Author Topic: HP 3561A Dynamic Signal Analyzer repair  (Read 11700 times)

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Offline slbender

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Re: HP 3561A Dynamic Signal Analyzer repair
« Reply #50 on: June 19, 2018, 04:00:08 pm »
Well, so far Q200 and Q201 on the analog video board, did turn out to be a TO-66 single diffused 4 Amp / 60 Volt complementary pair.  They were fairly well matched in terms of hfe, at 99 for the NPN and 67 for the PNP part, at low currents.  Both of these older parts seemed to be working and measured OK when off the board.  I'll add some MX-4 compound on them when they get resoldered.  Maybe I should check the smaller transistors too, as something is making the video garbled.  The power resistors seem fine, no burn or overheat spots on the board.  I pulled a few of the 10uF. 'Lytic caps but they too seemed healthy, and above their rated values.

While the scan of the Service Manual had put the polarities of Q200 and Q201 in doubt, since I could not see clearly which way the arrows were pointing, at this point, they do not seem to be the problem.  The "better than" 8 Amp / 150 volt pair of TO-220 parts, while they would have fit nicely, even onto the original heatsinks, the replacements, it seems were not needed.  So its back to square one - again.

Any suggestions?

-Steven
« Last Edit: June 19, 2018, 11:39:08 pm by slbender »
 

Offline Cubdriver

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Re: HP 3561A Dynamic Signal Analyzer repair
« Reply #51 on: June 19, 2018, 05:13:27 pm »
Unfortunately I don't currently have access to the analyzer or manual, but will try to offer further suggestions in a few days.

In the meantime, perhaps take a look at any caps on the power supply rails on that particular board?  I don't know if there are any dipped tantalums on there, but they are infamous for failing shorted (and sometimes imitating matches when they do; yours if present obviously haven't or you'd know it by now). 

-Pat
If it jams, force it.  If it breaks, you needed a new one anyway...
 

Offline slbender

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Re: HP 3561A Dynamic Signal Analyzer repair
« Reply #52 on: June 22, 2018, 10:45:25 pm »
I've hit so many brick walls with this unit you'd think I'd give up....  Nope, gluten for punishment, I bought a second HP-3561a which has different problems, and it is also a later unit.  DUT #2 is about several thousands newer according to the serial number, and features the CMOS memory board (A42) Option 1 instead of the Bubble Memory board (A65) Option 1.

The video comes up nicely, but it comes up with a 1.2.02 error, and at the default screen you don't see the random noise spectrum, so it has either a noise source failure or an FFT failure of some sort.

Switching the 'known working' Analog Display board into the first set - again, no change, still garbled video.  SO, that rules out that board as the source of the video problem.  Once I get some sleep, I'll try switching some of the set #1 boards into DUT #2 to see where and when that random noise on the default screen returns - if it does.

I'll also try to post pictures of the A42 Circuit Board.

-Steven
« Last Edit: June 23, 2018, 02:43:16 am by slbender »
 

Offline slbender

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Re: HP 3561A Dynamic Signal Analyzer repair
« Reply #53 on: June 24, 2018, 10:23:07 pm »
Sunday morning- lacking in luck!  I switched in three boards into unit #2 and I got even more errors.... :-

Now with the 03561-66510 Front end, 03651-66515 (Analog to Digital??) board and 03561-66520 FFT boards switched - it seems functionality is even worse...  Now DMA error detected, Front End error, 1.1.00 and now the Start, Auto, Half and Over LEDs are flashing continuously.

OK so that did not help, I will again sleep on this, I suspect mismatched levels, but still no noise displayed on the default screen, guess I was hoping for too much, the boards probably are individually matched to each other, still I thought I'd try and give it a shot...

-Steven
 


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