Date   

Re: TEK 475: Dead on Start Up.

Tom Lee
 

I don’t fully agree with that recommendation, although it is fine in many circumstances. The impedance of tants stays low at high freqs, while aluminums generally don’t. Tripling the capacitance doesn’t necessarily reduce the impedance. Above self-resonance the impedance is dominated by parasitics, not the capacitive reactance.

Sent from my iThing, so please forgive brevity and typos


If Changing to electrolytic, triple the value… 22 uF/20Volt tant -> 100uF/25, 35, or 50Volt electrolytic

Steven


Re: TEK 475: Dead on Start Up.

Steven Bender
 

1) I understand that I should start with checking the +50V (UNREG) and then 50V (REG)\, next the+ 110V, +15V, and then +5V, -8V and finally -15V.

Is this correct?.

4) I understand that TEK used a way too low margin in Voltage rating for the Tantum capacitors on power rails.
- Are there any which particularly have a bad reputation and should ALWAYS be replaced?.

or

5) Should I eventually replace ALL those tantalum caps on the various power rails with 105 deg. C electrolytic capacitors?
- or are there "solid aluminum" alternatives to the tantalums used in that era (mid 1970's - mid 1980 's ?



I’m not an expert on the 475, but I believe you are correct, starting in the 50 Volt lines.

Tant caps from the 1970’s & 1980’s had failures over time, due to impurities that crept in during manufacturing.

I tend to replace old 20V tants with 35V tants.

If Changing to electrolytic, triple the value… 22 uF/20Volt tant -> 100uF/25, 35, or 50Volt electrolytic



Steven


Re: Idle Question About the 485

Gary Appel
 

My own thoughts - for what they are worth.

I have owned two 485's, and they both displayed issues with intermittent attenuators. I would wiggle the knob and try to get a stable trace, but often the attenuation would not settle down, so I was often not able to trust the display.

I have given them both away.

Gary Appel


Re: Tek VAR Pot Repair Rings

Jim Adney
 

On Wed, Oct 20, 2021 at 07:30 PM, Dave Casey wrote:

For anyone needing more than just a repair ring, I have a handful of NOS
Tek Made pots in this style. Send your part number requests and I'll see
what I have.
That's a very generous offer and one that we should all keep in mind. I will add, however, that even a new pot may fail in this same way. My guess, and it's only a guess, is that the Tek assembly techs knew exactly how tight they could tighten these, but many of us, or previous owners, may have tightened them just a bit too hard. And then there's shrinkage and embrittlement over time, which may be the cause of failure.

If I ever have cause to touch one of these pots, I'd be tempted to add one of the rings, just to avoid future disappointment.


Re: Idle Question About the 485

redarlington
 

Jeff,

The 485 is the finest portable Tek made in its day. I paid $350 for mine
about 15 years ago and I'd gladly do it again if I had to, but obviously
would rather pay less. That 350MHz BW rating is highly conservative. I
prefer it over other scopes for some things (many of us have favorites for
certain tasks). If ya need one, it's probably the right one. If not,
it's still probably the right one unless you need 4 channels. Two
channels is just right for the work I used to do when I bought it
(amplifier design and prototyping). And the size is just right to plop
right up on the bench. Mine lives on a scope cart these days but it
really is right at home ON the bench -unlike a lot of our other boat
anchors.

-Bob N3XKB

On Thu, Oct 21, 2021 at 12:43 PM Jeff Dutky <jeff.dutky@...> wrote:

Walter,

I don't see the fusible element in the 485 schematics, maybe you're
thinking of the 7A19, or the 7A24?

My wife might not kill me if I got a 485, but I'm in the middle of a reorg
of my bench and lab (making storage and organization for a bunch of
plug-ins, and finding a reasonable way to arrange portable and bench-top
scopes along side other instruments for use) and I'm already thinking that
some of my scopes are surplus to requirements. A 485 would not make the
project any easier.

The 7903 is clearly superior to the 485, unless you have to travel with
it. My whole reorg is being done because I've become quite fond of a couple
of 7600s (two 7603s and a 7633) in recent months. My bench was organized
around a couple of portable scopes originally, which could be easily
arrayed around my desk sitting upright on the floor, but the 7600s demand
bench or shelf space. Having one 7600 on the bench as a tool doesn't leave
much space for a second one as a patient.

I have not technical need for a 485. My only emotional connection is that
I let a nice one slip through my fingers this past spring at a similar
price. It had a blue phosphor CRT! I suspect that another member of this
group might have bought it while I was napping.

-- Jeff Dutky






Re: 7704A - Delayed Sweep Intensity Too Bright

SCMenasian
 

Barry,
If it's that way with several plugins, it might be in hte receiving side of that interface in the 7704A.

Stephen


Re: rare lot

leonard scheepsma
 

What a fantastic translation. Ramp generator into "catastrophe" generator into "disaster". Google translate without context.
I love it!


Re: USPS shipments comments

Steven Bender
 

Hi All,

A few years back, (not Tek equipment) I won a beautiful, museum quality cosmetics, Bang & Olufson linear tracking turntable, 1980’s Made in Europe, heavy, IIRC around $225. and the weight was about 40 lbs. It was coming from nearby, less than 50 miles away (next state over). The mailman carried it up the steps, walked over, (I was at the door watching) as he got near to me, he tossed it forward three feet onto the cement. He managed to break almost everything possible to break in the unit. I had taken out full replacement insurance, while I was eventually paid (minus $50. - no reason given). What can you do?

I’ve seen UPS do worse… a Sony TC-650 RTR arrived with a side of the box ripped open, trailing packing material, dropped so the metal frame warped so bad, unable to be repaired, the nice wood sides were a thousand tiny toothpicks, picked up again to go to the UPS Evaluation Center (likely it was dumped in some green recycle bin) and I got a massive $100. back, which was like a third of the cost before shipping.


Steven


Re: rare lot

Tim Phillips
 

'Disastergenerator' ? I have some of those lying around here !! <grin>

Wasn't this setup a replacement for the 160 generators when Tek were
getting into Biophysical market.?
I understood they rather took a hit on the product.

Tim


Re: Idle Question About the 485

 

Walter,

I don't see the fusible element in the 485 schematics, maybe you're thinking of the 7A19, or the 7A24?

My wife might not kill me if I got a 485, but I'm in the middle of a reorg of my bench and lab (making storage and organization for a bunch of plug-ins, and finding a reasonable way to arrange portable and bench-top scopes along side other instruments for use) and I'm already thinking that some of my scopes are surplus to requirements. A 485 would not make the project any easier.

The 7903 is clearly superior to the 485, unless you have to travel with it. My whole reorg is being done because I've become quite fond of a couple of 7600s (two 7603s and a 7633) in recent months. My bench was organized around a couple of portable scopes originally, which could be easily arrayed around my desk sitting upright on the floor, but the 7600s demand bench or shelf space. Having one 7600 on the bench as a tool doesn't leave much space for a second one as a patient.

I have not technical need for a 485. My only emotional connection is that I let a nice one slip through my fingers this past spring at a similar price. It had a blue phosphor CRT! I suspect that another member of this group might have bought it while I was napping.

-- Jeff Dutky


rare lot

Miguel Work
 


Re: 7704A - Delayed Sweep Intensity Too Bright

n4buq
 

Mark,

Yes, I believe the intent is to "highlight" part of the trace; however, mine is highlighting much to bright. I'll have to check those voltage levels in the Z-Axis circuit and see if the plugins are somehow providing the wrong voltages.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Mark Vincent" <orangeglowaudio@...>
To: "tekscopes" <TekScopes@groups.io>
Sent: Thursday, October 21, 2021 10:17:14 AM
Subject: Re: [TekScopes] 7704A - Delayed Sweep Intensity Too Bright
Barry,

See if having the A/B intensity turned up and the crt bias up (more negative at
the grid) helps. If your S/N is <210000, check Q320, Q322, Q420 and Q422. These
are in the two heatsinks on the right side top. If these are leaky, use
KSP10BU. I do not see any internal intensity control in this model. It may be
that the delayed signal is to be brighter to give contrast.

Mark



Re: 7704A - Delayed Sweep Intensity Too Bright

n4buq
 

Stephen,

I'll have to check that. I think the problem is seen for other time-bases so not sure if it's a problem with the plugin but it could be.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "SCMenasian" <scm@...>
To: "tekscopes" <TekScopes@groups.io>
Sent: Thursday, October 21, 2021 11:04:37 AM
Subject: Re: [TekScopes] 7704A - Delayed Sweep Intensity Too Bright
Barry,

Maybe the discussion of Aux Z axis Control and Aux Z Axis Out on pages 3-16 and
3-17 of the 7B53A manual will give a clue. It describes the Z-Axis interface to
the mainframe. Since the 7B92A has a front panel contrast adjustment, the
interface probably has the ability to control intensity via a voltage level.
Perhaps a bad component in those sections of your 7B53A has that level pegged.

Stephen Menasian



Re: Idle Question About the 485

Ozan
 

Hi Walter,

On Thu, Oct 21, 2021 at 09:14 AM, walter shawlee wrote:
50 ohm protection on the 485 is a fusible ceramic element in the attenuator
chain, a rare and hard to find object.
---
485 has an active protection circuit that flips input relay to 1M-ohm setting to protect the 50-ohm attenuator. There could be a fusible element as well although I can't see it in the schematic or the pictures I took on my unit. Perhaps it was on certain serial number range.

Ozan


Re: Debugging begins: Tek 606

toby@...
 

On 2021-10-17 11:12 p.m., toby@... wrote:
Hi,
Was testing my Tek 606 yesterday, and after power on and the next few minutes it made about five "snap" discharge sounds with fluctuations in brightness. After the last one, I lost trace permanently.
Checked LV rails and all are spot on except for the +30 and +120 unregulated, which are off the HV transformer secondary. Before I go any farther, does anyone have a good idea of what the discharges might mean?
The next step seems to be to power the board to investigate further.

The HV section is basically this (but my unit shows some updates as mentioned previously): https://imgur.com/gtO35ue

Can anyone comment on whether it will be safe to operate this topology onnected to the LV supplies but with the CRT disconnected completely (grids, filament, cathode)? Or should I test with the CRT connected?

Either way I think I will probably be able to do this with the HV safety shield in place until I reach a point where I need to measure the HV itself.

--Toby



--Toby


Re: Idle Question About the 485

 

Jeff,

50 ohm protection on the 485 is a fusible ceramic element in the attenuator chain, a rare and hard to find object.
having said that, the 485 scope is very nice, but quite complex (especially in the vertical section) AND old, not a great combination today.

I was surprised at the relatively good condition of that 485 unit on ebay, it looks like a worthy overhaul candidate to me, especially considering the brightness of the unobtainable CRT. I was tempted myself, but aside from the fact susan would almost certainly kill me on its arrival, I have two (R)7903's which I far prefer for fast analog work. THAT is a great scope, and not adequately appreciated.

all the best,
walter
sphere research corp.


Re: 7704A - Delayed Sweep Intensity Too Bright

SCMenasian
 

Barry,

Maybe the discussion of Aux Z axis Control and Aux Z Axis Out on pages 3-16 and 3-17 of the 7B53A manual will give a clue. It describes the Z-Axis interface to the mainframe. Since the 7B92A has a front panel contrast adjustment, the interface probably has the ability to control intensity via a voltage level. Perhaps a bad component in those sections of your 7B53A has that level pegged.

Stephen Menasian


Re: USPS shipments comments

Dave Seiter
 

My brother-in-law worked for a law firm that specialized in maritime law.  He tells a story that happened at the port of Oakland- someone was importing two old MIGs, and they had survived the trip thus far without a scratch.  A team was supposed to move the planes (I would assume the fuselages at this point) onto flatbed(s) with forklifts.  They dropped the first one almost right away, thought they had figured out what they had done wrong (I guess, or didn't care), and then proceeded to drop the second one.  The customer was NOT happy, to say the least!
-Dave

On Thursday, October 21, 2021, 06:01:31 AM PDT, stevenhorii <sonodocsch@...> wrote:

I’ve been to quite a few warehouses to pick up stuff I had delivered by
freight. It’s a lot cheaper to pick it up compared with home delivery since
they need to dispatch a truck with a lift gate for most home deliveries
(unless you have a truck dock!) I have had to uncrate stuff in the customer
parking area when the crate was too large for my SUV.

I know why they generally do not allow customers to walk around the
warehouse. It’s dangerous. The forklift drivers zoom around and are not
expecting inexperienced folks to be on the floor. I have been allowed on
the floor when they were having trouble finding the crate I was expecting.
They did find it with my help - it turned out that it got moved to a
staging area for a later pickup day than I had told them.

I got talking with one of the foremen about the hazards of the fork lifts.
He told me that they are usually very good and that accidents with
shipments are few (but he would say that). He did tell me about a couple of
incidents with the driver running the forks through a crate. One of them
was a large screen flat-panel TV (in those days it meant a large insurance
payout). Things falling off the forks is another problem, but the drivers
usually know when they start to lift a pallet or crate if it is not far
enough back on the forks. I worried a little when they used a lift to get
my crate into my SUV. I could imagine the forks going through the rear
bumper or something. But the guy got it in and then raised the forks so the
ends of them were at the wood frame around the rear of the crate. He then
very slowly pushed it all the way into the back of the SUV managing to
avoid pushing into the backs of the front seats (I had folded the rear
seats down). These guys can be careful when they need to be.


On Thu, Oct 21, 2021 at 07:03 Michael A. Terrell <
terrell.michael.a@...> wrote:

That sounds like a Drew Carey show episode where Oswald smashed the scanner
in shipping while playing on a forklift.

On Wed, Oct 20, 2021 at 12:19 PM Jim Ford <james.ford@...> wrote:

Wasn't there a Dilbert strip like that where the company provided beer
for
the employees to loosen things up?  They ended up jousting with the
forklifts in the warehouse!  Jim Ford Sent from my Verizon, Samsung
Galaxy
smartphone
-------- Original message --------From: Ken Eckert <eckertkp@...>
Date: 10/20/21  8:51 AM  (GMT-08:00) To: TekScopes@groups.io Subject:
Re:
[TekScopes] USPS shipments comments My wife worked for a while in a BC
Liquour control board warehouse, guys would drive the forks into a pallet
just for a giggle............









Re: USPS shipments comments

Michael A. Terrell
 

I have driven forklifts and worked in a workbasket from one. That time, the
idiot driver who was assigned to the job kept disappearing. It ran out of
propane while I was working near the roof, running cables. He replaced the
tank, and opened the valve. It was leaking badly. I yelled to close the
valve. He just shrugged and said, "It'll stop", and walked off. My yelling
got the attention of the plant manager. They stopped the leaking propane,
and went to find him. The jackass could have destroyed the building and
killed over 100 production workers with a single spark. It took hours to
get the odor out of the building. They could only open all the doors to let
out the gas, because the contactors on the motors would have set off an
explosion if the machines were shut down.

On Thu, Oct 21, 2021 at 9:01 AM stevenhorii <sonodocsch@...> wrote:

I’ve been to quite a few warehouses to pick up stuff I had delivered by
freight. It’s a lot cheaper to pick it up compared with home delivery since
they need to dispatch a truck with a lift gate for most home deliveries
(unless you have a truck dock!) I have had to uncrate stuff in the customer
parking area when the crate was too large for my SUV.

I know why they generally do not allow customers to walk around the
warehouse. It’s dangerous. The forklift drivers zoom around and are not
expecting inexperienced folks to be on the floor. I have been allowed on
the floor when they were having trouble finding the crate I was expecting.
They did find it with my help - it turned out that it got moved to a
staging area for a later pickup day than I had told them.

I got talking with one of the foremen about the hazards of the fork lifts.
He told me that they are usually very good and that accidents with
shipments are few (but he would say that). He did tell me about a couple of
incidents with the driver running the forks through a crate. One of them
was a large screen flat-panel TV (in those days it meant a large insurance
payout). Things falling off the forks is another problem, but the drivers
usually know when they start to lift a pallet or crate if it is not far
enough back on the forks. I worried a little when they used a lift to get
my crate into my SUV. I could imagine the forks going through the rear
bumper or something. But the guy got it in and then raised the forks so the
ends of them were at the wood frame around the rear of the crate. He then
very slowly pushed it all the way into the back of the SUV managing to
avoid pushing into the backs of the front seats (I had folded the rear
seats down). These guys can be careful when they need to be.


On Thu, Oct 21, 2021 at 07:03 Michael A. Terrell <
terrell.michael.a@...> wrote:

That sounds like a Drew Carey show episode where Oswald smashed the
scanner
in shipping while playing on a forklift.

On Wed, Oct 20, 2021 at 12:19 PM Jim Ford <james.ford@...> wrote:

Wasn't there a Dilbert strip like that where the company provided beer
for
the employees to loosen things up? They ended up jousting with the
forklifts in the warehouse! Jim Ford Sent from my Verizon, Samsung
Galaxy
smartphone
-------- Original message --------From: Ken Eckert <eckertkp@...
Date: 10/20/21 8:51 AM (GMT-08:00) To: TekScopes@groups.io Subject:
Re:
[TekScopes] USPS shipments comments My wife worked for a while in a BC
Liquour control board warehouse, guys would drive the forks into a
pallet
just for a giggle............













485 input attenuation circuit protection modification

Mark Vincent
 

For those that have a 485, look at the S/N to see if it is in the lower range. At one point it was changed to protect the round IC from pluses from the relay coil when switching from 50 ohm to 1meg input. You can modify the circuit by adding the parts of the higher S/N to the lower to protect the IC. I did this in mine. The schematic will show both versions. The NPN transistor that is added is a 2N3904. A 2N2222/A or other will work.

There is also a 12V axial tantalum that is for the 9V filtering on each input. I removed the tantalums and put in a ULD 16V to prevent those tantalums from shorting. There is a 13V circuit that has 15V tantalums that will short. I used 47mfd 25V ULD types in this circuit.

Mark

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