http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz >>>> Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ >>>> Knowledge Base: http://kc.flex-radio.com/ Homepage: >>>> http://www.flex-radio.com/ >>>> >>>> >> >> >> _______________________________________________ >> FlexRadio Systems Mailing List >> FlexRadio@flex-radio.biz >> http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz >> Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ >> Knowledge Base: http://kc.flex-radio.com/ Homepage: >> http://www.flex-radio.com/ >> >> > _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
