Wavetek 23 croaks, anyone know of "notorious" falure areas?
in [Design]
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From: Joerg on 6 May 2010 09:59 Phil Hobbs wrote: > On 5/5/2010 12:09 PM, Joerg wrote: >> miso(a)sushi.com wrote: >>> On May 4, 2:22 pm, Joerg <inva...(a)invalid.invalid> wrote: >>>> So here I am, doing variable line frequency test and ... phssss ... >>>> PHUT >>>> ... *BAM* ... followed by a stench wafting about. I looked at what was >>>> supposed to be 265V/50Hz sine and found a totally distorted 1Hz, plus >>>> lots of heat in my amp which luckily survived. >>>> >>>> Turns out the Wavetek 23 function generator became totally "loose" in >>>> frequency. Have to wrap up some stuff today so I tried and was able to >>>> goose it to 50Hz by cranking it to 995Hz (above 1kHz it completely >>>> loses >>>> it). But that's a white-knuckle ride because the test runs mostly >>>> unattended. >>>> >>>> Does anyone know whether these things have a typical pathology that can >>>> be fixed? Like this or that cable always comes loose, etc.? I have >>>> re-seated the EPROM, battery is fine, re-seated connectors, nada. I do >>>> have the manual but diagnosing it from synthesizer to the end will take >>>> hours because it's a uC driven instrument. >>>> >>>> -- >>>> Regards, Joerg >>>> >>>> http://www.analogconsultants.com/ >>>> >>>> "gmail" domain blocked because of excessive spam. >>>> Use another domain or send PM. >>> >>> Hey, it's Livermore Swap meet this Sunday. >>> >>> To say I'm not a fan of Wavetek puts it mildly. Their stuff breaks >>> often. >> >> >> Well, mechanically the units do not make a very good impression. >> Electrically they are usually ok. Ok, was, for this one :-( >> > > My first Wavetek function generator, circa 1981, had a 50 ohm output > that blew up when I put 50 ohms on it. Had to replace the output > transistors with something much beefier, which slowed down the > edges--but at least the power supply could drive the 50 ohms! > Ouch! That doesn't exactly speak to the competence of the guys who designed it. Or maybe they didn't do design reviews? -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Tim Williams on 6 May 2010 13:31 "Joerg" <invalid(a)invalid.invalid> wrote in message news:84g0akFpaeU3(a)mid.individual.net... >> My first Wavetek function generator, circa 1981, had a 50 ohm output that >> blew up when I put 50 ohms on it. Had to replace the output transistors >> with something much beefier, which slowed down the edges--but at least >> the power supply could drive the 50 ohms! > > Ouch! That doesn't exactly speak to the competence of the guys who > designed it. Or maybe they didn't do design reviews? I have a Wavetek 193. Excellent generator, but then the output stage died. Same damn thing, driving a load at high amplitude...then suddenly not driving it. The output stage is an AC coupled RF follower using 2N3866 and 2N5160, one set to drive and two pair for output. (An op-amp controls bias, including "DC" output signals.) They all have heatsinks, but TO-39 isn't renouned for heat dissipation. Here's a picture of the layout. Schematics are on BAMA, IIRC. This is actually some guy's 191, which has the same main board as the 193, and looks the same as mine used to. Now I have two ugly TO-126 transistors on small heatsinks where the four outputs used to be. Risetime sunk to an appalling 50ns. :( http://myweb.msoe.edu/williamstm/Images/Wavetek_191_Output.jpg Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
From: Joerg on 6 May 2010 13:52 Tim Williams wrote: > "Joerg" <invalid(a)invalid.invalid> wrote in message > news:84g0akFpaeU3(a)mid.individual.net... >>> My first Wavetek function generator, circa 1981, had a 50 ohm output that >>> blew up when I put 50 ohms on it. Had to replace the output transistors >>> with something much beefier, which slowed down the edges--but at least >>> the power supply could drive the 50 ohms! >> Ouch! That doesn't exactly speak to the competence of the guys who >> designed it. Or maybe they didn't do design reviews? > > I have a Wavetek 193. Excellent generator, but then the output stage died. > Same damn thing, driving a load at high amplitude...then suddenly not > driving it. > > The output stage is an AC coupled RF follower using 2N3866 and 2N5160, one > set to drive and two pair for output. (An op-amp controls bias, including > "DC" output signals.) They all have heatsinks, but TO-39 isn't renouned for > heat dissipation. > > Here's a picture of the layout. Schematics are on BAMA, IIRC. This is > actually some guy's 191, which has the same main board as the 193, and looks > the same as mine used to. Now I have two ugly TO-126 transistors on small > heatsinks where the four outputs used to be. Risetime sunk to an appalling > 50ns. :( > http://myweb.msoe.edu/williamstm/Images/Wavetek_191_Output.jpg > The output on mine has never let me down. But somehow the transmission blew up :-( -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: JosephKK on 7 May 2010 06:33 On Wed, 5 May 2010 16:55:53 -0700, "Joel Koltner" <zapwireDASHgroups(a)yahoo.com> wrote: >"Joerg" <invalid(a)invalid.invalid> wrote in message >news:84edrgF637U1(a)mid.individual.net... >> He does have the right instincts. But IMHO it's more stuff for nerds and >> consumers who like new toys all the time. And there's plenty of those :-) > >Oh yeah, it's what drives the economy these days... > >If all your neighbors were like you -- fixing anything that had a pretty >simple fix when it broke, only buying new cars/computers/TVs/etc. when the old >one actually wore out, etc... what kind of economy would that be? :-) I mean, >I'd like to think we'd expend all our then-extra human capital on, I dunno, >finding a cure for cancer or feeding the hungry or something, but I'm kinda >dubious how likely that'd be... The good old USA went through the principate phase into the decadent phase of empire rather faster than any before it. It may be that both China and India may be on track to do it even faster. Now that is a scary thought.
From: Joerg on 7 May 2010 10:59
JosephKK wrote: > On Wed, 5 May 2010 16:55:53 -0700, "Joel Koltner" > <zapwireDASHgroups(a)yahoo.com> wrote: > >> "Joerg" <invalid(a)invalid.invalid> wrote in message >> news:84edrgF637U1(a)mid.individual.net... >>> He does have the right instincts. But IMHO it's more stuff for nerds and >>> consumers who like new toys all the time. And there's plenty of those :-) >> Oh yeah, it's what drives the economy these days... >> >> If all your neighbors were like you -- fixing anything that had a pretty >> simple fix when it broke, only buying new cars/computers/TVs/etc. when the old >> one actually wore out, etc... what kind of economy would that be? :-) I mean, >> I'd like to think we'd expend all our then-extra human capital on, I dunno, >> finding a cure for cancer or feeding the hungry or something, but I'm kinda >> dubious how likely that'd be... > > The good old USA went through the principate phase into the decadent > phase of empire rather faster than any before it. It may be that both > China and India may be on track to do it even faster. Now that is a > scary thought. In California it's even more scary, was on the CBS13 news a couple days ago: http://www.californiapensionreform.com/database.asp?vttable=calpers And we haven't even seen the tip of the iceberg yet. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |