TA-0315: Keithley 776 Frequency Counter does it have the 2.4 GHz option?
ฝัง
- เผยแพร่เมื่อ 27 ส.ค. 2024
- A great addition to my Keithley collection. sticker says 2.4 Option,lets see.
Had some microphone problems, but was able to amp it a bit.
Version 1.24: www.tonyplaza....
Some items i used:
GPSDO_Display go.tonyalbus.c...
GPSDO_NoDisp go.tonyalbus.c...
GPSDO_NoDisp go.tonyalbus.c...
GNNSDO go.tonyalbus.c...
Distributer10 go.tonyalbus.c...
Distributer0-200 MHz go.tonyalbus.c...
FDIS-5 go.tonyalbus.c...
FOS-3 Std go.tonyalbus.c...
RG316 Cable BNC-BNC go.tonyalbus.c...
RG316 Cable BNC-BNC go.tonyalbus.c...
RG316 Cable SMA-BNC go.tonyalbus.c...
RG316 Cable SMA-BNC go.tonyalbus.c...
10M-6PLL go.tonyalbus.c...
10 MHz BPF go.tonyalbus.c...
WB-SG1 go.tonyalbus.c...
WB-SG2 go.tonyalbus.c...
FA-2 go.tonyalbus.c...
FA-2 go.tonyalbus.c...
FA-2 Plus go.tonyalbus.c...
FA-3 go.tonyalbus.c...
#keithley #776
![[LIVE] : ONE ลุมพินี 76 | คู่เอก "ผึ้งหลวง vs สมิงดำ"](http://i.ytimg.com/vi/9SBshmGQOIM/mqdefault.jpg)
Tony, I bought the same counter about a year ago. It was $100 to $200 less than other popular used counters that I was looking at on the Internet. Most of the other counters I was comparing did not have the frequency range, 10-digit display with exponent, matched spec channel A and B (which is sort of rare), and a multitude of gate times. It even can display both positive and negative input voltage levels on channel A at the same time. Great for trigging determination. Overall, I really like this counter and have enjoyed it. When I watched your video, I went out and did some comparisons with mine which I hope will be useful information. I have an older firmware 1.24 and the processor is a P80C31BH. I used a Fluke IR thermometer gun like yours and measured 52C at the same coil area on the oscillator board. Since many of those IC are ECL they demand a lot of power, so this maybe normal. All PS regulators and the diode bridge were under 40C after four hours of operation with the cover on. From the manual the TCXO is 10MHz, 1ppm, 0-50C. I let my warm up for 30 minutes than over 2 hours about ever fifteen minutes I would lift the cover and make an adjustment. I got the counter to display a 10 MHz reference signal that would vary no more than 0.04 Hz (last digits on counter .82 to .78). After five hours I took the cover off for 1 hour and the display did change by 4.45 Hz. Like you I will be using my 10MHz lab reference and not the internal Xtal oscillator. Also, I measured my max counter frequency using the same generator you have and it was approximately 2.65 GHz. Thanks for posting the video, I always enjoy them.
Thank you John, wow lots of research, that really helps. that gift me a better feeling about the 500 MHz multiplier circuit... i will just replace the TCXO with a Vectron OCXO, i have still a few also 5 Volts and square 5v out.. the board around the TCXO says 12v but the 5volt regulator is also there.
Yes mine also has the TSC80C31 (different brand prob same) . i made a copy of the EPROM for you, mine is ST M27C256 or M27256, i have it in BIN,HEX and Motorola S format.
will put it for download below the video. Thanks again for your tests, it is really helpful for me and others. i pinned your message.
@@TonyAlbus Thanks Tony I downloaded the firmware and I have a GQ 4x4. I corrected my original post I meant to state that I have the 1.21 firmware and not the 1.24.
@@jwrtiger Hi John, perfect you have the same GQ 4x4 i read with that one here :)) yes i understood you had a before 1.24 .. hope it works for you!
Great video Tony!
I own a Keithly 776 which is stuck in Ukraine. I can't get a lot of my equipment out due to export restrictions imposed with the war.
On my TXCO the electrolytic capacitor at the top right corner leaked. I didn't get it replaced before I left. Watching this video helped me prepare for my future service on my 776.. Thank you!
73 Chuck ND5CH UT1ZT
thanks, and all-my best wishes to you and your family
Very nice counter, Tony. Please do a video of your OXCO modification - it sounds like many people would benefit from doing this mod. I added a Vectron OXCO to my HP 5315B counter and now it is so accurate and stable that most of the time I use it without an external reference! Regards, David
Thanks David, yes i will! good to know it worked well for you on the HP.
Hi Tony, bit of a shame they couldn't have put an ocxo in a nice counter like that, thanks for the video
Hi, Thanks, now i need to do that myself :) and i will
I had to test and repair around 25 Keithley pieces of equipment of that vintage. After having a couple of 10 uF tants pop during the 24 hour burn-in I did I started checking each cap's temperature with the IR thermometer. By the 3rd one I was just replacing all of the 10 uF tants. (I bought 500 new caps.) Keithley had apparently purchased a large, bad batch of them and built them into their new gear at the time. So ALL of those caps in boxes of the vintage with 7-segment LED displays are questionable. The unit I kept for myself was one I'd just checked the temperatures on and only replaced 1 hot cap. Over the next 6 months it blew 2 more of the tant. caps, and they pop real good, sputtering noises, pops, and smoke. It led me to stop trusting Keithley gear in general. That cap purchase really hurt their reputation as far as I'm concerned.
Hi John, that does not sound good.... keep in mind this series was a Racal, i do have a few Keithley DMM's from 80's and those still run fine. i like the Keithley brand
The temperature compensation can only go as far as you saw it go. It does compensate, but the curves of the compensating elements don't exactly match the frequency drift curves. So, the better option would be to replace the internal reference with an oven-based.
Thanks, yes i will, have still a few Vectrons
Does seem like a lot of drift over such a short time span. The OCXO retrofit will be interesting to see, and just how elegant you can make it.
was thinking ducktape and tyrips :))
Nice! 👍
Thank you Sir.
Hi Tony, one thing you could try is to measure the output frequency of the TCXO with another counter, to see what its frequency is. If its faulty you will see that (% diff from spec) and that may lead you to look at the driving circuitry around it if it seems ok.
Hi Stephen, circuit around also used for external ref. i still have a few of those ovenized Vectrons also 5 volts square..those are good.
Perhaps the TCXO is not expecting such a sudden temperature transition. I would leave that set up "somewhere else" to see if it may take a while for the compensation to work.
Yes a good one...maybe i just replace it with a OCXO, still have a Vectron
👍👍 Hi....!! Very..Very Good...!!
Thank you!
By coincidence I’m currently working on a 775A which has just the base oscillator. No surprise it’s not even close to as good as the TCXO option you have. I’m thinking an OCXO upgrade may be in the future. I do notice some similarities in the main board layout between the two. Does the 776 also use an 8031 processor or did they change to something newer? Thanks for the video!
I also have the 776 and the chip I have is the P80C31BH.
Yes like John says, 80C31 also.. i will put a Vectron OCXO in it.. also 5 volts and square.
My private investigation revealed that these instruments were originally made by Tabor Electronics. Also sold under Kontron and Racal brand. They are nice looking, but much slower measurement refresh rate than Racal Dana 1991, 1992 etc set for same resolution.
Thanks, nice to know!
@@TonyAlbus Check out Tabor 6020; Keithley 776; Racal 2201 to be precise
@@doktorpyta5904 Thanks, with my options its Tabor6030 .. but cool! .. that racal is like 2 raindrops.
@@doktorpyta5904 Thanks for the information, I did not know that and I assume Keithley made the 776. Interesting that those units seem to have a 9 digit display (excluding exponent) but the Keithley has a a 10 digit display.
🙂👍 fajny
Thank you!
OCXO upgrade. coming soon . That lid effect is capacitance coupling?
Yes agree, going to do that. yes good point, was thinkimg the same, and did hold the lid only above the circuit, but having space to cooldown... same affect. -> OCXO :)