HP 3561A

It might be a good idea to check. Google for "HP part number cross reference" and you'll find various lists. This one looks good:

Thanks, that might come in handy.

Looks like I have to RTFM even with what I got. This thing shut down with a slip of the probe and now appears to need to be reset. There doesn't seem to be any bad components but there is no drive to the power supply choppers . I am going to make surer of that later today I think. It is difficult to access anything to test so I'll do hat I usually do - stick a wire on it an d slide the card back in.

The way this thing is put together I can't even find the main transformer ! I pretty much know where it is but can't see hide nor hair of it.

This is another one where I look at how it is built and go "Why ?". They go t the choppers on a standup car, the transformer on the motherboard and the rectifiers on another standup card. The logical assumption is they intende d for service to be able to be performed on a modular level. All fine and g ood, but a part of me goes "Are you kidding ?".

I can't bitch. I couldn't design the thing at all. But I can go "Huh ?".

Anyway, thanks. And if you catch wind of any "reset" routine for HP stuff l et me know. I am going to triple check that there are no blown components, like fuzibes n shit.

With everything on sub-boards the first suspects are the card edge connectors. Take a close look at the sockets to see if the plastic is breaking down and the body of the edge connector socket is spreading out at the middle.

Of course clean the PCB edge connectors, etc...

John :-#)#

There is a lot of info on the 3561A on the Yahoo HP-Agilent_equipment group including a PSU schematic in the files section. You might want to sign up with them. A quick read through and there's a lot about flyback burnup but I'm not familiar with the unit. I can send the PSU schematic if your email address is valid, size 3MB

I couldn't find anything on a "reset" procedure. Maybe try the operating manual instead of the service manual:

Incidentally, the 7912 regulator is short circuit protected and should easily recover from a short to ground. It's probably something else that blew. I would guess(tm) a fuse.

Not this time. I understand what you are saying but in this case that isn't it. I did look at the connectors actually and they are that blue plastic. I KNOW that blue plastic is not stronger or better due to its color but I t hink they have a tendency to only use that color for really good plastic. T haat is really only an impression I got, but it is based on real world obse rvations.

At any rate, I looked at them pretty good and they are not splitting. And t he fact that the new fault came after I sliped with the probe, that ain't i t, at least right now.

Been wiping the edge down with LPS2 which is really fantastic. Never ever b ecomes conductive and really does the job better than I thought it should. Someone showed it to me about 35+ years ago and I have been sold ever since . I have never ever used Deoxit, I simply have no need for it.

th a slip of the probe and now appears to need to be reset. There doesn't s eem to be any bad components but there is no drive to the power supply chop pers. I am going to make surer of that later today I think. It is difficult to access anything to test so I'll do hat I usually do - stick a wire on i t and slide the card back in.

er ! I pretty much know where it is but can't see hide nor hair of it.

y got the choppers on a standup car, the transformer on the motherboard and the rectifiers on another standup card. The logical assumption is they int ended for service to be able to be performed on a modular level. All fine a nd good, but a part of me goes "Are you kidding ?".

ff let me know. I am going to triple check that there are no blown componen ts, like fuzibes n shit.

I would GREATLY appreciate the PSU print. It is JURB six zero zero six at g mail dot com. (numbers are numerals) That would be great so I can see what I have to do to get at least back to where I started. I am starting to thin k it needs some sort of software reset but that might not be true. No way t o tell.

emailed it to you, let me know if you don't receive.

I got it. Thanks.

Next, once it is up and running again I got to tackle that vertical circuit . I noticed alot of hash on the output of a 12 volt regulator, not sure if that is the cause of the problem. I don't even know what supplies it runs o ff of. I did see the vertical drive waveform but I did not note its amplitu de. It could have been ten volts or fifty. I wasn't looking for amplitude, I was looking for that little glitch in it. It was there. It indicates an u pset for the feedback loop, because of the inability of the circuit to impr ess the voltage on the (yoke) coil to result in a sawtooth current.

We will be getting back to that soon. I will check everything.

If you want to spend some beans the manual is here for download

There's a guy here with one, recent blog, maybe you can help each other out.

And if not, I posted it here:

Cheers

Phil Hobbs

has both the service and the operating maunuals. Keysight it the latest name change for HP test equipment.

They actually do not have volume two of the service manual. We just got it, ON PAPER. Quite illustrating. The unit is up and running again with the replacement of a 7912. Apparently my shenanegins made leaky the device inside there.

I am back to the vertical sweep problem now. I'll probably get back into it next weekend. Give it some thought in the meantime.

So now, with the coveted volume two in hand, I see they call the vertical horizontal and the horizontal vertical. The print does depict what I had been reverse engineering. I think on page 7-249.

The vertical circuit does not use a boost cap, switcher or diodes as far as I can tell. Simple transconductance (current) amp run off a ramp.

It has vertical foldover, that is usually caused by not enough voltage peak on retrace. In an old TV it would almost certainly be a bad lytic. But this does not use that type of circuit.

Actually it might be a bit of fun doing this. I have to put leads on the board to test it because it is shielded. What's more, the way it is I have to use insulated wire. Alot of times I have just used solder, but that won't work with this.

Well well well, they did not misname them, the raster lines are vertical. So I finds a cap off the flyback causing the compression.

Now the phasing is off. I looks like there is a foldover on the bottom but there isn't. Turning up the brightness to the point of seeing the whole raster it is fine.

How the hell do these posts get on other websites ?

They're just like Google Groups--parasitic but sometimes useful. electronicsrelated.com is the same sort of thing.

Cheers

Phil Hobbs