Racal Dana 1996 Frequency counter - Page 1
Forum section: electronics / testgear

author: saturation
author_rank: Super Contributor
timestamp: December 03, 2012, 06:24:09 pm
content: I've been waiting for a good version of either a 1992, 1996, 1998 or 1999 to pop up, and one finally did after some years of waiting. There are no tear downs of this model series on the Internet so here is an offering for those interested in acquiring any within the series and to discern internal differences [ the 1995 is without GHz capability, the 1996 is an upgrade of the 1994; they are designed to be rack mountable, while the 1992 design was transportable.]The 1994-96 were made in the late 1980s and offered slightly more calculations or control over input signals than the 1992. They were less plagued with switch defects that appear in used models 1991, 1992. Because they were not made to be transported, the rack mount series are likely to be in better physical shape.Large photos:http://www.flickr.com/photos/igsaturation/8241558668/#All boards and components are easily accessed on this design compared to the compact 1992. The large green PCB is the dedicated 68000 computer board that does all the calculations. The gold board is the data input and preconditioning board. The "copper wire" seen crossing from the front to rear in the middle is a type SMB connector cable to the divide-by-64 prescaler for 1.5 GHz rated Input C. Item marked "B" in yellow is the ovenized oscillator.

author: slburris
author_rank: Frequent Contributor
timestamp: December 03, 2012, 06:50:04 pm
content: I have a 1992 and a 1998 counter, and I just love these Racal/Dana counters.My 1998 is currently out of service because it has developed the front panelswitch problem that plagues these units, and I haven't yet figured out a niceway to machine replacement switches.I also have an EIP 545A microwave counter I'm just starting to play with.Scott

author: saturation
author_rank: Super Contributor
timestamp: December 03, 2012, 07:00:06 pm
content: The 199x series are all great units, a model for their entire class and still in demand. I found recently that BKPrecision makes a series of counters that at a high of ~ $500, will match the capabilities of a 1999 but without the risk of age related failures; so getting an old Racal is really tied to what price/performance you can muster over eBay.Thanks slburris for your prior posts on them and photos. Worrying about having to replace those switches over time made me wait for the right one to come along, although appearance wise, the whole 199x series seems to have the same design but it maybe tied to when they were made, yet some have them, some not.Do you know the build date of your 1998 and 1992? There are stickers or stamped dates all over the internals.Quote from: slburris on December 03, 2012, 06:50:04 pm

author: muvideo
author_rank: Frequent Contributor
timestamp: December 03, 2012, 07:20:46 pm
content: Nice machine saturation.The heart (counter and interpolator) seem similarto the 1992, the single shot resolution is the same, butthis one has many more functions: rise and fall times forpulses from 5nS, gate window programmable, higher voltagecapability and statistical calculation, so more useful than the1992, good catch!edit: also one more digit on the display 10 vs 9, easier toread for high resolutions.I found some specs here:http://www.teknetelectronics.com/DataSheet/RACALDANA/RACAL_199590030.pdfWhat timebase do you have? If it's the 9462 (04E) shouldbe good, my 1992 holds pretty well against Rb clocks.The 199x switch problems are annoying, but thanking tothem I was able to pay few dollars for very good counter, inmint conditions, the fix was few hours of work and fewcheap switchesFabio.

author: saturation
author_rank: Super Contributor
timestamp: December 03, 2012, 07:38:42 pm
content: Thanks muvideo, and also thanks for your photos on the archives. That helped me a lot too. I think the prescaler board is identical too, I have blow ups on the flikr site and I compared it to your photos. The additional functions are great as it give me the capability to do some measurements that normally you'd need a 1 GHz grade scope to do.Yes, it has the ovenized reference, 04e option. Its good to know it hold well against a Rb clock, so I can hold off on getting one for now.Regardless, I agree with your comments on any effort repair these! These counters are well worth the effort, my only fear is a firmware or memory failure, but in reviewing prior posts on any model in this series, no spontaneous failures have been reported unlike some early HP3456 DVM.My unit had a small pouch will the old firmware ROMs still in them inserted on the mobo, so I have a backup in case of diasasterFWIW, BK's model:Is actually fairly close to the 1999. Listed at $470, you can deal it down to the high $300s, which will match the highest end price some eBay sellers want for many 199x series.Quote from: muvideo on December 03, 2012, 07:20:46 pm

author: slburris
author_rank: Frequent Contributor
timestamp: December 24, 2012, 04:58:58 am
content: My 1998 has circuit boards with '88 date stamps and a QC sticker with an Apr '89 date handwrittenon it. I haven't cracked open my 1992 yet since it's working like a charm.I saw another 1992 pop up on Ebay (it's still there) for $100, but it's from Surplus TestMart in Israel, and for some reason a lot of their stuff looks like it got run over by a tank.This one is no exception -- it looks rather squished. Maybe you could harvest frontpanel switches from it, but since they all seem to go bad eventually, that's probablynot a good investment.And now darn it, I'm going to have to look at that BK model too.Quote from: saturation on December 03, 2012, 07:00:06 pm

author: nctnico
author_rank: Super Contributor
timestamp: December 24, 2012, 03:27:58 pm
content: Surplus Test is pricy and they are not very eager to accept a reasonable offer for something that obviously was picked up at a scrap yard and needs a lot of TLC to get it working.Anyway, if you are going to spend a lot of cash on a frequency counter it might be interesting to know that many spectrum analysers have this feature as well. Another problem I've found with some frequency counters is that their sensitivity at higher frequencies is quite poor.

author: saturation
author_rank: Super Contributor
timestamp: December 24, 2012, 03:55:59 pm
content: Yes, its impressive they want so much money for what I think are consistently the most battered equipment I've seen on eBay.Yes, if you do get a modern SA, the counters in them are exceptional, like the new Rigol SA815. A good counter is a bit redundant now, also good SAs accept external references for improved accuracy. But until Rigols 815, most SA of some decency are in the $5k range, and in eBay, many sub $1000 used SA don't have high accuracy counters.The Racal's are fairly sensitive throughout their range, you can read it on their spec sheet. The input C board for 1.5 GHz is 10x more sensitive than the mainboard A,B inputs.Yes, I was under the impression that the 199x series was the year it was made, but its just a model number. The series begins in late 1980s and any future revisions can be found on the mobo and in the manuals, I think the most recent in mid 1995.Quote from: slburris on December 24, 2012, 04:58:58 amQuote from: nctnico on December 24, 2012, 03:27:58 pm

author: poodyp
author_rank: Regular Contributor
timestamp: December 24, 2012, 07:43:34 pm
content: Well that's interesting. I too have a 1996 off ebay and it had spare EEPROMs inside it. Are they included from the factory?

author: saturation
author_rank: Super Contributor
timestamp: December 24, 2012, 08:19:00 pm
content: Not sure, but its the prior firmware revision in mine, so I have a backup should the old one die, FWIW!Quote from: poodyp on December 24, 2012, 07:43:34 pm

author: slburris
author_rank: Frequent Contributor
timestamp: December 25, 2012, 12:33:30 am
content: I've convinced myself I need multiple counters for my setup.Normally, I run a Trimble Thunderbolt as an external 10Mhz reference toall of my equipment. So I have one counter running off the Thunderbolt.I use a second counter as a sanity check on the 10Mhz output of theThunderbolt.Currently my 1992 is that sanity check. I'm quite impressed with the OXCOin it. At maximum resolution, I'm seeing 10Mhz on the dot +- 1 digit even overtemperature variations in my lab room.I do have a couple of rubidiums as backup, but I rarely power them up.The talk of firmware reminds me I need to image my firmware in case of problems.There isn't a list of firmware revisions floating around somewhere, is there?Scott

author: poodyp
author_rank: Regular Contributor
timestamp: December 25, 2012, 08:54:31 am
content: Here's my 1996. It's reading a second 9462 I got along with the 1996. They're "off" .05ppm relative to each other. Unfortunately I can't figure out what the long term drift and/or aging is. The scope is showing 10Mhz from the second 9462, and 5Mhz from before the frequency doubler on the first one.

author: saturation
author_rank: Super Contributor
timestamp: January 02, 2013, 05:33:10 pm
content: @poodyp: nice. You'll need time to calculate the long term drift rates; as these Racals are old units the good news is very likely the reference have stabilized, and at this point the drift rate would be at its lowest, unless is about to break!@slburris: I think its always good to have a minimum of 2 of each type of equipment, if its mission critical to you. How can one know its off if we have but one device? I personally try to acquire 3 types of each so there is a tie breaker.Can you compare the Racal XCO to the Thunderbolt? Being the latter is more accurate, I'd like to know how the Racal crystal compares. I've always read it compares very favorably, but never heard its quantified, say its off ppm or ppb.

author: slburris
author_rank: Frequent Contributor
timestamp: January 09, 2013, 03:26:06 am
content: Oooh, there's a 1992 on eBay right now for $80 with no bids. Looks to be in pretty decent shape.I will not buy it. Say it with me.... :-)Scott

author: saturation
author_rank: Super Contributor
timestamp: January 09, 2013, 04:49:04 pm
content: I see itI think final sale price of a 1996 is often close to a 1992; they have similar specs as counters but the 1996 has a stat function built in and voltage readouts too. I find the stat function very useful, as it simplifies making stability calculations and the large size of the chassis makes it easier to work with.1992 is nevertheless, a good machine, looking for a good home!

author: poodyp
author_rank: Regular Contributor
timestamp: January 10, 2013, 02:53:51 am
content: Quote from: saturation on January 02, 2013, 05:33:10 pmOops, I meant to say I couldn't figure out what the rated long term drift was other than a single line in the manual stating "Aging: < 5 * 10-10per day". I know it's highly unlikely to be too far off, I just need to get a thunderbolt or something to check against. The oscillator that came in my 1996 has the serial number of 300 something, so it could beveryold, but I doubt it's drifted by ~5E-10 * 24 * 365.

author: Unknown
author_rank: Unknown
timestamp: January 10, 2013, 06:52:20 am
content: 5e-10 * sqrt(24 * 365) might be a better estimate, although you should be able to find at least 1y specs.

author: saturation
author_rank: Super Contributor
timestamp: January 10, 2013, 01:03:13 pm
content: ... yes in the end, a best test would be to compare it empirically against a Rb clock or a GPS disciplined one. The Racal's ovenized XO is not that far off. I've read 2 -3 reports of comparisons against a Rb clock stating its fairly close, alas, but not quantified with a number, one is by Fabio on this thread.In his brief post he summarized all the key differences between the 1992 and 1996.Quote from: poodyp on January 10, 2013, 02:53:51 am

author: muvideo
author_rank: Frequent Contributor
timestamp: January 10, 2013, 01:19:30 pm
content: Quote from: saturation on January 10, 2013, 01:03:13 pmHello, it happens that now I have on the bencha GPS, some Rb clocks, the counter and somelogging scripts on the pc. So I could try to quantifythe statement I made before, I need only to findsome free time for some time tests...Fabio.

author: saturation
author_rank: Super Contributor
timestamp: January 10, 2013, 01:26:35 pm
content: Awesome! As your time allows, thank you, Fabio!Quote from: muvideo on January 10, 2013, 01:19:30 pm

author: muvideo
author_rank: Frequent Contributor
timestamp: January 11, 2013, 12:24:17 am
content: Well, I couldnt resist the tentation to make a quick checkof the absolute error of my unit.Please consider that I'm still learning to deal with precisetime measurements, so feel free to check and correct myprocedures. Also the room temperature is far from ideal.Measuring the output of a pair of FE5680A that I trimmedagainst GPS (manually, no GPSDO still in my hands), thecounter was aroud 70-75 mHz high, so I was expectingthe internal oscillator a little on the low side, and it was lowby about 7.3x10^-9 :The interesting part is top right, where I have data and linearinterpolation together. The line is the phase betweenthe GPS pps and internal 10MHz reference, so a positiveslope means that the 10MHz is lagging the pps -> slow.It's not bad, the counter was never touched by me, andprobably not trimmed from a lot of time. According to themanual it was still in spec, since the manual calls for recalonly past +-3x10^-8 deviation.Ok time to try to trim the counter, I lightly touched thefine adustment, after turning the pot the counter movesback and forth slowly a pair of times, it takes several minutes, andthen stabilizes very slowly. Not an easy process, better to takenote of the screwdriver movements, and wait many minutesbetween the adjustments. This is how the phase changedfrom lagging to tracking the pps while I corrected the frequency:This means that the two signals track each other, anda quick check with the FE5680A confirms that I'm near,somewhere around 2x10^-10 slow:Now time to go to bed. As I have more data I will post them,I think it will be difficult to show aging effects (unless I log theunit for many days or the quartz is gone), since the unitis aged and the aging should very slow now. Probablyit will be easier to try to see temperature effects.Fabio.

author: saturation
author_rank: Super Contributor
timestamp: January 13, 2013, 03:18:28 pm
content: Most excellent Fabio, this is the best characterized data for the 199x series with OXCO against a better standard. Your performance improvement is fantasticbut I'd risk it only myself if I had a better standard to compare it against, as you have.

author: lewis
author_rank: Frequent Contributor
timestamp: January 13, 2013, 03:22:38 pm
content: Here's the schematic if anyone needs it:http://www.schematicsunlimited.com/?z=racal_dana

author: muvideo
author_rank: Frequent Contributor
timestamp: January 13, 2013, 03:45:44 pm
content: Quote from: saturation on January 13, 2013, 03:18:28 pmThank you saturation, but that was only early data,against a gps.I kept retouching the trim in last two days, last adjustmentsare very very touchy. Now I'm unexspectly seeing a secondorder change in drift, so I'm seeing the oscillator changefrequency, and I still dont know if it is it's natural agingor it's stabilizing after the trimming. The fact that it's slowingis compatible with the fact that it was low, I was not expectingsuch a visible drift, but I've still not wotked the numbers, I willwait few days and log the behaviour.I'm now regretting to have changed the trim so early,I should have logged the counter for a week before,just to see the stability level it had before trimming.I will post more details net week, and will describethe setup I'm using, it's easy to setup.Fabio.

author: slburris
author_rank: Frequent Contributor
timestamp: January 15, 2013, 05:06:29 am
content: I keep meaning to ask, where are you finding the BK counter under $470?I was also wondering if you had an opinion on the 1856D, their 3.5 GHz counter for about $525?ScottQuote from: saturation on December 03, 2012, 07:38:42 pm

author: saturation
author_rank: Super Contributor
timestamp: January 15, 2013, 11:37:22 am
content: Hi Scott,http://www.tequipment.net/BK1823a.htmlhttp://www.transcat.com/catalog/productdetail.aspx?itemnum=1823AWait for live chat to come on line and ask for the best price, its not advertised ... the price I received was before 2012 when everyone was doing holiday sales and end of year sales target attempts.I don't own either, but the 1856D has less measurement functions, it more a raw counter. The 3.5 GHz input use an N connector.The measurement capabilities of these counters are limited to the A channel, B is used for comparisons against A, C is typically just a frequency counter.Quote from: slburris on January 15, 2013, 05:06:29 am

author: muvideo
author_rank: Frequent Contributor
timestamp: January 16, 2013, 12:50:16 pm
content: Saturation,here the results, almost 4 days after trimming,the OCXO now is slowing constantly about 1x10^-10 par day.I stopped the logging because the lab temperature is solow that the results are not that meaningful, but the counterwill be kept working, I will recheck the drift after some monthesto see if it will be changed. Surely it will slow down, since itwas more stable before the trimming.The setup:the system I'm using seem unnecessary complex, thereason is I have it ready for use for other purposes.I'm using the counter in TI A->B mode,Input A DC falling edge and input B DC rising edge COMA(I.E. connected to input A) so I can measure the width ofa negative pulse.I have a frontend that takes the 10MHz and GPS PPS andemits the negative pulse.The falling edge of this pulse is synchronized to PPS risingedge, the rising edge is syncronyzed to the second risingedge of the 10MHz reference that comes immediately afterGPS rising edge.The result is a pulse that goes from 100nS to 200nS thatrepresents the phase between the 10MHz and PPS.If the 10MHz is too slow it's phase will raise from 100 to 200nSand then restart.If the 10MHz is too fast the pulse will go from 200nS to 100nS.The only limit is that the frequency must be enugh close tohave enough points between rollovers, otherwise the data canbe unusable or worse aliased. For example to have at least 10 pointsbefore rollover the 10MHz need to change phase less than 10nSper second, this translates in one part in 10^-8, i.e. less than 0.1Hzof error on the 10MHz.The remaining work is done by a script that unscrambles the data and appliessome processing.I attach two graphs:the first is phase data- top left raw data, pulse width- top right unscrambled data- bottom left the same that top right, but with a linear drift removed, not very useful here- bottom right ambient temperaturesecond graph:- top left is the unscrambled data averaged- top right is the first derivative of phase, i.e. relative error of 10MHz period,when it's zero the frequency is spot on, now is 2.8x10^-10 i.e. the frequency is2.8x10^-10 low, i.e. 0.0028Hz low.- bottom left is second derivative, i.e. relative error variation per second, lastreading is 1.3x10^-15 (x86400=1.1x10^-10 per day)Fabio.

author: robrenz
author_rank: Super Contributor
timestamp: January 16, 2013, 01:24:45 pm
content: Nice work there muvideo!

author: saturation
author_rank: Super Contributor
timestamp: January 16, 2013, 04:46:20 pm
content: Thanks Fabio, for the good data and your extensive work; I think you have the best characterized effect of trimming an ovenized clock on the net; others who have posted were not as thorough.What I was surprised to find is how long the clock will take to settle, so one should not touch adjustments unless one'sreferenceis known stable and reliable as tracking drift will require dedication for some time, weeks at least.I am on time-nuts too [ readers here should read the archives there for the story]. It reads others have experienced adjustment instabilities but didn't document as well as you, Fabio, kudos!Quote from: muvideo on January 16, 2013, 12:50:16 pm

author: bingo600
author_rank: Super Contributor
timestamp: January 17, 2013, 12:38:35 pm
content: Same goes from me Fabio.I have a Racal 1991 here , and a OPT-4E OCXO waiting to be installed in thereI have a PM6680 to test the Racal with , and a Tbolt for 10Mhz.If you'd post the schematic of the phasedetector it would be nice/Bingo

author: muvideo
author_rank: Frequent Contributor
timestamp: January 17, 2013, 07:56:39 pm
content: Thank you robrenz,saturation are you one of the participants of this topic over there (time nuts)?Bingo, the 6680 is a very capable timer, 250ps single shot,should be nice for interval measurements, you are well equipped for timemeasurements with that and the Thunderbolt.The schematic is the logic part of this circuit, the output is OUTD pin:Measuring this OCXO for the first time I was feeling the real accuracyand stability of an average Rb oscillator. So I tried to make a a comparison:I used the same setup with an Rb, it's period error was around -1x10^-11,the period error variation is less than 10^-16 per second -> lessthan 1x10^-12 per day, but buried in the noise, so these data arenot really accurate. (See second attachment below).The funny thing it that the Rb was powered form cold immediatelybefore the start of the graph, the frequency error could be trimmedout by the serial interface interface, but my Rb has nothermostabilization yet, so nothing to gain.The abrupt frequency variation at 90000s reflects an internalDDS frequency variation, probably due to some temperaturecompensation, I'm still figuring out this aspect.That's all, for now

author: bingo600
author_rank: Super Contributor
timestamp: January 17, 2013, 09:14:34 pm
content: Fabio thankyou for the detailed explanation.I'll see if i can hack a phasedetector together/Bingo

author: muvideo
author_rank: Frequent Contributor
timestamp: January 17, 2013, 09:32:26 pm
content: Bingo, probably you know better than me, so what I write hereis not for you but for other readers, maybe can be userful...That circuit is only a TAC (Time to Analogue Converter)experiment. By the way, on time nuts, in a recentdiscussion i was warned to use a different approach,there is a very nice design example over there byDr Bruce Griffiths.To make phase measurements a decent counteris enough, just use two channels in start-stop mode,and collect results.Start with the PPS and stop with the reference.Any decent counter like the Racal Dana or thephilips/fluke PM6680/81 or many HP 53xx cancope with these intervals with nS or less resolution.Fabio.

author: poodyp
author_rank: Regular Contributor
timestamp: January 19, 2013, 01:07:00 am
content: Quote from: lewis on January 13, 2013, 03:22:38 pmIt seems there's like 2 copies of the manual out there, both the same scans, but one's completely out of order. Also I have no idea how part of the page gets cut off and put on the opposite side of the page. If I could find a paper manual I'd scan it myself if they weren't almost as much as what I paid for the 1996.

author: saturation
author_rank: Super Contributor
timestamp: January 19, 2013, 03:49:53 pm
content: Download open source PDF architect and you can rearrange the pages, if you have time. These manuals aren't the best but its better than nothing, and these are widely available. I just rearrange pages in my head, its faster.http://www.pdfarchitect.org/Quote from: poodyp on January 19, 2013, 01:07:00 am

author: saturation
author_rank: Super Contributor
timestamp: January 19, 2013, 04:14:07 pm
content: Thanks for these Fabio, I'm not a heavy participant on time nuts as I lack time to maintain my own atomic clock, but I'm very interested in the topic; its eventually how I settled on the 1996 versus any older HP counter, at least to 1.5 GHz. I need more volt nuts, so I spent more time posting there.From what you've already posted, attempting to recalibrate the 199x is going to be time consuming, and one needs already a stable reference. As of this writing, at least the internal 1996 reference is rock stable and its measurements highly repeatable, so I can make relative measurements with high confidence and absolute ones may only need a simple algebraic correction to offset any error from my units calibration status.Quote from: muvideo on January 17, 2013, 07:56:39 pm

author: PappyTG
author_rank: Newbie
timestamp: March 08, 2013, 08:17:41 pm
content: I've was wondering if anyone has run into error code 63 when doing the self test on your 1996. I've had the unit I currently have for serveral years now and it's been working great other then failing this self test. The manual indicates that the error involves the input circuit but I haven't been able to trace it out on the schematic. One thing I did notice is that if I have the unit in standby overnight and power it up in the morning it pass the self check but after about 15 minutes I get the Error 63 again. Appreciate any input. Plus I've been checking it daily this against my GPS and Argo Systems AS210 and I'm usually running 10.00000003 MHz ±2 counts

author: saturation
author_rank: Super Contributor
timestamp: March 08, 2013, 09:48:10 pm
content: Hi,A common issue with system errors after warm up in old gear can be traced to the power supply, its the most likely item to go from age compared to all the subsystems [ other than the EEPROM]. It may pay to check the filter caps or the ripple on the main rails. It can save a lot of troubleshooting legwork.Quote from: PappyTG on March 08, 2013, 08:17:41 pm

author: slburris
author_rank: Frequent Contributor
timestamp: May 08, 2013, 02:21:07 am
content: Well, it turns out my 1992 is deaf on the channel C input.So I went ahead and picked up the BK precision counter andit seems to work like a charm. It's nice to have 1 workingfully functional counter.It's got a few things to complain about compared to the 1992.Doing high precision measurements takes a gate time of 10sec.The 1992 is much faster, presumably because it uses a differentmeasurement technique? The internal oscillator seems moredrifty than my 1992, which has the ovenized standard.You can't get more than 8 digits without using an external standard,presumably due to the same drifty internal oscillator.I'm using it now in external standard mode, connecting it to myTrimble Thunderbolt.The 1992 is still in service for frequencies less than 160Mhz, butnominally goes on my list of things to repair, which is quite long now:Racal Dana 1992Racal Dana 1998EIP 545A 18Ghz frequency counterHeathkit GC-1000 clockTektronix 2246A scopeTektronix 2465 scopeHeathkit H8 computerand a few other odds and ends.Scott

author: edpalmer42
author_rank: Super Contributor
timestamp: May 08, 2013, 05:25:20 am
content: Quote from: slburris on May 08, 2013, 02:21:07 amIn case you haven't thought of it, a quick thing to do for your deaf 1992 is to check the fuse that's hidden inside the connector.Also, your list of things to fix seems rather short. You're not trying very hard, are you?Ed

author: grumpydoc
author_rank: Super Contributor
timestamp: May 08, 2013, 06:59:58 am
content: QuoteTake the 1.3Ghz prescaler out of the 1998 and put it in the 1992 (assuming that it's not why the 1998 needs repairing).I'm pretty sure that they are the same board.Service manuals readily available for both on the 'net

author: saturation
author_rank: Super Contributor
timestamp: May 08, 2013, 02:32:28 pm
content: My 1996 on arrival had trouble with Channel C. I reinserted the board, it read erratically but worked. I then connected the 10 MHz out of the Racal into C to check the calibration, it read the signal and worked fine every since.

author: hwengineer
author_rank: Newbie
timestamp: December 06, 2015, 07:21:43 pm
content: Great forum. Found while researching some new equipment. I've had a 1996 for several years. I worked last time I powered it up, maybe 9 months ago. When I turned it on earlier this week to test a new pulse generator I got pretty much nada. No error codes. Some evidence a POST was start by a number of LEDs coming on for a half second and then stalling with only the GATE and both TRIG LEDs on. I see some evidence of charring around negative voltage regulator U49 but I don't think it is recent. +5 and +15V testpoints show the correct voltage.I'm currently without a scope until January. A component failure I can maybe fix. One fear is the EPROMs have gone senile. Looking for any hints before I start digging deep. Thanks.

author: saturation
author_rank: Super Contributor
timestamp: December 07, 2015, 05:28:50 pm
content: Assuming the PSU is fine, a can't hurt test is reseating all socketed boards and ICs, taking due static precautions.Quote from: hwengineer on December 06, 2015, 07:21:43 pm