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HP8510 loosing detection above 20GHz

 

After a long endeavor and with much help of several goups.io members to repair my HP8510 system, I'm now start to see light in the tunnel.
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With a borrowed HP85102B as IF-Detector the system? works perfectly, up-to the max 26.5GHz
When I use my own HP85102B in the same setup, It works almost OK up to 20GHz (only small glitches) but when the sweep comes exactly above 20GHz the trace is lost (full scale noise).
I checked the gain of A9-A11-A13-A14 IF-Mixer's and they seems OK. I also replaced all PNP's in one of modules but without effect.
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An amplitude or VTO pre-tune issue ????
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Anyone experience with this strange behavior ?
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My current setup:
HP85101B
HP85102B own, HP85102B (with option HP85103B installed) borrowed
HP8515A
HP8340A
 

What do you mean by "exactly above 20 GHz?" When I hear exactly for a number, I have to think a digital decision may have been made, according to specs or such. Maybe there's some kind of model specific things limiting the range unless it's enabled somehow.
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Ed
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Have you ran the Built in Self test from the software menu (22 Service Program) ?
You need a special widget (Service Adapter) to check the IF box with it's 10 test paths; then you can check the RF+IF boxes full path(s) with high confidence.
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There is also BIST for the synthesizer, which is worth a try for your symptom.
For a 20-26GHz issue, it's probably the Synth or RF Samplers (mixers).
 

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I¡¯ve a 8510C I¡¯ve the same problem twice . The first time was the YTO on test set . The second time the multiplier and amplifier module on sweeper. In both cases the SRDs failed. Is the most common death cause in this great equipment. ?The power loose on the higher band happens slowly , you can check it on test set performing the basic test using the raw parameters a1 a2 ¡­ as described on service manual. For sweeper the maximum leveled output power goes down above 20GHz ¡­ should be more than 7dBm at 26.5 GHz for 83630A ( or similar ) model.?
Both modules are becoming hard to find. They are available on repaired version from Keysight at absolutely expensive prices.?
I observed that this deterioration are proportional to working hours, the frequency range is also implortant as higher frequency there are more stress on SRDs . To provide an excellent stability I used to left the instrument on 24/7 ¡­ now I take care to reduce the working hours to minimum.?
Regards , Patricio?

Ing. Patricio A. Greco
Taller Aeron¨¢utico de Reparaci¨®n 1B-349
Gral. Mart¨ªn Rodr¨ªguez 2159
San Miguel (1663)
Buenos Aires
T:?+5411-4455-2557
F:?+5411-4032-0072

On 13 Nov 2024, at 05:09, David Vieira via groups.io <dpvieira@...> wrote:

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Have you ran the Built in Self test from the software menu (22 Service Program) ?
You need a special widget (Service Adapter) to check the IF box with it's 10 test paths; then you can check the RF+IF boxes full path(s) with high confidence.
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There is also BIST for the synthesizer, which is worth a try for your symptom.
For a 20-26GHz issue, it's probably the Synth or RF Samplers (mixers).
 

All thanks for your support.
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David: I'm searching for such a special connector to build a HP85102B testkit, W.I.P.
Could be that the hard stop has to do with bandswitching in the HP8340A, I don't know the bandlimits, but as said it works perfectly with another HP85102B.
I could not find the BST for the synthesizer, is this in the HP8510 service menu ?
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Patricio: The strange thing is that the whole system works perfectly up-to 26.5GHz with only a different IF-Detector HP85102B.
I measured the 26.5GHz RF level of the Sweeper HP8340A, this is just below 20dBm, so quite strong.?
I also observed the 20MHz level on a1 and a2: starting at a RF of 1GHz it drops constantly till the highest frequency 26.5GHz. But this is what we should expect as the harmonic mixing output goes down with 20LOG(n), I don't know what 20MHz amplitude I should expect on a1 and a2 (above 20G)
 

Maybe there is problem with sweep signal §àr sweep ADC inside 85102?
 

Is there a design behind HP's option numbering ?
I used to have a spectrum analyser plugin (8558. I think) with an H-something option, which in that case indicated a 75 ohm input and, iirc, dBuV scales for use in cable TV work. But purchase options usually seem to be numeric only.?
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Question - is your 85102 a "native B" model or an upgraded A model.? If it is an upgrade, there were two different upgrades for the A.? It is possible that only one of them was made.? There is an HP note on this,? I will look to see if I can find it.? Otherwise some one else who has the upgrade note handy could supply it.
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Testing the 85101/85102 with the 8510 test set emulator connector is also strongly advised.? You can purchase the test set emulator or build one yourself, there are pictrues posted in the groups wiki.
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Cheers!
Bruce
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If you like let me see the traces.?
Ing. Patricio A. Greco
Gral. Mart¨ªn Rodr¨ªguez 2159
San Miguel (1663)
Buenos Aires
T:?+5411-4455-2557
F:?+5411-4032-0072

On 13 Nov 2024, at 10:47, Maarten PA0MHE via groups.io <maarten.heuvelman@...> wrote:

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All thanks for your support.
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David: I'm searching for such a special connector to build a HP85102B testkit, W.I.P.
Could be that the hard stop has to do with bandswitching in the HP8340A, I don't know the bandlimits, but as said it works perfectly with another HP85102B.
I could not find the BST for the synthesizer, is this in the HP8510 service menu ?
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Patricio: The strange thing is that the whole system works perfectly up-to 26.5GHz with only a different IF-Detector HP85102B.
I measured the 26.5GHz RF level of the Sweeper HP8340A, this is just below 20dBm, so quite strong.?
I also observed the 20MHz level on a1 and a2: starting at a RF of 1GHz it drops constantly till the highest frequency 26.5GHz. But this is what we should expect as the harmonic mixing output goes down with 20LOG(n), I don't know what 20MHz amplitude I should expect on a1 and a2 (above 20G)
 

Found some info about differences between A and C, but not B versions of 85102.
I think, you need to compare partnumbers of A16, A20 and A23 of both 85102B you have.
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A16 Remote Applications
85102A - Not Assigned
85102C - 85102-60235
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A20 Sweep ADC
85102A - 85102-60020
85102C - 85102-60234
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A23 Main Phase Lock
85102A - 85102-60023
85102C - 85102-60227
 

There¡¯s also a ceramic disc capacitor fitted between if memory serves, pins 1 and 4 on the back side of the motherboard. I don¡¯t recall the exact value, maybe 1 or 10nF. The part specified has a silly 1 kv voltage rating. As near as I can tell there¡¯s no good reason for that other than the lead spacing matches the gap between pins, and probably that it fit and HP probably had them lying around. Being on the backs side of the motherboard, it¡¯s easily overlooked while one are upgrading the cards.
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It seems to me that the 8530R and 8510C systems had it. It also seems to me, if memory serves, that its utility might be moot if using an an 8360 or 8370 sweeper and not otherwise using the analog sweep output voltage. I¡¯m not sure about for an 8340, but I think it was specifically there for an 8350 or older sweepers with plugins.
 

I could very well be that there is indeed a upgrade in PLL sensitivity or Sweep ADC. I can't open the 85102C as it is borrowed, but it is very interesting to understand the differences/improvements.
Does anyone has the schematics of this:
A20 Sweep ADC????????? 85102C - 85102-60234
A23 Main Phase Lock ?85102C - 85102-60227
Or has anyone perhaps these boards surplus ?
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I will al;s look to this capacitor.
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