HP 5316A Gate Time Delay Switch

[C-47]

Recently acquired the above counter #2304A--- so quite old, but its had a hard life, the time delay switch was destroyed, so removed from board. Of the 4 solder points, the right side 2 are just anchor's, no electrical connections, I need to determine which of the remaining 4 are for the pot, the remaining 2 should then be for the hold function, but my copy of the schematics / manual are quite poor quality so impossible to read, any info appreciated.

Also the Mouser 3310H-013-504 listed as a possible replacement pot is no longer available, any ideas of options.
Two leaking 3900uF input caps, thankfully the plastic coating had contained them and the unit did power on.

Thanks for any info. Alan. 

[HalFoster]

This is it on the schematic - should be easy enough to figure out from here.

[C-47]

Thanks Hal, much clearer than the copy I have, appreciated. Alan.

[HalFoster]

Should be a valid link to the manual that came from...

https://drive.google.com/file/d/1Shwi26I4Ns7tVSjJOPEEUHVBmfuM9pRG/view?usp=sharing

Hal

[C-47]

Thanks mate, much clearer. Have some replacement caps on slow order, when here will install and power up, have located the switch circuit using the diagram you sent earlier, so for testing will use an external delay pot, if all well, will chase down a small pot to go internally. Will update on progress. Thanks, Alan. 

[C-47]

Update:
Thanks to Hal for the clearer schematics I was able to trace out the lines for the Time Delay switch / pot, the attachments provide the info.
Looking from the front of the unit, of the 6 mounting holes, the right 2 are not used, thus the 2 remaining at the front are for the Pot the left most being the input from the 2.2K Resistor network R2D to the winding / trace the next (centre) is for the wiper and goes to pin 1 on IC RQ8307. The pot I got from RS components does not have an integral switch and is slightly smaller dimensionally than the original. The back row is not used, but the Left and Centre pin holes would be used for the Hold Switch function.

The input capacitor's are on a slow boat from "somewhere" and when installed will be able to power up and see what I have. 

[C-47]

Update 2:
Capacitors arrived and installed, system powered up with no smoke  10meg GPS input signal read close, but some adjustment / alignment will be required, 3 power rails already done, channel C showed signs of life then nothing, read 1v PP is max input, sig gen was set at 3v so may have blow / cooked something, what a diabolical process / location to make any adjustments to this board.

I see board A6 analogue to digital needs GPIB connection for adjustment, something I don't have, is there any workaround to this or do I have fork out some extra, seeing there is a slew of National Instrument cards available, but I suspect many of these are not original and I'm loath to support knockoffs, but the Keysight ones are also an eye watering price, any suggestions in the area would be appreciated. Thanks, Alan.

[lowimpedance]

For the channel  c there is an in line fuse in the  bnc , hopefully it's what popped and not the unobtainable HP amp or divider on the pcb.

[C-47]

Thanks, the fuse checks OK, but still nothing when on 50meg input, channel A is ok, so board removed for now, will investigate further when time permits. Have found a GPIB board so when it arrives a new learning curve begins for aligning the thing. 

[C-47]

The C input option 003 is playing up, while it reads correctly occasionally, it mostly shows 000, has anyone had any luck troubleshooting this board.
The base A & B inputs, 100Mhz section work fine at this stage, while the manual says I should be getting around 110mv between TP 1 and 2  on A9 board I get 5.0v and its not adjustable via HY trimmer. Attached the setup necessary to get at the board while powered up. Any input appreciated. Thanks.

[C-47]

Hunt continues:
Have traced the input signal from the BNC  C input through to the 1000pF C9 cap where it ends before going into IC U1, so have ordered some replacement, 2 weeks delivery. I lifted and checked almost all components, diodes / caps / resistors on the input side to the above and all seemed within spec as did C9 but the scope says it ends there, can only get 49Mhz out of my signal gen, but don't believe that to be a problem, famous last word's.

[C-47]

Update:
Replacement Cap C-9 installed, still the same problem, no signal from the output side, but traceable for the input point.

Does anyone have a good photo of the A9 board so I can compare component orientation, also any thoughts on what else to look for.

Thanks, Alan.
 

[C-47]

Partly solved:
In a moment of frustration temporarily bypassed the C-9 cap completely and the thing works, reads input frequency correctly, then put a .1uF cap in and again it reads correctly, so why the .001uF cap blocks the signal is an unknown to me, any thoughts ?.
According to the parts diagram C-9 is 1,000pF at 100 volts rating so 102 which is what came out originally and it checks correctly, the replacement also checks correctly.

The voltage at input to the cap is 110mV a bit low as the max is limited to around 300mV.
Since the parts manual is from the late 80's there could have been updates which are not incorporated, great learning experience working with older equipment.

[HalFoster]

Thinking without much caffeine yet, changing the cap only changes the HP filter prior to the differential amps Fc from 3.12MHz to 31KHz... what input F are you testing with?  I would trace the signal through the following biasing stage and see if it doesn't go squirrely there. I can try to find more relevant manual pages here but it will be over the weekend before I can get a chance to look.

Hal

[C-47]

Hal, thanks for the input, hope you've had a couple more coffee's by now. Not much done today, my function gen goes to 49Mhz before getting squirely and that's what the input was at.
With a .1u cap (104) in the C-9 position for a short time, maybe around 1.5 minutes, the thing indicated as close to the above freq as possible and was stable at a 1 volt input. I will measure some voltages / frequencies tomorrow as I don't want to blow the thing up, but why the signal will not pass through the listed value C-9 is still a mystery to me.

[C-47]

Progress, I think:
After much schematic reading and testing the area that indicators pointed to, was the C channel gain control for the unstable and mostly non functioning readout, therefore the two 2N4391  N channel JFET's board number Q2 & 3 were replaced with same spec parts from Mouser, not cheap A$18 each, but the functional problem seems to be solved. Some alignment will be done next. Thanks to all for their input in saving this piece of useful equipment from the scrap bin, much appreciated.