Test Equipment Anonymous (TEA) group therapy thread

[URI]

Repair of my HP 6114A was stalled because of my work eating up all my free time and is still stalled because the soldering iron stays cold with these temperatures.

Oh, what was the deal with it? I had forgotten you were working on one. I have one good one (bought it already fixed up) that stays on the bench and a mysterious one that I haven't checked out yet (no longer remember what its story was).

Look here:
https://www.eevblog.com/forum/repair/hp-6114a-repair-(fault-regulation-seems-to-work-voltage-low-output-ripple)/msg1461808/#msg1461808

Mainly dead filter elkos but after I got the service manual from ArtekMedia I decided to do the changes/corrections described in there also. 

A very nice Power supply. I like it very much.

I'm looking for a second unit - e.g in case I want to power circuits that need a positive and a negative rail..  TEA, you know? 

[bitseeker]

You discovered a lot in your 6114A. Thanks for posting the schematic correction. I added that to my 6114 folder.

Yeah, having a second one is a good thing, hence the broken second one I have. Eventually, they'll both be operational.

[tggzzz]

I don't kick boat anchors.  I have, however, dropped numerous heavy items on bare feet including a Dell poweredge server and an APC smartUPS 1500 with batteries of course.  I went a stretch of just over a year without toenails on both big toes.  As soon as one grew completely in, dropped more heavy crap to lose the nail again. "Holy F**k, that hurts!" was fairly common.

My normal outdoor shoes are £25 "Earthworks" trainers with steel toecaps. I like them because, providing they fit in the shop, the end will never start to rub my toes.

Plus, when she was a teenager, I could stand on my daughter's toes and not worry when she stood on mine

[Brumby]

My schlumping around footwear are the Aldi steel cap workboots, size 11.  Don't know what it is - but they are so close to a perfect fit out of the box, breaking in a new pair takes about an hour.

The steel caps have been handy a couple of times.

[bd139]

gah. woke up this morning and the neigbour’s old rotten tree has fallen on my antenna and pulled it down due to the crazy wind last night 

I was planning to fix the D83 HT but looks like that is off now. Grr.

As for shoes, wonky ankles here so have worn Berghaus GTX for the last 15 years (not the same pair). They’re expensive at £110 a pair but if you keep your eyes peeled you can pick some for £30. I tend to buy a couple of pairs then and stockpile them.

[Specmaster]

gah. woke up this morning and the neigbour’s old rotten tree has fallen on my antenna and pulled it down due to the crazy wind last night 

I was planning to fix the D83 HT but looks like that is off now. Grr.

As for shoes, wonky ankles here so have worn Berghaus GTX for the last 15 years (not the same pair). They’re expensive at £110 a pair but if you keep your eyes peeled you can pick some for £30. I tend to buy a couple of pairs then and stockpile them.

Thats a bummer but with winds of upto 45 mph today, you might as well just make the antenna safe for now and then get back on the D83.
Did it do much damage or just pulled it down?

[bd139]

Well it snapped the pole unfortunately. It’s a fishing pole so no big deal but another £20 down the drain. Have taken it down for now.

D83 it is this evening when my youngest has gone to bed as she is in crazy mode today.

[mnementh]

When I was erecting the antenna for grand-dad's old Yaesu, I discovered that my local homeowner hell stocked 1" & 3/4" EMT in 20 foot lengths. Slipped the 3/4" inside the 1" about 3' deep, pop-riveted them together, then used strap-and-bracket chimney mounts (2 full kits for rigidity) to put the entire antenna about 33 feet above the roof. This was up north; we often had lots of snow load but not sure if we had winds that high.


mnem
*Back into the pit*

[bd139]

I’m thinking about something a little more sturdy now so that would be good. The fecking problem is that it has to be temporary or the neighbours get uppity.

Knee deep of bits of D83. Considering the space they had available inside the chassis they basically said hahaha to anyone doing maintence. 45 mins in and I still haven’t got the HT board out.

[med6753]

This is local to me. Like in the same town. Thinking about it. I'd jump on it right away if it were vacuum tube. It isn't...it's one of the early transistor units. I'm sure regardless it will need a complete re-cap.

[bd139]

I’d buy that. Early transistor stuff is cool.

D83 lives. First power up and we have HT with no whining or dropping out. Unfortunately I have lost intensity control but I suspect that is HT setup. Photos to come...

[bd139]

Well bugger me one of the HT resistors just exploded. Fucks sake this is a demon scope.

Will order some more....

[Specmaster]

Good, congratulations on bringing it back to life again, never any doubt really was there once you get to work on anything.

[Specmaster]

Oh oer I spoke too soon did I I still have every confidence in you reviving it successfully 

[tautech]

Well bugger me one of the HT resistors just exploded. Fucks sake this is a demon scope.

Will order some more....

The existing ones or new you'd installed ?

Edit
Of the images you showed of it earlier it looked like the originals had already been changed from carbon comp to metal film and 1 watters. I used 2W metal film in the D83 I had.
Carbon comp has the advantage they tend to drift open so as not to create fireworks.

[Specmaster]

There are some real muppets on Evilbay, there's a scope I'm interested in but although the seller claims it powers up and shows 2 beams, he also claims that he doesn't understand how to use it, fair enough, but he does not show any photos of it powered. I asked to see some photos of it powered and he has replied that he has stated that he does not know how to use it so he can't post any photos of it working     

[med6753]

Well bugger me one of the HT resistors just exploded. Fucks sake this is a demon scope.

Will order some more....

The existing ones or new you'd installed ?

Edit
Of the images you showed of it earlier it looked like the originals had already been changed from carbon comp to metal film and 1 watters. I used 2W metal film in the D83 I had.
Carbon comp has the advantage they tend to drift open so as not to create fireworks.

Don't metal film resistors tend to have much lower voltage ratings? Such as typical 375V max? As opposed to carbon comp which have much higher voltage ratings.

[bd139]

Oh oer I spoke too soon did I I still have every confidence in you reviving it successfully 

Might have to leave it a couple of weeks for me to cool down 

Well bugger me one of the HT resistors just exploded. Fucks sake this is a demon scope.

Will order some more....

The existing ones or new you'd installed ?

Edit
Of the images you showed of it earlier it looked like the originals had already been changed from carbon comp to metal film and 1 watters. I used 2W metal film in the D83 I had.
Carbon comp has the advantage they tend to drift open so as not to create fireworks.

I didn't actually bother replacing the ones in there as the HV ones were all nice metal film ones and the problem was clearly with the capacitors rather than the resistors. It was one of those. It powered up fine for a few seconds then blew a hole in the encapsulation. Grr. One resistor didn't like the suddenly properly working HT supply!

At least the HT wasn't arcing over. It was dead silent and running nicely. The tube in it is super duper bright as well which is good. Could use it as a projector.

I will order some resistors when I fancy approaching this one again. And some diodes as these ones are mega-fragile after 40 years. I lost about 5mm of leg off each one unravelling them

For now, some pictures:

Shitty old caps removed. The Efco ones were totally knackered. One of them had bulged at one end as you can see:



New caps installed. I had to remove the HT transformer to get the board out. It usually sits in front of this. No 22n caps around so I just bought twice as many 10n ones and wound them together.



Win. Ish. Before kaboom that is.



And screw this I'm going to bed as it's half past midnight now.

There are some real muppets on Evilbay, there's a scope I'm interested in but although the seller claims it powers up and shows 2 beams, he also claims that he doesn't understand how to use it, fair enough, but he does not show any photos of it powered. I asked to see some photos of it powered and he has replied that he has stated that he does not know how to use it so he can't post any photos of it working     

Tell him he's a numpty.

Well bugger me one of the HT resistors just exploded. Fucks sake this is a demon scope.

Will order some more....

The existing ones or new you'd installed ?

Edit
Of the images you showed of it earlier it looked like the originals had already been changed from carbon comp to metal film and 1 watters. I used 2W metal film in the D83 I had.
Carbon comp has the advantage they tend to drift open so as not to create fireworks.

Don't metal film resistors tend to have much lower voltage ratings? Such as typical 375V max? As opposed to carbon comp which have much higher voltage ratings.

Carbon composition resistors actually vary resistance depending on voltage so they just need to go away and die really. Apart from a few things like pulse handling, they are dead and should stay dead.

You can get glazed metal film ones such as the Vishay VR25 / VR37 / VR68 etc which is what will go in this. They are rated 1.6KV, 3.5KV and 10KV respectively. Most stuff is really low voltage these days (under 30V across all potentials) so they just don't bother with the usual cheap MF ones being more than 300V or so.

[mnementh]

Well bugger me one of the HT resistors just exploded. Fucks sake this is a demon scope.

Will order some more....

*Chuckling softly*

"For Fuck's sake..." was one of my grandfather's favorite "intentional intensifiers"; one he was always saying in front of me, and getting yelled at (or worse yet, "the look") from my grandmother. As a result, my eyes lit on that part first without me even thinking about it... and I heard the entire thing in my head spoken in his long, deep southern drawl.

Made me both smile and a little wistful at the same time. 


mnem
Thank you.

[tautech]

Hmmm, the EHT diodes (DC restorer) in mine were different to those but I had to replace them too for exactly the same reason.
Be sure to upgrade the wattage for the EHT dividers, it's not like you're limited for room. I was a tight as until I'd been in there a couple of times then threw caution to the wind and did a proper rework job, caps and all ! 

Never ventured into the EHT after that but did have the 150V zener crap out on the CRT socket.
Because of all the work I'd done on mine and it was my first scope I did find it hard to move it on at the time but I'm well over that now. 

[nixiefreqq]

its always something!

was noodling away in the basement using my pulse generator and hp54502a to tdr some coax cables.  was getting good results and was as happy as a bag of mostly salty water can be on a saturday night.

then the scope died and the basement filled with the smell of something that had zorched.

damn.

despite having my cooking criticized and being called a low life module swapper on this thread, I am not one to be daunted in public  (is hemingway still required reading anywhere?).  so I pulled the power supply from my hp 54504a and sat it beside the dead smelly one.  took about 3 minutes of comparison between the golden unit and the dead one to be 99% sure that one of 4 parallel 8amp 35 volt diodes in the 5.2v section had shorted.  (80sq035).   will pull the diodes tomorrow and see which one blew.  my plan is to then hook the 3 good ones back up and see if the damn thing works.

or maybe since they are in parallel it would be better to wait for new ones from amazon and replace them all? 

https://www.amazon.com/5PCS-80SQ035-DIODE-SCHOTTKY-DO-204AR/dp/B019EB8K7A


in any case..... this feels like vindication for my "have two of everything and don't be afraid to compare them" theory. 







 

   

[mnementh]

Comparative analysis is a valid troubleshooting technique; one I've been guilty of more than a few times. As long as substitution doesn't become your only repair method, there's no shame in using it as a diagnostic tool.

Just because I'm capable of component-level repair doesn't make me feel obligated to do it that way every time; my time IS worth something, after all. If I can buy a working XYZ board on fleabay for $20, how much diag time can I afford to spend on the original? Sure... figuring out the fault to repair and stow the original board for a spare is a good idea... if you have discretionary time; but I have a bin full of such boards from the Plasma Screen years that are little more than donors for heat sink material and Tesla coil projects now.

I'd definitely replace all 4 at once to be sure your rectifier array all have similar forward voltage drop. Or better yet, replace all 4 with a modern high-current rectifier in a TO-3PJ package.

But first, look for the flaky cap that probably caused the failure.

Here's a thread on this power supply; it links to a hand-drawn schematic which I've attached below.

Hope that helps.


mnem
*tzzzt*

[bd139]

To be honest I’m a big fan of substitution and module level repair. The only problem is I never have a module to replace the dead one with when it comes to TEA. It really isn’t worth repairing some consumer electronics for example when a new module costs virtually nothing.

[Specmaster]

Well bugger me one of the HT resistors just exploded. Fucks sake this is a demon scope.

Will order some more....

*Chuckling softly*

"For Fuck's sake..." was one of my grandfather's favorite "intentional intensifiers"; one he was always saying in front of me, and getting yelled at (or worse yet, "the look") from my grandmother. As a result, my eyes lit on that part first without me even thinking about it... and I heard the entire thing in my head spoken in his long, deep southern drawl.

Made me both smile and a little wistful at the same time. 


mnem
Thank you.

Haha that's also one of my intensifies when shit goes wrong too. [emoji16]

[Berni]

Yep that's usually my problem too.

Normally when fixing a piece of test gear i only have one of them. If i had boards i could swap out i could really quickly track the problem down to the board so that i can focus my debugging efforts on that.

Sometimes there is a simply unobtainable part and you need to buy a broken donor unit to rip it out of. I tend to be pretty careful on what broken gear i buy so that its a easy fix, but you never know. Oh and careful with buying donor units. It can make your TEA worse as i seen cases where someone buys a donor unit but then figures out the donor in the end is actually in really good condition so they buy another donor unit to replace the parts in it and get it working, but then also find the spare board for cheap and in the end they end up with 3 working units tho they only wanted to get 1 working.