Test Equipment Anonymous (TEA) group therapy thread

[factory]

Can anyone help Martin.M with parts for a Solartron 7075? The display is in poor condition and the front glass/perspex appears to have a delamination problem; https://www.vintage-radio.net/forum/showthread.php?t=224911

There are displays in the USA, but the cost would almost certainly exceed the value of the DVM.

David

[AVGresponding]

Can anyone help Martin.M with parts for a Solartron 7075? The display is in poor condition and the front glass/perspex appears to have a delamination problem; https://www.vintage-radio.net/forum/showthread.php?t=224911

There are displays in the USA, but the cost would almost certainly exceed the value of the DVM.

David

Was going to post there but seems my account is "Banned for inactivity". Fair enough, it has been a few years...   

It is definitely worth checking drive voltages, the difficulty being it needs a high impedance meter to do it without loading the circuit. That display filter is baked, but I can't see how the Panaplex's would do that; they run warm, but not hot.   

[factory]

Are you sure the account is actually banned, they do set inactive accounts to dormant now, something to do with hacked accounts & spammers, see here for how to reactivate* accounts; https://www.vintage-radio.net/forum/showthread.php?t=197553

*unlike hifiengine, where inactive accounts can't be recovered and they don't want new members, at least it gives me an excuse to avoid unwanted AV equipment repairs.

The display filter problem, I've had this with a HP 3440A, the glue between layers had gone white in places, looking something like a cataract. The layers were loosened & pried apart after a long soak in water, the glue is very smelly, I've haven't put that one back together, as the pieces are now banana shaped.

David

[squadchannel]

it looks an orange transparent plate, couldn't you make it out of acrylic?

[Robert763]

And here I am still asking again myself why I am not buying a NanoVNA in the next 10 minutes

In my case it's because it's difficult to find one that isn't a shitty Chinese low ball version. They have TERRIBLE supply chain and cloning issues and half the official resellers are shipping junk ones out. The fake ones used to fail cal but they now load in firmware which ignores that cal step  .

The ones direct off the TINDIE are still all legit, right...?  https://www.tindie.com/stores/hcxqsgroup/

Even for 2 bills... seems a helluva lot of bang/buck.  What's THIS? NanoVNA V2 Plus4 Pro $329...? 

Hardware revisions

You can check your hardware revision by selecting CONFIG > VERSION in the menu. Please see https://nanorfe.com/nanovna-versions.html

          Name                          Release Date   Remarks

• V2 Plus4 Pro (V2.4)     2022              4 inch display. Up to 90dB dynamic range. Adjustable bandwidth for measuring narrowband devices. 6x faster sweep (0.16s per sweep). Note: V2 Plus5 has been renamed to V2 Plus4 Pro.
• V2 Plus4 (V2.4)          2020/10          4 inch display. Up to 90dB dynamic range. 4x faster sweep (0.25s per sweep).
• V2 Plus (V2.3)            2020/10          2x faster sweep (0.5s per sweep). Noise improvements. PCB text still indicates "V2_2".
• V2.2                          2019               The earliest version of the V2 hardware. No longer sold. V2.2 has been discontinued since October 2020, and all V2.2 versions still on the market are clones. To ensure you get a supported hardware version, look for V2 Plus and Plus4 versions only.

https://nanorfe.com/nanovna-v2.html

https://nanorfe.com/images/V2Plus4_Manual_NC4BR.pdf

https://nanorfe.com/nanovna-v2-user-manual.html

https://groups.io/g/NanoVNAV2


mnem
*drops back & punts*

Very old post but a used NanoVNA V2 Plus4 popped up in my ebay searches. Now I have a number of VNAs - Agilent, Anritsu, R&S DG8SAQ up to 20GHz and including portable so don't need another. But this is TEA so I made made a low ball offer £50 and it was accepted. That's not a bad price even if it's a clone. I don't think it's a clone but we will see. I've allways been a bit cynical of these devices so we will see what it's like. At least this one is not supposed to be running on harmonics.

Robert.

[factory]

it looks an orange transparent plate, couldn't you make it out of acrylic?

Here is what the pieces look like, I would have posted this earlier, but hadn't taken a picture.
I'm not sure about the middle layer of film, it immediately curled up into an unusable state.
I've got a red filter somewhere from a HP counter, maybe see what it looks like.

Most HP kit seems to use a single piece of display filter material, but the older UK built ones often have several layers. The thickness is critical in these DVMs, but there are other problems still to fix first.

David

[AVGresponding]

Are you sure the account is actually banned, they do set inactive accounts to dormant now, something to do with hacked accounts & spammers, see here for how to reactivate* accounts; https://www.vintage-radio.net/forum/showthread.php?t=197553

*unlike hifiengine, where inactive accounts can't be recovered and they don't want new members, at least it gives me an excuse to avoid unwanted AV equipment repairs.

The display filter problem, I've had this with a HP 3440A, the glue between layers had gone white in places, looking something like a cataract. The layers were loosened & pried apart after a long soak in water, the glue is very smelly, I've haven't put that one back together, as the pieces are now banana shaped.

David

I quoted their exact wording. I messaged the Mods there and then to re-activate my account, let's see how it goes.

[m k]

Are multiple layers for thickness or transparency?

Colored Transparent Plastic Sheet 3/5/8mm
https://www.ebay.com/itm/353279193675

[factory]

Are multiple layers for thickness or transparency?

Colored Transparent Plastic Sheet 3/5/8mm
https://www.ebay.com/itm/353279193675

Really I need to find the HP opto-electronics databook I have here somewhere, to answer why it's multiple layers. The thickness does need to be right, as all the black plastic pieces around the display don't fit together properly, without the correct thickness filter in place.

It's a problem for when I've figured out why they only work with the -35V rail set low, note the overrange problem in the picture, the top one has the rail set to -31V by a previous owner, it also goes overrange with it set to -35V.

David

[Robert763]

Try Bitsavers, They have multiple copies of the opto catalog.
http://www.bitsavers.org/components/hp/

Robert.

[AVGresponding]

Are multiple layers for thickness or transparency?

Colored Transparent Plastic Sheet 3/5/8mm
https://www.ebay.com/itm/353279193675

I believe it is so that they can combine different attributes, such as tint, UV stability/blocking, scratch resistance etc

[Robert763]

Skanky HP 435A anyone 
www.ebay.co.uk/itm/136993192024?
Or a NOS (not) 4CX250B
https://www.ebay.co.uk/itm/136973136917?

[KungFuJosh]

Are multiple layers for thickness or transparency?

Colored Transparent Plastic Sheet 3/5/8mm
https://www.ebay.com/itm/353279193675

That's not a particularly good supply for plastic. I buy acrylic sheets for my lasers from jpplus.com, but if you need small quantity/cheaper or whatever, Amazon has a lot of options too.

[rdenney]

I'm not exactly sure why I bought it, except that I needed a better signal generator, but I have an HP 8904A arriving today. The first thing to think about is the PCB battery, assuming it works as claimed (otherwise, it's going back).

For those who might know: Does the power supply keep RAM alive when the unit is plugged in? When it is powered on? I'm wondering if I can keep RAM alive while replacing the battery if I don't turn it off. I realize that requires making sure the soldering iron is isolated from the unit, plus a decent bit of care.

I've already been reading about the memory-location hack for activating software options that may or may not already be activated.

Rick "liking the way it can stack channels to an output with amplitude and phase control for each channel" Denney

[AVGresponding]

I'm not exactly sure why I bought it, except that I needed a better signal generator, but I have an HP 8904A arriving today. The first thing to think about is the PCB battery, assuming it works as claimed (otherwise, it's going back).

For those who might know: Does the power supply keep RAM alive when the unit is plugged in? When it is powered on? I'm wondering if I can keep RAM alive while replacing the battery if I don't turn it off. I realize that requires making sure the soldering iron is isolated from the unit, plus a decent bit of care.

I've already been reading about the memory-location hack for activating software options that may or may not already be activated.

Rick "liking the way it can stack channels to an output with amplitude and phase control for each channel" Denney

Been trying to score one of these buggers for years

-sulks-

[srb1954]

For those who might know: Does the power supply keep RAM alive when the unit is plugged in? When it is powered on? I'm wondering if I can keep RAM alive while replacing the battery if I don't turn it off. I realize that requires making sure the soldering iron is isolated from the unit, plus a decent bit of care.

The service manual (HP 08904-90008) recommends that an external DC power supply be used to keep the RAM alive during battery replacement rather than keeping the instrument powered up. There is a certain amount of unit disassembly required to get access to replace the battery and doing so with the unit powered up would potentially risk damage to other parts of the circuitry.

[factory]

Be careful not to have a long length solder wire if working on the board in the chassis, as a few have lost cal data with some HP DMMs, when solder might have contacted the chassis while soldering, shorting the battery supply to the chassis.

I've used the remove & isolate the board (with other TE with battery backed RAM) and attached a temporary battery while removing & replacing the main battery. The same was done at work with train control equipment.

David

[factory]

Skanky HP 435A anyone 
www.ebay.co.uk/itm/136993192024?
Or a NOS (not) 4CX250B
https://www.ebay.co.uk/itm/136973136917?

Given the location & state of that power meter, I'm wondering if they pulled it out of the sea.
It must be unique in having a fHz power measurement ability too. 

If it was a more sensible price it could be a foot & panel meter casing donor, along with anything else not ruined by water. Not that I need any meter casings at the moment, since finding a few ex-HP panel meters at the Telford hamfest.

David

[Robert763]

My latest purchase, another VNA arrived today. It's the Nano VNA2 Plus 4 I took a punt on at £50. I was hoping it wasn't a fake or a clone. The fakes are the V1  hardware that uses harmonics and the clones use under specified chips. Both have poor noise and dynamic range. I knew it had early firmware which the fakes use. So I flashed it with the latest stable firmware  and it works and is low noise. Not played with it a lot but it seems to give sensible readings but is much easier to use in remote mode on a PC. I can see wh people like them but it's confirmed my feeling that a 2.8" one running harmonics would be a pita to use. So that is 5 VNAs but at least it's a LOT smaller than any of the 4 I got rid of last year.

[factory]

The VNA looks very anonymous from the front, no idea why?

I've bought another counter I don't need, a Macaroni TF2410 which is good for up to 120MHz if it still works, there is almost nothing online about these, except for a couple of magazine adverts from and the 1969/70 Marconi catalog. Not many extra plug-ins seem to have been made for this, one video amplifier module and two converter modules for 600MHz & 3.3GHz.

David

[Gertjan]

What is the best way to repair a HP knob like this?


https://www.miedema.dyndns.org/co/2025/IMG_4757_Broken_HP_knob-2000pix.jpg

I tried before using epoxy glue (Bison Combi snel/rapide). But that did not work too well. So I am curious what you are using...


This particular knob belongs to a HP 5300A + 5303A counter, made in 1971.
The counter came in my possession with an IC missing. At that time there was no service manual available.


https://www.miedema.dyndns.org/fmpics/Circuits_online/HP5303A/IMG_3565__HP_5303A_missing_IC-2000pix.jpg

This resulted in a nice topic: HP 5303A counter is missing unknown IC... with a lot of (tear down) photos. With some detective work the correct part number was found. A bit later, Dave of Artec found a 5303A manual, and scanned it for me. It confirmed that the found part number was correct.

But now I have to glue the knobs again....

regards, Gertjan.

[TERRA Operative]

I use Loctite 401 superglue which is very strong, but often the cracks appear because the plastic shrinks around the metal insert over time so you won't be able to completely close the gap to an invisible join.
Older Tektronix knobs have this problem too.

I found the only real fix to make it 'perfect' is to carefully peel the plastic section from the insert, then glue the plastic together and carefully ream it out just enough for the insert to be able to be reinstalled with no outward pressure on the plastic, then superglue it in place.

In your example, you may be able to remove the grubscrews and push the insert out the top of the knob.
Then apply glue and tape the cracks closed before carefully filing a little plastic out the middle then glueing the insert back in.

[squadchannel]

Dichloromethane, sold in Japan as an acrylic adhesive is a good choice.

I think a adhesive that can melt the material together is best.
considering availability, epoxy is the best choice.

[Robert763]

I second Dichloromethane. Sold to modellers in the UK as EMA plastic weld.
https://www.amazon.co.uk/Plastic-Cement-Stick-Plastics-Weald/dp/B00QQNNWIW
Works perfectly for these knobs. Apply to the inside (under skirt or top cap) I use a short length of tiny ptfe tube used to insulat component leads. Capillary action will draw the solvent into the crack.

Interestingly Dichloromethane is very hard to get in the UK other than this. It was banned from it's main use, paint stripping.

Robert.

[rdenney]

I had no luck repairing these knobs, for the reason stated above that they shrank and the metal core caused them to split.

Furthermore, removing the metal core is no mean feat. The set screws on my 339A were so tight that I couldn't make any headway using the good-quality .050 hex key that would fit them. Once they stripped, I was done. I ended up using a very small diamond burr on a Fordham tool to cut a slot in the metal collar to get it off the shaft. Then, I scrounged on ebay for replacement knobs (long-term patience required). These are expensively made knobs, but they probably couldn't have predicted shrinkage after 3-5 decades.

Rick "thought he might have to machine new knobs from scratch" Denney