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Re: HP 5385A Counter - Crowbar strikes when it's off
Looking at the 5V output of the supply - when the instrument is in "Standby", there is a 25kHz sawtooth waveform about 2.7V p-p riding on the 5V.? It smooths out quite a bit when the load is put
By jerry-KF6VB · #143556 ·
Re: New booklet
Another excellent book Gianni, well done. If you ever decide to cover any Marconi Instruments, do talk to us... We would be happy to collaborate if you require any assistance. Regards Nigel Adams -
By nigel adams · #143555 ·
New booklet
Should someone be interested, here a new booklet about non-HP nor Tek instruments: http://www.k100.biz/ebooks/Adventures.pdf It can be accessed also from my web page www.k100.biz ( http://www.k100.biz
By Gianni Becattini · #143554 ·
Re: simplified 1GC1-4210 replacement for ESA E44xx LO unlock
Well, I fixed it. I opted for the more prudent 2x HMC862 option; I had the feeling that using the MC100EP32 for the second stage division was more of a risk and would require 4-5 more passives, making
By fenugrec · #143553 ·
HP 5385A Counter - Crowbar strikes when it's off
Hello! The other day, I went out to align a ham radio ( Drake TR-7 ) with the help of my trusty HP5385A.? Alas, the HP was INOP.? No display, nothing.? The 2A DC fuse on the back panel was blown.
By jerry-KF6VB · #143552 ·
Re: More Investigation of the Malfunctioning Time Base RESET Lamp in my HP-1421A.
I remember looking at that 1821A on eevblog and it took me a while to realize that the push-button and lamp were both in the same component. I thought that was rather nice but then if you can't
By n4buq · #143551 ·
Re: More Investigation of the Malfunctioning Time Base RESET Lamp in my HP-1421A.
The same problem I mentioned with my 1821A then, in the "how to test an NE75" thread a while back, at least you have access to the neon in 1421A. David
By factory · #143550 ·
Re: More Investigation of the Malfunctioning Time Base RESET Lamp in my HP-1421A.
Glad you finally got it . [email protected]> wrote:
By Jeremy Nichols · #143549 ·
Re: More Investigation of the Malfunctioning Time Base RESET Lamp in my HP-1421A.
Since I had access to both sides of the existing lamp, I clipped in one of my new A9A neons across it. The new lamp works perfectly so "it's the bulb" was the correct answer. Thanks everyone for being
By n4buq · #143548 ·
Re: More Investigation of the Malfunctioning Time Base RESET Lamp in my HP-1421A.
I had considered making the LED permanent; however, it should have its own DC supply and there's not one handy (unless I include a significant dropping resistor from the +100V rail). I think I'm going
By n4buq · #143547 ·
Re: More Investigation of the Malfunctioning Time Base RESET Lamp in my HP-1421A.
Or both of us are right and both lamp and transistor are weak. Alternatively, if he got it to work with a LED instead of the neon, with the existing transistor, then swap out the neon for the LED
By Peter Gottlieb · #143546 ·
Re: More Investigation of the Malfunctioning Time Base RESET Lamp in my HP-1421A.
Well, one of us has to be right.? Lamp first, transistor second, bet one of them solves it. Harvey
By Harvey White · #143545 ·
Re: More Investigation of the Malfunctioning Time Base RESET Lamp in my HP-1421A.
Q109 doesn't look like it's turning on all the way.? Insufficient holding current to maintain the ionization. Harvey
By Harvey White · #143544 ·
Re: More Investigation of the Malfunctioning Time Base RESET Lamp in my HP-1421A.
In mine, the base of Q109 shows a pulse but it is significantly deeper than 20mV. It is more like 250mV. The emitter, however, shows a pulse of about 20mV which I'm thinking is probably incorrect.
By n4buq · #143543 ·
Re: More Investigation of the Malfunctioning Time Base RESET Lamp in my HP-1421A.
If you are seeing 95 volts across the neon lamp and it isn't firing it is bad and needs to be replaced.? You will see exactly this as they age.? It is normal, once it fires, to have a lower voltage
By Peter Gottlieb · #143542 ·
Re: HP8484A failure modes
I just looked again at the OP, noticing the 7 dB down figure. I'm not sure if these are full-or half-wave detectors, but if full, then there are two diodes. If one burns out, then I think it will be
By Ed Breya · #143541 ·
Re: More Investigation of the Malfunctioning Time Base RESET Lamp in my HP-1421A.
I was able to get clips across DS101 and monitor its voltage. When the trigger circuit turns it off, there is 28V across the neon which makes sense. When the trigger circuit attempts to turn it on,
By n4buq · #143540 ·
Re: HP8484A failure modes
The 8484A is spec'd for only a very low power level range (I forget the number), but it can safely take around 20 or 23 dBm. It's really just a diode detector, which could have been set up for quite a
By Ed Breya · #143539 ·
Re: HP8484A failure modes
I tested a 8481A I have here and the VSWR is very low, like 1.01 or better up to 3 GHz but below 20 MHz starts rising and hits 1.4:1 at 14 MHz whereas the spec calls for it to not exceed that down to
By Peter Gottlieb · #143538 ·
Re: HP8484A failure modes
I set the source output on my VNA (Anritsu) to -20dBm by engaging the source attenuator (Source -> Source 1 power between -5 and +15dBm to 0dBm and also Source -> Port 1 attenuator to add an extra
By Alan Bain · #143537 ·
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