How To Repair Hp 8569b

HP8565A Spectrum Analyzer Repair

2020/1/8

This is a monster, big, heavy and mysterious device. The dealer said that it could ability up, and no more guarantee. I got skillful bargain then, less than 150$ include delivery. It's been nigh half twelvemonth since i got it in 2019'southward summertime.

I recall after power it on, a loud hum bursted. I pretty sure it's the transform. I immediately turned information technology off . I noticed, except several led blinked, no trace showed upwardly. I figured the line voltage is wrong.

Line voltage selection is 120V , simply i got 220V. Lucky, earlier i dig into how select the line voltage, a 220V to 110V transformer come to rescue me. Still, no trace, skilful sign is the frequency windows responded to tune knob.

The dealer must plugin 220V wall line and power information technology on for a long time, seal cloth flow outside from the transformer. I was afraid it had been and then damaged, it might could not dorsum to work once again.

Kickoff step, select right line voltage, of course. Reference Service Transmission : Line Voltage Choice, page 28

Voltage showed on Top-left is the one actuate !

After choose suitable line voltage, device calmed down finally. NO trace showed up, of form. Outset LO output totally dead. Not so proficient.

Since there is no trace, and then first thing, checking the high voltage module. Examination betoken A seems not right. Pull out the module, manifestly the FUSE is good. And finally i notice the 158V voltage was gone.

Reference SM, folio 440.

Open the back cover, located the chief ability supply board, a row of test point lined at that place. I found the 5V, 30V FUSE and 158V FUES blowed upward. Replace with a new one, then 5V recovered, simply 30V still downwards. 158V dead -- ~30V .

Supply schematic is in the last page of Service manual.

Voltage on U9 pin 7 is 45V, and pin half dozen got 15V, output test indicate is also 15V. Pin4 of U9, is floating, other than expected 10V. Parrallen a new zender with VR15 did nothing. So, there must no electric current flow through the U9.

U9 : LM741, replacement might be: TL071, NE5532

I finally got a uc741, and 30V recovered. Because the 158V still downwardly, 30V supply bring zip back, perchance the YIG.

voltage on Q31/Q29 push pull bespeak is seems correct --- 220V, obviously Information technology'south trying to drive Q9. Base of Q28 is almost zippo, and easy to identified it shorted, all three leads, any two of them is shorted.

With KTC4419 soldering into Q28 position, the output still pretty low, farther checking point the R47 is burned to open circuits. A new resistor put on it, simply smoked immediately. Accident upwardly the FUSE again.

On fixing ability supply, I should've checking the Q9 kickoff, but i did not. Now I came to Q9, institute it deadly shorted. The most disturbing problem is find a suitable replacement. And here is the original transistor listing and my enquiry for alternative.

btw, Q28 is current limiting, remove Q28 could isolating current protecting circuits.

2SC4544 TO-220F Ft=fifty Mhz Hfe>xxx 100mA, 8W Vcbo 300V Vceo 300V Vebo 7V

2SC5858 1700V hFE>30 200W

2SC2688 Ft>=50Mhz Hfe>=xl Ic:200mA 10W Vcbo 300V Vceo 300V Vebo 7V

NOTE following loftier voltage transistor, hFE is likewise low, and could not supply plenty current. Minimum hFE around 80mA/5mA = xvi, merely thirty is recommend.

2sc5387: loaded slow beginning from 100V, <=130V low hFE=ten

2sc3320: loaded slow start from 120V , <=136V low hFE=10

KTC4419: works fine. VCBO 500 V VCEO 400 V IC 5A PC thirty W hFE(ane)=20 (VCE=4V, IC=0.1A )

2N3440 replacement:

all-time replacement MPSA42: Hfe >=forty(identical with 2N3440).

2SC2688 : 0.2A, 300V , 50Mhz (EBC), hFE >=50

2SC1507 (300V 1W, BEC, hFE>fifty),

low hFE: MJE13002 , 2SC4913, MJE340(BCE)

2N3054/2N3055/2N6055(Not 158V)

2N6055 DARLINGTON 100W TO3

2sc5387 is first transistor i picked up for Q9. Unlucky, output almost zero. Q9 , Q28 is good. I suspect the output is protected. And information technology did so, later isolated Q30(by lift up on pb of VR9), output attain to 220V!!!

Further checking indicate the U10 pin6 always stay on 25V ( +15V UNREG is 30V), no affair output is zip or 220V. meanwhile, U10, Pin2 is college than Pin3 --- this suggested the U10 is broken. Another UC 741 is sacrificed for protecting other circuits.

Replace UC10 solved the trouble, even though output merely 125V. The scan trace emerged on screen, BIG PROGRESS. And Now is fourth dimension to address why voltage is depression. It's simple, though, without load it's 156 Volt. So It's considering of the hFE of the transistor.

I supersede the 2sc5387 with 2sc3320, just both them is not function well. finally i plant KTC4419 is the right transistor I'1000 looking for.

2sc5387: loaded slow kickoff from 100V, <=130V low hFE=10

2sc3320: loaded dull outset from 120V , <=136V low hFE=10

KTC4419: works fine. VCBO 500 V VCEO 400 Five IC 5A PC thirty W hFE(one)=twenty (VCE=4V, IC=0.1A )

Earlier whatever further experiment, volta must be alignment. After lightly wiggle the adjustment POT on the supply board, all voltage almost precisely on the value of the Spec.

Led display all SA setup, it's cute and user-friendly, almost identical as digital one. And I prefer this LED version.

Each LED display the unit of measurement, gone dark. The led control board located simply beneath the CRT. Remove the screw of that board, unplug the cable so you could have it out.

I found the root crusade at once, i of cable connected to the LED is totally slip off from socket. This is an happy stop, and pretty weird.

Next step, going to play around my new toy. For few days investigated, I notice something miss aliment and some good things.

Symptom:

No zero shell response except on very narrow span per div.
0.01 - 1.8Ghz working well aliment panel calibrige pots.
The 1.7G-four.1Ghz ring reading result is 10 dB less than bodily betoken level : confirmed by HP432.
More than higher band: unknown.

Skillful one:

0.01 - i.8Ghz band aamplitude pretty precisely alignment, this mean the IF amplifier , filters, YTO driver, mixer bias still stay alignment.
All bands show browse line.
All command knob is working well, except the Attenuator knob is broken, not a big deal since we had LED brandish.

Trying Conform Frequency Response - the dBm Amplitude accuracy

one.7G - 4.1G band is convenient band. I had several YIG oscillator on mitt, dainty to accept a SA to play YIG Oscillator. Since dBm reading is most 10 dB less than actual value, I doubtable something get wrong. I initially call back some alignment must exist washed to bring back the accuracy.

There is no zero chirapsia, that is suspecting symptom. Service Manual give a brief tabular array, list all adjustment Pots. I detect there is YTO/YTF adjustment. Obviously, I supposed to tune YTO offset, let the null shell response sally on screen.

The CAL output is accuracy plenty for me (-0.45 dBm) . Reference level easily align by 100 Mhz CAL source. Tune YTO offset POT A19R5, let zero beat show on screen, and then tune A19R8, YTO Gain, permit all CAL sources harmonic align with vertical line.

On harmonic bands, each band use 1 harmonic component of the YTO, so each ring acquaintance with a number N: represented the harmonic which it gonna to use.

On harmonic "N" ring, a YTF switch in as band pass filter, cover 1.7Ghz - 22Ghz.

YTF must tracking the YTO to ensure correct response. I realized this after i badly tried to conform the frequency response(B2A,B2B, B2C) for hours.

Band ane.7-4.1 is just controlled by YTF-First(A19R14), and YTF GAIN(A19R17). According the Service transmission, you should turn on a YTO Test switch on A19, so the YTF response will displayed on CRT, and use sweeping signal source to help melody YTF offset and YTF GAIN. I don't have a the sweeping microwave signal source at all, I realized i could apply main melody knob, under aid the this switch to checking the YTF response.

While you aliment YTF response, Delight keep the YTF top knob stay middle point.

I did non take any microwave signal source bachelor. But I did had several YIG oscillators. Bench Power supply had electric current limiting is suitable to drive the YIG tuned coil -- for safe, serial with 5-ten Ohm resistor.

Even though tune the YTF Offset and Gain is easy but checking the response is pretty awful , without a sweep point source.

Proficient matter happened, I finally become band 1.7-four.one working well.

BTW: I had advanst YIG, which output 40mW form 2G to 4Ghz, pretty powerful, and near flat(several dents reach to 30mW). And information technology's harmonics also stiff and extended to 10Ghz. This help me a lot a while late.

Now, band 1.vii-iv.1 works, I wonder, why not effort three.8-viii.5, five.eight-12.9Ghz. It seems pretty simple: each band had its own OFFSET, simply share same Proceeds, I suppose the Proceeds command somehow the Cease of one band. I reallize this is non how the tracking works, after spend hours and hours trying to adjust each offset.

Before going any further, I better briefly reading the alignment procedure. First of all, I need effigy out why a SA read correct dBm on CRT, what ensure this accuracy.

For the harmonic N band, following essential setup ensure the frequency response:

YTF must tracking YTO: This ensure a correct response
Each band had to have it's own frequency response compensation. Mixer it'south cocky response pretty flat, this correction is very small - few db maximum.

Arrange should post-obit this table. The about important group is A, B and C is some kind of linear aligning. I judge they are non beed messed up, even they are not perfect, still could get meaningful reading after group A is finished successfully.

I spends eight hours to figout how these things piece of work together. Here is bold NOTES:

All band share a same Starting time actually.
N2-N5 is simply very slight adjustment: N2: 5db Range, N3: 10 dB N4: 20dB. Don't evng thing utilize N2-N5 aliment each private band.
All Band share same Proceeds: grouping A's GAIN adjust should be gradually reduce to become proper response if everything is going right.

Afterward spend desperating 8 hours, not all of them is meaningless, I gain a method could apace cheque the response without a sweeper, and don't need to employ Test mode. The key idea is, the "Preselector peak" knob help you sweeping the YTF.

Quick Checking YTO response

Apply YIG and it's harmonic.
YIG frequency at kickoff of the band, around 2Ghz, it's harmonics is 4G, well done.
Rotating "preselector peaking" knob, if either side the response leftover is on same level, the tracking is correction.
Now, the tracking response on both end simultaneously present.

Suggest:

These group of Pots is protected by a aluminum shield on purpose.
This advise don't' affect them, unless you know what yous are doing.
While you need from these pots to get accuracy response, the error must exist very small maybe less than +- 3 db.
In other words, these brand the response perfect, not intend to brand them just work: delight brand sure YTF tracking is well alignment.

I spends hours to arrange the Pots, but could not make all band tracking correctly. I then suspect how exactly the tracking work?

First of all, they share same YTF GAIN, what's is GAIN exactly?
They and so share same offset (YTF Commencement), N2-N5 just could adapt a little bit, they are not intend to make tracking work, they intend to brand tracking perfect.

I practise non how to discover this, merely they actually working prety uncomplicated: YTO and YTF tune line should be overlap.

YTO and YTF are pretty linear, plus it had linearity correction circuits. They are suppose two lines on mv-Mhz coordinate system.
YTF share same Browse Ramp voltage which control the YTO, now the YTF GAIN jump in: YTF GAIN control change this Ramp's Gradient to YTF's slope. So, YFT alter same amount of Mhz with YTO.
YTF also share same Eye voltage with YTO. YTF OFFSET gonna make YTF tune line overlap with YTO tune line: 2 tune lines already share same slope . And now , with YTF OFFSET correctly, there share a same mv-Mhz point. then, they are same line, so, perfect tracking gonna happen.

Good Do on Arrange YTF Tracking

Knowing how does help you adjust the YTF Tracking, only not and so much. I spend hours again, on how to make them alignment. I finally establish the YTO Start impact the tracking a lot.

And, Of Course, It does : YTO and YFO both are not perfect linear line, especially on offset of the ramp. This explicate everything: the naught span should not on the first of Sweep, Naught Bridge should move to a little bit right. 50Mhz is minimal request. Fiannaly, offset 70Mhz give a good YTF alignments.

Following steps is tring recovery the alignment without totally go through all alignment items. This is far from perfect, only enough for hobbyist, especially no exam device bachelor supporting the alignment procedure.

Footstep past Steps :

Put N2-N5 on middle position and dont' touch on them on tracking alignment: they can't make TRF track happen, they make them perfect.
Adapt YTO Get-go, locate the zero span on 50Mhz-100Mhz far away from Sweep outset. Offset from 50Mhz. And so use CAL every bit Philharmonic Source, Adjust the YTO GAIN.
On band ane.seven-four.1, put yig signal and harmonics like the left photo. Utilise the "Preselector Peak"knob to checking the ring ends YTF response.
Adjust YTF OFFSET, make the depression cease of band one.seven-iv.ane response correctly.
Conform YTF Gain, brand the low terminate of band 1.7-4.1 response correctly.
Switch to other Bands, use YIG and "pinnacle" knob to check band ends YTF response.
The YTF Proceeds(high cease response) might need be fine tuned tiny little bit.
Checking the left end YTF response, If response almost good, ie: while "peak" knob stay middle. we should got maximum response level . IF so, go next band. (On band N4, could tolerate a little scrap more than than this, YTF Commencement N4 does could bring +- 10dB back.) If checking failure, go back to pace 2, put YTO OFFSET in some other position, beginning over.
OFFSET (Non the Nx which suggested past post-obit Tabular array)