Repair broken Tek 485 or buy good used 2465/A/B?

[[email protected]]

Greetings,

I have a ('77 ?) Tektronix 485 scope (serial starts with a 'B' or an
'8', number is 167020) that I received 4 years ago. At the time it
worked, although I was (still am somewhat) pretty "green" regarding
electronics as I am more of a hobbyist than a professional as I love
to learn and "tinker". In the past, I have serviced tube amplifiers
for friends. Right now I have a 3M (Mincom) M56 professional
multitrack tape recorder I am currently in the process of aligning. I
guess you could say I am an "analog dinosaur" of sorts... LOL.

When I initially got the 485, the unit powered up and I could do some
basic sweeps, but I have not really used it since I initially got it
(mainly due to getting married, having kids and buying a new house -
funny how those things take up gobs of your life ;-). When I went to
turn it on about a year ago, I noticed a clicking or chirping with no
beam. Apparently as I understand it based on some quick research on
the 'net, this is not an uncommon symptom on these 'scopes having a
power supply trying to start but failing due to current overload of
some sort (capacitors?).

So, I did a search on Tektronix repair and came up with a person that
thinks they will be able to fix it.

However, for the price of the repair (and maybe a little more), I am
wondering if I wouldn't be better served with something like a 2465/A/
B?

Here's some reasons why maybe I think I should go with the 2465:

1) Compared to the 485, it's a newer 'scope with perhaps less hours
than my 485 (don't know how much use my 485 has had; it appears to be
in average or slightly better condition)
2) Less "mechanical" parts in the 2465 (e.g., pots, etc. from my
understanding) to fail
3) Lots think this is the epitome of the analog oscilloscope

Reasons why I should maybe stay with my 485:

1) Better proprietary IC availability (?, don't beat me up; I thought
this was what I read...)
2) Easier to service/repair than the 2465
3) More robust for the beginner

Obviously if I am thinking like this, I have no idea what I should
ultimately do. What does everyone think? <ducking>

 

[James Sweet]

Greetings,

I have a ('77 ?) Tektronix 485 scope (serial starts with a 'B' or an
'8', number is 167020) that I received 4 years ago. At the time it
worked, although I was (still am somewhat) pretty "green" regarding
electronics as I am more of a hobbyist than a professional as I love
to learn and "tinker". In the past, I have serviced tube amplifiers
for friends. Right now I have a 3M (Mincom) M56 professional
multitrack tape recorder I am currently in the process of aligning. I
guess you could say I am an "analog dinosaur" of sorts... LOL.

When I initially got the 485, the unit powered up and I could do some
basic sweeps, but I have not really used it since I initially got it
(mainly due to getting married, having kids and buying a new house -
funny how those things take up gobs of your life ;-). When I went to
turn it on about a year ago, I noticed a clicking or chirping with no
beam. Apparently as I understand it based on some quick research on
the 'net, this is not an uncommon symptom on these 'scopes having a
power supply trying to start but failing due to current overload of
some sort (capacitors?).

So, I did a search on Tektronix repair and came up with a person that
thinks they will be able to fix it.

However, for the price of the repair (and maybe a little more), I am
wondering if I wouldn't be better served with something like a 2465/A/
B?

Here's some reasons why maybe I think I should go with the 2465:

1) Compared to the 485, it's a newer 'scope with perhaps less hours
than my 485 (don't know how much use my 485 has had; it appears to be
in average or slightly better condition)
2) Less "mechanical" parts in the 2465 (e.g., pots, etc. from my
understanding) to fail
3) Lots think this is the epitome of the analog oscilloscope

Reasons why I should maybe stay with my 485:

1) Better proprietary IC availability (?, don't beat me up; I thought
this was what I read...)
2) Easier to service/repair than the 2465
3) More robust for the beginner

Obviously if I am thinking like this, I have no idea what I should
ultimately do. What does everyone think? <ducking>

The 485 is a really excellent scope, and the problem you describe should be
fairly easy to repair. There's no sense in upgrading, as a beginner you
probably won't use a large portion of the features the 485 provides even.

 

[Mike McGinn]

Greetings,

I have a ('77 ?) Tektronix 485 scope (serial starts with a 'B' or an
'8', number is 167020) that I received 4 years ago. At the time it
worked, although I was (still am somewhat) pretty "green" regarding
electronics as I am more of a hobbyist than a professional as I love
to learn and "tinker". In the past, I have serviced tube amplifiers
for friends. Right now I have a 3M (Mincom) M56 professional
multitrack tape recorder I am currently in the process of aligning. I
guess you could say I am an "analog dinosaur" of sorts... LOL.

When I initially got the 485, the unit powered up and I could do some
basic sweeps, but I have not really used it since I initially got it
(mainly due to getting married, having kids and buying a new house -
funny how those things take up gobs of your life ;-). When I went to
turn it on about a year ago, I noticed a clicking or chirping with no
beam. Apparently as I understand it based on some quick research on
the 'net, this is not an uncommon symptom on these 'scopes having a
power supply trying to start but failing due to current overload of
some sort (capacitors?).

So, I did a search on Tektronix repair and came up with a person that
thinks they will be able to fix it.

However, for the price of the repair (and maybe a little more), I am
wondering if I wouldn't be better served with something like a 2465/A/
B?

Here's some reasons why maybe I think I should go with the 2465:

1) Compared to the 485, it's a newer 'scope with perhaps less hours
than my 485 (don't know how much use my 485 has had; it appears to be
in average or slightly better condition)
2) Less "mechanical" parts in the 2465 (e.g., pots, etc. from my
understanding) to fail
3) Lots think this is the epitome of the analog oscilloscope

Reasons why I should maybe stay with my 485:

1) Better proprietary IC availability (?, don't beat me up; I thought
this was what I read...)
2) Easier to service/repair than the 2465
3) More robust for the beginner

Obviously if I am thinking like this, I have no idea what I should
ultimately do. What does everyone think? <ducking>

I had the same problem with my 485. Took me a few hours to isolate (due
to the disassmebly required) but it was caused by a shorted tantalum
cap. I used to fix T & M equipment for a living, so I may be more
adventurous than you. The 485 is a classic, probably the best portable
scope ever made. I bet if you got your head and hands in the 485 you
could find and fix the problem.

Good luck

 

[Sam Goldwasser]

The 485 is a really excellent scope, and the problem you describe should be
fairly easy to repair. There's no sense in upgrading, as a beginner you
probably won't use a large portion of the features the 485 provides even.

I agree 100 percent.

My first guess would be one or more of those imfamous tantalum gumdrop
caps have decided to turn into short circuits. These are on the power
supply PCB on the bottom. Save yoursefl some grief and replace them all
(maybe 2 dozen). I have just been putting in aluminum electrolytics.
Not sure how much difference it makes.

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[[email protected]]

I agree 100 percent.

My first guess would be one or more of those imfamous tantalum gumdrop
caps have decided to turn into short circuits. These are on the power
supply PCB on the bottom. Save yoursefl some grief and replace them all
(maybe 2 dozen). I have just been putting in aluminum electrolytics.
Not sure how much difference it makes.

Or can I just stick with tantalum replacements? Mouser shows some,
though I have no idea values.

http://www.mouser.com/search/Refine...ntalum&N=1323038 3805535&Ntk=Mouser_Wildcards

I assume radial termination style?

You say you've been putting in AL 'lytics. Do tants come polarized?

Say I go with Nichicon AL 'lytic radials. Is there a preferred series?
They have all kinds...

http://www.nichicon.co.jp/english/products/alm_mini/daia_f.htm

 

[Scott Dorsey]

The 485 is a really excellent scope, and the problem you describe should be
fairly easy to repair. There's no sense in upgrading, as a beginner you
probably won't use a large portion of the features the 485 provides even.

Agreed, and I bet a nickel the issue is that there is too much dust and
dirt providing leakage paths in the high voltage section. Have the tech
give it a good cleaning and you will probably be fine.

I'm still using a Tek tube scope at work and it's always been flawless
although the calibration guys hate me.
--scott

 

[soundhaspriority]

Greetings,
[snip]

However, for the price of the repair (and maybe a little more), I am
wondering if I wouldn't be better served with something like a 2465/A/
B?

Stay away from the 2465A/B at all costs. Some time during the production of
the A series, they sold the hybrid operation. Quality of the hybrids dropped
precipitously, leading to a near 100% failure rate. These hybrids available
only occasionally at extreme cost. The 2465 also has cooling problems.

The original 2465 is better, but spares are still a bitch.

Regards,
Bob Morein
(310) 237-6511

 

[Jim Yanik]

[email protected] (Scott Dorsey) wrote in

I'm still using a Tek tube scope at work and it's always been flawless
although the calibration guys hate me.
--scott

I'm surprised the CRT trace is still viewable.What model? 547?

 

[Jim Yanik]

...

Greetings,
[snip]

However, for the price of the repair (and maybe a little more), I am
wondering if I wouldn't be better served with something like a
2465/A/ B?

Stay away from the 2465A/B at all costs. Some time during the
production of the A series, they sold the hybrid operation. Quality of
the hybrids dropped precipitously, leading to a near 100% failure
rate. These hybrids available only occasionally at extreme cost. The
2465 also has cooling problems.

The original 2465 is better, but spares are still a bitch.

Regards,
Bob Morein
(310) 237-6511

I've never heard of any 2465 cooling problems,although I have heard of
people heatsinking the horiz output IC to try to avoid it's early failure.

The only IC problem was with that horiz output amp IC.
The other hybrids were fairly reliable.

TEK sold the ICO/Hybrid operation to Maxim(after I warned them about
it),who then forced a "last-time buy" because of low volume.
They were then forced to cease making the 2400 series scopes.

I'd take a 2465 over a 485.

 

[West]

The 485 is a really excellent scope, and the problem you describe should be
fairly easy to repair. There's no sense in upgrading, as a beginner you
probably won't use a large portion of the features the 485 provides even.

Hi James. I had a 485 many years ago to use for field work ( not that easy
schlepping it around the country). I think it had a 250 MHz bandwidth. It's
really packed so be careful when attempting repairs. Starting with checking
the low voltage power supplies is a good idea. Also be careful if sending it
out prepaid for service. Check the service place thoroughly for references
and for viable guarantees. The 485 is a professional scope that way exceeds
the hobbyists requirements. So if you can repair it reasonably, you will own
a classic gem.

Cordially,
west

 

[Jim Yanik]

Hi James. I had a 485 many years ago to use for field work ( not that
easy schlepping it around the country). I think it had a 250 MHz
bandwidth. It's really packed so be careful when attempting repairs.
Starting with checking the low voltage power supplies is a good idea.
Also be careful if sending it out prepaid for service. Check the
service place thoroughly for references and for viable guarantees. The
485 is a professional scope that way exceeds the hobbyists
requirements. So if you can repair it reasonably, you will own a
classic gem.

Cordially,
west

if you ship it anywhere,**pack it very well**,with at least 3-4 inches of
padding on EVERY side,top,and bottom.

Using loose peanuts is a great way to have your scope smashed up.
Better to pack the peanuts in plastic bags,making "pillows" and place those
around the scope.

I've seen plenty of poorly packed instruments,and UPS/FedEx/DHL/USPS is not
liable for poorly packed items.

 

[Doug McDonald]

I'm an expert on these things. The 485 is the best portable
analog scope ever made. It is arguably the best analog scope ever made,
though the 7904 series competes well on the bench. Do anything you
can to keep one working. There is no substitute for a 485/7904,
and I've used them all, including $50,000 digital ones. For repairing
analog electronic oddities, digital frequently simply
doesn't work.

A 485 is 350 MHz scope.

The 2465 is a very poor substitute, though a good scope.

Doug McDonald

 

[[email protected]]

I'm an expert on these things. The 485 is the best portable
analog scope ever made. It is arguably the best analog scope ever made,
though the 7904 series competes well on the bench. Do anything you
can to keep one working. There is no substitute for a 485/7904,
and I've used them all, including $50,000 digital ones. For repairing
analog electronic oddities, digital frequently simply
doesn't work.

A 485 is 350 MHz scope.

The 2465 is a very poor substitute, though a good scope.

Hi Doug,

Thanks for your thoughts.

Do you do repairs on these scopes? Or does anyone in the group know
some noteworthy techs I can send my scope to for repair?

It seems most here think I should just stick with the 485. I have no
problem with that. However, it's good that I brought this thread up as
now I've learned that there may be issues with the 485 to be concerned
about, namely the attenuator problem Mr. Yanik has brought up (that is
somewhat disconcerting).

BTW, how long do the CRTs last on these scopes?

 

[Jim Yanik]

I'm an expert on these things.
Oh?

The 485 is the best portable
analog scope ever made. It is arguably the best analog scope ever made,
though the 7904 series competes well on the bench. Do anything you
can to keep one working. There is no substitute for a 485/7904,
and I've used them all, including $50,000 digital ones. For repairing
analog electronic oddities, digital frequently simply
doesn't work.

A 485 is 350 MHz scope.

The 2465 is a very poor substitute, though a good scope.

Doug McDonald

IMO,the 485 is much worse than a 2465,having lots of flaky attenuator
problems,a bitch of a power supply repair-wise,and less accuracy than the
2465 series.And you get a better CRT display with the 2465.
The 2465 was the best portable scope TEK ever made.What killed it was TEK
selling off the ICO/Hybrid plant to Maxim,and Maxim cutting TEK's throat
by forcing a last-time buy on TEK-made ICs.
The 485s are getting really old,the HF switch contacts are degrading and
unavailable.
The 2465 is more serviceable -if you can get the parts.
the 485 has the same problem.

I worked for TEK for 21.5 years in their Field Service centers repairing
and calibrating these scopes.I'd much rather work on a 2465 than a 485.
485s were a PITA even when TEK was still issuing the mod summaries on
fiche.There were SO many ECO changes,you couldn't keep up with them all.

I agree about the 7904 lab scopes being great.Had one on my bench.

 

[Bret Ludwig]

I no longer recommend owning or using Tektronix analog scopes,
period. Yes, they were very well built, but none of them are 100%
supported and they all lose the same parts. The hybrid issue is a big
one, but CRTs, attenuators, and high voltage parts on all solid state
Teks are getting unavailable even through the back channels.

If some company decided to FULLY SUPPORT certain Tek models,
guaranteeing availability of every part from new production-or at
least every part that is getting scarce-I'd say yes.

Ironically you can still get every possible part for many tube Teks,
but the size, weight, power draw and heat make them nonstarters. That
is why the parts are available.

Buy a new scope.

 

[James Sweet]

I no longer recommend owning or using Tektronix analog scopes,
period. Yes, they were very well built, but none of them are 100%
supported and they all lose the same parts. The hybrid issue is a big
one, but CRTs, attenuators, and high voltage parts on all solid state
Teks are getting unavailable even through the back channels.

If some company decided to FULLY SUPPORT certain Tek models,
guaranteeing availability of every part from new production-or at
least every part that is getting scarce-I'd say yes.

Ironically you can still get every possible part for many tube Teks,
but the size, weight, power draw and heat make them nonstarters. That
is why the parts are available.

Buy a new scope.

New scopes are expensive, used Teks in good working order are relatively
cheap and still offer excellent performance. There's millions of them out
there and parts units can still be found. If you're a business with budget
to burn then yes, buy a fancy new scope, but if you're a hobbyist on a
budget, you can't beat an old Tek.

 

[Doug McDonald]

New scopes are expensive, used Teks in good working order are relatively
cheap and still offer excellent performance. There's millions of them out
there and parts units can still be found. If you're a business with budget
to burn then yes, buy a fancy new scope, but if you're a hobbyist on a
budget, you can't beat an old Tek.

There is only one problem: there are no "new scopes" that will
substitute for a 485/7904 for some purposes of work on analog signals.
Period. They don't exist.

We don't know what the use of the original poster is supposed to
be. The "have to have analog" ones generally involve visual
detection of rare events in analog signals. The dead time of
fast digital scopes can cause hopelessly great "down time fraction"
for this.

For most purposes digital scopes are fine.

Doug McDonald

 

[Michael A. Terrell]

I no longer recommend owning or using Tektronix analog scopes,
period. Yes, they were very well built, but none of them are 100%
supported and they all lose the same parts. The hybrid issue is a big
one, but CRTs, attenuators, and high voltage parts on all solid state
Teks are getting unavailable even through the back channels.

If some company decided to FULLY SUPPORT certain Tek models,
guaranteeing availability of every part from new production-or at
least every part that is getting scarce-I'd say yes.

Ironically you can still get every possible part for many tube Teks,
but the size, weight, power draw and heat make them nonstarters. That
is why the parts are available.

Buy a new scope.

I agree 100%!!!!!!!! Buy a brand new chinese scope with no support,
and throw it away when it dies. Repeat till you're tired of using crap,
then buy a used US made scope.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[[email protected]]

We don't know what the use of the original poster is supposed to
be.

See my original post:

"In the past, I have serviced tube amplifiers for friends. Right now I
have a 3M (Mincom) M56 professional
multitrack tape recorder I am currently in the process of aligning."

Probably going forward, much of the same.

 

[David DiGiacomo]

There is only one problem: there are no "new scopes" that will
substitute for a 485/7904 for some purposes of work on analog signals.
Period. They don't exist.

Iwatsu still makes high performance analog scopes. They used to be resold
by LeCroy, but now I think you have to get them from Japan.