On Thursday, 28 January 2016 1:04 PM, Bob Camp <kb8tq@n1k.org> wrote:

 On Thursday, 28 January 2016 5:02 AM, paul swed <paulswedb@gmail.com> wrote:

Hi I suspect that a few connectors get added to that list. On the 5335 there is a *lot* more on the board. So, you need to source a handful of 1970’s era switches and connectors. The connectors (obviously) need to mate with whatever is on the other side. That could be pretty easy. It could be a big issue. At least at the shaft -> knob or “front face” level the new switches (and pots ..) need to be very similar to what is already in there. Again, that may be pretty easy. It also could turn into a really big deal. Bob > On Jan 27, 2016, at 8:44 PM, Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote: > > The boards also contain the input attenuator, input clamp diodes, high impedance buffer and various threshold, hysteresis and risetime setting controls as well as the polarity select controls. Apart from a dual opamp that sums some control signals and LC low pass filters on the supply line and a couple of input coupling capacitors there is little else. > NB the interconnection inductance in series with the emitters of a long tailed pair ultimately limits its bandwidth. Adding a small series resistor will extend the bandwidth at the expense of the gain. The gain can be made up with additional stages.When using individually packaged transistors (or chips in a hybrid) this is about the only option apart from using monolithic differential pairs with a low inductance emitter emitter connection. > > Bruce > > > On Thursday, 28 January 2016 1:04 PM, Bob Camp <kb8tq@n1k.org> wrote: > > > Hi > > Ok, what else is on the same board as the front end? > > Is this a “chop a big hole in the board” project or is it a more elegant, replace the whole board approach. If you are just going to chop > a hole in the board, what else buried in there. > > There is way more to this than just an input circuit. > > Bob > > >> On Jan 27, 2016, at 3:38 PM, Bruce Griffiths <bruce.griffiths@xtra.co.nz> 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@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@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@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 >>>> _______________________________________________ >>>> 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. >>> >> _______________________________________________ >> 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. >> >> >> <5370FrontEnd.PNG>_______________________________________________ >> 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. > > > > _______________________________________________ > 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.