HP Agilent 3561A Dynamic Signal Analyzer. Finally I managed to secure this interesting device. But unfortunately, shit happens!

The unit came ok from outer physical appearance, but inside, seemed like someone has smacked this unit down. I saw some cracks from the outside (on the front cover and back feet/holder). But inside, things went worst.

As we can see from outer appearance, the unit seems ok. No crack or any major scratches. Buttons are intact and responsive. Sticky a bit, but should not be any problem. I do hope the CRT is fine, but can’t say anything much until I can power on this unit.


The manual books are there. This unit’s age itself is over 30 years…


Below is picture of inside of the unit. This is simply like old computer. It has several slots and daughter cards plugged to it. So it’s like module and each will have it’s own function.

I have to admit the design is excellent and well planned. No wonder, this HP Agilent 3561A was priced around US$ 10.000 at that time! At present time, new version of such equipment is easily priced at 5 digits in US$ or EUR.

Each module also marked with sequenced number and also color coded. You can see red, orange, yellow, green, and blue. At the other side, all are black. This to make sure you will not plug the module in the wrong direction.


The component used also on the top of the line. Sprague capacitor used dominantly inside this equipment. I also can see some high precision Dale resistor inside. The PCB also very high quality with thick copper. I don’t see any degradation considering this equipment has been there for more than 30 years.


All PCBs are easily plugged or removed from the socket. On the power supply section below. the construction is a bit complicated with several cables connecting different board. Need to be very careful to make sure no high voltage still present there. We are dealing with CRT module here, which similar with tube application (means high voltage). Extra caution is mandatory.


Some test points made by high quality copper. Some premium high precision Dale resistor. PCB is quite thick and the soldering quality is awesome. No crack or any other deterioration seen so far.


As the display is still using CRT technology, then this kind of adjustment definitely exist near the back of the CRT tube. Again, the aluminum used for the chassis frame also very high quality one.

7_CRT Adjustment

The side board of the unit. Combination of different brand, manufacturer, and country of origin. Most – if not all – are the top quality parts that anyone can find in its era.


Below is the picture of 5 main modules. There are some more, but I don’t put them below. In sequence from top to bottom, they are 03561-66520, 03561-66530, 03561-66560, 03561-66540, and 03561-66550.


Old timer computer freak might know that below logo is AMD (Advanced Micro Devices). See the date code? 1981 or 34 years old!


Color coded modules. This colorful plastic is used to push the module out from the socket.


Each board will have its own part number. This one is 03561-66520. The prefix 03561 means the product model (3561A), while the 66520 means the module with specific function.


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