Greg Burnett wrote: > Joe, > > I think 1 o'clock (instead of 12 o'clock) might still be OK and/or typical? > Maybe some other 5370A users can tell us where their Trigger Level pots are > pointing when centered for triggering on a weak signal. (The pots point to > 12 o'clock on my 5370B, but I can't remember exactly where they might point > on a typical "A".) > > My 5370A triggers on the frequency standard output on either the START or STOP inputs set to 10x attenuation when the Level setting knobs are at the ~1 oclock position. The average of the threshold settings when the trigger level is just above and just below the point at which the trigger light flashes is 20mV or less. Not a particularly precise measure as it depends on the waveform symmetry. Both channels trigger (10x input attenuation switched in) on the frequency standard output when the the threshold is preset. It is unfortunate that their is no readout of the EXT arm input trigger level although there is a trigger LED. > I do know that some of the 5370A A3/A4 Input Amp & Schmitt Trigger I.C.s > developed "I.C. rot" many years after manufacture (due to a contamination > problem during manufacture). For units so afflicted, the symptom was that > "Preset" trigger level was no longer correct, but the trigger level could > still be successfully set manually. For these cases, as the years progressed > (and the "rot" worsened), you had to turn the manual trigger level pot > further and further to one direction to find trigger. As the years of > deterioration continued, there came a point where both trigger level > setability and sensitivity were no longer acceptable. > > If you have only a small trigger level issue in "Preset" mode, my thinking > is that you can still correct for it by doing the A3/A4 input adjustments. > > Best, > Greg > Bruce

oh yeah-cool :-) Don Joseph Gray > So now all your HP equipment looks like a 1950's parking lot, huh? > > On Sat, Oct 10, 2009 at 4:16 PM, Don Latham <djl@montana.com> wrote: >> Hi All: I put extended fins on my 1980's Hp equipment by drilling and >> tapping the existing sink. I used the white heatsink grease from Radio >> Shack to help. >> Don Latham >> >> Joseph Gray >>> The heatsink on my unit is quite hot, also. I'm thinking about putting >>> a fan on it after I get everything working. >>> >>> >>> On Sat, Oct 10, 2009 at 9:24 AM, Greg Burnett <gbusg@comcast.net> >>> wrote: >>>> Roy, >>>> >>>> The HP 5370A rear mounted heat-sink typically heats up to around 61 >>>> degrees >>>> C. This is very hot to the touch, so I suspect your unit's temperature >>>> is >>>> normal (unless it's running way hotter than 61 degrees C). >>>> >>>> The buzzing transformer might just be due to loose, vibrating >>>> laminations. >>>> You might try tightening the transformer's bolts to see if that >>>> reduces >>>> the >>>> buzz? >>>> >>>> Best, >>>> Greg >>>> >>>> P.S. I agree that the rear mounted heat sinks of most other HP >>>> equipment >>>> run >>>> significantly cooler. The models that run so hot to the touch are the >>>> 5370A/B, 5359A, and many of the legacy HP pulse generators (from >>>> Boblingen >>>> Division). >>>> >>>> >>>> ----- Original Message ----- >>>> From: "Roy Phillips" <phill.r1@btinternet.com> >>>> To: "Discussion of precise time and frequency measurement" >>>> <time-nuts@febo.com> >>>> Sent: Saturday, October 10, 2009 4:08 AM >>>> Subject: Re: [time-nuts] 5370A >>>> >>>> >>>> Hi Joe >>>> I have a similar problem so I would be pleased to hear from you with >>>> any >>>> useful information. The basic problem with mine is that the power >>>> supply >>>> is >>>> suspect - it works, but there is excessive heat, much greater than any >>>> other >>>> HP instrument that I have, from the rear mounted heat-sink, this is >>>> too >>>> hot >>>> to hold your hand on ! There is also a very obvious buzz from the >>>> power >>>> transformer, even when it is on "stand-by" - so I guess at worst it >>>> could be >>>> shorted turns in the power transformer, or probably better, a faulty >>>> bridge >>>> rectifier,or one or more of the large reservoir caps -  this an early >>>> model >>>> (1984), so perhaps it is to be suspected. I also think the performance >>>> is >>>> not to specification, but I will check-out the perceived problem with >>>> PSU >>>> before I investigate this matter.  I am just about to start the >>>> investigation of the prime problem. >>>> Roy >>>> >>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@febo.com >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>>> >>>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >> >> >> -- >> Dr. Don Latham AJ7LL >> Six Mile Systems LLP >> 17850 Six Mile Road >> POB 134 >> Huson, MT, 59846 >> VOX 406-626-4304 >> www.lightningforensics.com >> www.sixmilesystems.com >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com

> I plan on doing the A3/A4 adjustments. I just don't know where I'm > going to get a pulse generator or the fancy scope with the 1GHz > sampling plugin. Not the type of equipment on your average test bench. You won't need any exotic gear for the DAC voltage adjustments or the A3/A4 input assembly adjustments, which is what comes first in the manual. As I recall the scope is only used for symmetry adjustments in that section of the manual, so the risetime is not all that important as long as it will give you a stable trigger. You can skip the pulse-response adjustment unless you have reason to suspect a specific problem. Watch for the pots that this step calls for, and don't center them at the beginning of the alignment process when the manual tells you to. As I recall there are various typos in the manual, so watch out for that too. :) In general, the 5370 alignment instructions are crap by HP's usual standards, so *be careful*. Read and understand everything before doing anything. The A18 DAC adjustments should actually be done first IMHO. Don't worry if the test limit voltages are not achievable -- they aren't, on any 'B' model I've ever aligned -- as long as they are symmetrical. For example, +/- 1.9 volts is OK, instead of the +/- 2.2 volts called for in some versions of the manual. If you don't have an 8082A pulse generator and a fast scope, you will want to stop there, and not mess with A19/A20. Likewise you probably do not need to align the A21 multiplier (which is the only step that requires a spectrum analyzer) if you don't have reason to suspect a problem with it. I believe some people have found that the standard-deviation floor can be improved by realigning A21 but I haven't done that myself. The instructions that call for a 1 GHz sampling scope don't actually need a sampling scope; they can be followed with a Tek 2467-class scope as well. But again, the front-end work should be doable with a good 100 MHz+ model, and the rest should not be attempted without an 8082A pulse generator. The nasty thing about aligning a 5370 is the fact that the steps generally begin with setting all the pots and trimmers to a fixed position, usually midpoint. Ordinarily it's best not to disturb the alignment of a stage that's already in tolerance, but they don't give you that option with the 5370, and you may get pretty far before you discover that your test equipment such as the pulse generator is not up to the task. When they call for an 8082A in the A19/A20 section, they *mean* an 8082A, and you don't want to get halfway into that procedure before you realize that. -- john, KE5FX

John, Thanks for the good advice. I definitely need to pull the front panel to replace the flakey BNC. After that, I'll do what I can with the A3/A4 adjustments. I just took another look at what I was doing last night and the two input channels do need adjusting. The B channel is worse. I have a few other things that need to get done this weekend, so the 5370A will be on the bench for a little while. I'll get back to you after I get the inputs adjusted. Joe Gray KA5ZEC On Sat, Oct 10, 2009 at 6:07 PM, John Miles <jmiles@pop.net> wrote: > >> I plan on doing the A3/A4 adjustments. I just don't know where I'm >> going to get a pulse generator or the fancy scope with the 1GHz >> sampling plugin. Not the type of equipment on your average test bench. > > You won't need any exotic gear for the DAC voltage adjustments or the A3/A4 > input assembly adjustments, which is what comes first in the manual.  As I > recall the scope is only used for symmetry adjustments in that section of > the manual, so the risetime is not all that important as long as it will > give you a stable trigger. > > You can skip the pulse-response adjustment unless you have reason to suspect > a specific problem.  Watch for the pots that this step calls for, and don't > center them at the beginning of the alignment process when the manual tells > you to.  As I recall there are various typos in the manual, so watch out for > that too. :)  In general, the 5370 alignment instructions are crap by HP's > usual standards, so *be careful*.  Read and understand everything before > doing anything. > > The A18 DAC adjustments should actually be done first IMHO.  Don't worry if > the test limit voltages are not achievable -- they aren't, on any 'B' model > I've ever aligned -- as long as they are symmetrical.  For example, +/- 1.9 > volts is OK, instead of the +/- 2.2 volts called for in some versions of the > manual. > > If you don't have an 8082A pulse generator and a fast scope, you will want > to stop there, and not mess with A19/A20.  Likewise you probably do not need > to align the A21 multiplier (which is the only step that requires a spectrum > analyzer) if you don't have reason to suspect a problem with it.  I believe > some people have found that the standard-deviation floor can be improved by > realigning A21 but I haven't done that myself. > > The instructions that call for a 1 GHz sampling scope don't actually need a > sampling scope; they can be followed with a Tek 2467-class scope as well. > But again, the front-end work should be doable with a good 100 MHz+ model, > and the rest should not be attempted without an 8082A pulse generator. > > The nasty thing about aligning a 5370 is the fact that the steps generally > begin with setting all the pots and trimmers to a fixed position, usually > midpoint.  Ordinarily it's best not to disturb the alignment of a stage > that's already in tolerance, but they don't give you that option with the > 5370, and you may get pretty far before you discover that your test > equipment such as the pulse generator is not up to the task.  When they call > for an 8082A in the A19/A20 section, they *mean* an 8082A, and you don't > want to get halfway into that procedure before you realize that. > > -- john, KE5FX > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > >