Products > Test Equipment

Vintage HP 3721A Correlator : Repair, Restoration and Enhancement

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dazz1:
Hi
I have just purchased a vintage HP 3721A Correlator.  An item of test equipment far more interesting and capable than its name suggests.
This one is in good condition except for some broken knobs and a developing fault, likely on the power supply for the CRT beam controls.
It is original except for an ugly cooling fan mod.

This topic is a continuation of this one.  https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/136750/

KE5FX:
Fascinating piece of hardware.  I had to look that one up, it was a bit before my time.  Are you going to pair it with a 3720A and 3722A?

dazz1:

--- Quote from: KE5FX on September 26, 2024, 01:56:26 am ---Fascinating piece of hardware.  I had to look that one up, it was a bit before my time.  Are you going to pair it with a 3720A and 3722A?

--- End quote ---

Sadly there is practically zero chance of me finding or owning a HP 3720A or HP 3722A.

Kean:
The asset sticker seems like a warning...  >:D

dazz1:
Hi
This thing was made to be maintained.   The shelf opens out for access both sides and inside.  The connections are made by plugs so the shelf can be removed in a few minutes.  Very nice.  You could call it high quality or over-engineering.  Still nice.

The glass device is 1970's bit data storage.  I am not sure how many bits it can store.

I am about 1/3rd of the way through the functional tests.  All the front panel controls and indicators work. 
The CRT trace is almost perfectly steady in vertical. 
The clock output on the rear panel is not working as it should do.  This may be the first fault.  That is why I opened up the unit.

No sign of any rework inside. 
The power supply transistors heat up the rear panel and may be why the fan was installed.

I have fitted a couple of knobs as temporary until I get proper knobs.

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