Date   

Re: 7S12 problem

ycui7
 

Mine DC knob was separated into two of press too hard. You can try push the pot back into one piece from the back side.

Worth a try.

Yang Cui

On Mon, Jun 21, 2021, at 7:09 PM, Chris van Lint wrote:
Hi all,

My 7S12 sudden stopped working in a TDR configuration, using a S6 and
S52 plug-in.  I know that the S52 and the S6 are OK, as they have been
tested on a different 7S12.  The problem appears to be in the DC balance
circuitry.  Turning either or both the coarse and fine balance control
knobs does not result in any vertical movement of the trace. The
horizontal trace is there and can be varied in terms of speed.  I wonder
whether somebody who has experience with this beast can give me some
idea where to start looking, as this is quite a daunting bit of gear.

Chris







Re: Type CA module in a 545

Morris Odell
 

You should check the voltage divider from pin 15 of the plugin connector. That pin needs to sink 150 mA at 75 volts in all plugins. The 75 volts is derived from the +100 in the mainframe dropped through a couple of 12.6 volt tube heaters. In many plugins including the CA it is connected to a combination of tube heaters and divider resistors with taps to provide bias for various parts of the circuit. In the CA there are also interconnection networks with the +100 and +225 pins. One of those voltages from the divider network is +37.5 that supplies the suppressors of the output amplifier tubes. If that voltage is not right it could affect the gain of those stages. There are also +69 and +12.5 volt taps that are used for DC balance adjustment and to set operating conditions for other parts of the circuit.

Let us know what you find.

Cheers,

Morris


Re: 6DJ8 substitute idea - reverse engineering

Shaun M
 

Foks,
I have some experience with the Russian 6N23P tubes from various vendors.

To summarize:
Most vendors I have dealt ship from Ukraine and the shipping time can be quite long (up to 8 weeks) to Canada.
I check all the tubes on a curve tracer (uTracer) and run a set of plate curves to sort them.
The quality of the tubes is variable, but I have had many more fair-weak tubes than very good-excellent ones.
I bought the cheaper lot quantity tubes (say 20 tubes) rather than the ones marketed to the audio crowd (date matched, matched quad, etc., etc.)
I have received refunds for tube lots that were really junk and sold as "tested" or "new".
I have used the 6N23P in vintage gear in place of the 6DJ8; in fact, the initial reason I investigated the 6N23P was the HP 428B which uses two of them.

Shaun Merrigan


7S12 problem

Chris van Lint
 

Hi all,

My 7S12 sudden stopped working in a TDR configuration, using a S6 and S52 plug-in.  I know that the S52 and the S6 are OK, as they have been tested on a different 7S12.  The problem appears to be in the DC balance circuitry.  Turning either or both the coarse and fine balance control knobs does not result in any vertical movement of the trace. The horizontal trace is there and can be varied in terms of speed.  I wonder whether somebody who has experience with this beast can give me some idea where to start looking, as this is quite a daunting bit of gear.

Chris


Re: Type CA module in a 545

Tom Lee
 

I agree with Jim. It's not the filaments per se. They don't age that way. The resistance is coming from someplace else.

Cheers
Tom

Sent from an iThing; please excuse the terseness and typos

On Jun 21, 2021, at 6:59, "Jim Adney" <jadney@vwtype3.org> wrote:

On Sun, Jun 20, 2021 at 02:32 PM, David Kuhn wrote:

Everything looked the same except the filament resistance. Pin 15 to
ground is supposed to be ~65 ohms. On the good module is ~74 ohms. On
the weak one, it is 100 ohms.

So I guess I am looking at some old/bad tubes.
I'd be surprised if the actual filaments changed resistance that much. Check the pin to pin resistances right on the tubes and then see if there's a high resistance connection somewhere else. Frankly, 74 Ohms sounds much too high for a cold filament. There must be something else in that path.






Re: 7854 printed manuals and their revisions

Martin Hodge
 

Whoops, I left another thread hanging, sorry.

Immediately after Albert's reference to Artek Manuals I purchased a downloadable version from them in the SN range matching my scope. (I still want an original printed manual someday though)

Thanks all!


Re: Another interesting Tektronix web site

Dave Wise
 

Maybe 275-1N or 7110-0.5 or 7110-1.0 . The latter can be had for $8 each at https://www.shopbdproduct.com/product_p/7110-1.0.htm .

Dave Wise

From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of stevenhorii via groups.io
Sent: Monday, June 21, 2021 3:52 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Another interesting Tektronix web site

All on this thread,

There are Barry mounts which come in various sizes and damping abilities:

https://novibration.com/<https://novibration.com>

Scroll down the pages of this distributor’s Web site until you get to “Ball
mount series” which sounds like what you are looking for.

I have no conflict of interest with this company. I have seen Barry mounts
used quite a bit in various pieces of equipment when isolation from
vibration is important.

Steve Horii



On Mon, Jun 21, 2021 at 14:34 Dave Wise <david_wise@phoenix.com> wrote:

Thank you, Daniel, for your research and ideas.

The natural shape is a hollow ball. It must have been molded.
The screw plays no role in normal use; it limits motion extremes to keep
the cushions from tearing or coming out of the mounting holes.

I replaced all the cushions in my D and H, maybe ten years ago, with
new-old-stock I bought from Stan Griffiths. (They all have the same orange
paint stripe.) Most are fine but one is a mosaic of cracks. I’ve read
that making rubber is not 100% science. I figure there was a bad batch.

A solid ball with a hole through the middle would be too stiff unless the
rubber was exceptionally soft.

Another TekScopes member created a photo album, "541 Flip-flop fan
mounts", in which he created fan mounts from the sole of an old sandal. It
seems to me that I could combine that with your tubing idea.

- Long screw or stud, nuts, washers
- Thick-wall latex or silicone tubing, with 5/16” outside diameter (slip
fit in the mounting hole) when the screw is in
- Three foam rubber disks with 5/16” hole

- Put screw through tubing
- Thread first disk onto it
- Slide into first mounting hole
- Thread second disk onto it
- Slide through second mounting hole
- Thread third disk onto it
- Add washer and nut just snug

The foam rubber disks cushion axial motion, the tubing cushions radial
motion, and the screw holds it all together.

I will look around for an old mouse pad. Cut into disks with scissors and
hole with a paper punch. This just might work!

Dave Wise

From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Daniel Koller via groups.io
Sent: Sunday, June 20, 2021 5:42 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Another interesting Tektronix web site

Hi all,
I took a look at my D. My shock mounts are not gray - they are black.
They are just so oxidized on the surface they look grey, but they darkened
up with rubbing.
They have the consistency of latex surgical tubing, which makes me
wonder if A) that is what they are made of, and B) maybe that is what they
can be made of. I think if allowed to expand fully, they would be closer
to "I" shaped - a tube with flanges on the ends, rather than "ball
shaped". They take on the ball shape because they are compressed in their
mounts. You might be able to approximate them with surgical tubing. I
don't know if latex can be formed like thermoplastics, but if so, you could
try heating a section of tubing and blowing into it to bulge it out.
Donno. But making a flange would be hard. That might have to be molded.
Regarding molding hollow things - maybe mold the solid part, then
freeze it and drill out the center in a drill press? Keep it frozen in the
mold until drilled. Might be able to cast it in RTV that way. But the
resulting part will still be stiffer, in my opinion, than the original,
just based on poking at the ones I have on the chassis.
Another possible option is to 3D print. I have been playing with a very
soft thermoplastic polyeurethane (TPU) in my 3D printer. One needs a
special extruder with very little clearance between the extruder gears and
the feed tube, OR a direct extruder that goes right into the print head, in
order to be able to "push" the plastic through. But it does work, and I
have successfully printed lens caps and gaskets. I have not yet tried
stand-offs and vibration mounts, but I do plan on printing a door bumper
for a car, which has some of the features of the D's mounts. In the end,
the consistency will be a bit stiffer than RTV I think. There is
"Ninjaflex" TPU available, which is even softer, but I have not tried it
yet.
Ok, and lookie here:
https://www.plasticballsupply.com/1-2-in-0-5-black-buna-rubber-resin-balls/?utm_campaign=shopping&utm_medium=cpc&utm_source=google&gclid=CjwKCAjwzruGBhBAEiwAUqMR8HA-hPxNS7QI8J9bTUim39oKHQD8fSUIEJESdlbOjltfInNCf-jM_xoCt7EQAvD_BwE<https://www.plasticballsupply.com/1-2-in-0-5-black-buna-rubber-resin-balls/?utm_campaign=shopping&utm_medium=cpc&utm_source=google&gclid=CjwKCAjwzruGBhBAEiwAUqMR8HA-hPxNS7QI8J9bTUim39oKHQD8fSUIEJESdlbOjltfInNCf-jM_xoCt7EQAvD_BwE>
<
https://www.plasticballsupply.com/1-2-in-0-5-black-buna-rubber-resin-balls/?utm_campaign=shopping&utm_medium=cpc&utm_source=google&gclid=CjwKCAjwzruGBhBAEiwAUqMR8HA-hPxNS7QI8J9bTUim39oKHQD8fSUIEJESdlbOjltfInNCf-jM_xoCt7EQAvD_BwE<https://www.plasticballsupply.com/1-2-in-0-5-black-buna-rubber-resin-balls/?utm_campaign=shopping&utm_medium=cpc&utm_source=google&gclid=CjwKCAjwzruGBhBAEiwAUqMR8HA-hPxNS7QI8J9bTUim39oKHQD8fSUIEJESdlbOjltfInNCf-jM_xoCt7EQAvD_BwE>
Rubber balls. You still need to put a hole through them. The
dermatologist can provide the answer. Just go have a mole removed and ask
them for the hole-punching razor tool they use to circumscribe the mole.
I saved one or two and they are about 3 and 5 mm in diameter or so, with
various sizes available. This is cheap if insurance pays for the
service. Otherwise, you can get biopsy punches on amazon.


https://www.amazon.com/Biopsy-Punch-Sterile-Stainless-Steel/dp/B07R25NHBR/ref=pb_allspark_dp_session_sims_pao_desktop_5/141-2449543-9055469?pd_rd_w=4kBMY&pf_rd_p=3ac2ce50-9d75-4bd3-868d-72b252a0623c&pf_rd_r=1B8PSTPQSFTG3WBK8GEW&pd_rd_r=59842b2f-725a-4e66-90d4-d34a3844db5d&pd_rd_wg=wZjGh&pd_rd_i=B07R25NHBR&psc=1<https://www.amazon.com/Biopsy-Punch-Sterile-Stainless-Steel/dp/B07R25NHBR/ref=pb_allspark_dp_session_sims_pao_desktop_5/141-2449543-9055469?pd_rd_w=4kBMY&pf_rd_p=3ac2ce50-9d75-4bd3-868d-72b252a0623c&pf_rd_r=1B8PSTPQSFTG3WBK8GEW&pd_rd_r=59842b2f-725a-4e66-90d4-d34a3844db5d&pd_rd_wg=wZjGh&pd_rd_i=B07R25NHBR&psc=1>
<
https://www.amazon.com/Biopsy-Punch-Sterile-Stainless-Steel/dp/B07R25NHBR/ref=pb_allspark_dp_session_sims_pao_desktop_5/141-2449543-9055469?pd_rd_w=4kBMY&pf_rd_p=3ac2ce50-9d75-4bd3-868d-72b252a0623c&pf_rd_r=1B8PSTPQSFTG3WBK8GEW&pd_rd_r=59842b2f-725a-4e66-90d4-d34a3844db5d&pd_rd_wg=wZjGh&pd_rd_i=B07R25NHBR&psc=1<https://www.amazon.com/Biopsy-Punch-Sterile-Stainless-Steel/dp/B07R25NHBR/ref=pb_allspark_dp_session_sims_pao_desktop_5/141-2449543-9055469?pd_rd_w=4kBMY&pf_rd_p=3ac2ce50-9d75-4bd3-868d-72b252a0623c&pf_rd_r=1B8PSTPQSFTG3WBK8GEW&pd_rd_r=59842b2f-725a-4e66-90d4-d34a3844db5d&pd_rd_wg=wZjGh&pd_rd_i=B07R25NHBR&psc=1>
I think careful use of one of those punches can put a neat hole through
a rubber ball, and rubber washers seem to be available in plenty of sizes
on the interwebs! Good luck.
I'd be curious to know how you replace these. My 503 has latex
isolation mounts in parts of the circuitry. I'm betting they are getting
pretty dried up.
Dan

On Sunday, June 20, 2021, 04:16:31 PM EDT, teamlarryohio <
larrys@teamlarry.com> wrote:

Been far too long, but the ones I used were the same type generally as the
fan mounts. Otoh, McMaster has a huge variety of hardware bits.
G'luck!
-ls-














Re: Shockmounts, stand-offs and top pouches... all at stuff day

Dave Wise
 

Those 1dollar parts look like they could be adapted to 500 series fans.

Dave Wise

From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of walter shawlee via groups.io
Sent: Monday, June 21, 2021 2:47 PM
To: TekScopes@groups.io
Subject: [TekScopes] Shockmounts, stand-offs and top pouches... all at stuff day

There have been several threads about people looking for shockmounts, I posted the two types we have up to the stuff page, please see: https://www.sphere.bc.ca/test/stuffday.html#1dollar<https://www.sphere.bc.ca/test/stuffday.html#1dollar>

much bigger ones are here: https://www.sphere.bc.ca/test/stuffday.html#2dollar<https://www.sphere.bc.ca/test/stuffday.html#2dollar>
plus some great stand-offs for assembly.

there's also a great assortment of Tek top accessory pouches here:
https://www.sphere.bc.ca/test/stuffday.html#tekfans<https://www.sphere.bc.ca/test/stuffday.html#tekfans>
along with a great Ballantine time mark generator for timebase calibration.

and there's an amazing amplifier and distortion analyzer here:
https://www.sphere.bc.ca/test/stuffday.html#needslove<https://www.sphere.bc.ca/test/stuffday.html#needslove>

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


Re: Another interesting Tektronix web site

stevenhorii
 

All on this thread,

There are Barry mounts which come in various sizes and damping abilities:

https://novibration.com/

Scroll down the pages of this distributor’s Web site until you get to “Ball
mount series” which sounds like what you are looking for.

I have no conflict of interest with this company. I have seen Barry mounts
used quite a bit in various pieces of equipment when isolation from
vibration is important.

Steve Horii

On Mon, Jun 21, 2021 at 14:34 Dave Wise <david_wise@phoenix.com> wrote:

Thank you, Daniel, for your research and ideas.

The natural shape is a hollow ball. It must have been molded.
The screw plays no role in normal use; it limits motion extremes to keep
the cushions from tearing or coming out of the mounting holes.

I replaced all the cushions in my D and H, maybe ten years ago, with
new-old-stock I bought from Stan Griffiths. (They all have the same orange
paint stripe.) Most are fine but one is a mosaic of cracks. I’ve read
that making rubber is not 100% science. I figure there was a bad batch.

A solid ball with a hole through the middle would be too stiff unless the
rubber was exceptionally soft.

Another TekScopes member created a photo album, "541 Flip-flop fan
mounts", in which he created fan mounts from the sole of an old sandal. It
seems to me that I could combine that with your tubing idea.

- Long screw or stud, nuts, washers
- Thick-wall latex or silicone tubing, with 5/16” outside diameter (slip
fit in the mounting hole) when the screw is in
- Three foam rubber disks with 5/16” hole

- Put screw through tubing
- Thread first disk onto it
- Slide into first mounting hole
- Thread second disk onto it
- Slide through second mounting hole
- Thread third disk onto it
- Add washer and nut just snug

The foam rubber disks cushion axial motion, the tubing cushions radial
motion, and the screw holds it all together.

I will look around for an old mouse pad. Cut into disks with scissors and
hole with a paper punch. This just might work!

Dave Wise

From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Daniel Koller via groups.io
Sent: Sunday, June 20, 2021 5:42 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Another interesting Tektronix web site

Hi all,
I took a look at my D. My shock mounts are not gray - they are black.
They are just so oxidized on the surface they look grey, but they darkened
up with rubbing.
They have the consistency of latex surgical tubing, which makes me
wonder if A) that is what they are made of, and B) maybe that is what they
can be made of. I think if allowed to expand fully, they would be closer
to "I" shaped - a tube with flanges on the ends, rather than "ball
shaped". They take on the ball shape because they are compressed in their
mounts. You might be able to approximate them with surgical tubing. I
don't know if latex can be formed like thermoplastics, but if so, you could
try heating a section of tubing and blowing into it to bulge it out.
Donno. But making a flange would be hard. That might have to be molded.
Regarding molding hollow things - maybe mold the solid part, then
freeze it and drill out the center in a drill press? Keep it frozen in the
mold until drilled. Might be able to cast it in RTV that way. But the
resulting part will still be stiffer, in my opinion, than the original,
just based on poking at the ones I have on the chassis.
Another possible option is to 3D print. I have been playing with a very
soft thermoplastic polyeurethane (TPU) in my 3D printer. One needs a
special extruder with very little clearance between the extruder gears and
the feed tube, OR a direct extruder that goes right into the print head, in
order to be able to "push" the plastic through. But it does work, and I
have successfully printed lens caps and gaskets. I have not yet tried
stand-offs and vibration mounts, but I do plan on printing a door bumper
for a car, which has some of the features of the D's mounts. In the end,
the consistency will be a bit stiffer than RTV I think. There is
"Ninjaflex" TPU available, which is even softer, but I have not tried it
yet.
Ok, and lookie here:
https://www.plasticballsupply.com/1-2-in-0-5-black-buna-rubber-resin-balls/?utm_campaign=shopping&utm_medium=cpc&utm_source=google&gclid=CjwKCAjwzruGBhBAEiwAUqMR8HA-hPxNS7QI8J9bTUim39oKHQD8fSUIEJESdlbOjltfInNCf-jM_xoCt7EQAvD_BwE
<
https://www.plasticballsupply.com/1-2-in-0-5-black-buna-rubber-resin-balls/?utm_campaign=shopping&utm_medium=cpc&utm_source=google&gclid=CjwKCAjwzruGBhBAEiwAUqMR8HA-hPxNS7QI8J9bTUim39oKHQD8fSUIEJESdlbOjltfInNCf-jM_xoCt7EQAvD_BwE
Rubber balls. You still need to put a hole through them. The
dermatologist can provide the answer. Just go have a mole removed and ask
them for the hole-punching razor tool they use to circumscribe the mole.
I saved one or two and they are about 3 and 5 mm in diameter or so, with
various sizes available. This is cheap if insurance pays for the
service. Otherwise, you can get biopsy punches on amazon.


https://www.amazon.com/Biopsy-Punch-Sterile-Stainless-Steel/dp/B07R25NHBR/ref=pb_allspark_dp_session_sims_pao_desktop_5/141-2449543-9055469?pd_rd_w=4kBMY&pf_rd_p=3ac2ce50-9d75-4bd3-868d-72b252a0623c&pf_rd_r=1B8PSTPQSFTG3WBK8GEW&pd_rd_r=59842b2f-725a-4e66-90d4-d34a3844db5d&pd_rd_wg=wZjGh&pd_rd_i=B07R25NHBR&psc=1
<
https://www.amazon.com/Biopsy-Punch-Sterile-Stainless-Steel/dp/B07R25NHBR/ref=pb_allspark_dp_session_sims_pao_desktop_5/141-2449543-9055469?pd_rd_w=4kBMY&pf_rd_p=3ac2ce50-9d75-4bd3-868d-72b252a0623c&pf_rd_r=1B8PSTPQSFTG3WBK8GEW&pd_rd_r=59842b2f-725a-4e66-90d4-d34a3844db5d&pd_rd_wg=wZjGh&pd_rd_i=B07R25NHBR&psc=1
I think careful use of one of those punches can put a neat hole through
a rubber ball, and rubber washers seem to be available in plenty of sizes
on the interwebs! Good luck.
I'd be curious to know how you replace these. My 503 has latex
isolation mounts in parts of the circuitry. I'm betting they are getting
pretty dried up.
Dan

On Sunday, June 20, 2021, 04:16:31 PM EDT, teamlarryohio <
larrys@teamlarry.com> wrote:

Been far too long, but the ones I used were the same type generally as the
fan mounts. Otoh, McMaster has a huge variety of hardware bits.
G'luck!
-ls-














Shockmounts, stand-offs and top pouches... all at stuff day

 

There have been several threads about people looking for shockmounts, I posted the two types we have up to the stuff page, please see: https://www.sphere.bc.ca/test/stuffday.html#1dollar

much bigger ones are here: https://www.sphere.bc.ca/test/stuffday.html#2dollar
plus some great stand-offs for assembly.

there's also a great assortment of Tek top accessory pouches here:
https://www.sphere.bc.ca/test/stuffday.html#tekfans
along with a great Ballantine time mark generator for timebase calibration.

and there's an amazing amplifier and distortion analyzer here:
https://www.sphere.bc.ca/test/stuffday.html#needslove

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


Re: SG 502 Assistance?

Eric
 

Cory,
Ill help where I can I have made it a habit to repair a scope or two. Your AA501A is configured exactly the same as mine. You should also have a filter labeled "A weight" this is a fixed tuned curve the A stands for "Audio" It puts some EQ on the input filter. The manual has the exact response curve in it if I remember correctly. It was supposed to be a pleasing response specifically for testing audio gear. To truly do a cal on it if that is you goal you will need a SG505 Option 1 as well. The bread and butter of the AA501 is in the audio listening range, But it is a very capable instrument under 100 Khz. And will the 200 Vac input rating it is definitely less finicky then a spectrum analyzer.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of sweetbeats
Sent: Monday, June 21, 2021 5:13 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] SG 502 Assistance?

Thanks again, Eric!

I will be careful with the scope…would love to just send it somewhere and pay a reputable Tek tech to make it right but I’m not sure where to turn for that, so in lieu of that hoping I can get some assistance here.

My AA 501A is fitted with Option 1…I’ll have to test the SG 502 again…there are independent 30kHz and 80kHz LPFs and a 400Hz HPF on mine.

Cory


Re: SG 502 Assistance?

sweetbeats
 

Thanks again, Eric!

I will be careful with the scope…would love to just send it somewhere and pay a reputable Tek tech to make it right but I’m not sure where to turn for that, so in lieu of that hoping I can get some assistance here.

My AA 501A is fitted with Option 1…I’ll have to test the SG 502 again…there are independent 30kHz and 80kHz LPFs and a 400Hz HPF on mine.

Cory


Re: 'splitting' A2 and A3 PCBs when recapping Tek 2465

Jon Nicoll
 

Thanks Jared, your video looks useful and interesting in any case.

I was hoping you might go through the removal of the main board, but I see not ... ;-/

Cheers, Jon N


Re: 6DJ8 substitute idea - reverse engineering

Joe
 

Hello,

Quite a while ago I was in need of about 30 pcs 6DJ8 for my 585A. Some more that I could locate in my vaults including Siemens E88CC, RCA 6922 and such. So I decided to buy a 50's pack 6N23P from a mil surplus dealer in the middle of Ukraine. NOS and well packed, they arrived safe and sound. So I let them all burn in for 24 hrs and put them on my French Metrix Pont 661 tube tester. One of my criteria was that both systems of each tube should match in transconductance by 5% or closer. What can I say: The cohort behaved just as Carl Friedrich Gauss would have predicted and I ended up with approval for the quantity just needed. Ok, this is just a snapshot showing the "new" status and we will wait and see how they are ageing. However, I found one gassy tube within that brand new "mil-spec" lot.

Regards, Joe


Re: 6DJ8 substitute idea - reverse engineering

cmjones01
 

On Mon, Jun 21, 2021 at 4:40 PM Stephen <stephen.nabet@gmail.com> wrote:

On Mon, Jun 21, 2021 at 04:24 AM, Carl Hallberg wrote:

Thanks, Stephen.
I meant ECC88, not EEC88. Are they a good type?
Carl
Are ECC88 Good? It depends on want the application is. Now if you’re asking about British made tubes, they are usually top notch quality, all of them.
European-built Tek scopes, from Guernsey and Heerenveen, are full of
locally-made ECC88 tubes. As far as I'm concerned they're 100%
interchangeable with 6DJ8, and Tek seemed to think the same. I have a
small replacement supply of E88CC (same as ECC88/6DJ8 but 'special
quality', for whatever that's worth) made by Tesla in communist
Czechoslovakia. They seem to work absolutely fine, and were cheap
because they're not, or at least weren't, a brand desirable to the
golden-ears club.

Chris


Re: Tek 485 erratic baseline sweep all time base

 

Kevin,

from your description of the symptoms it sounds like dirty switch contacts. Specifically, because you said that it "sometimes" settles out it suggests that this is not temperature related, and it's not an outright failed component. If you look in the service manual you will see that the horizontal sweep selector switches have a few columns that are engaged for almost all positions, and they overlap to cover all positions. If only a couple of those switch contacts were dirty it would clobber the entire sweep system, and dirty contacts do sometimes make good contact if you exercise them enough, and hold your tongue at just the right angle.

Another possibility is that one of the horizontal deflection plates is not connected, or the connection is dirty. This would be most likely if the "not full width" that you mention is in fact the right or left half of the screen, though I can imagine a way for dirty contacts on the CRT pins to produce a "not full width" sweep that manifests merely as reduce horizontal deflection.

Both of these possibilities are easy to check and address, one by cleaning the contacts in the timing drum switch, the other by checking the connections to the CRT horizontal plates.

Otherwise, someone with more skill and experience will need to advise you on what components may be failing. My only experience with loss of horizontal sweep is from a completely failed electrolytic capacitor in a 475, and that just took the sweep out altogether. It looked nothing like what you are describing.

DISCLAIMER: I've got no experience specifically with the 485, but I've worked on a couple 475s and 475As.

DISCLAIMER #2: cleaning leaf contacts in drum switch should be done with strips of 100% rag bond paper and anhydrous isopropyl alcohol.

DISCLAIMER #3: There are dangerous voltages around the CRT, including a high voltage charge that the CRT itself can retain for quite a long time after the instrument has been switch off. Exercise caution around the CRT to avoid injury from electric shock.

-- Jeff Dutky


Re: Another interesting Tektronix web site

Dave Wise
 

Thank you, Daniel, for your research and ideas.

The natural shape is a hollow ball. It must have been molded.
The screw plays no role in normal use; it limits motion extremes to keep the cushions from tearing or coming out of the mounting holes.

I replaced all the cushions in my D and H, maybe ten years ago, with new-old-stock I bought from Stan Griffiths. (They all have the same orange paint stripe.) Most are fine but one is a mosaic of cracks. I’ve read that making rubber is not 100% science. I figure there was a bad batch.

A solid ball with a hole through the middle would be too stiff unless the rubber was exceptionally soft.

Another TekScopes member created a photo album, "541 Flip-flop fan mounts", in which he created fan mounts from the sole of an old sandal. It seems to me that I could combine that with your tubing idea.

- Long screw or stud, nuts, washers
- Thick-wall latex or silicone tubing, with 5/16” outside diameter (slip fit in the mounting hole) when the screw is in
- Three foam rubber disks with 5/16” hole

- Put screw through tubing
- Thread first disk onto it
- Slide into first mounting hole
- Thread second disk onto it
- Slide through second mounting hole
- Thread third disk onto it
- Add washer and nut just snug

The foam rubber disks cushion axial motion, the tubing cushions radial motion, and the screw holds it all together.

I will look around for an old mouse pad. Cut into disks with scissors and hole with a paper punch. This just might work!

Dave Wise

From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Daniel Koller via groups.io
Sent: Sunday, June 20, 2021 5:42 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Another interesting Tektronix web site

Hi all,
I took a look at my D. My shock mounts are not gray - they are black. They are just so oxidized on the surface they look grey, but they darkened up with rubbing.
They have the consistency of latex surgical tubing, which makes me wonder if A) that is what they are made of, and B) maybe that is what they can be made of. I think if allowed to expand fully, they would be closer to "I" shaped - a tube with flanges on the ends, rather than "ball shaped". They take on the ball shape because they are compressed in their mounts. You might be able to approximate them with surgical tubing. I don't know if latex can be formed like thermoplastics, but if so, you could try heating a section of tubing and blowing into it to bulge it out. Donno. But making a flange would be hard. That might have to be molded.
Regarding molding hollow things - maybe mold the solid part, then freeze it and drill out the center in a drill press? Keep it frozen in the mold until drilled. Might be able to cast it in RTV that way. But the resulting part will still be stiffer, in my opinion, than the original, just based on poking at the ones I have on the chassis.
Another possible option is to 3D print. I have been playing with a very soft thermoplastic polyeurethane (TPU) in my 3D printer. One needs a special extruder with very little clearance between the extruder gears and the feed tube, OR a direct extruder that goes right into the print head, in order to be able to "push" the plastic through. But it does work, and I have successfully printed lens caps and gaskets. I have not yet tried stand-offs and vibration mounts, but I do plan on printing a door bumper for a car, which has some of the features of the D's mounts. In the end, the consistency will be a bit stiffer than RTV I think. There is "Ninjaflex" TPU available, which is even softer, but I have not tried it yet.
Ok, and lookie here:https://www.plasticballsupply.com/1-2-in-0-5-black-buna-rubber-resin-balls/?utm_campaign=shopping&utm_medium=cpc&utm_source=google&gclid=CjwKCAjwzruGBhBAEiwAUqMR8HA-hPxNS7QI8J9bTUim39oKHQD8fSUIEJESdlbOjltfInNCf-jM_xoCt7EQAvD_BwE<https://www.plasticballsupply.com/1-2-in-0-5-black-buna-rubber-resin-balls/?utm_campaign=shopping&utm_medium=cpc&utm_source=google&gclid=CjwKCAjwzruGBhBAEiwAUqMR8HA-hPxNS7QI8J9bTUim39oKHQD8fSUIEJESdlbOjltfInNCf-jM_xoCt7EQAvD_BwE>
Rubber balls. You still need to put a hole through them. The dermatologist can provide the answer. Just go have a mole removed and ask them for the hole-punching razor tool they use to circumscribe the mole. I saved one or two and they are about 3 and 5 mm in diameter or so, with various sizes available. This is cheap if insurance pays for the service. Otherwise, you can get biopsy punches on amazon.

https://www.amazon.com/Biopsy-Punch-Sterile-Stainless-Steel/dp/B07R25NHBR/ref=pb_allspark_dp_session_sims_pao_desktop_5/141-2449543-9055469?pd_rd_w=4kBMY&pf_rd_p=3ac2ce50-9d75-4bd3-868d-72b252a0623c&pf_rd_r=1B8PSTPQSFTG3WBK8GEW&pd_rd_r=59842b2f-725a-4e66-90d4-d34a3844db5d&pd_rd_wg=wZjGh&pd_rd_i=B07R25NHBR&psc=1<https://www.amazon.com/Biopsy-Punch-Sterile-Stainless-Steel/dp/B07R25NHBR/ref=pb_allspark_dp_session_sims_pao_desktop_5/141-2449543-9055469?pd_rd_w=4kBMY&pf_rd_p=3ac2ce50-9d75-4bd3-868d-72b252a0623c&pf_rd_r=1B8PSTPQSFTG3WBK8GEW&pd_rd_r=59842b2f-725a-4e66-90d4-d34a3844db5d&pd_rd_wg=wZjGh&pd_rd_i=B07R25NHBR&psc=1>

I think careful use of one of those punches can put a neat hole through a rubber ball, and rubber washers seem to be available in plenty of sizes on the interwebs! Good luck.
I'd be curious to know how you replace these. My 503 has latex isolation mounts in parts of the circuitry. I'm betting they are getting pretty dried up.
Dan

On Sunday, June 20, 2021, 04:16:31 PM EDT, teamlarryohio <larrys@teamlarry.com> wrote:

Been far too long, but the ones I used were the same type generally as the fan mounts. Otoh, McMaster has a huge variety of hardware bits.
G'luck!
-ls-


Re: 6DJ8 substitute idea - reverse engineering

Liam Perkins
 

Or, and if you need them, you could buy current production parts from
Eurotubes https://www.eurotubes.com/store/pc/E88CC-6922-or-6DJ8-c52.htm who
can provide them curve tracer, section-to-section matched and noise graded.
They have the RoeTest curve tracer and an ex-Tek guy, Matt Kamina working
with them. They know what they're doing. Here are a couple links to the
RoeTest site http://roehrentest.de/EnglishInfo.html
http://roehrentest.de/RoeTest2.html.
I wouldn't even consider downgrading to the 6BQ7, such a move is neither
productive nor necessary.
Liam

On Mon, Jun 21, 2021 at 12:10 PM Jeff Dutky <jeff.dutky@gmail.com> wrote:

Keith wrote:

With any non-Tek prepped NOS 6BQ7 OR current production 6N23P we could
do the very same thing. Burn in and section balance measurements are
not very
difficult to do. You just have to tell yourself the truth when
measurements show
that you have to to reject six of those seemingly "economical" 6N23P.
Allowing for
waste, these seemingly less expensive tubes might suddenly "cost" you $5
or
more a pop, plus the time wasted burning in and measuring.
Of course you just turn around and resell the "failed" tubes to the
audiophools on eBay for $10 each as "burned in and tested." It wouldn't be
a lie, or even an exaggeration.

-- Jeff Dutky






Re: 6DJ8 substitute idea - reverse engineering

 

Keith wrote:

With any non-Tek prepped NOS 6BQ7 OR current production 6N23P we could
do the very same thing. Burn in and section balance measurements are not very
difficult to do. You just have to tell yourself the truth when measurements show
that you have to to reject six of those seemingly "economical" 6N23P. Allowing for
waste, these seemingly less expensive tubes might suddenly "cost" you $5 or
more a pop, plus the time wasted burning in and measuring.
Of course you just turn around and resell the "failed" tubes to the audiophools on eBay for $10 each as "burned in and tested." It wouldn't be a lie, or even an exaggeration.

-- Jeff Dutky


Re: Another interesting Tektronix web site

Dave Wise
 

Keith, if you go ahead with your idea I will be looking forward to a report.
Meanwhile, if you want to save your strength for other projects, the 348-008 fan mount used in the 500 series can be drop-in replaced by McMaster-Carr part number
9376K15 or 9213K11. One is neoprene, the other natural rubber. Same dimensions and hardness.
I bought a bag years ago and was giving them away, but my supply has finally dwindled.
There are dozens if not hundreds of similar parts sold at Amazon and so on.

Dave Wise

From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Keith via groups.io
Sent: Monday, June 21, 2021 6:16 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Another interesting Tektronix web site

re: fan vibration isolators, p/n 348-008 and similar

Well, I've looked at these some already, and I am about to have to address this on my 575 rebuild. I'm toying with the idea of adapting Sorbothane and forming my own version of isolator replacements for Tek 348-008. I know it won't be original, but Sorbothane will outperform rubber any day of the week for vibration isolation. I hate fan vibration noise.

Sorbothane is fairly easy to find and comes in different elasticity values. Here are examples;

As equipment feet: https://www.scientificindustries.com/shock-absorbing-feet-microplate-genie-4.html?gclid=CjwKCAjw8cCGBhB6EiwAgORey0tSiIJkrFdHmkW8wP__jf58xSHbQzOQ1nzrseGZL9EtzNimuAH6jBoCWScQAvD_BwE<https://www.scientificindustries.com/shock-absorbing-feet-microplate-genie-4.html?gclid=CjwKCAjw8cCGBhB6EiwAgORey0tSiIJkrFdHmkW8wP__jf58xSHbQzOQ1nzrseGZL9EtzNimuAH6jBoCWScQAvD_BwE>

As disc bushings adaptable to various uses; https://www.amazon.com/Isolate-Sorbothane-Vibration-Isolation-Circular/dp/B00X6R47N0/ref=asc_df_B00X6R47N0/?tag=hyprod-20&linkCode=df0&hvadid=343351339353&hvpos=&hvnetw=g&hvrand=13667055082900351822&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9025850&hvtargid=pla-692662753862&psc=1&tag=&ref=&adgrpid=67841369743&hvpone=&hvptwo=&hvadid=343351339353&hvpos=&hvnetw=g&hvrand=13667055082900351822&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9025850&hvtargid=pla-692662753862<https://www.amazon.com/Isolate-Sorbothane-Vibration-Isolation-Circular/dp/B00X6R47N0/ref=asc_df_B00X6R47N0/?tag=hyprod-20&linkCode=df0&hvadid=343351339353&hvpos=&hvnetw=g&hvrand=13667055082900351822&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9025850&hvtargid=pla-692662753862&psc=1&tag=&ref=&adgrpid=67841369743&hvpone=&hvptwo=&hvadid=343351339353&hvpos=&hvnetw=g&hvrand=13667055082900351822&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9025850&hvtargid=pla-692662753862>

I've used this before. It is really a much better material than Buna-N rubber.

Of course, we have to accept that it won't look quite NOS original, which will definitely cost us points at the Concours d'Elegance judging events for our restored scopes. :-)

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