Author Topic: Test Equipment Anonymous (TEA) group therapy thread  (Read 2996433 times)

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Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2625 on: October 07, 2017, 12:31:25 pm »
The other one I have is earthed. Not sure I trust it to be floating :)

Heathkit’s design methodology was run everything hard.  I had a counter that needed from them that needed more than an amp through the regulator so they just whacked a big 3W carbon comp resistor across it to bleed current. Worked but ran hot!

This one is in series with the blue wire returned from the mains switch. I’d post the picture but I want to avoid eating up data on the road.

Check the 9.1 ohm resistor on the top of the range wafer switch. This is usually the cause of ohms measurement errors. When a numpty sticks it in ohms and measures D.C. volts it goes pop! Mine had a big hole in it. I replaced it with a selected 10 and 100 ohm pair in parallel and it’s bang on now. I’m quite impressed at how stable and accurate the resistors in it were. They were panclimatic ones.

Anyway driving back now...
 

Offline Cerebus

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2626 on: October 07, 2017, 02:57:11 pm »
Strange, I didn't think that funerals took place on weekends, maybe they just so busy at the moment, anyway look on the brighter side, you'll be able to either play with or patch up the damage tomorrow. :-+

When funerals were almost exclusively church affairs they typically didn't take place on Sundays for the obvious reason of clashing with the usual Sunday services. As Sundays are a working day for the clergy it can't be a rest day and all good churchmen are going to obey the 4th commandment and have a day of rest, and for most clergymen I've known they have picked that to be Saturday.

Sunday is normal church services, the vicar has Saturday off and so funerals don't happen at weekends. Of course, many (most?) funerals now are secular affairs so that logic doesn't apply and funerals can, in theory at least, happen on any day. In the UK and Ireland some localities have by-laws banning Sunday funerals.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2627 on: October 07, 2017, 03:05:28 pm »
There have always been funerals on Saturdays since Greggs opened on a Sunday. Mmm steak slice.
 

Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2628 on: October 09, 2017, 07:30:24 am »
Back again. Managed to get down to it on the VTVMs. New one was a turd inside. Has been modified, gain and resistors were all over the place. Decided I’d had enough so have bodged a good one together and got rid of them as a pair. Need to prioritise projects a bit...

...but fell down the hole again: just won a dead and dirty Tek 475 with DM44 module for just under £30. The DM44 module works but the scope is dead. If it’s not HT related it should be easy enough to fix. Fixed about ten of these over the years from that series.
 

Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2629 on: October 09, 2017, 08:37:55 am »
Thats TEA for you alright, makes fall down holes that others would avoid like the plague  :-DD

VTVMs seem to be dogging you don't they, so if you made a good one out of the two, why did get rid them both  :wtf:,

They can be a pig to find as well, I know, I was after one for about 8 months before I struck gold and I'd seen a few pigs in that time as well, anything half decent seemed to go for stupidly high amounts of money, I must have been bidding against all the other TEA's out there I reckon.  :popcorn:
Who let Murphy in?

Brymen-Fluke-Solartron-HP-Thurlby-Heathkit-Thander-Tek-Extech-Black Star-GW-Advance-Avo
 

Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2630 on: October 09, 2017, 09:58:44 am »
I think I just know when to quit on these things. TBH it was the third zap of the second one thanks to some distinctly dodgy wiring that did it for me. I eviscerated the bastard, got the other one going with a whole pile of valve swapping thanks to a suddenly dying 12AT7, I'd had enough by about 2AM. Couldn't stand to look at the thing for much longer.  Ergo, straight in a box and off to someone else with more patience.

An anatomy of a "working v-7a":



new baby - note the "crustyness". May be an interesting one. Apparently the DM44 module powers up which is slightly hopeful:

 
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Offline tggzzz

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2631 on: October 09, 2017, 10:56:17 am »
just won a dead and dirty Tek 475 with DM44 module for just under £30. The DM44 module works but the scope is dead.

Good snipe. I saw that, but couldn't be bothered to flog over to HH to pick it up.

Besides, I ought to sell my working "IBM" 475+dm44 (plus my working 465s and working 2445b and working HP1650A LA) to pay for my latest acquisitions. Stupidly high offers via PM, please :)
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2632 on: October 09, 2017, 11:09:43 am »
I'm actually at RNOH in Stanmore tomorrow which is half way between here and there so I figured I'd roll in late afternoon and grab it for an extra 45 mins or so. I have sorely missed my 475 since I sold it so I'm slightly excited. Quick natter with the seller came up with the typical outcome which was he was a tech years ago and it has been sitting on the shelf in the garage (heated no less) for a number of years. He was actually just going to take it to the tip but thought someone might want the knobs or something. Makes me wonder how many of these ended up in a skip. If it's not the power supply caps I'll eat my hat. If it's the HT, I'll cry and proceed to give you a sensible offer for your IBM 475 ;)

I think my other half would kill me if I made you some sensible offers however. She already gave me the lecture this morning about "I thought you just bloody sold the great big beige one?". "That's not how TEA works dear!".
 

Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2633 on: October 09, 2017, 11:30:29 am »
Hmm, I wonder if that VTVM was originally a 120V one thats been imported and hence the wirewound resistor on the neutral as a volt dropper?

That 475 does look crusty, has the appearance of a barn find, is it 200Mhz or 250Mhz and am I right in thinking that the DMM is like my Keithley 160, DC only?
It has a nice linear power supply, none of this SMPS rubbish but does the 475 use any of these bloody hybrids that are both hart to find and expensive if required?
Who let Murphy in?

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Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2634 on: October 09, 2017, 11:41:32 am »
I thought that to start with but it's actually marked up as a V-7A/UK and has a UK made meter in it.

They usually clean up pretty well. I've had some far worse ones come up looking new. The meter is DC / ohms and interestingly time and reciprocal of time (frequency) which can be pulled off the delayed timebase settings so you can use it for measuring phase, frequency, rise time etc numerically with reasonable accuracy.

While not hybrids, the 475 has quite a few Tek ASICs in it. There are the vertical preamps, trigger, miller integrator. These are all pretty reliable from experience though. I'll have a dead one now I've said that!

If you want a scope that is "infinitely repairable", look out for a Tektronix 453 (50MHz bandwidth) or 454 (150MHz bandwidth). A revisions have bigger CRTs and newer styling. They are fully discrete and built like NASA build space craft. Only bit that is a dick is the tunnel diodes but you can get funky russian ones that do the job. Also the first FET buffer on earlier ones isn't a FET, it's a little tube (nuvistor).  Stuff looks like this:





Glorious machines. I had a 453. Another regretful sell. It had a trolley for it as well.
« Last Edit: October 09, 2017, 11:45:23 am by bd139 »
 

Offline AF6LJ

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2635 on: October 09, 2017, 11:46:48 am »
I've seen worse, that 475 is in decent shape..
Looks like it had a rich life, and wants more.
Sue AF6LJ
Test Equipment Addict, And Proud Of It.
 

Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2636 on: October 09, 2017, 12:14:38 pm »
Nice, I have been thinking about a 475 or similar for some time now but the thought of hybrids fills me with dread, but that is only based on the repair videos I have seen on line where it nearly is the hybrid thats gone and the troubles they have locating them.

If I was go for a Tek, it would have 150Mhz upwards and I already have a Rapid 25Mhz, Hitachi 40Mhz, Iwatsu 60Mhz, LG 100Mhz and a HP 1740A on the bench being repaired, but if I'd need to sell the Rapid I think, break my heart to do so as it really is in pristine condition and has only had a few of use in its life, but it is the least capable of them, so logic says it is the one to go first.

Am I right in thinking that the IBM 475 is exactly the same as the Tek 475 but it also sports the IBM logo, presumably because they used them on their computers and wanted them customised with their logo? Or is even deeper than that and has custom functions / ranges for their use?
Who let Murphy in?

Brymen-Fluke-Solartron-HP-Thurlby-Heathkit-Thander-Tek-Extech-Black Star-GW-Advance-Avo
 

Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2637 on: October 09, 2017, 12:57:29 pm »
If you have two of them then it's less of a problem. It's probably the most cost effective way of handling repairs on older kit like that. The individual part prices are scary. Sometimes I think about getting into that side of things to top up the income a bit but it kills me parting out repairable equipment.

I'd keep the 25MHz Rapid scope. You're not going to get much cash for it. I'd expect £25 and then you have to fuzz around with couriering it and stuff and get screwed for paypal/ebay fees.

The IBM 475 is the same AFAIK. It just had IBM printed on it. Here's some history about the IBM association: http://readingjimwilliams.blogspot.co.uk/2011/07/scope-sunday-3.html

I've seen worse, that 475 is in decent shape..
Looks like it had a rich life, and wants more.

Yeah it past the "am I going to get screwed by sphere.ca for knobs?" test :D
 

Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2638 on: October 09, 2017, 01:44:33 pm »

I'd keep the 25MHz Rapid scope. You're not going to get much cash for it. I'd expect £25 and then you have to fuzz around with couriering it and stuff and get screwed for paypal/ebay fees.

I must have the midas touch then because I recently sold another Rapid scope (20Mhz) that was in fair shape for £80 on Ebay. Did you know that Rapid still sell these for around £500 plus VAT?

I remember reading a while ago about IBM requiring a scope that would fit under a airline seat, then that link you sent me brought it all home, that was where I read it from :-+
Who let Murphy in?

Brymen-Fluke-Solartron-HP-Thurlby-Heathkit-Thander-Tek-Extech-Black Star-GW-Advance-Avo
 

Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2639 on: October 09, 2017, 01:58:13 pm »
Wow. That's pretty impressive! Sell it if you have the touch :D
 

Offline AF6LJ

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2640 on: October 09, 2017, 02:12:30 pm »
I thought that to start with but it's actually marked up as a V-7A/UK and has a UK made meter in it.

They usually clean up pretty well. I've had some far worse ones come up looking new. The meter is DC / ohms and interestingly time and reciprocal of time (frequency) which can be pulled off the delayed timebase settings so you can use it for measuring phase, frequency, rise time etc numerically with reasonable accuracy.

While not hybrids, the 475 has quite a few Tek ASICs in it. There are the vertical preamps, trigger, miller integrator. These are all pretty reliable from experience though. I'll have a dead one now I've said that!

If you want a scope that is "infinitely repairable", look out for a Tektronix 453 (50MHz bandwidth) or 454 (150MHz bandwidth). A revisions have bigger CRTs and newer styling. They are fully discrete and built like NASA build space craft. Only bit that is a dick is the tunnel diodes but you can get funky russian ones that do the job. Also the first FET buffer on earlier ones isn't a FET, it's a little tube (nuvistor).  Stuff looks like this:





Glorious machines. I had a 453. Another regretful sell. It had a trolley for it as well.
The problem with the Tek 453 is there are as many as four versions of that scope, and only three manual versions online.
Yah I have the fourth version here and no correct manual.
Sue AF6LJ
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Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2641 on: October 09, 2017, 02:15:55 pm »
I had the same problem with mine. It had the nuvistor front end instead of the FET manual. They’re pretty easy to debug though. Nothing is hidden so you can trace the signals with an eye shut.
 

Offline AF6LJ

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2642 on: October 09, 2017, 02:40:54 pm »
I had the same problem with mine. It had the nuvistor front end instead of the FET manual. They’re pretty easy to debug though. Nothing is hidden so you can trace the signals with an eye shut.
This is a OPTTFI scope...
(Other People Tried To Fix It)
I suspect there are technician induced issues.
Sue AF6LJ
Test Equipment Addict, And Proud Of It.
 

Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2643 on: October 09, 2017, 02:49:44 pm »
Ahh yeah that's not good. Been there before.

"Hmm, vertical amp gone, let's not even try and diagnose the problem, make up a load of assumptions and then whack two random BFY51's in we had in a rusty box of cack in the workshop because they're the same size and shiny" ... "bang!" .... "BER - write off".

I'm hoping this Tektronix 475 hasn't been played with. Doesn't sound like it has.
 

Offline AF6LJ

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2644 on: October 09, 2017, 02:54:09 pm »
Ahh yeah that's not good. Been there before.

"Hmm, vertical amp gone, let's not even try and diagnose the problem, make up a load of assumptions and then whack two random BFY51's in we had in a rusty box of cack in the workshop because they're the same size and shiny" ... "bang!" .... "BER - write off".

I'm hoping this Tektronix 475 hasn't been played with. Doesn't sound like it has.
Good luck, My 475 needs a little TLC it works although one of the vertical gain switch contacts is a bit buggy, I can deal with that.
Sue AF6LJ
Test Equipment Addict, And Proud Of It.
 

Offline THDplusN_bad

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2645 on: October 09, 2017, 03:01:26 pm »
Good Day,

but, my fellow Tektronix-enthusiasts, I am sure you know http://w140.com/tekwiki/wiki/453 and the Tektronix yahoo group, don't you?  :-+

And I'd like to refer you to Ralf's superb website, too: http://amplifier.cd/Test_Equipment/Tektronix/Tektronix_other/475.htm
Most of his website is bilingual EN/DE, but your favourite online-translator is your friend. 

My congratulations to your new "baby", the 475, bd139! Looks like there is some happy repair time ahead for you!

Cheers,

THD+N_bad
 

Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2646 on: October 09, 2017, 03:16:59 pm »
Already on there and a regular visitor to amplifier.cd. I'll document my repair Ralf style on my web site as well :)
 

Offline Cubdriver

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2647 on: October 09, 2017, 03:53:00 pm »
I had the same problem with mine. It had the nuvistor front end instead of the FET manual. They’re pretty easy to debug though. Nothing is hidden so you can trace the signals with an eye shut.
This is a OPTTFI scope...
(Other People Tried To Fix It)
I suspect there are technician induced issues.

Someone perhaps failed to obey the tenth commandment?:

Maketh not unauthorized modifications to equipment, but causeth thou to
be recorded all field changes and authorized modifications made by thee, lest thy
successor tear his hair and go slowly mad in his attempt to determine what manner of
creature hath made a nest in the wiring of such equipment.

-Pat
If it jams, force it.  If it breaks, you needed a new one anyway...
 
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Offline bitseeker

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2648 on: October 09, 2017, 05:15:44 pm »
I've seen worse, that 475 is in decent shape..
Looks like it had a rich life, and wants more.

The crusty ones are the most satisfying to finally see cleaned up and working.
I TEA.
 

Offline Mr. Scram

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #2649 on: October 09, 2017, 05:32:17 pm »
The crusty ones are the most satisfying to finally see cleaned up and working.
Is it "things your wife said"?
 


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