Advantest R5373 microwave counter

[Antonio90]

Hello. I have a (probably not fully working) R5373 frequency counter.
According to the user manual, the low frequency input is a fused, screw-on, BNC connector. The unit, however, has the BNC (and fuse) missing.
Could anyone tell me which connector type is it? (See attached).
It measures 13mm external diameter ~1/2 inch, and ~9.5mm internal, with the threads on the outer diameter, and some kind of stop pin on the inside.
EDIT: Also, do you know whether a service manual is available or not?
EDIT2: corrected a wrong measurement. Maybe something similar to a 16-7 DIN connector? With the slit in the inner ring.
Attached is the operating manual's page in which the fuse replacement procedure is described.
Thanks!

[pico61]

Below are two photos of the BNC connector of my R5372P frequency meter. I believe it is impossible to find because it was specially built.
I have had the frequency meter for about 20 years and have never been able to find the service manual.
Greetings, Pietro

[Antonio90]

Thank you very much Pietro, I really appreciate the answer.
Do you know if, at least the external threads, match any common RF connector?
If that is the case, I might be able to connect a coax or adapter in a somewhat hacky way, and insert the fuse later in the line.

Otherwise I guess I will just scrap it or sell it for parts.

Regards,
Antonio.

[pico61]

Hi Antonio, the thread, as you will also notice, should be a Whitworth 26G with a half inch diameter. I don't think there is a connector with this thread.
The closest, the TNC connector, has a slightly smaller diameter. Without taking into account the different threading.
However, why scrap the frequency counter? Wouldn't it be easier to replace Advantest's proprietary connector with a BNC?
I think that the fuse is also partially useful and you can easily do without it, having a little caution when connecting any source to the frequency meter...
Greetings, Pietro

[Antonio90]

Hi Antonio, the thread, as you will also notice, should be a Whitworth 26G with a half inch diameter. I don't think there is a connector with this thread.
The closest, the TNC connector, has a slightly smaller diameter. Without taking into account the different threading.
However, why scrap the frequency counter? Wouldn't it be easier to replace Advantest's proprietary connector with a BNC?
I think that the fuse is also partially useful and you can easily do without it, having a little caution when connecting any source to the frequency meter...
Greetings, Pietro

You are right. I went full tunnel vision here.
I will open it and see if the connector change is feasible for my skill-level. Also, I don't think there is any teardown of this instrument yet on EEVBLOG, so it would be a good opportunity.

Thank you very much for the help.

[Antonio90]

@Pico61, have you taken the RF block out at some point?
The user manual is not clear about this, and talks about removing the side panel, which is structural and has the transformer, oven and another unknown to me piece of hardware attached.

I have access to two screws securing it, but there seems to be two more closer to the front panel.

It is such a pity advantest gear doesn't have service manuals. The build quality of these devices is quite impressive.

Edit: photos added. The RF block from the bottom side of the instrument, and a general top view. The side panel, which is a single, machined piece, holds the RF block (leftmost), the oven, and the unknown device under it, and the transformer. When the manual states to remove the side panel, I don't think it can be referring to that.

[Antonio90]

A few more photos attached.

The side pannel, with the two RF-block screws around the left-middle part, the NiCd batteries leaking (first time I see this shape of battery), a seemingly bodged axial cap in place of two radial ones (there is another axial on the back of the PSU), and the unknown device I was talking about in the previous post.