Hi Razvan,

I don't have a schematic, but mine has an Artesyn NFN40-7608. The datasheet is here.

Is the standby light on, or do you get nothing?

Tom

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Hi All I'm Looking for a HP service manual for the 8562A but not the one that seems commonly available (08562-90062 for serial number prefix 2913A) my serial number is 2923A, I'm looking at the log amp detector and the trouble shooting? seems completely wrong so I suspect there has been changes, If anyone has prefix 2923A or later or could point me in the right direction i would be grateful, thanks

Hey everyone,

Is there any information out there on the power supply used in these units? Mine appears to have died (I can't measure any output), and I can't find the schematic in the CLIP files.

The full part number of the PSU seems to be JW 1287, JW being the manufacturer.

This isn't the first time it failed. Many years ago a resistor went open, but I don't remember how I troubleshooted that, and I didn't take any notes...

Cheers,
Razvan

Hi,

While trying to fix my HP8662A I'm trying to work out if?it is missing an output attenuator relay drive cable - or not.

There appear to be at least two attenuator configurations in these instruments. My machine has two attenuator units, each with a ribbon cable attached - which I assume are the relay drive signals. I have seen pictures of other revs of the instrument with a single larger attenuator with a drive cable that comes from the motherboard, but no ribbon cables. I attach a picture of both configs, as far as I can research them.

I can't find any HP update/change documentation on the internet about when the configuration of the attenuators for this instrument changed - or indeed, if it is an instrument option.

My question regards the attenuator drive cable. In my own instrument with 2 attenuators there is no drive cable plugged in to the motherboard (see circled area in pictures). In the single attenuator model this cable exists (again, see picture). So should my instrument have that cable (i.e. it is missing), or do the ribbon cables carry those signals and therefore does not need one?

I hope that is clear!

Many thanks

Tony

With the offset is set to -2.00 Vdc, the output of U502 reads -13.240.

1) anode of CR501 = -7.891 Vdc
2) emitter of Q501 = -1.0263 Vdc
3) cathode of CR502 = -9.446 Vdc
4) emitter of Q502 = 1.0324 Vdc
5) top of R511 (node 47) = .0024 Vdc

Thanks,
David

On Sun, May 29, 2022 at 09:21 PM, Swiss wrote:

...
U501 they call an offset current compensation amplifier, and U502 they call the offset voltage control. I measured the output of both U501 and U502 at different offset output settings, and here are the results,

U501

-7 Vdc = 9.037
-5 Vdc = 9.014
-2 Vdc = 8.990
0 Vdc = 8.749
20 mVdc = -.0906 <-- I included this because of the results I was seeing from U502
1 Vdc = -2.0732
2 Vdc = -3.3286
5 Vdc = -6.935
7 Vdc = -9.305

U502

-7 Vdc = -13.526
-5 Vdc = -13.256
-2 Vdc = -13.252
0 Vdc = -13.252
20 mVdc = -13.123 <-- At approximately 28 mV, the output changes from -13.123 V to -0.7800??
1 Vdc = -.6912
2 Vdc = -.6774
5 Vdc = -.6600
7 Vdc = -.6544

------
When offset is set to one of the settings that produce -13.2V at the output of U502, what voltages do you measure at
1) anode of CR501?
2) emitter of Q501?
3) cathode of CR502
4) emitter of Q502
5) top of R511 (node 47)

Ozan

So I did some more reading and I was wondering what comes after the DAC output control from A2. As mentioned before, I measured the output of the DAC and listed the voltages in my first post. They were slightly out of spec according to the repair manual, but not so much that I was concerned about it. I kept following the trail and ended up at U501 and U502.

U501 they call an offset current compensation amplifier, and U502 they call the offset voltage control. I measured the output of both U501 and U502 at different offset output settings, and here are the results,

U501

-7 Vdc = 9.037
-5 Vdc = 9.014
-2 Vdc = 8.990
0 Vdc = 8.749
20 mVdc = -.0906 <-- I included this because of the results I was seeing from U502
1 Vdc = -2.0732
2 Vdc = -3.3286
5 Vdc = -6.935
7 Vdc = -9.305

U502

-7 Vdc = -13.526
-5 Vdc = -13.256
-2 Vdc = -13.252
0 Vdc = -13.252
20 mVdc = -13.123 <-- At approximately 28 mV, the output changes from -13.123 V to -0.7800??
1 Vdc = -.6912
2 Vdc = -.6774
5 Vdc = -.6600
7 Vdc = -.6544

U502 feeds the inputs of Q501 and Q502. It doesn't look like U502 is working properly to me. All the components surrounding U502 look in good shape and measure fine as well.

I thought about injecting variable DC into the input of R509 to see if I would get a different response, but I decided against that as I didn't want to subject the output of another function generator or the input of the amplifier without breaking the circuit. U502 is an OP-07CP an they are readily available. I ordered a couple. In the mean time, (tomorrow if I am able) I may remove U502 and try injecting a signal into the system to see if it the culprit, or I may open the other unit I have, and compare measurements.?

I'm still not 100% sure if this is the trouble spot, but it looks to be very suspect.

Thanks,
David

Has anyone measured the additional phase noise from this clock multiplier module, or others?

Thanks, Ron
-

Thanks to all who replied.
I used to design fiber optic systems, among my other system design tasks, and am aware of the fact the receiver cannot sometimes track the source because of long delays in the cable or fiber.? I have slowed the sweep and have not noticed any appreciable discrepancies with the data.? So my conclusion is that using a 30 Meter (my tip of the hat to Dr, Kirkby) cable should enact the calibration, and would not be an issue for the 8753C.? I agree with Tom about only the phase being a factor in the port extensions.? But I am not using port extensions.? I have a piece of software that will allow me to enter data for measurements taken at various points along a fixed length of cable, and can "BACk OUT" the cable to reflect the actual data at the calibration plane.
All of that experimentation with that software and real world measurements seem to correlate correctly.??? This question from the very beginning, excepting my original mistake, was somewhat academic.? I have been using this method for a number of years and it does work.?
I guess recently I've become a bit bored looking for some new project to undertake.
I truly respect the groups knowledge and time putting up with my questions.

Regards,
Karin

According to the CLIP the A4 assembly is the Log Amp and Cal assembly. J3,J4,J5,J7 and J8 are 50 Ohm SMB connectors according to the parts list. I have not identified the EXACT designation of the RED SMB coaxial lead in question yet. I'll have a look next weekend.

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A few comments on SMB connectors :

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What is the signal involved? HP often used SMB for DC bias or things like RF detector outputs when they just wanted a well screened cable. If that is the case here then a slightly squidged cable is not a problem (assuming it still has continuity and isn't shorted of course!)

I did check the supplies. Sorry I forgot to mention that. If I remember correctly the +15 V supply was off, and it wasn't off by much. It was in the millivolts range if I recall. I was able to get that back into range with no trouble.It didn't catch me off guard as I would expect these to drift out of range slightly over time.

I will double check these values again this evening before I move on to recapping a Monsanto 101A counter. Like this nixie tube counter too. Pretty neato.

Thanks,
David

I'll also give the warming up trick a try as well and I'll check the continuity as well. Thanks.

David.

George,
I will confirm if there is a connector on the other end and the exact length this coming weekend. Thank you.

David.

Hi David

Having looked at the photograph I would first try slightly warming the cable and then using my thumb and a finger try to roll the damage out of the coax.

?

SMB connectors are not normally used in high frequency RF or critical circuits so a little cable damage may not matter.

?

To remove an SMB pull on the sleeve nearest the matting connector as they are a latch fitting.

?

G Edmonds

Hi David

This is an SMB connector.? The cable is almost certainly 50 Ohms impedance as is the SMB connector.

The red is just for identification, does it have connectors on both ends?

What is the length?

G Edmonds