Bristol wrenches (was: Re: [TekScopes] Extracting a buggered knob grubscrew)
Miguel Work wrote on 2/2/2021 8:29 AM: Yes, is a allen key, but now try a torx key with the grubscrew. Hello-- I misread "allen" as "alien", which reminded me of the Bristol screws that were sometimes used in WW II equipment: <> Now I'll have to paw through the tool chest and see whether I still have a set of the wrenches, just in case....<g> 73-- Brad? AA1IP
|
Re: 7603 + voltage rails high
Downloaded a readable copy of the manual from Tekwiki, and indeed the bulk +50 volt supply is shown to be +53v, so a value of 55-60 volts would be reasonable.
If you find Q869 has developed a c-b short, then the +179volts would be applied to the collector of Q860 and Q876 which may have damaged them and Q863 as well.
Before replacing any semis in the +50 volt regulator, I would check them all (in the +50 volt regulator), before prior to powering it up again.
Dave
toggle quoted message
Show quoted text
On Tue, Feb 2, 2021 at 05:03 AM, Dave Hills wrote:
The schematic copy I have is very poor, partially un-readable, and I can't
make out the bulk voltage value feeding Q869, 872, 874. However 75v seems
very high for a 50 volt regulator. Is your line voltage 220/240VAC? If yes,
is it possible the line voltage selector is set to 115VAC? What is the bulk
supply volts across C809? If it is 55-60v I'm thinking Q869 has a c-e short,
or CR868? is leaky or shorted. If Q869 or CR868 are bad, then very possibly
Q872 and Q874 are also blown due to excess b-c voltage.
Dave
|
Re: Extracting a buggered knob grubscrew
Yes, is a allen key, but now try a torx key with the grubscrew. -----Mensaje original----- De: [email protected] [mailto: [email protected]] En nombre de keith@... Enviado el: martes, 2 de febrero de 2021 10:38 Para: [email protected]Asunto: Re: [TekScopes] Extracting a buggered knob grubscrew Thanks for all the tips. I removed one of the 'good' setscrews (from the same knob) and looked at it under the magnifier; it definitely is for an Allen key, not Torx. I have a selection of imperial and metric allen keys, a 1.5mm or 1/16th is the closest fit, the latter being slightly tighter than the former. However it won't grid at all, I think I'm going to have to drill the thing out. If I can find a 3/32 left handed drill bit I might have some luck. Scanned by McAfee and confirmed virus-free. Find out more here:
|
Re: Extracting a buggered knob grubscrew
Where did you get your set of left-handed drills ???
toggle quoted message
Show quoted text
On 02/02/2021 12:31, - wrote: I have a set of them and I keep them in their own protective box and they're
used only to remove stubborn set screws and broken bolts. For me left hand
bits work *much* better than Easy Outs for removing broken bolts and
buggered set screws.
On Mon, Feb 1, 2021 at 8:43 PM Bob Albert via groups.io <bob91343=
[email protected]> wrote:
|
Re: 7603 + voltage rails high
The schematic copy I have is very poor, partially un-readable, and I can't make out the bulk voltage value feeding Q869, 872, 874. However 75v seems very high for a 50 volt regulator. Is your line voltage 220/240VAC? If yes, is it possible the line voltage selector is set to 115VAC? What is the bulk supply volts across C809? If it is 55-60v I'm thinking Q869 has a c-e short, or CR868? is leaky or shorted. If Q869 or CR868 are bad, then very possibly Q872 and Q874 are also blown due to excess b-c voltage.
Dave
|
Re: Extracting a buggered knob grubscrew
As a last resort you can drill out the screw. But always use a *left hand* drill bit. I've found that most of the time a *left hand* bit will dig in and will turn the screw and cause it to unscrew itself from the hole and will leave the threads relatively unscathed. Left hand bits aren't easy to find but you can order them. I have a set of them and I keep them in their own protective box and they're used only to remove stubborn set screws and broken bolts. For me left hand bits work *much* better than Easy Outs for removing broken bolts and buggered set screws. On Mon, Feb 1, 2021 at 8:43 PM Bob Albert via groups.io <bob91343= [email protected]> wrote: I have been watching this thread and have a related problem. The main
tuning knob on my Kenwood TS-940S cannot be removed, as the set screw has a
ruined hole and when I try to turn it, it's frozen.
I don't need to remove it but I'd like to know how.
Bob
On Monday, February 1, 2021, 05:30:04 PM PST, greenboxmaven via
groups.io <ka2ivy@...> wrote:
Because there are two grubscrews, remove the good one that did loosen,
apply penetrant to the stuck one, both on it and also down the hole of
the other one. Find a good high strength bolt about an inch long of the
same thread as the good grubscrew, install it, and tighten it sensibly-
not too much! Loosen and tighten it several times to "work" the
bushing inside the knob. Take it easy, the bushing does flex, and that
can help work things loose. I have done this many times with great
results. Grub srews have a cone shaped recess on their tip to dig into
the shaft. Working that loose is key to getting the screw out.
Bruce Gentry, KA2IVY
On 2/1/21 19:14, Michael A. Terrell wrote:
Torx was developed in 1967 and patented in 1971. Bristol was in use during
WW-II
On Mon, Feb 1, 2021 at 5:33 PM snapdiode via groups.io <snapdiode=
[email protected]> wrote:
In the 500 series, there are no Torx screws anywhere AFAIK, rather they
are Pozidriv.
|
[Solved] 5440 scope vertical creep/jitter (intermittent)
This turned out to be a cold solder joint on the delay line at the vertical board.
|
Re: [Tek 485] No intensity control
On Tue, Feb 2, 2021 at 02:29 AM, <marcosjl31@...> wrote: Second question : I have seen (EEVBLOG 485 Repair&Restoration thread) that
some people changed the tantalum by electorlytic caps... Is this a good
alternative (as tantalum are quite expensive)? It surely depends on what board you're changing them : it is certainly possible for some caps on the PSU board... but for the Horiz Board? ´³´Ç²õ¨¦
|
Re: Tek 576 alignment without calibration fixture?
On Tue, Feb 2, 2021 at 09:19 AM, Martin wrote:
Did anybody make these alignment steps without the fixture and what has been the setup to do them?
Yes all the time, using a set of "calibrated" resistors. The newer manual, 070-0905-01, contains two versions of Performance Check / Calibration. One using the resistors and the other using the Cal Fixture. This manual is on TekWiki. /H?kan
|
Re: [Tek 485] No intensity control
On Fri, Jan 29, 2021 at 05:15 AM, <marcosjl31@...> wrote:
Probably the first thing to do is replace this 3 diodes.
Hi, I was wondering if prevently replacing 15uF/20V tantalum caps as well on the Horizontal Amplifier Board could be a good idea ? As per R. Dickinson list, It's 5 caps : Orig inal Repla ce W/ Vc Vc On Schematic Board C1099 15 20 15 50 20 R B Trig Gen Hor Amp C1130 15 20 15 50 20 R Pwr Distribution Hor Amp C1131 15 20 15 50 20 R Pwr Distribution Hor Amp C1139 15 20 15 50 20 R Pwr Distribution Hor Amp C1199 15 20 15 50 20 A Pwr Distribution Hor Amp Second question : I have seen (EEVBLOG 485 Repair&Restoration thread) that some people changed the tantalum by electorlytic caps... Is this a good alternative (as tantalum are quite expensive)? Thanx! ´³´Ç²õ¨¦
|
Re: Extracting a buggered knob grubscrew
I'm pretty sure that the mentions of Torx were from folks who weren't paying close attention to your subject line. I am very doubtful that Tek ever used Torx set screws in any knobs, so I'm not surprised at what you found.
One other thing I once tried in desperation was to insert the tightest driver I owned, and then heat the tool with a soldering iron. That expanded the gap enough to get things started, fortunately before any plastics started to melt. I don't know if I could recommend this procedure, but I really didn't want to drill it out.
Good luck with whatever procedure you end up trying!
-- Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
toggle quoted message
Show quoted text
On 2/2/2021 01:38, keith@... wrote: Thanks for all the tips. I removed one of the 'good' setscrews (from the same knob) and looked at it under the magnifier; it definitely is for an Allen key, not Torx. I have a selection of imperial and metric allen keys, a 1.5mm or 1/16th is the closest fit, the latter being slightly tighter than the former. However it won't grid at all, I think I'm going to have to drill the thing out. If I can find a 3/32 left handed drill bit I might have some luck.
|
Re: Extracting a buggered knob grubscrew
Thanks for all the tips. I removed one of the 'good' setscrews (from the same knob) and looked at it under the magnifier; it definitely is for an Allen key, not Torx. I have a selection of imperial and metric allen keys, a 1.5mm or 1/16th is the closest fit, the latter being slightly tighter than the former. However it won't grid at all, I think I'm going to have to drill the thing out. If I can find a 3/32 left handed drill bit I might have some luck.
|
Tek 576 alignment without calibration fixture?
Hi all,
I find alignment of the 576 a rather pleasant excercise, until it comes to the point where you're supposed to use the calibration fixture - particularly for the step generator. Then the guesswork starts. The fixture seems to apply resistors or shorts between connectors. Or a voltage and/or current.
Did anybody make these alignment steps without the fixture and what has been the setup to do them?
Thanks & cheers
Martin
|
Re: Tek 576 possible power supply failure
Hi all, I put the schematic of those 2 supplies together with the voltages (hopefully readable) in failure mode in the files section. See if anyone finds the faulty transistor from that information alone...
/g/TekScopes/files/2021.01.31%20-%20Tek%20576%20power%20supply%20failure%20mode.pdf the winner is: Q837. My first thought was of Q834, but alas no, it was Q837 with a sufficient short across CE (behaves exactly like a resistor). Its the current limiting transistor and the supply sprang to life as soon as I took it out. I think I could have guessed it by looking at the CB-voltages, which are very close. This fault developed over time - at first the Tek went dark after an hour or so, a year later I barely could make a measurement before it happened. Thats what made me think of a capacitor rather than a transistor. Curiously, all capacitors in this rather old unit seem to be OK... My repairing of the step generator succeeded... it took me an afternoon understanding how it works (good manual), making tons of measurements to follow up the signal path until the counter, just to end up with a working step generator without having changed anything. The wiggling of the ICs and transistors must have done the trick. There's an excellent review of the step generator here (in german): The guy found out the there is an inherent design issue with the generator, as they are applying relatively slow ramping signals to the TTL logic. The old ones in the 60ies do switch at some point and thats OK, but the newer ones are faster and tend to switch forth and back during the time the signal is in the undefined area. At the very end this produces two or more clock pulses in a row, making the generator jump the corresponding steps. The best way to correct this is to replace the 7400 by a 74LS132 that has schmitt triggers at the entrance. cheers Martin
|
Worked on the Invert switch too, yesterday, after PS and Step Generator repair and before alignment.
The switch actually worked, but took 30 minutes to come out... I disassembled the horizontal switch to gain access and applied 1 or 2 tiny drops of "Ballistol" (with a syringue) to each end of the switch and the retaining mechanism. After some movements of the cam that made it come out normally.
I still need to push the invert switch harder than the others, but it hase more contacts than any other, too.
cheers
Martin
|
Re: Extracting a buggered knob grubscrew
Not Tek or knobs, just Torx in general products (Apple, etc).
-Dave
toggle quoted message
Show quoted text
On Monday, February 1, 2021, 10:22:02 PM PST, Tom Lee <tomlee@...> wrote: What products post-2000 have used Torx set screws in their knobs? -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 2/1/2021 22:19, Dave Seiter wrote: ? Are there any Torx in ~pre-1985...1990 Tek products?? I don't think I've ever run across one.? Plenty of Torx in post-2000 consumer stuff.
-Dave
? ? ? On Monday, February 1, 2021, 09:35:40 PM PST, Tom Lee <tomlee@...> wrote:
?
? I've never seen one. That's not the same as declaring that they don't
exist, but I feel safe in saying that they certainly are rare, if they
exist, in Tek scopes.
Tom
|
Re: Extracting a buggered knob grubscrew
What products post-2000 have used Torx set screws in their knobs?
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
toggle quoted message
Show quoted text
On 2/1/2021 22:19, Dave Seiter wrote: Are there any Torx in ~pre-1985...1990 Tek products?? I don't think I've ever run across one.? Plenty of Torx in post-2000 consumer stuff.
-Dave
On Monday, February 1, 2021, 09:35:40 PM PST, Tom Lee <tomlee@...> wrote:
I've never seen one. That's not the same as declaring that they don't
exist, but I feel safe in saying that they certainly are rare, if they
exist, in Tek scopes.
Tom
|
Re: Extracting a buggered knob grubscrew
Are there any Torx in ~pre-1985...1990 Tek products?? I don't think I've ever run across one.? Plenty of Torx in post-2000 consumer stuff.??
-Dave
toggle quoted message
Show quoted text
On Monday, February 1, 2021, 09:35:40 PM PST, Tom Lee <tomlee@...> wrote: I've never seen one. That's not the same as declaring that they don't exist, but I feel safe in saying that they certainly are rare, if they exist, in Tek scopes. Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 2/1/2021 21:30, Larry McDavid wrote: However, I was wrong earlier saying I had not seen a tiny-size Torx.
On checking, I actually have a Wiha Torx set from T1 through T10.
So, I wonder if there are small set screws with a Torx recess. Has
anyone actually encountered such a set screw?
Larry
On 2/1/2021 7:19 PM, Dave Seiter wrote:
? I've *never* seen a Tek knob with a torx set screw.-Dave
???? On Monday, February 1, 2021, 12:29:01 PM PST, Joseph Orgnero
<josepho@...> wrote:
? ? In my experience Tek uses only Torx screws on their equipment,
trying to use
Allen or Bristol wrenches is asking for trouble.
Jose Orgnero VE7LBI
-----Original Message-----
From: Jeff Kruth via groups.io
Sent: Monday, February 01, 2021 11:56 AM
To: [email protected]
Subject: Re: [TekScopes] Extracting a buggered knob grubscrew
While I am sure there are many tips that others have, I found a thin hot
soldering iron pressed into the iron screw socket head will sometimes
add
enough heat(expansion) to get things going. I have also filed cheap
jewelers
screwdrivers into an appropriate sized chisel point and, using
friction fit,
tapped them into the end of the reamed out set screw with a small
hammer.
This can then be grasped with a small pair of vice grips and the
screw may
give.YMMVJeff Kruth In a message dated 2/1/2021 2:46:57 PM Eastern
Standard
Time, snapdiode@... writes:
They are typically 1/20" or 0.050" keys. Sometimes it's Bristol drive
but if
someone forced a hex key in there it's probably not a Bristol drive
anymore.
Unfortunately I have found no way to extract a stuck set screw of
that size.
You might try a 1.3mm key, sometimes they really are 1.3 and not 1.27
so you
get a bit more grip. I don't know, seems random.
|
Re: Extracting a buggered knob grubscrew
My left-hand bit set has saved me about 7 times in the past year.? They work amazingly well, but as you say, they don't work in reverse!? Back in the spring, I set up a friend's mishap in my mill to show him how great they work, only to realize that the mill doesn't have a reverse.? I felt pretty stupid, but at least I made the realization before actually trying it!
-Dave
toggle quoted message
Show quoted text
On Monday, February 1, 2021, 09:27:40 PM PST, Larry McDavid <lmcdavid@...> wrote: I've never seen a set screw with a Torx recess. The other larger screws that look like Phillips are most likely PoziDriv. There have been lots of good suggestions here on how to remove a tight set screw. Sometimes, when all else fails, you just gotta drill the little buggers out... Left-hand drills can be a big help with all kinds of stuck screws; you must turn them counterclockwise, of course. Larry On 2/1/2021 7:19 PM, Dave Seiter wrote: ? I've *never* seen a Tek knob with a torx set screw.-Dave
? ? ? On Monday, February 1, 2021, 12:29:01 PM PST, Joseph Orgnero <josepho@...> wrote:
?
? In my experience Tek uses only Torx screws on their equipment, trying to use
Allen or Bristol wrenches is asking for trouble.
Jose Orgnero VE7LBI
-----Original Message-----
From: Jeff Kruth via groups.io
Sent: Monday, February 01, 2021 11:56 AM
To: [email protected]
Subject: Re: [TekScopes] Extracting a buggered knob grubscrew
While I am sure there are many tips that others have, I found a thin hot
soldering iron pressed into the iron screw socket head will sometimes add
enough heat(expansion) to get things going. I have also filed cheap jewelers
screwdrivers into an appropriate sized chisel point and, using friction fit,
tapped them into the end of the reamed out set screw with a small hammer.
This can then be grasped with a small pair of vice grips and the screw may
give.YMMVJeff Kruth In a message dated 2/1/2021 2:46:57 PM Eastern Standard
Time, snapdiode@... writes:
They are typically 1/20" or 0.050" keys. Sometimes it's Bristol drive but if
someone forced a hex key in there it's probably not a Bristol drive anymore.
Unfortunately I have found no way to extract a stuck set screw of that size.
You might try a 1.3mm key, sometimes they really are 1.3 and not 1.27 so you
get a bit more grip. I don't know, seems random.
-- Best wishes, Larry McDavid W6FUB Anaheim, California? (SE of Los Angeles, near Disneyland)
|
Re: 2235 Horizontal Calibration Issue
Hi Stephen,
These voltages look OK except pin 5 is a little low. The imbalance you are seeing in this stage could be making up for the offset of discrete amp following U760 so unless you see a waveform shift when you turn on horizontal x10 mode no need to touch R749. Step 3 of page 5-15 explains R749 adjustment but this is not the reason for nonlinearity.
At this point I have no other suggestions, may be the IC became slightly nonlinear over time.
Only thing that bothers me is pin 5 voltage is low. Pin 5 has two diodes and a 300-ohm resistor in series to pin 4 (-5V). I expected the current through R751 to flow into pin 5 :
I_pin5=(29.955-(-3.3835))/24.3k= 1.37mA.
This should generate 2*Vbe+300*I_pin5-V_pin4=-3.188V at pin 5
Service manual marks even higher voltage at -3V but you are measuring -3.38V.
If the bias currents to diff pairs inside U760 are low, they would become nonlinear at two ends of the swing because they would be current starved.
Either chip drifter over time (nothing to do), or 24.3k resistor became higher over time (unlikely), or there is a leakage path at pin5 (unlikely without physical evidence).
Ozan
|
zenith5106
Martin