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HP3325A Troubleshooting - 03325-66502 Rev. C

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No.Mad:
Hi all,

Recently I obtained HP3325A with Option 001. Initial examination revaled blown fuse, unit was not powering up. When fuse was replaced and cord connected fuse was blowing up, even when not powered (power button on Standby). Further investigation showed (after opening enclosure) that voltage was set at 120VAC. Uh-oh.

Fuse replaced (good I bought bulk), voltage set to correct one (240VAC), button pushed - nothing. I took a peek at PCB - no massive damage visible (pic.1)

That was the time for service manual - I followed steps for power section debug: disconnected W22 from A2P5 and grounded pin 10. Voltage rails for +15V and -15V showed +15.043V and -15.091V. Nice.
+5V rail was sitting on -0.6V. OK, problem sits with 5V regulator section. I checked Q1, Q2, Q3 and Q10. They seemed fine, no short or open circuit.

Then I noticed open circuit on track (pic.2). Fixed it with solder wick. I found almost invisible discolouration on substrate where big polarised caps are located. Desolered showed another problem: open circuit right next to vias. It was fixed with copper foil (in progress) and Milimax gold plated pin sockets (pic.3)

I will continue to debug it and report it here for your entertainment and my sanity  :-+

Here is the time for small cry for help:
1) Does anyone have schematic for Rev.C of 03325-66502? I spent las week searching for it in interwebs but no luck. I have Rev. F, but layout changes don't help xD
2) Could somebody help me identify Q1, Q2, Q3? Again, information is scarce, some posts indicate Q1 as TIP36. I would like to know beforehand part numbers so I could source spare parts.

Lorenzo_1:
I have an old Rev E board that stopped working. Q1 is marked 3-453 A8101 Logo not recognized but looks to be map of Texas with indecipherable letter/s inside.  Q2 is 4-800 8810 - looks like Motorola logo. Q3 is K 713 3-450 also Motorola.  These are original parts from look of solder/heat shrink.  Can’t help with Rev C schematic. My manual only has Rev F.

No.Mad:
Hi Lorenzo_1,

Thanks for reply. Indeed, Q2 and Q3 are Motorola brand, TO-220 package. That would indicate MJExxxx part number (M - Motorola, JE - power plastic case). I found MJE800, which could be Q2 one, but it's Darlington. That got me thinking, if it wouldn't be drawn on schematic as such, not as single transistor.

There is also MJ450, but that's totally different case: TO-3. The problem with these two is if naming was done in accordance to JIS standard or Motorola internal standard.

Q1 is Texas Instruments, so by their nomenclature (naming things for non-english crowd  ;) ), part number should be TIPxxx (Texas Instruments Power).

This guessing game is giving me a headache. I will ask senior engineers at workplace today as they probably worked with these transistors back in a day.

EDIT: Added photo of transistors mentioned, from left to right: Q1, Q3, and Q2

EDIT2: Corrected misidentifed Q2 and Q3 with help from wn1fju and Lorenzo_1

Lorenzo_1:
That's quite different from this set - photo attached. Perhaps this will be useful.

Lorenzo_1:
I think I misunderstood your post. I thought you were just looking to identify what ICs were fitted but seems you want to work out what they are and where to source them. Apologies for that.  Attached what data I could find from part numbers in manual for Rev F board and cross-references to NSN numbers. Q1 and Q2 references look as though they might be reliable. Q3 data looks unreliable. Slim pickings.

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