Date   

Re: Failed Transistor with Low h(FE)?

Ozan
 

I agree with others hFE's measured look OK if the transistor is healthy otherwise.

To rule out anything wrong with U330:
When you look at pin 17 of U330 with a scope do you see 250us high (>1V) , 750us low (<400mV)?

To check if Q348 is doing its job:
When you look at base of Q350 do you see 250us of ~ 4.3V and 750us of ~ 5V?

Ozan


Re: Shipped They Are

Paul Amaranth
 

Mine showed up yesterday. We had no mail deliver the other day
because of road conditions. They generally don't plow our road
until the day after a big snow and I can't blame the Mail folks
not wanting to run those cheapie trucks down an unplowed road.

Anyway, they look fantastic! This will be a fun little project.
I haven't built a kit since forever and that's pretty much
what this is turning out to be.

Many thanks to Larry for handling this and Jared for the design
(and documentation!) work.

Paul

--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix/Linux - We don't do windows


Re: Help replacing a resistor/inductor in SG503

Stephen
 

On Thu, Feb 18, 2021 at 06:29 AM, - wrote:

Also I've never seen one wound on that low of a resistance.
Are you SURE that the coil is open and that you're not reading the DC
resistance of the coil and not the resistor? Usually the resistance of the
resistors used in that practice are 100,000 Ohms or more. Several orders of
magnatude more than the coil.
The schematic clearly shows a 47R... 🤷‍♂️


Re: Help replacing a resistor/inductor in SG503

 

I feel like we had this same conversation when I was looking at replacing some CC resistors in the Z-axis amp of my 475A a couple months ago, but shouldn't a metal film resistor have some inherent inductance of it's own (because of the spiral cut in the film)?

Also, it looks like the part might be sensitive to very small (i.e. single ohm) changes in the resistor value, so it could well be that the CC resistor has drifted out of spec.

-- Jeff Dutky


Re: Help replacing a resistor/inductor in SG503

Roy Thistle
 

On Thu, Feb 18, 2021 at 08:30 AM, Jared Cabot wrote:


is a plain 20nH axial inductor without the resistor ok to use?
It's labeled LR140, and its manufacturer is manufacturer 8009... that's Tektronix.
To me, the LR designation indicates the R is important for the circuit... but, that's my analysis.
Just the same... the "golden rule"... well espoused here on TekScopes, by cranky seniors... is... if you don't know what the part does in the circuit... then don't alter the component.
Forming a low value inductance (nH), around a resistor body, and soldering the ends to the resistor leads... used to be a common way to wind small value inductors... using the resistor body as a coil form... you'd see this in Ham radio RF construction... all the time... where you'd see specd.. so many turns, of such and such diameter enameled cu wire, around a CC resistor, of so and so a wattage [just because CC resistors were common, and their body dimensions...dependent on their heat dissipation/wattage were well specd... so you could get/construct the inductor value specd ... of reasonably good tolerance. This method of low value (nH) coil winding/forming was also frequently used by manufacturers too, before automation.
I'd measure the wire diameter (with a mic)... also, the number of turns of the wire .. and the resistor body diameter with a vernier ... the winding spacing too... so as too calculate... at least... the value of the "single turn wound, air core inductor." If you know that calculated value in nH... you can compare tp what Tektronix has specd, for LR140.
Posting a pic of the part may help.


Re: Help replacing a resistor/inductor in SG503

-
 

Winding inductors on the body of a carbon comp resistor is an OLD
practice that you very seldom see any more. I don't know how well it would
work on a film resistor but I would think that the film might affect it's
inductance. Also I've never seen one wound on that low of a resistance.
Are you SURE that the coil is open and that you're not reading the DC
resistance of the coil and not the resistor? Usually the resistance of the
resistors used in that practice are 100,000 Ohms or more. Several orders of
magnatude more than the coil.

Yes, a 2nH coil should be fine. Everytime that I've seen a coil wound on
a resistor body, the resistor resistance was FAR higher than the inductance
of the coil and the resistor had no effect on the circuit..

Also the film resistors have a very different inductance than the carbon
comp resistors so that could be interferring with your circuit as well.

On Thu, Feb 18, 2021 at 11:30 AM Jared Cabot via groups.io <jaredcabot=
protonmail.com@groups.io> wrote:

Hi all,
I recently got myself an SG503 Leveled Sine Wave generator for a good
price and I am currently repairing it back to operational condition.

I found a few components in the oscillator section were damaged, from what
I guess, is from some ham-fisted poking from someone's previous repair
attempt.
Most parts were easy to replace, but I'm a bit stuck on one. LR140 is a
20nH inductor consisting of a couple turns of fine wire around a 1/8w 47ohm
carbon composite resistor.
It looks like it has been poked at and one leg was broken off.
Below is linked a page from the schematics with the part highlighted in
red.

https://groups.io/g/TekScopes/photo/260912/0/SG503%20Oscillators%20LR140%20Detail.jpg

My question is, How's the best way to recreate this sort of part? I tried
winding a few turns on a 1/8 metal film resistor and didn't have much luck,
I have a DE-5000 LCR meter and a HP 4276A etc but it's a little difficult
to measure such small values reliably.
Should I get a carbon composite resistor from Digikey/Mouser to recreate
the part more true to the original design instead of the metal film I used?
Or is a plain 20nH axial inductor without the resistor ok to use? Any other
ideas or suggestions?

Thanks!






Re: Help replacing a resistor/inductor in SG503

Stephen
 

On Thu, Feb 18, 2021 at 05:51 AM, Jared Cabot wrote:


That would be awesome and greatly appreciated! :) The wire looks to be around
32 or 33 AWG.
If you are able to whip something up, are you able to send it to Japan? I can
paypal you any costs involved.

Thanks!
Jared.


On Fri, Feb 19, 2021 at 01:39 AM, Stephen wrote:


In my spare time I’m a guitar pickup winder. Been doing that for over 35
years. I have very fine wire available, and tons of Allen Bradley carbon
comp
resistors.
I could probably build you one.
I have an SG503. I’ll take a look at that inductor and see what I can come up with. Don’t worry about the cost for now.
AWG 32 or 33 are pretty thick compared to what I usually work with (AWG 42 and 43). These are hair thin.
Give me time to investigate.


Re: Help replacing a resistor/inductor in SG503

Jared Cabot
 

That would be awesome and greatly appreciated! :) The wire looks to be around 32 or 33 AWG.
If you are able to whip something up, are you able to send it to Japan? I can paypal you any costs involved.

Thanks!
Jared.

On Fri, Feb 19, 2021 at 01:39 AM, Stephen wrote:


In my spare time I’m a guitar pickup winder. Been doing that for over 35
years. I have very fine wire available, and tons of Allen Bradley carbon comp
resistors.
I could probably build you one.


Re: Help replacing a resistor/inductor in SG503

Ed Breya
 

If you have the original, broken part, then you have a good reference point. The damping resistance may be important, or it may be just a handy coil form, but it's hard to tell. It's best to just replicate it reasonably closely.

Ed


Re: Help replacing a resistor/inductor in SG503

Stephen
 

In my spare time I’m a guitar pickup winder. Been doing that for over 35 years. I have very fine wire available, and tons of Allen Bradley carbon comp resistors.
I could probably build you one.


Re: Failed Transistor with Low h(FE)?

Jared Cabot
 

Pending further testing of the transistors, I wouldn't expect those hFE numbers to be indicative of a faulty part unless they were single digits or up in the thousands, ie. orders of magnitude away from where they should be.


Help replacing a resistor/inductor in SG503

Jared Cabot
 

Hi all,
I recently got myself an SG503 Leveled Sine Wave generator for a good price and I am currently repairing it back to operational condition.

I found a few components in the oscillator section were damaged, from what I guess, is from some ham-fisted poking from someone's previous repair attempt.
Most parts were easy to replace, but I'm a bit stuck on one. LR140 is a 20nH inductor consisting of a couple turns of fine wire around a 1/8w 47ohm carbon composite resistor.
It looks like it has been poked at and one leg was broken off.
Below is linked a page from the schematics with the part highlighted in red.
https://groups.io/g/TekScopes/photo/260912/0/SG503%20Oscillators%20LR140%20Detail.jpg

My question is, How's the best way to recreate this sort of part? I tried winding a few turns on a 1/8 metal film resistor and didn't have much luck, I have a DE-5000 LCR meter and a HP 4276A etc but it's a little difficult to measure such small values reliably.
Should I get a carbon composite resistor from Digikey/Mouser to recreate the part more true to the original design instead of the metal film I used? Or is a plain 20nH axial inductor without the resistor ok to use? Any other ideas or suggestions?

Thanks!


Re: Failed Transistor with Low h(FE)?

Ed Breya
 

Better look for different suspects to blame for the failure. Those Qs are probably just fine. To be sure, just install the new ones and see if that fixes it. I doubt it. Ed


Failed Transistor with Low h(FE)?

 

I'm trying to fix a DM501 that I damaged by plugging it into a faulty backplane. One of the display digits is stuck on and I think that I've narrowed the cause down to one of two transistors that drives the display chip select lines (Q348 or Q350). I removed both transistors, but when I checked them in my component tester neither one looks "blown". Q348 however (a 2N3565) has a lower hFE than the replacements I have in hand.

Here are the measured hFE for the suspect and replacement parts:

old 2N3565 (Q348): hFE=287, Vf=683
old 2N2907 (Q350): hFE=227, Vf=667

new 2N3565 (two tested): hFE=(443, 343), Vf=(673, 645)
new 2N2907 (one tested): hFE=288, Vf=673

I was expected to find the failed part as a short or open. Could a failed transistor simply have a decreased gain?

-- Jeff Dutky


Re: 155-0001-00 repair or replacement?

 

Well crap. Someone beat me to it already, even though I replied minutes after I saw the post :(
Whoever you are, how about selling me one of them?
thanks.


Re: Stan Griffiths estate sale

n4buq
 

Hi Walter,

Las August, I tried emailing Sphere regarding the CRTs advertised on the Stuff Day pages but never received a reply so thought I'd try here.

Regarding the CRTs below, can you tell me whether either of them have the internal graticule? I think that was an option which might not be reflected in the part number but not sure.

https://www.sphere.bc.ca/test/stuffday.html#catalog

(1) D14-363GH/123 Rect.
(1) D14-363GY/123 Rect.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "walter shawlee" <walter2@sphere.bc.ca>
To: TekScopes@groups.io
Sent: Thursday, February 18, 2021 8:55:19 AM
Subject: Re: [TekScopes] Stan Griffiths estate sale

The post-demise sale of guys with lots of gear is always a bit sobering.
Part of the reason Suzie and I are running the Stuff Season event is to
help move
useful bits out to anybody that can use them, rather than have a
dumpster fire
event at the end, or calling 1-800-got-junk.  At 71, I have to consider
that the
window to do that is a bit limited, so we are putting some real effort
into it.

In any case, we are filling up the stuff shelves with things we think
are of interest,
please let me know if there's something special you want to see there,
and we will make
it happen if we can. So far here's the stuff:
https://www.sphere.bc.ca/test/stuffday.html

Things I still have lots of are Tek semi's, pots and knobs, plus CRTs,
tubes, probes, transformers,
trim parts and Tek, Hp, Fluke and Boonton gear of all kinds. However,
putting it on line takes a lot
longer then setting out boxes at stuff day, so it's hard to know where
to devote effort among
the zillions (a common Canadian metric unit) of parts sitting here. The
toughest things are
"scrap" items, broken units I am disinclined to fix, and have no idea
whether anyone is
interested in or not. Their low value and high shipping cost is a
problem, it's much easier at
stuff day to just set them on a shelf, and say, "take it away..." For
example, I have a nice
looking 2336 portable with several faults that has been sitting a long
time. Cost a lot to buy,
but now worth maybe $25 to me.

I really screwed up at the last event, and didn't put in many bench
power supplies. This time, I got my
son to photograph them all for me, and as a result, there is a HUGE pile
of them from 7 to
2,000 volts there now, and more coming. We scored some fantastic Xantrex
lab supplies
(made here in BC), at a good price, so they are pretty reasonable, and
are really first class units.

Let me know if you want or need anything, you never know what the answer
may be.
Direct email is better than clogging up the list.

all the best,
walter (walter2 -at- sphere.bc.ca)
--

Walter Shawlee 2
Sphere Research Corp. 3394 Sunnyside Rd.
West Kelowna, BC, V1Z 2V4 CANADA
Phone: +1 (250-769-1834 -:- http://www.sphere.bc.ca
+We're all in one boat, no matter how it looks to you. (WS2)
+All you need is love. (John Lennon)
+But, that doesn't mean other things don't come in handy. (WS2)
+Nature is trying very hard to make us succeed, but nature does not depend on
us.
We are not the only experiment. (R. Buckminster Fuller)







Re: Making a Replacement Output High Level Knob for a PG502

 

Thanks Jared,

I don't think I need dimensions. It looks like I just need the metal core from a 475 trigger slope knob and I can cut off half of the base on the opposite side from the set screw. I might have some damaged slope knobs in my salvage box.

The knob on my PG502 was completely missing, not merely smashed. I've currently got a trigger slope knob on there, just to have something, and the inner diameter on that knob is correct for the high level shaft. I just needed to know where the index mark went in relation to the stops.

-- Jeff Dutky


Re: Making a Replacement Output High Level Knob for a PG502

Jared Cabot
 

Here's the knobs from my PG502, the red line on the paper indicates where the white line on the small knob is to help with indexing.

https://groups.io/g/TekScopes/album?id=260906

If you need dimensions, let me know and I'll measure them up.


Re: Stan Griffiths estate sale

 

The post-demise sale of guys with lots of gear is always a bit sobering.
Part of the reason Suzie and I are running the Stuff Season event is to help move
useful bits out to anybody that can use them, rather than have a dumpster fire
event at the end, or calling 1-800-got-junk.  At 71, I have to consider that the
window to do that is a bit limited, so we are putting some real effort into it.

In any case, we are filling up the stuff shelves with things we think are of interest,
please let me know if there's something special you want to see there, and we will make
it happen if we can. So far here's the stuff: https://www.sphere.bc.ca/test/stuffday.html

Things I still have lots of are Tek semi's, pots and knobs, plus CRTs, tubes, probes, transformers,
trim parts and Tek, Hp, Fluke and Boonton gear of all kinds. However, putting it on line takes a lot
longer then setting out boxes at stuff day, so it's hard to know where to devote effort among
the zillions (a common Canadian metric unit) of parts sitting here. The toughest things are
"scrap" items, broken units I am disinclined to fix, and have no idea whether anyone is
interested in or not. Their low value and high shipping cost is a problem, it's much easier at
stuff day to just set them on a shelf, and say, "take it away..." For example, I have a nice
looking 2336 portable with several faults that has been sitting a long time. Cost a lot to buy,
but now worth maybe $25 to me.

I really screwed up at the last event, and didn't put in many bench power supplies. This time, I got my
son to photograph them all for me, and as a result, there is a HUGE pile of them from 7 to
2,000 volts there now, and more coming. We scored some fantastic Xantrex lab supplies
(made here in BC), at a good price, so they are pretty reasonable, and are really first class units.

Let me know if you want or need anything, you never know what the answer may be.
Direct email is better than clogging up the list.

all the best,
walter (walter2 -at- sphere.bc.ca)
--

Walter Shawlee 2
Sphere Research Corp. 3394 Sunnyside Rd.
West Kelowna, BC, V1Z 2V4 CANADA
Phone: +1 (250-769-1834 -:- http://www.sphere.bc.ca
+We're all in one boat, no matter how it looks to you. (WS2)
+All you need is love. (John Lennon)
+But, that doesn't mean other things don't come in handy. (WS2)
+Nature is trying very hard to make us succeed, but nature does not depend on us.
We are not the only experiment. (R. Buckminster Fuller)


Re: 155-0001-00 repair or replacement?

 

PM sent!
I got a reasonable ebay offer on an S-4 "not working, bad offset" and I figure I can fix anything else except the hybrid. So I guess I'll accept once I confirm with Walter :)

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