[Test-Equipment] HP 8640B Fuse Question

[Barry]

I'm now the owner of another HP 8640B.  It appears to be a very early model (serial number 13xxxx making it a 1973 model).

The -5V and Fan Driver board (A18) is not working and I've discovered the on-board fuse is blown.  It is labeled "2A" on the board and is designated as a "2A 125V SLO-BLO" (GMW 2A); however, the specs I've seen for a GM 2A show this to be a fast-acting fuse.

What's odd is the board has a "GMW 1-1/2" in it and it appears this is from the factory.  The fuse is soldered in and there's no indication of desoldering and resoldering.

I'm wondering if I can jumper in an ordinary 2A fuse to see if the board will work again.  The fuse points are conveniently brought up to test points at the top of the board so this should be pretty easy to do.  If the fuse holds, then I can replace the GMW with another on-board fuse but I hate to waste any of these as they're pretty expensive.

I'm wondering, also, if the reason the existing fuse could be because the wrong rating fuse was put in at the factory and the circuit perhaps draws at or perhaps slightly above 1.5A causing the fuse to blow prematurely.

Anyone seen anything like this before in an 8640B?

As a side note, I was pleasantly surprised to see that the gears are in fine shape.  I expected that at that age, they would be in very poor condition but perhaps the early models used a different composition?  Also, I'm not seeing the little finger-style switches and, instead, just ordinary rotary switches.  Did the early models have a different switching system from the later ones?

Thanks,
Barry - N4BUQ