Hi,

I recently picked up a used 141t with a 8552 if and a 8553 rf front
end. the anlayzer works, but the center frequency is about 24 mhz
off. Does any one know a procedure recal the center frequency? I
have tried to adjust the "tuning range" adjustment, that had no
effect.

Thanks

john

Hi all,
I have a Tek 2432 which fails the following;
1: 7000 CCD
2: 8000 PA
3: 9000 TRIGS
I also have a Tek 2432A which fails;
1: 5000 WP
2: 8000 PA -- no pass/fail message
3: 9000 TRIGS -- no pass/fail message
Is this an almighty going round in circles job or has anyone been through this before? Before you suggest it - the batteries are ok.
I may donate these if they require a lot of time to fix to somebody who has the time.
Regards
Gearoid Loughnane
Dublin
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----- Original Message -----

From: factory_peasant

To: hp_agilent_equipment@...

Sent: Monday, November 01, 2004 11:38 PM

Subject: [hp_agilent_equipment] Re: Schematics for HP 54510A scope

--- In hp_agilent_equipment@..., "Harlan Gustafson"
<accellodyne@n...> wrote:
> Does anyone know where I could find schematics for my HP 54510A
digital oscilloscope?? I've looked in a few places without luck.
> Thanks,
> Gus

could you be more specific about what it is you're looking for? are
you looking for board level diagrams or actual circuit schematics.
most of the older service/troubleshooting manuals at least had board
level troubleshooting diagrams. if you could give me some more info i
might be able to help you.

Dear All,
I have a HP 8690B, the mainframe is in a very bad condition but the plug-in
unit works well.
I think about making my own power supply and ramp generator to drive the
plug-in module.
I found a military calibration manual but no schematic or indication about
the voltages/signal which are send to the plug-in module.

Does anyone has information, schematic ??

Regards
David / F1URI



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----- Original Message -----

From: DON CRAMER

To: HP Agilent Group

Sent: Monday, November 01, 2004 2:06 AM

Subject: [hp_agilent_equipment] E4411A spectrum analyzer low gain fixed

I thought I should document repair to an E4411A (alias ESA-L1500A) 1.5Ghz spectrum analyzer in the event anyone here might find the information useful.

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The symptom was low gain (~28dB low) but with flat response and all other functions ok.? The HP service manual only goes down to the module level, which is doubly unfortunate for this instrument because the one RF assembly module contains everything from the front panel input connector all the way back to the 2nd IF input.? The manual helped confirm the fault was in the RF assembly module, but at that point they say don't service it, get a replacement instead.? That would be ok except the replacement price is $6120 exchange.? For an analyzer that probably went for $8K new, I bet they don't get too many takers.? As the SA was initially free, I didn't have too much to lose by violating the recommendation and taking a peek inside the RF assembly.

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The clever RF assembly comprises one PCB, with castings that sandwich the board in between providing circuit isolation.? The service manual does give some information as to what's in there via a coarse block diagram and a page or two of explanation.? I was able to find a shorted transistor (Q6) in what I believe is the 2nd mixer (could be the tail end of the 1st IF).? This was located using the diode function of a DMM; I did not have to power up the assembly.? Normal was about a 0.45V diode drop from "dot" (I thought base, but turned out to be gate) to the other leads.

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The transistor is a "pill package" 4 lead part with "211" as the sole ID marking.? Some hunches lead to the identity of the part being most likely an HP (Agilent) ATF-21186 GaAs FET, which is used in numerous locations in the front end of the RF assy.? Regarding the 0.45V drop, what I was measuring I believe is a schottky barrier gate structure.? I don't work in RF; FETs in my line are all insulated gate (enhancement mode) devices, so this has been an interesting experience.

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The bad news was the ATF-21186 was discontinued in 2001.? Newer parts don't use the pill package.? However, I did find a small lot of '21186 parts (9805 lot code) via a helpful broker at about $14 each, with a required lot buy of 16 pieces.? My analyzer is SN prefix "US37.." so the parts are less than a year apart in manufacture date.? Upon arrival I was pleased to find the new parts looked identical to the old.? BTW, a "-STR" suffix on the ATF-21186 designates the part packaged in a strip of 10.?

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I did not attempt to "match" devices or anything--I just replaced the bad part with one of the new ones.? Input welcome if someone knows better.

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One tool I found helpful in putting the RF assy castings back together with the zillion M3 screws used is a good torque screwdriver to get everything down evenly.? The tightening torque is 9 in-lbs on everything (casting screws, casting to instrument screws, and instrument case screws).? As there is no give to the housings, it is crucial all screws get tightened down the same amount.? Over tightening one screw will make the adjacent one loose for instance.? It takes two of three passes around them all to get to final torque.? I used a Proto 6106 (now apparently owned by Stanley) driver which supposedly will not over torque screws even with multiple attempts to retighten them.

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The replacement transistor seems to have solved the problem.

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One other hint.? The one?piece?rubber membrane key pad has thin walls where the raised key caps drop down to the sheet.? They are easily torn if you do something silly like drive the key cap sideways through overzealous cleaning for instance.? I found a reasonable fix was to build a "hinge" between the torn key cap and base sheet using a flowable silcone product made for car windshield gasket sealing: Permatex Windshield and Glass Sealer.??I found a?1.5oz tube of the stuff available at the local hardware store.

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Don C

Beaverton, OR

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