Products > Test Equipment
Fool for the 8656A Sig Gen
jrharley:
Thanks Tony_G,
I will stay the course.
On a side note, it occurred to me that I might want to see if there was any output from the unit when powered up. Just curiosity.
I don't currently have any connectors or adapters that will connect to the RF output on this guy. I know I can rig something up, but it got me looking into the connector a little more closely. What is this thing?
Any clues as to what this connector is, would be appreciated. It's larger than the SMA ham radio stuff I see. The parts list isn't a lot of help as to what this thing is called. I gotta' believe it's at least available, and I'm just clueless. This connector to BNC female would be sweet.
Updates forthcoming.......
JRH
Swainster:
Hi,
You need a 'N' Male to BNC Female connector to convert the output to BNC. Or better to switch to type N connectors on your cables, and just use N to BNC cables for BNC stuff. If you start working microwave band stuff (300MHz upwards) then N connectors will be pretty much standard for test equipment.
I've been following along with interest as I have a couple of 8656Bs, one of which is working but the other is incomplete. Someone has asked about buying the working one so my interest in getting the non-working one up and running is much higher (it's missing the power transformer and GPIB connector, but according to the previous owner everything else is OK).
Tony_G:
--- Quote from: Swainster on January 06, 2023, 03:45:13 am ---...but according to the previous owner everything else is OK...
--- End quote ---
Heard that before :) Much liked "Pulled from a working environment"...
That said, I think the unit should work without the GPIB board (for clarity I mean A13 and not the main processor board where all the actual GPIB smarts are but you'd need to check the schematic/service sheet) but I'm actually not sure - it certainly won't work without the power supply.
As for the adapters - These probably suck in terms of RF quality but in terms of getting you something that you can look at they should work OKish:
https://smile.amazon.com/Adapter-Connector-Extension-Antennas-Female/dp/B091C5W4HM/
As Swainster said, the output on this unit is a N-Type connector - The ones on HP gear are typically good up to 18GHz (in "as new" condition). The actual connector spec is only good to 12GHz I think from memory but HP did some higher specs up to 26.5GHz but this unit should only have a standard 18GHz one.
There is a whole bunch of information on how to confirm that the connector is in spec but seeing that the 8656A only goes up to 1GHz you're probably fine with whatever the connector is right now.
TonyG
jrharley:
Thanks guys, BIG time saver! Appreciate it.
I'll source some cheap versions to aid in my testing and order the $30 versions for when I'm testing microwave antennas for a fighter jet. ;) Seriously though guys, I really appreciate this dialogue, it gives me hope that I just might be able to get this piece of equipment up and running again.
Thanks for weighing in swainster! You're in a good place with 8656B's from what I understand, they've got a better rep than the A version. I'm glad you're following the conversation.
Tony-G - Thanks for the info and insight. It seems there's quite a science to RF connectors!
I've had my eye on a suspicious Triac in the power rail that I want to test. (Q3 on the A10 board). Think I'll pull it this weekend and see what I can learn. Continuity testing of it, in circuit. has yielded confusing results.
The Brute Force tech team stumbles on.............
JRH
jrharley:
8656A update here:
OK, so I pulled the "TRIAC", Q3 from the A10 board, which is more precisely an SCR, and proceeded to beat on it for a bit. Just for grins, I powered the unit up without the device in circuit. No change. Although I don't fully understand how the thing would act in the circuit, it's part of a "Crowbar" arrangement intended to protect the attenuator I think, so it's not entirely surprising that it's condition, in or out of circuit, doesn't change anything here.
As for it's condition, I'm basically getting "open lead" no matter how I measure it. I tried turning it on with a 1.5V AA battery thru a 7ohm resistor, but it didn't seem to stick. No resistance could be measured across the legs after pushing a little current through it. But it's also possible that I've pushed a bit too much current through it. The battery was putting out about 200 mA, if my poorly timed measurement of the battery set up was correct. In a head slapping episode of realization, I decided to check the data sheet and it says the maximum triggering current for the device is 15mA. DOH! I may have screwed the pooch here. Hard for this Bodger to know at this point. The SCR, aka Thyristor, is an RCA 2N3528. The TO-8 package for any substitute for this device seems to be hard to find, based on a brief search, but maybe you folks know of a good substitute. There are other form factors that could sub available, but that would be tacky. Who knows though, the thing could be fine.
In any event, I am pretty certain at this point that it's not a factor in the fault I'm chasing. I put it back in.
Meanwhile, the weekend has revealed that my B&K 1430 3 channel power amp, seems to have lost a channel. Since I've got to have tunes, I need to detour for a while to try and get that guy up and running again.
Appreciate the interest in my efforts folks, and any feedback is welcomed.
JRH
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