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Fool for the 8656A Sig Gen
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jrharley:
HP8656A update here ya'll,

I've got the existing components in the attenuator assembly re-installed with new "grommets". Cleaned the traces, and bolted everything back down. We'll see if things are back in place correctly, it was a little surprising how easily the assembly went back together. I still have the gaping maw of the missing section to deal with, but its siblings are at least now; all ready for a power up.

As for what to do about the missing parts, I've reconciled the available options for my situation I think. Tough choices no matter what. Balancing time, money and feasibility seemed to point to a parts unit as the best option overall. It should arrive Monday. As an interesting aside, I naturally did what anyone would do and said to myself, "how much is this thing worth versus just getting a modern one?" Pokin' around the web quickly affirmed the decision to spend just a little bit on this beast. Using bandwidth alone as a comparative criteria, even a modern unit from Asia is north of a $1000. I'll take the 8656's interface any day for that money.

Meanwhile, still rubbin' on the Delco......... :) I'll post up when the A9 board is re-populated and we're ready to see if we've got any "clackin'" going on.

Later,

JRH
jrharley:
8656A update -

Well........ in a nutshell, everything has changed with the arrival of the parts unit. Much to my surprise, the parts unit appears to be functional. Since it doesn't make sense to destroy a functioning attenuator to fix a broken one, we are re-thinking everything at this point. It will be a little bit before I can figure out how to proceed, but in any case, the strategy is now to make the best unit I can out of the two units I have. I'll report back with progress when it's informative. Appreciate the interest in this project and all the helpful feedback!

Later,

JRH
Tony_G:
It's always the way, you go from less than one working unit to more than 1 working unit :-DD

I would probably approach this by addressing anything majorly wrong with the working unit - By that I mean, are any chassis rails bent, how is the N type on the front, Fans not working, etc - Swapping good parts from the non-functional unit into the working one.

Then I'd address the cosmetic issues like case panels, front panels, buttons (if there are labels, wear, etc), and so on. The goal is to get the best looking and working unit and then you can either keep the parts mule as a backup or sell it (and clearly state what is missing, damaged, etc).

Personally, I tend to keep the parts mules because this stuff is old, and having it go tango uniform is not unexpected - When I end up with 2+ parts mules then consolidate and sell off or recycle so I have 1 parts mule.

Look forward to hearing what you end up doing - And the follow-on test/calibration cycle...

TonyG
jrharley:
Of course Tony_G, all of that makes perfect sense in light of the new situation. It’s always very interesting to observe the differences between units, with each one having a different story to tell. Here’s what I’ve observed so far, with “unit A” being the original unit, and “unit B” being the new unit:

The two case designs are different, with unit B more closely corresponding to the ARTEK manual drawings. Unit A has better component cosmetics all around, so combining them is going to improve things.

Unit A’s filter caps are in pretty good shape, unit B’s, not so much. They seem to have seen some heat in the past, though they don’t seem to run hot with a quick test. The listed 13,000 uF cap in B has been replaced with a 24,000 uF unit, which doesn’t test great, …ok, but not great. My current thinking is to just swap cap sets.

The F1 fuse in unit B appears to be original, but is 5A @ 125V, not the listed 4A.

I’m sure that the attenuator grommets in unit B are wearing out, as they do, but I’m going to let that Dog sleep until I can’t.

I will be swapping out the faceplate/keyboard assembly from unit A onto unit B. along with feet and handle hardware.

Quick aside, and maybe I should post this on the HP forum, but does anyone know what the “warm gray” color numbers are for this era of HP gear? They used it a lot back in the day (80’s) and I assume it comes from the Government Standard 595 colors, but don’t know. I’d like to source some touch up paint in that color. The “Beige” color of the same era might also come in handy.

Anyway, that’s just a little “color” on what’s going on. Always appreciate any feedback.

Later,
JRH
Tony_G:
There are a number of posts on the HPAK group about the grey color - Worth just doing a search.

TonyG
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