Date   

Re: worst condition Tektronix scope?

 

Paul Amaranth wrote:

Well, if you want to enjoy the madness, I have a pair of 468s to get rid of. One was
working pretty much but is showing signs of bad filter caps and the other is a parts scope.
I would actually be interested in the 468s, especially if there's work required (that's at least half the fun).

I'm willing to pay shipping. Is there other compensation you would like?

-- Jeff Dutky


Re: There is no good time to be SICK

tek_547
 

Good to hear it´s going better Dennis so keep safe and watch out for THE virus.
René


Re: 475A Z-Axis Amp and Q1338 Confusion

 

I haven't got either a DMM with the socket and Hfe setting, nor do I have a curve tracer. I'm trying to limit my acquisition of new boat anchors, as I've already filled my work area with 400-series and 2200-series scopes (I started out with a 475 and a 2213 that belonged to my father, then I bought several parts 475s, one of which is a 475A, in order to ensure that I could keep my father's scope running. Then I saw that the 2215 had a neat feature that the 475 lacked, and was pretty cheap. Finally, after losing an auction for a 475A+DMM44 I saw that there was a 2200-series scope, the 2236, with a DMM/Counter-timer built in, and now I am up to my ears in scopes).

I'm a little surprised that I haven't seen an external curve tracer that could be attached to a scope operating in X-Y mode. I know that you can do some kinds of component checks using a scope in X-Y mode, but I haven't gotten around to learning exactly how to do that.

I've been wanting to get a reliable ESR meter, and some of them appear to have component test sockets as well, but the range of choices has been beyond my analysis-paralysis threshold. If someone had a solid recommendation for a reliable, but not too expensive meter with these features, I would be grateful for the suggestion.

-- Jeff Dutky


Re: Resistor in series

Michael A. Terrell
 

VIAsMicrodyne built their business on equipment built around their low
phase noise Synthesizer. It had undergone many minor changes over several
decades, until our source for some bare ceramic disc capacitors dried up.
They were installed over a 1/8" VIA, to solder the back side to the boards.
One of the newer 'know it all engineers didn't even bother to see what they
were used. He simply changed the BOM to a SMD cap, on edge, and marked a
spot on the top side of the VIA to mount each of them. This caused many
problems. He chose the cheapest cap available. The new mounting
repositioned the flying leads that were soldered to the other end, and the
open VIAs caused impedance bumps in the board's ground plane. Even worse,
some of these spots were part of the band switching for the 350 to 510 MHz
VCO board. It was split into three bands, to divide the total range into
tree smaller, overlapping ranges. The switching was done electronically.
The VCO's inductor was switchable at two points, to ground. The one end was
permanently grounded. The poor tech that had been doing them for years
suddenly had 100% failure rate. The only reply from the Engineer was 'My
ECO can't be the cause, just do your damned job!" He was about to quit,
because of frustration. I was pulled off my work. I noticed the difference
between the old and new design right away. Sure enough, the problems had
started with the first new unit. That 'Engineer' didn't follow procedure to
have a sample tested by production before issuing the ECO. It took me a
little while to absorb the total design. It looked like it should work, but
in the back of my mind, I was thinking about lead length inductance causing
problems at 500 MHz. So, I filled the empty VIAs, one at a time as I
watched the Phase Noise drop. The last were the two band switching
circuits, which simply turned on one or two forward biased diodes, hard.
They were very close to the worst of the original design, which could be
brought into spec by repositioning some flying leads. Moving the new caps
to the center of the filled VIAs made that unit pass. Slight realignment of
the flying leads made it cleaner than any of the gold standards. I
documented the modifications needed to make them pass. He raised hell with
me, in front of my supervisor who was the head of the Production Test
Department. He refused to admit to his mistakes, and to issue a new ECO.
You didn't do that to me, and get away with it. When I was pulled from my
regular work to troubleshoot production problems, I found the problems, and
I either got results, or heads would roll. I already had a reputation,
after dragging the Division VP out of his office onto the production floor
to demand action on bad lighting. I had also complained about the poor
copies of copies of copies schematics the print room gave out, rather than
doing a new reduction from a master. Another time, they refused to release
the preliminary documentation for a critical test for a design
modification. Needless to say, I got some people fired. Office politics be
damned, we needed documents, ECOs and competent engineers. It was taken out
of his hands. Someone else did the ECO, as I wrote it. He was transferred
to sales, but he didn't last. I had to take one ECO to one of the semi
retired engineers who founded Microdyne to get approval for a new test
procedure. It had two tests that were interactive with a MC1496. The MC1596
had just been discontinued, which could barely pass both. Only one was
important to the board, and any attempt to improve the other severely
affected it. No one, including the director of Engineering had the guts to
challenge any of HIS designs. I caught him during his next visit. I
explained the problem. I pointed out in an old Motorola data sheet that
that test did nothing good for us. I informed him that particular parameter
was no longer guaranteed on a current Datasheet, and simply told him, We
waste hours per board to pass them for something we don't need. It also
lowers the overall quality of the products using this board. He was a
little red faced. It was one of his first designs, but as we discussed it,
he finally agreed to delete it. Quality went back up, and production time
went down. Then I redesigned the test fixture. You had to set test voltages
accurately, but Engineering had simply given Production the proof of
performance/first article jig. The most critical voltage was 0.400 Volts.
We had no precision Lv references in house so I used a forward biased
1N4001, and a series resistor to allow the 0-10V pot to become a
0-0.425Volt pot. This further reduced test time, and improved quality. It
also eliminated the frequent replacement of the 1/8" shaft, panel mounted
pots.

I realize that this is long, and some may view it as off topic, but many
engineering problems are not obvious without taking the time to really
understand the functions. I hated drudge work, and I hated careless design
or spec changes, even more. Like a 5% spec on a circuit wit two 10%
resistors, and a 20% pot in series. That was my first encounter with a bad
document. I was brushed off with a 'We don't do ECOs on older designs, so
forget it!'. That wasn't an answer, it was a challenge! Then there was the
odious ISO9001 moron contractor brought in to set up our system...

My job title was 'Production Test Tech', but I worked jobs in most
departments because they wanted someone to fix a problem, simply and at low
cost without upsetting everyone in the process. What the heck? I loved
challenges!








On Fri, Nov 27, 2020 at 10:23 PM Stephen Hanselman <kc4sw.io@kc4sw.com>
wrote:

Dennis,

I saw similar things when I was working on Silicon Valley 700W FM
amplifiers. The physical orientation of the ATC caps was critical. We
noted that sometimes two or three caps needed to be placed on edge or even
stacked on top of each other.

RF is always fun but this added a new twist.

Regards,

Stephen Hanselman
Datagate Systems, LLC
On Nov 27, 2020, at 14:50, Dennis Tillman W7pF <dennis@ridesoft.com>
wrote:

There is another explanation for doing something like this which is not
as obvious.
If you look at the schematic for the 067-0681-01 Tunnel Diode Pulse
Generator designed by John Addis at Tektronix
http://w140.com/tek_067-0681-01.pdf

There are three 1/8W 1Kohm resistors (R4, R5, and R6) connected in
series going to the tunnel diode. Several years ago I asked him why he did
not use one 3Kohm resistor instead. What he knew and I learned was that the
body capacitance of each of these 3 resistors in series was far less than
the body capacitance of one 3Kohm resistor. The TD is being driven by the
collector of the transistor which is high impedance, and the three 1Kohm
resistors in series reduces the time constant of the pulse going to the
Tunnel Diode without adding any additional capacitance across the Tunnel
Diode that would slow it down.

I doubt this had anything to do with Tek portable scopes since their
frequency response is almost two orders of magnitude slower than the fast
edge of the Tunnel Diode Pulse Generator but sometimes there are other
explanations for why you might encounter things that are not obvious.

Dennis Tillman W7pF


-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Milan Trcka
Sent: Tuesday, November 24, 2020 9:09 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Resistor in series

Jeff, the resistors connected end to end are an attempt to make a
required resistance that was not available as a standard resistor value.
Shortage of parts? Engineering change? Select in test? Who knows. I have a
few of those in my 453 scope.







--
Dennis Tillman W7pF
TekScopes Moderator









Re: 475A Z-Axis Amp and Q1338 Confusion

Roy Thistle
 

On Sat, Nov 28, 2020 at 03:26 PM, Jeff Dutky wrote:


are there other tests
If you've got one of those DMMs that have a socket, and a Hfe setting... along with a transistor that is packaged so that the pins cooperate (or rig up a kludge)... you measure the current gain... and see if it is in spec. (Many of the very cheap Amazon DMMs have that.)
You can also measure the current gain with your DMM on uA (base to emitter current)... and on mA( collector to emitter current) to see the current gain.
If you know your circuit parameters, you can also investigate/measure to see if the particular transistor in the circuit is meeting those specs.
Do you need a curve tracer? ... well they're kind of cute... the old ones have lots of gravity to hold things down.... and, their probably cheaper than an iPhone.


Re: (OT) Where to go for 70s IBM hardware? I'm looking for a terminal.

Roy Thistle
 

On Sat, Nov 28, 2020 at 01:26 AM, Martin wrote:


electro-mechanical computer, I inherited some modules I wonder if anybody can
shed some light on them.
It's reading 204
That's a Cannon D Submini connector
Looks to me that you have 3 synchros (selsyns) and a resolver... along with a motor
And 2 Bridge circuits
You've got some cams that active some microswitches, and gear trains.
The outputs appear to be on the linear pots.
It seems like a state machine to me... it executes a mechanical program... and also sends data. (position?... and feedback)
Potentially it seems like you've got 3 dependent degrees of control, with feedback.


151-0367-00 and 151-0402-00 transistors

Mark Vincent
 

These are likely to be leaky from C to E as a diode while checking normal
as an NPN. An hfe meter will show way off hfe on the leaky ones. If they
have round leads (tarnished above the socket), they are all leaky. If the
flat face is black with square leads, they likely will be leaky. Check
EVERY one. Some will be leaky and some not even in the same piece. If the
flat face is blue with square leads, it will be fine. The blue flat ones
must be a manufacturing change or different supplier. The 151-0402-00 is in
the 7D15. It may be in other plug-ins. The same checking applies to the
0402. I found that KSP10BU will replace them. Mouser carries these
transistors. The pinout is BEC so be careful when inserting them. The flat
will be turned different than original ones. I had some plug-ins and scopes
that were not quite right in operation after restoring them. These
transistors were the problem. In the Q list of parts, they will have "SEL
FROM 3571TP" under "name and description".

Mark


Re: 475A Z-Axis Amp and Q1338 Confusion

 

Ramond,

Okay, I have a couple of DMMs with diode check mode. I did as you said, and using that method the Q1338 shows a diode voltage of 0.773 from base to collector and the same (or nearly so) from base to emitter (red always connected to the base, black to either the collector or emitter), which means that this is definitely an NPN transistor, and the cheap component checker was wrong.

Okay, that clears up the core of my confusion. I'm not nearly as concerned with specific part numbers in different service manuals as I am with a completely different sort of transistor in the actual circuit than is specified in the schematic.

As for whether I got the pinout right: I had thought that the component checker didn't care and would try all combinations, but I just tried putting the transistor in with the pins offset by one position (the checker has a ZIF socket where the pins are labeled 1, 2, 3, 1, 1, 1, 1 so you can connect the part either as 1,2,3 or as 2,3,1, or as 3,2,1 if you flip it over), and now it gets correctly identified as an NPN transistor. This is what I get for $15: no manual, and a cargo-cult approach to electrical engineering.

For the record, the other three transistors that I used the component checker to identify as bad, I actually went back and checked them with the multi-meter, so I'm pretty sure that they were, in fact, bad: one was a dead short between all three terminals, the other two were complete open circuits between all three terminals. Clearly something fairly dire happened to the beam intensity amp which blew out two diodes and three transistors. I just hope I've fixed whatever the problem was.

-- Jeff Dutky


Re: Fair Radio Sales Lima Ohio

Eric
 

Kyle once the covid is over ill take you up on that.

On Sat, Nov 28, 2020, 8:20 PM Kyle Rhodes <ksrhodes@gmail.com> wrote:

Mendelson’s was ridiculous, such an enormous space and quantity of stuff.
I recently bought 26 gaylords worth of resistors, wire, chips, diodes,
transistors, pneumatic actuators, hardware, etc, etc. So much stuff, all
still sitting in my warehouse mostly unsorted. Soon though, once we’re
caught up after our Black Friday sale, I’m looking forward to going through
it all! Anyone in the Cincinnati / Dayton area is welcome to come to the
shop, just drop me a line.



On Nov 28, 2020, at 7:33 PM, David Kuhn <Daveyk021@gmail.com> wrote:

“ Mendelsons”

That’s it! Closing? <sad> I was out in July and never thought of them.

On Sat, Nov 28, 2020 at 6:46 PM David Holland <
david.w.holland@gmail.com>
wrote:

Mendelsons

In the process of closing now. It was supposed to have closed several
months earlier but they're still trying to clean out the building.

David

Sent via mobile annoyance thingy, please pardon any typos.

On Sat, Nov 28, 2020, 6:35 PM David Kuhn <Daveyk021@gmail.com> wrote:

" Hello, I live about 2 miles from Fair radio."

One more question Tim. When I lived in Cincinnati (from 1985-1999),
sometime early to mid of being there, probably around 1990, there used
to
be a HUGH HUGH surplus electronics warehouse in Dayton, Ohio. It was
in
a
very old building, but it was HUGH HUGH. I bought a heavy industrial
cart
from them that I still have and use. Then I forgot about that place,
life
got in the way, all I was interested in was modern stuff, etc., yada,
yada,
yada, and I didn't re-visit in the 1990s anymore and then moved back to
central PA. Is there still a surplus store in Dayton, like that? I
imagine it went bye-bye like most others.

Dave

On Fri, Nov 27, 2020 at 8:21 PM Tim Laing <laingt@wcoil.com> wrote:
Hello, I live about 2 miles from Fair radio. I know the owner Phil,
not
a
close friend though. I am not sure what will happen when he
retires....
I do not know if the show room is open to the public at this time.
I
can do some checking. I can stop in but if I do I generally need to
have
at
least 2 hours free to wander around and get my fix.... I have gone
there
on missions for other people in the past. I could check on plug ins.
My first visit was probably when I was 13 or 14 years old, I am 59
now.
I took my future wife to Fair Radio on our first “date”. Maria and I
are still Married going on 31 years.
Prices are not cheap but he has a lot of overhead costs. I have a
bunch of pictures that I have taken there in the past, I am afraid of
the
day I find out they are closing. I wish I had taken pictures in the
old
dairy buildings located on Eureka Street. Tim Laing





















Re: Fair Radio Sales Lima Ohio

Kyle Rhodes
 

Mendelson’s was ridiculous, such an enormous space and quantity of stuff. I recently bought 26 gaylords worth of resistors, wire, chips, diodes, transistors, pneumatic actuators, hardware, etc, etc. So much stuff, all still sitting in my warehouse mostly unsorted. Soon though, once we’re caught up after our Black Friday sale, I’m looking forward to going through it all! Anyone in the Cincinnati / Dayton area is welcome to come to the shop, just drop me a line.

On Nov 28, 2020, at 7:33 PM, David Kuhn <Daveyk021@gmail.com> wrote:

“ Mendelsons”

That’s it! Closing? <sad> I was out in July and never thought of them.

On Sat, Nov 28, 2020 at 6:46 PM David Holland <david.w.holland@gmail.com>
wrote:

Mendelsons

In the process of closing now. It was supposed to have closed several
months earlier but they're still trying to clean out the building.

David

Sent via mobile annoyance thingy, please pardon any typos.

On Sat, Nov 28, 2020, 6:35 PM David Kuhn <Daveyk021@gmail.com> wrote:

" Hello, I live about 2 miles from Fair radio."

One more question Tim. When I lived in Cincinnati (from 1985-1999),
sometime early to mid of being there, probably around 1990, there used to
be a HUGH HUGH surplus electronics warehouse in Dayton, Ohio. It was in
a
very old building, but it was HUGH HUGH. I bought a heavy industrial
cart
from them that I still have and use. Then I forgot about that place,
life
got in the way, all I was interested in was modern stuff, etc., yada,
yada,
yada, and I didn't re-visit in the 1990s anymore and then moved back to
central PA. Is there still a surplus store in Dayton, like that? I
imagine it went bye-bye like most others.

Dave

On Fri, Nov 27, 2020 at 8:21 PM Tim Laing <laingt@wcoil.com> wrote:
Hello, I live about 2 miles from Fair radio. I know the owner Phil,
not
a
close friend though. I am not sure what will happen when he retires....
I do not know if the show room is open to the public at this time.
I
can do some checking. I can stop in but if I do I generally need to
have
at
least 2 hours free to wander around and get my fix.... I have gone
there
on missions for other people in the past. I could check on plug ins.
My first visit was probably when I was 13 or 14 years old, I am 59 now.
I took my future wife to Fair Radio on our first “date”. Maria and I
are still Married going on 31 years.
Prices are not cheap but he has a lot of overhead costs. I have a
bunch of pictures that I have taken there in the past, I am afraid of
the
day I find out they are closing. I wish I had taken pictures in the old
dairy buildings located on Eureka Street. Tim Laing

















Re: 475A Z-Axis Amp and Q1338 Confusion

Harvey White
 

There are a number of ways to test a transistor (bipolar type).

One is to use an ohmmeter to check the BE and BC junctions.  The problems with this can be that the older meters not only have more voltage than is good for the transistor, and the current used could be more than the transistor would like.

Another option is to use a transistor tester (they're very common on Amazon and EBAY).  They apply voltages to each lead, and measure voltage and current in other leads.  They're not bad, but not infallible.  They're good for lead identification.

Another option is the classic transistor tester, leakage, beta, etc.  It does require you to understand which leads are which, though, for best results.

The last is a curve tracer.  Be prepared to spend money to get one of these unless you can build one.  There are older units, B&K and Heathkit, they'll cost who knows how much, but they ought to work well enough.  Next come the Tektronix plugins, specifically the 7CT1N (if you have a 7000 series scope) and the 5CT1N (for a 5000 series scope).  The prices seem to be unreasonable on these.  There are also specific Tektronix curve tracer scopes and instruments.  They seem to be equally expensive.  The problem with all of these is that while they give you very exact and meaningful data, you have to know how to interpret it.

Perhaps your best bet is the transistor tester, and a DVM with a transistor tester (beta) setting.

Curve tracers are wonderful, but $$$$.


Harvey

On 11/28/2020 6:26 PM, Jeff Dutky wrote:
I'm still waiting for one component to replace the blown transistors in my sick 475A, so I decided to investigate the similarities/differences between the 475A and a 475 parts scope. The first thing I checked was Q1338, which is not bad in my 475A, but which does not seem to match what is found in the schematic or parts list.

Q1338 is shown as an NPN transistor in the schematics for both the 475 and 475A, and also listed as such in the parts list ("Silicon, NPN, SKA6516) but the parts that I find in the 475A and the 475 both measure as a PNP transistor, and both bear the markings "151367 TI811" which appears to be a Motorola SPS8811 part.

I have found some other Tek service manuals that list part # 151-0367-00 as a Motorola SPS8811, but the both the 475A and 475 service manuals list that same part number as an SKA6516. I can't seem to find any data sheets for either a Motorola transistor with part number SPS8811 or a transistor with the part number SKA6516.

The Semiconductor Common Design Parts Catalog does nothing to clarify matters, listing 151-0367-00 as an A5T3571, an NPN transistor with a minimum hFE of 100 (@ 6V/5mA) and a minimum fT of 1.2 GHz (@ 6V/5mA). I have found a data sheet for the TI A5T3571 which is listed as an NPN transistor having a "minimum calculated f[max]" of 2.2 GHz, so that is at least is the same ballpark as the Tek docs. I have not yet found a source for this part.

The fact that all of the documentation insists that the part is an NPN transistor, while the physical parts that I find on the physical boards test as a PNP transistor is quite confounding. I'm perfectly willing to believe that my component tester is lying to me (it's one of those cheap kits, but it's gotten good reviews from the EEV community on YouTube, so I figured it was better than nothing. Still, maybe it's not ALWAYS better than nothing).

How should I go about testing the the actual parts myself? I know that I can use the diode test function of a multi-meter to check the CB and EB voltage drops, and determine if this is an NPN or PNP based on the polarity, but are there other tests I can/should do?

Again, I'm not currently counting this as a failed part, but the fact that my tester identifies it as something other than what the service manuals say it should be is confounding (and, unless I can explain it, really SHOULD count as a failure). The fact that I don't seem to have an replacements that don't also read as the wrong part (and that I can't seem to find is the only reason I'm not calling this a failed part.

-- Jeff Dutky





Re: Fair Radio Sales Lima Ohio

David Kuhn
 

“ Mendelsons”

That’s it! Closing? <sad> I was out in July and never thought of them.

On Sat, Nov 28, 2020 at 6:46 PM David Holland <david.w.holland@gmail.com>
wrote:

Mendelsons

In the process of closing now. It was supposed to have closed several
months earlier but they're still trying to clean out the building.

David

Sent via mobile annoyance thingy, please pardon any typos.

On Sat, Nov 28, 2020, 6:35 PM David Kuhn <Daveyk021@gmail.com> wrote:

" Hello, I live about 2 miles from Fair radio."

One more question Tim. When I lived in Cincinnati (from 1985-1999),
sometime early to mid of being there, probably around 1990, there used to
be a HUGH HUGH surplus electronics warehouse in Dayton, Ohio. It was in
a
very old building, but it was HUGH HUGH. I bought a heavy industrial
cart
from them that I still have and use. Then I forgot about that place,
life
got in the way, all I was interested in was modern stuff, etc., yada,
yada,
yada, and I didn't re-visit in the 1990s anymore and then moved back to
central PA. Is there still a surplus store in Dayton, like that? I
imagine it went bye-bye like most others.

Dave

On Fri, Nov 27, 2020 at 8:21 PM Tim Laing <laingt@wcoil.com> wrote:

Hello, I live about 2 miles from Fair radio. I know the owner Phil,
not
a
close friend though. I am not sure what will happen when he retires....
I do not know if the show room is open to the public at this time.
I
can do some checking. I can stop in but if I do I generally need to
have
at
least 2 hours free to wander around and get my fix.... I have gone
there
on missions for other people in the past. I could check on plug ins.
My first visit was probably when I was 13 or 14 years old, I am 59 now.
I took my future wife to Fair Radio on our first “date”. Maria and I
are still Married going on 31 years.
Prices are not cheap but he has a lot of overhead costs. I have a
bunch of pictures that I have taken there in the past, I am afraid of
the
day I find out they are closing. I wish I had taken pictures in the old
dairy buildings located on Eureka Street. Tim Laing














Re: 475A Z-Axis Amp and Q1338 Confusion

 

On Sun, Nov 29, 2020 at 01:15 AM, Raymond Domp Frank wrote:


To check if NPN or PNP with DMM:
With most (not expensive) DMM's: Using your battery-operated DMM, set to 2kOhm
range, connect the red (+) lead to the base and the black (-) lead to either
the collector or emitter. You should see something like 0.68 V, with a
slightly lower voltage with B-C than B-E.
Check the other way around (black vs red) and you'll see overflow.
If so, it's an NPN that isn't completely dead, might even be fine. Be a bit
careful with static, it's an HF transistor with small capacitances, so more
easily zapped than LF transistors.
Actually, same as in Diode Check mode, if your DMM has one.

Raymond


Re: 475A Z-Axis Amp and Q1338 Confusion

 

On Sun, Nov 29, 2020 at 12:26 AM, Jeff Dutky wrote:


The fact that all of the documentation insists that the part is an NPN
transistor, while the physical parts that I find on the physical boards test
as a PNP transistor is quite confounding. I'm perfectly willing to believe
that my component tester is lying to me (it's one of those cheap kits, but
it's gotten good reviews from the EEV community on YouTube, so I figured it
was better than nothing. Still, maybe it's not ALWAYS better than nothing).

How should I go about testing the the actual parts myself? I know that I can
use the diode test function of a multi-meter to check the CB and EB voltage
drops, and determine if this is an NPN or PNP based on the polarity, but are
there other tests I can/should do?
Q1338 *is* an NPN transistor. Are you sure you've got the pinout right?
To check if NPN or PNP with DMM:
With most (not expensive) DMM's: Using your battery-operated DMM, set to 2kOhm range, connect the red (+) lead to the base and the black (-) lead to either the collector or emitter. You should see something like 0.68 V, with a slightly lower voltage with B-C than B-E.
Check the other way around (black vs red) and you'll see overflow.
If so, it's an NPN that isn't completely dead, might even be fine. Be a bit careful with static, it's an HF transistor with small capacitances, so more easily zapped than LF transistors.

Raymond


Re: Poorly 485

 

On Sun, Nov 29, 2020 at 12:31 AM, Ondrej Pavelka wrote:


What do you think is causing the defunct ranges above 10uS?
The first suspect would be a bad contact in a timing switch associated specifically with times above 10 us/div (SM, dwg page 10, "Timing Switches"). At time base settings longer than 10 us/div, switch A26 is (supposed to be) engaged. So have a look at the functioning of the switch and associated components, like R877 (dwg 7) and don't forget the associated contact of relay K879, also on dwg 7.

Raymond


Re: Fair Radio Sales Lima Ohio

David Holland
 

Mendelsons

In the process of closing now. It was supposed to have closed several
months earlier but they're still trying to clean out the building.

David

Sent via mobile annoyance thingy, please pardon any typos.

On Sat, Nov 28, 2020, 6:35 PM David Kuhn <Daveyk021@gmail.com> wrote:

" Hello, I live about 2 miles from Fair radio."

One more question Tim. When I lived in Cincinnati (from 1985-1999),
sometime early to mid of being there, probably around 1990, there used to
be a HUGH HUGH surplus electronics warehouse in Dayton, Ohio. It was in a
very old building, but it was HUGH HUGH. I bought a heavy industrial cart
from them that I still have and use. Then I forgot about that place, life
got in the way, all I was interested in was modern stuff, etc., yada, yada,
yada, and I didn't re-visit in the 1990s anymore and then moved back to
central PA. Is there still a surplus store in Dayton, like that? I
imagine it went bye-bye like most others.

Dave

On Fri, Nov 27, 2020 at 8:21 PM Tim Laing <laingt@wcoil.com> wrote:

Hello, I live about 2 miles from Fair radio. I know the owner Phil, not
a
close friend though. I am not sure what will happen when he retires....
I do not know if the show room is open to the public at this time. I
can do some checking. I can stop in but if I do I generally need to have
at
least 2 hours free to wander around and get my fix.... I have gone there
on missions for other people in the past. I could check on plug ins.
My first visit was probably when I was 13 or 14 years old, I am 59 now.
I took my future wife to Fair Radio on our first “date”. Maria and I
are still Married going on 31 years.
Prices are not cheap but he has a lot of overhead costs. I have a
bunch of pictures that I have taken there in the past, I am afraid of the
day I find out they are closing. I wish I had taken pictures in the old
dairy buildings located on Eureka Street. Tim Laing










Re: Fair Radio Sales Lima Ohio

David Kuhn
 

" Hello, I live about 2 miles from Fair radio."

One more question Tim. When I lived in Cincinnati (from 1985-1999),
sometime early to mid of being there, probably around 1990, there used to
be a HUGH HUGH surplus electronics warehouse in Dayton, Ohio. It was in a
very old building, but it was HUGH HUGH. I bought a heavy industrial cart
from them that I still have and use. Then I forgot about that place, life
got in the way, all I was interested in was modern stuff, etc., yada, yada,
yada, and I didn't re-visit in the 1990s anymore and then moved back to
central PA. Is there still a surplus store in Dayton, like that? I
imagine it went bye-bye like most others.

Dave

On Fri, Nov 27, 2020 at 8:21 PM Tim Laing <laingt@wcoil.com> wrote:

Hello, I live about 2 miles from Fair radio. I know the owner Phil, not a
close friend though. I am not sure what will happen when he retires....
I do not know if the show room is open to the public at this time. I
can do some checking. I can stop in but if I do I generally need to have at
least 2 hours free to wander around and get my fix.... I have gone there
on missions for other people in the past. I could check on plug ins.
My first visit was probably when I was 13 or 14 years old, I am 59 now.
I took my future wife to Fair Radio on our first “date”. Maria and I
are still Married going on 31 years.
Prices are not cheap but he has a lot of overhead costs. I have a
bunch of pictures that I have taken there in the past, I am afraid of the
day I find out they are closing. I wish I had taken pictures in the old
dairy buildings located on Eureka Street. Tim Laing






Poorly 485

Ondrej Pavelka
 

Hi folks,

I acquired abandoned abused lonely 485 for equivalent of $40. I couldn't leave her there.

When the time base is 10uS or shorter it works but it's rather blurred, very far from nice sharp trace. At settings shorter then 10uS I can even run delayed B sweep and all behaves rather well.

Ventilator is not turning
6 pots are missing knobs
Vertical amps look both OK

I will start by checking the PSU and clean and lubricate all the switches and pots but I don't think this will resolve the problems with times above the 10uS.

What do you think is causing the defunct ranges above 10uS?

Thanks


Re: Fair Radio Sales Lima Ohio

David Kuhn
 

" Hello, I live about 2 miles from Fair radio. I know the owner Phil, not
a close friend though. I am not sure what will happen when he retires..."

I ordered a 3A6 module from him for $52, I think. The web site states that
shipping will be charged when they process the order, so I don't know the
shipping. I see on my bank site that a $52 charge is pending from "Fair
Radio", so I don't know if he charged me shipping or not. I thought the
module was $52, maybe it was less. Yes, I just looked it was $52. I had
emailed him and he tells me all tubes and everything are in it. He sent me
pictures and it looks good.

You say he is pricey. On EBAY a 3A1 is trying to be sold for $400. So, I
thought $52 was reasonable.

Is Fair Radio a family business? From the sounds of your message, it
sounds like he is pretty old and you are worrying about him finally
retiring. I would like to make a trip out to there when this virus BS is
finally over.

Dave

On Fri, Nov 27, 2020 at 8:21 PM Tim Laing <laingt@wcoil.com> wrote:

Hello, I live about 2 miles from Fair radio. I know the owner Phil, not a
close friend though. I am not sure what will happen when he retires....
I do not know if the show room is open to the public at this time. I
can do some checking. I can stop in but if I do I generally need to have at
least 2 hours free to wander around and get my fix.... I have gone there
on missions for other people in the past. I could check on plug ins.
My first visit was probably when I was 13 or 14 years old, I am 59 now.
I took my future wife to Fair Radio on our first “date”. Maria and I
are still Married going on 31 years.
Prices are not cheap but he has a lot of overhead costs. I have a
bunch of pictures that I have taken there in the past, I am afraid of the
day I find out they are closing. I wish I had taken pictures in the old
dairy buildings located on Eureka Street. Tim Laing






475A Z-Axis Amp and Q1338 Confusion

 

I'm still waiting for one component to replace the blown transistors in my sick 475A, so I decided to investigate the similarities/differences between the 475A and a 475 parts scope. The first thing I checked was Q1338, which is not bad in my 475A, but which does not seem to match what is found in the schematic or parts list.

Q1338 is shown as an NPN transistor in the schematics for both the 475 and 475A, and also listed as such in the parts list ("Silicon, NPN, SKA6516) but the parts that I find in the 475A and the 475 both measure as a PNP transistor, and both bear the markings "151367 TI811" which appears to be a Motorola SPS8811 part.

I have found some other Tek service manuals that list part # 151-0367-00 as a Motorola SPS8811, but the both the 475A and 475 service manuals list that same part number as an SKA6516. I can't seem to find any data sheets for either a Motorola transistor with part number SPS8811 or a transistor with the part number SKA6516.

The Semiconductor Common Design Parts Catalog does nothing to clarify matters, listing 151-0367-00 as an A5T3571, an NPN transistor with a minimum hFE of 100 (@ 6V/5mA) and a minimum fT of 1.2 GHz (@ 6V/5mA). I have found a data sheet for the TI A5T3571 which is listed as an NPN transistor having a "minimum calculated f[max]" of 2.2 GHz, so that is at least is the same ballpark as the Tek docs. I have not yet found a source for this part.

The fact that all of the documentation insists that the part is an NPN transistor, while the physical parts that I find on the physical boards test as a PNP transistor is quite confounding. I'm perfectly willing to believe that my component tester is lying to me (it's one of those cheap kits, but it's gotten good reviews from the EEV community on YouTube, so I figured it was better than nothing. Still, maybe it's not ALWAYS better than nothing).

How should I go about testing the the actual parts myself? I know that I can use the diode test function of a multi-meter to check the CB and EB voltage drops, and determine if this is an NPN or PNP based on the polarity, but are there other tests I can/should do?

Again, I'm not currently counting this as a failed part, but the fact that my tester identifies it as something other than what the service manuals say it should be is confounding (and, unless I can explain it, really SHOULD count as a failure). The fact that I don't seem to have an replacements that don't also read as the wrong part (and that I can't seem to find is the only reason I'm not calling this a failed part.

-- Jeff Dutky

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