[time-nuts] HP5370B & HP5345B Front-End IC Redesign Effort

Bruce Griffiths bruce.griffiths at xtra.co.nz
Wed Jan 27 22:22:46 UTC 2016


Achieving a bandwidth of 100MHz is easy. To get useful output at 500MHz 
inductive peaking of the collector loads of the input stage will be required.
Correctly proportioned Bridged T-coils should work well.
Cascoding the input stage may also help.

Bruce

On Wednesday, January 27, 2016 08:38:15 PM Bruce Griffiths wrote:
> Something like the attached schematic should suffice however an extra gain
> stage would probably be necessary to achieve the 100mV sensitivity.NB Vcc =
> 15V, Vee = -15V. Bruce
> 
> 
>     On Thursday, 28 January 2016 5:02 AM, paul swed <paulswedb at gmail.com>
> wrote:
> 
> 
>  Some great comments and like all of you I like my 5370s and 5345s. Real
> buttons no mouse. Must be a throw back to the dark ages.
> Always knew about the fan issue on the 5370 and have added fans to my main
> operating unit.
> But it had not occurred to me that the way the front panel is laid out
> there may be little actual airflow across those chips. Thats quite a
> thought.
> So for those with working units that may be a completely seperate thread.
> How hot do they get? Then some solution for that.
> Essentially fix it before it dies.
> Then there is the question I posed.
> Skipping all of the details like adjustable slicing polarity and such.. What
> is the minimum to get a signal into the counter as a way to return it to
> some usable service and certainly verify the bad frontend. Lets call this a
> poor but useful answer.
> From that point it returns to this discussion.
> But a full new front panel. As Perry says most likely not.
> I do have 2 X5345s that I am pretty sure I need to dive into the front end
> on. My excuse other projects...
> Regards
> Paul
> WB8TSL
> 
> On Wed, Jan 27, 2016 at 7:46 AM, Bob Camp <kb8tq at n1k.org> wrote:
> > Hi
> > 
> > Ok, well let’s put some dimensions on it.
> > 
> > Say that the new board for the counter costs $400 each. (and that’s
> > probably low). How many are people likely to buy?
> > 
> > If so how much would you pay for a working 5370?
> > 
> > Bob
> > 
> > > On Jan 26, 2016, at 11:08 PM, Perry Sandeen via time-nuts <
> > 
> > time-nuts at febo.com> wrote:
> > > Hi,
> > > Wrote: Since the front end chips are mixed signal ASIC’s, it will take
> > 
> > more than a bit of time to replace them directly. Re-doing the entire
> > front
> > panel board is the most likely way to “fix”the problem. The question is -
> > why do that at all? Just do a PC instrument that does the same thing as
> > the
> > counter with way less effort…..
> > 
> > > Well, I have two reasons not to.
> > > First I have about $1800 invested in my 3 5370’s including  the new CPU
> > 
> > boards and blowing that off is not in my budget. I’ll kludge the living
> > daylights out of my units before blowing off my investment.
> > 
> > > Second, I haven’t the slightest clue on how to do a PC instrument and I
> > 
> > have to many other projects to finish to learn something new.
> > 
> > > Also there was much discussion about A and B cooling in the past and it
> > 
> > seems the only things some did to their units was the addition of fan(s)
> > on
> > the cooling fins.  I had an external fan on a B I was running and the
> > thing
> > still was too hot.
> > 
> > > IMNSHO, I believe the front end chip failure is aggravated by the high
> > 
> > interior heat level.  I’m committed to a number of other projects so it
> > will be a while before I can work on mine.
> > 
> > > I’ll either rip the whole PS out and put it on another chassis, try
> > 
> > better 3 terminal regulators instead of the installed pass transistors,
> > install switching regulator PS’s in place of the original PS, cut holes in
> > the top lid and install 10 or 12 computer fans. Or a combination of the
> > afore mentioned.
> > 
> > > I don’t give a rat’s behind how it will look. I’m only interested in it
> > 
> > working properly.  I’ve spent 50 years in the electronics industry and I
> > will find a way to skin this cat. I’ve done this to other equipment
> > before.
> > And when done I’ll tell the list how I did it.
> > 
> > > Regards,
> > > Perrier
> > > _______________________________________________
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