Author Topic: Test Equipment Anonymous (TEA) group therapy thread (Read 35581104 times)

mnementh · « **Reply #35750 on:** July 28, 2019, 04:31:59 am »

Uh oh. Looks like bean has too much blood in his caffeine circulatory system.

mnem
*toddles off to ded*

beanflying · « **Reply #35751 on:** July 28, 2019, 04:34:47 am »

Caffeine level has been corrected and am now flying high on Cork Adhesive

tautech · « **Reply #35752 on:** July 28, 2019, 04:40:54 am »

Quote from: beanflying on July 28, 2019, 04:34:47 am

Caffeine level has been corrected and am now flying high on Cork Adhesive

Didn't I warn you about just that yesterday ? Oh that's right it was sealant fumes so you're going for the sealant fumes tomorrow.

Quick, someone confiscate all bean's paper and plastic bags.

Specmaster · « **Reply #35753 on:** July 28, 2019, 08:34:52 am »

@bd139, where is this ham fest today, is it indoors or out, hope that its in or other wise another couple of days to dry your shoes out again.

bd139 · « **Reply #35754 on:** July 28, 2019, 08:51:10 am »

Outdoors. Sunny. On way home already. Was only there for 30 minutes. Left by the time it had opened

. Not a lot going but bagged a Keithley 177 of unknown condition for £3 and a Heathkit VTVM for a tenner.

Specmaster · « **Reply #35755 on:** July 28, 2019, 08:52:18 am »

Blagged your way in early again then

Dave likes that Keithley 177, has a reasonable spec for 4.5 digit DMM

bd139 · « **Reply #35756 on:** July 28, 2019, 09:23:23 am »

Early is the only way at these. People had already bagged some of the better stuff when I got there at 8:30. No sign of tggzzz which was good. No competition

... either that he was earlier and got all the good stuff

Just got home. Need to go do some shopping then I’ll see what crappy state this 177 is in inside.

Specmaster · « **Reply #35757 on:** July 28, 2019, 10:32:20 am »

Awaiting further updates, I shall have to enjoy TEA via your score this week I think, too much going on here in other things to get stuck back into my radios and hi-fi audio bits for a while.

bd139 · « **Reply #35758 on:** July 28, 2019, 11:04:00 am »

Well assuming I don't get three lemons that is

. Keep us posted on the radio and hi-fi bits - always interesting to see things working again and the struggles to get them there.

Honestly I probably won't go to that one again. It was pretty dead and most of the good stuff had been stolen before I even got there as sellers were setting up. There was no "entry gate" so you just ambled onto the site. Needless to say I got there at 08:25 and was gone at 08:55.

From the left to the right:

1. Comark 10mV/100mV voltage reference. Looked interesting. Worst case it's a nice 10 turn pot and an interesting enclosure for £2
2. Heathkit VTVM. Seems to have good switches and the meter face is intact. otherwise unknown. £10. Worst case it'll make back the initial investment on ebay.
3. Keithley 177 microvolt DMM. totally unknown. Suspiciously open on one side and soldering iron burn on the front. unknown but figured it was worth a punt at £3 whole!

Not sure where to start. Probably the keithley. Hopefully it's not a wreck inside. I fully expect something to be knackered on it.

med6753 · « **Reply #35759 on:** July 28, 2019, 11:34:49 am »

I've almost pulled the trigger on a 177 several times. I'll be interested to see the inside.

Too bad you're across the pond. I need a meter for the Heath VTVM sitting in the closest.

bd139 · « **Reply #35760 on:** July 28, 2019, 11:39:24 am »

Yeah it’s interesting inside. It has a whole computer on a daughter board this one. 6802 based. For GPIB.

The whole meter is unfortunately dead. I’ve just hooked it all up to a power supply to bring it up and the 5v line is not actually taking any power which is weird. Assume there’s an open somewhere.

VTVM is good. Battery leaked but didn’t do any damage! There is a manky capacitor or two and a selenium hand grenade in there though. I have all parts on hand to refurb that.

Specmaster · « **Reply #35761 on:** July 28, 2019, 12:08:09 pm »

Quote from: bd139 on July 28, 2019, 11:39:24 am

Yeah it’s interesting inside. It has a whole computer on a daughter board this one. 6802 based. For GPIB.

The whole meter is unfortunately dead. I’ve just hooked it all up to a power supply to bring it up and the 5v line is not actually taking any power which is weird. Assume there’s an open somewhere.

VTVM is good. Battery leaked but didn’t do any damage! There is a manky capacitor or two and a selenium hand grenade in there though. I have all parts on hand to refurb that.

The 177 looks like a nice meter, shame about it being dead but if anyone can get it working, its you, the biggest drawback with them is its a manual ranger. VTVM are always a good investment provided of course that the meter movement is good, so many of them have been blown O/C and there is no way to know without taking it apart and testing it. I've had my share of then duff.

bd139 · « **Reply #35762 on:** July 28, 2019, 01:52:36 pm »

Ok It was user error on my part. I was reading the wrong scale on the 6V output on my 6236B so it was only getting 1.4V out.

Now chasing a weird issue. It actually entirely works but only if you press down in the middle of the board. If you don't do that it reads wrong. I've tracked it down to an attenuator issue, possibly switching. The entire DMM after the attenuator is good. Signal tracing through the front end now...

Fingers crossed

Not sure the manual ranger is a bad thing TBH. I have more trouble with auto rangers! Display is amazing. It's huge and red LEDs. When it is working the thing is bang on cal though which is good

tggzzz · « **Reply #35763 on:** July 28, 2019, 02:06:27 pm »

Quote from: bd139 on July 28, 2019, 09:23:23 am

Early is the only way at these. People had already bagged some of the better stuff when I got there at 8:30. No sign of tggzzz which was good. No competition ... either that he was earlier and got all the good stuff

You probably missed some stuff from stallholders that arrived after I did.

I was in sell only mode. Sold some stuff that would otherwise have gone to the tip; that's what car boot sales are for. One person told me he thought my 2465 was a very reasonable price, another wanted to contact me later.

There were a lot of stalls; presumably stall holders thought it would be nice to be out.

There weren't many punters; presumably they wanted to be out elsewhere.

bd139 · « **Reply #35764 on:** July 28, 2019, 02:29:43 pm »

Yeah that sounds like a fair assertion. There was one stall which was selling hats and some boxes of crap not fit for even a boot sale. Why?!?

Still arguing with this 177. Slowly testing all switch combinations by hand to find errors $:=\$ ... I hope it’s a switch and not the PCB. That’ll be a bugger to trace out.

med6753 · « **Reply #35765 on:** July 28, 2019, 02:32:52 pm »

med6753 · « **Reply #35766 on:** July 28, 2019, 02:40:19 pm »

Gee....I wish all fixes were this easy. 7A26 plug-in acting out on channel 1. Of course 20mV and .2V ranges the worst (always seems to be the case).

Opened it up. Pulled the attenuator blocks. Careful application of Deoxit Gold G5 on visible leaf switches with a cotton swab. Short sprays on the back side. Insert and test. Perfect.

bd139 · « **Reply #35767 on:** July 28, 2019, 02:54:57 pm »

Lucky you. I fixed the attenuator problem. Shitty soldering probably from factory!

Now the chopper amp won’t Zero. It drifts off and stops responding. Grr.

Specmaster · « **Reply #35768 on:** July 28, 2019, 03:02:04 pm »

Oh, it was soldering then, I'd have suspected dirty contacts on that large bank of switches, non the less I expect you've probably already given them a dosing of switch cleaner

I'm currently watching the Amazon delivery man drive all around me and yet the screen still shows that he's 2 stops away

, waiting for a battery replacement kit for my sons iPhone 5 which has suddenly developed a huge bulge in the old battery and is pushing the screen out.

EDIT Delivery tracking screen just updated and it now says driver still has a few more deliveries to make on route to my address and the map shows him being 1/4 of a mile away, just how the hell has his route been worked out when he has driven past my house, just 2 roads away???

mnementh · « **Reply #35769 on:** July 28, 2019, 03:27:44 pm »

EEEEEEEEEEK!!! OUT OF COFFFEEE!!!

None to brew... no instant left... not even the cheap mexican shit.

mnem
*chewing on a used coffee filter*

tggzzz · « **Reply #35770 on:** July 28, 2019, 03:41:34 pm »

Quote from: bd139 on July 28, 2019, 02:29:43 pm

Yeah that sounds like a fair assertion. There was one stall which was selling hats and some boxes of crap not fit for even a boot sale. Why?!?

Still arguing with this 177. Slowly testing all switch combinations by hand to find errors $:=\$ ... I hope it’s a switch and not the PCB. That’ll be a bugger to trace out.

I didn't see the hats, but I did see such crap. It reminds me of 40 years ago when, in Brick Lane market, I saw old men with a card table with their wares: broken and incomplete watches. That was an eye-opening, and made me sad.

Consider the fault might be a solder joint; stresses could accumulate by the range switches and similar. Reflowing the solder would be quick and easy. Add deoxit thereafter.

bd139 · « **Reply #35771 on:** July 28, 2019, 04:04:46 pm »

I actually reflowed most of the bottom of the board and by coincidence unfortunately found the problem. It wasn't switches. It was worse. The main Caddock resistor network for the chopper amplifier is knackered. One of the legs is actually floating and the substrate under it has crumbled. Based on this it looks like it has been dropped at some point. Where it has broken means no repair unfortunately

So what do we do? Well we shove it in the cupboard and wait for another one to come up on ebay and buy that. Then we have a parts mule.

Anyway photos:

CPU board overlaying everything. 6802 CPU (6800 + SRAM + clock) and 6821 PIA plus some glue and an EPROM.

Gubbins underneath that:

The faulty Caddock resistor network is pictured in the middle of the unit in DIP package. I suspect it cracked as the middle of the board has very little support and flexes inside the chassis.

Specmaster · « **Reply #35772 on:** July 28, 2019, 04:39:23 pm »

Oh dear that's a bummer, still not a bad buy for £3, you'd be really unlucky to grab another with the same fault on it and then rightly so, you have a parts mule ready for it

Update on Amazon, parts arrived 90 minutes later, watched the driver on line drive all around me in complete circle before delivering, very weird route but I suspect some clever piece of software optimised his route for him

bd139 · « **Reply #35773 on:** July 28, 2019, 04:41:42 pm »

Yeah can’t moan for £3 at all. An afternoon of debugging fun is a pretty cheap exercise. I’d be annoyed if I’d spent £10 on it.

0culus · « **Reply #35774 on:** July 28, 2019, 04:50:23 pm »

Quote from: med6753 on July 28, 2019, 02:40:19 pm

Gee....I wish all fixes were this easy. 7A26 plug-in acting out on channel 1. Of course 20mV and .2V ranges the worst (always seems to be the case).

Opened it up. Pulled the attenuator blocks. Careful application of Deoxit Gold G5 on visible leaf switches with a cotton swab. Short sprays on the back side. Insert and test. Perfect.

How do you get them out without damaging those tiny wires with a ferrite bead that seems to connect the attenuator board(s) with the amplifier?

I suspect my 7A26 needs some deoxit as well.

[edit] I think you mean the metal covers on the top side? That say "caution delicate board".


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Author Topic: Test Equipment Anonymous (TEA) group therapy thread (Read 35581104 times)

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