Date   

Re: USPS shipments comments

Ken Eckert
 

I had a very light meter, Huntron Tracker, that I shipped via Canada Post/USPS. The meter arrived with the back of case smashed and a damaged PCB. The box was totally stove in on one side. After much, much hassle (and not helped by an uncooperative recipient) Canada Post coughed up a partial refund on the shipment. And that was with complete documentation.

They didn't do more since "I didn't pack for machine handling of the package" Bloody hell, the damage was from being crushed. I have packed stuff for years, that damage was not from machine handling.

In talking with our UPS driver, he worked for a while in the warehouse, he watched package handlers deliberately damage shipments by dropping, throwing or hitting packages. The supervisors do nothing.

Great..............


Re: Replacement caps for DC 505A

Dave Peterson
 

Using UHEs was what came to mind while sleeping on it. They definitely have the small diameter.
I'd prefer an axial solution. Superficially for the aesthetics, more significantly for the long distance between leads/trace locations: about 70mm. Using a radial will require wiring a jumper.
Not egregious, but my first choice would be an axial, if available.

On Wednesday, October 20, 2021, 07:45:10 AM PDT, Mark Vincent <orangeglowaudio@...> wrote:

Dave,

Would these fit? https://www.mouser.com/ProductDetail/Nichicon/UHE1C562MHD6?qs=%2Fha2pyFaduhn2raJlu2%2F0FQLbgkwz6LZB1%252BS6xn%252B0yk%3D

Mark


Re: Replacement caps for DC 505A

Mark Vincent
 


Replacement caps for DC 505A

Dave Peterson
 

Since we seem to be on the subject of filter caps:

Last night I got a DC 505A apart so I could confirm that the +5v filter caps C25 and C26 are bad. Oh yeah, they're long gone. According to my Peak Atlas ESR70 one is open and one is "leaky" with an ESR of 6.8. Nominal capacitance of these is 5000uF and Tek manual calls for 10v. The cans say they are 15v.

Mouser has just a couple of Vishay axial caps, but they are 1" (25mm) in diameter. The caps in the unit are 0.75" (20mm). As this is a plug in, there is no room to spare. So the Vishay's on Mouser are a no-go. Searching axial caps on Mouser only yields these couple of Vishays.

Aside from getting some work done for my paying job, a goal for today is to broaden my search across the web for suitable replacements. But I thought I'd ask y'all here as I suspect someone might have some experience with this. Where might I find suitable axial replacement caps for these? Or will I have to adapt some radial electrolytics into place?

Thanks,
Dave


Re: TEK 475: Dead on Start Up.

Mark Vincent
 

Replacing the filter cans is a good idea. I did it in mine using high temp and long life types. If you can get low ESR types for these in addition to the long life and temp., good. Raising the values is fine. The 1.5A bridge rectifiers should be 4A. If you have any that are higher in voltage rating of the original, 200V, fine. It will not hurt to put in a higher voltage type. The higher current is the main thing. Make sure to put jumpers between the negative pads if you use snap-in or radial leaded types as replacements. The output filters on the supplies can be raised in value, e.g. 10mfd to 47mfd. I use Nichicon ULD or UHE for these. The former has the lower ESR. The UHE is also a great choice. C1304 and C1374 I put in a film type. Decoupling types can be left in unless bad.

Check VR1416. If open, use BZX85B9V1.

Check all 151-0367-00 transistors. Any that are leaky C to E, use KSP10BU as replacements. The pinout of these is BEC.

Some resistors I replaced with a higher wattage because the originals were too small and the heat changed the resistance making it out of tolerance or open in some cases. R1378 is likely out tolerance. I used the Vishay VR37 series as the replacement. The symptom of this resistor being too high, about 28meg and higher, is the trace will be bright at turn on then dim down as it warms up over 15 minutes. I have seen this problem enough times.

Mark


Re: TEK 475: Dead on Start Up.

Michael W. Lynch
 

Tom is spot on. I have repaired dozens of these scopes and do not subscribe to the "shotgun" approach of replacing all tantalum's. When they fail, tantalum caps usually do so in spectacular fashion and typically announce failure with a quantity of "magic smoke". I replace tantalum caps only if the related supplies or circuits exhibit symptoms that can be contributed to no other source. 2X voltage rating or more is best. That scheme has worked for me and I have seen relatively few failures. The Bulk filter caps are typical failure points so that is where you can spend your initial investigation. I have found that you can solder a good cap across the pads of the bulk filter cap of the offending supply and restore function as "proof" that the filter cap is the issue. it is possible that the bridge rectifier for the +15V circuit is bad, but that will become apparent upon testing of the bulk filters. Check ripple on all supplies while you are at it. and repair as needed. Good luck! ,

--
Michael Lynch
Dardanelle, AR


Re: FG504 Q1040 equivalent? 151-0438-00 -> 151-0712-00 -> MPSH81

EJP
 

I will note that on examination Q1040 is a TO-3, not TO-92, along with its three fellows in that stage. I can't see a wattage reason for that, as the stage is strictly a voltage amplifier, with an output stage to follow. Is it for some stability reason?

EJP


Re: TEK 475: Dead on Start Up.

Tom Lee
 

Here are some of my answers to your questions.

Re: order of checking voltages. The order in which you check doesn't matter, frankly. Just check 'em all. You merely want to assess what's broken, and in which way. Then take those clues and act on whatever they imply.

Common causes of what you're seeing include the caps you mention, but you should also check the bridges. I've seen more than a couple where one or two of the internal rectifiers was defective.

If you find a shorted tant (very common and, without any other information, I'd suspect that as the cause of your problem) and wish to replace it with another tant, Tek recommended that the replacement have a voltage rating that is at least 2x the nominal applied voltage. You could replace them with standard aluminum electrolytics, but be advised that they likely won't have the low ESR or ESL of tants. That difference can be important in some critical circuits. If you want to move away from tants (and I wouldn't blame you if you did), I'd recommend polymer-aluminum electrolytics. They've gotten good enough that I would be using them all the time where one would have previously selected a tantalum, except that I have a large quantity of tants.

Some folks recommend wholesale replacement of all caps, on the theory that one failure implies that the rest are likely to follow in the not too distant future, so you might as well reset the lifetime clock now, so to speak. I generally don't follow that practice, because the chance of killing something in the act of replacing any one cap is nonzero. Perhaps small, but nonzero nonetheless, so the probability of doing more bad than good becomes uncomfortably high when computing the overall proabilities. There are pros and cons of complete recaps, and how that resolves for me is very much vintage- and type-dependent, as well as on the skills of the person doing the work. For a 475, I would just replace what's dead, as it isn't all that onerous to open up. Others here will shortly chime in with their opinions.

I'm sure that you will be able to resurrect that fine scope without too much drama. Good luck with the repair!

-- Cheers
Tom


--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 10/20/2021 01:50, Redguuz via groups.io wrote:
Hello Specialists,

Maybe you could give me some advice how to "debug" my broken TEK 475.

It had worked the hour before and I switched it off.
Realized that I might need it later, I repowered it again, but the Fan started and stopped immediately and the graticule lighting was off. No trace.

I have the ARTEK manuals and the Repair manuals of the US Military. (I have not opened the scope yet).
I concluded that at least the +15V Power Supply has failed but I understand (from the SM manual P172/240), that there is a "hierachy" of power supplies and that, if a PS "higher" in the hierarchy fails, it will influence the lower ones.
Apparently to protect circuits from unbalanced voltages. (is this correct?).

Questions;
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?.

3) Are the composed PS Buffer electrolytic capacitors still available as New Old Stock?
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 ?

Appreciate your advice, before I will be embarking on a repair attempt.

NB.
I have a HAMEG HM-605 (60 MHz) which I had to repair (broken Bridge rectifier (1 diode interrupted) in a -12V supply rail) , before I could trying to repair the TEK.
The HAMEG suits me well, but the TEK 475 has a much higher bandwidth (200 MHz).

So I like to resurrect the TEK 475.




TEK 475: Dead on Start Up.

Redguuz
 

Hello Specialists,

Maybe you could give me some advice how to "debug" my broken TEK 475.

It had worked the hour before and I switched it off.
Realized that I might need it later, I repowered it again, but the Fan started and stopped immediately and the graticule lighting was off. No trace.

I have the ARTEK manuals and the Repair manuals of the US Military. (I have not opened the scope yet).
I concluded that at least the +15V Power Supply has failed but I understand (from the SM manual P172/240), that there is a "hierachy" of power supplies and that, if a PS "higher" in the hierarchy fails, it will influence the lower ones.
Apparently to protect circuits from unbalanced voltages. (is this correct?).

Questions;
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?.

3) Are the composed PS Buffer electrolytic capacitors still available as New Old Stock?
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 ?

Appreciate your advice, before I will be embarking on a repair attempt.

NB.
I have a HAMEG HM-605 (60 MHz) which I had to repair (broken Bridge rectifier (1 diode interrupted) in a -12V supply rail) , before I could trying to repair the TEK.
The HAMEG suits me well, but the TEK 475 has a much higher bandwidth (200 MHz).

So I like to resurrect the TEK 475.


Re: USPS shipments comments

John Parkins G8KVP
 

Hello All,

Just a word of warning......... from the UK.

I run the parts department of an agricultural dealer, as you can imagine some of the parts that are delivered to us are large, heavy and you would think unbreakable. Don't you believe it, in the past year we have had more damaged, broken, delayed parts than ever before and not to mention the parts that just don't turn up at all. On top of that because of our wonderful, self inflicted, Brexit we have had no end of problems with customs. At the moment we are trying to send an engine (£25,000 worth) back to Germany, so far it's made 5 trips and been returned each time. We're not told why it comes back...........

Costs have gone through the roof, a regular customer had a near monthly order. It used to cost £30 to get it there, it now costs £180! 6 times as much.

So the moral is, pack extremely well, then do it better. Photograph everything so you have a record of not only what you've sent but how you've packed it. Do the paperwork and then get someone else to check the paperwork. Give it to the courier and wave goodbye.........

Some couriers are better than others, but they have all let us down at some point.


--
Best regards,
John mailto:john@...


454A cover and mesh CRT screen

 

Hi all,

I really like the recently acquired 454A that has found a new home with me. The ruggedized construction definitely seems beefier than the other 400 series scopes I've played with. The 150 Mhz rated bandwidth is very conservative, I was able to easily see a 230 Mhz signal from a SG503. The cascade input mode for 400 microvolt sensitivity is a neat feature too. When I got it, was missing the front cover. The snap-in mesh screen over the CRT is pretty rough. Anybody have a cover and/or screen laying around they want to part with? You can contact me off list at radeng9805@....


Re: FS: Leigh Turner's (VK5LT) RF lab

Paul McClay
 

On Tue, Oct 19, 2021 at 08:36 PM, Mark Vincent wrote:

I looked up gdiwriter as the seller.
Yup - that works.


Sounds like there will be more. From Mr. Turner:
"There is quite a lot of stuff including a classic 7904 mainframe and full suite of 7000 plug-ins...but that is too big and heavy to (economically) ship outside Australia."


Re: Debugging begins: Tek 606

toby@...
 

On 2021-10-19 10:20 p.m., Mike Dinolfo wrote:
Toby:
I don't have a 606, and I'm not very well versed in circuit design, but
it appears to me that the polarity of CR591 (in the schematic that you
provided a link to) appears to be incorrect.  I think the cathode rather
than the anode of CR591 should be connected to R593.
Hi Mike

CR591 isn't even on this board - the schematic snippet is from the Z Amplifier board.

What is pictured is the HV board (where all parts are prefixed with 7-) and I don't have any schematic for _this version_ of the HV board. Sorry about any confusion there, I tried to head that off with my comments below.

This unit was fully working until a couple of days ago.

--Toby



Mike Dinolfo N4MWP
On 10/19/21 9:52 PM, toby@... wrote:
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? At the moment I would plan to check the rectifiers CR756,
CR760 on those secondary taps and their smoothing capacitors C756,
C758 and C760.

Hoping the transformer itself isn't toast...
I eventually realised that my HV board is modified from the manual.
There is a manual update page at the back of the manual that describes
a similar change to the Z amplifier board, but not the cluster of
components on the HV board that look like a similar rail splitting
circuit. I wonder if there is a later HV board change? My SN is B0116xx.


Pics: https://imgur.com/a/njNQwj4

-- I've included the manual change even though it's for a different
board, just to illustrate the similarity to the circled change in the
HV board ...  even down to the 1µF tantalum(?)
-- I've overlaid the schematic plan on the actual board to show the
substantial changes, not limited to the circled area, that are not in
my SM.


I'm still hoping that the two low rails do not involve the
transformer. The transistor pictured seems to be open circuit.

If anyone reads this who's worked on a 606, any hints might be good. I
can probably just go ahead and replace the transistor although the
markings are not very googleable (and not in Tek Xref that I can see).

Markings appear to be:
  F01
  9000
  740


--Toby



Thanks for any hints.

--Toby









Re: Debugging begins: Tek 606

Mike Dinolfo
 

Toby:

I don't have a 606, and I'm not very well versed in circuit design, but
it appears to me that the polarity of CR591 (in the schematic that you
provided a link to) appears to be incorrect.  I think the cathode rather
than the anode of CR591 should be connected to R593.

Mike Dinolfo N4MWP

On 10/19/21 9:52 PM, toby@... wrote:
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? At the moment I would plan to check the rectifiers CR756,
CR760 on those secondary taps and their smoothing capacitors C756,
C758 and C760.

Hoping the transformer itself isn't toast...
I eventually realised that my HV board is modified from the manual.
There is a manual update page at the back of the manual that describes
a similar change to the Z amplifier board, but not the cluster of
components on the HV board that look like a similar rail splitting
circuit. I wonder if there is a later HV board change? My SN is B0116xx.


Pics: https://imgur.com/a/njNQwj4

-- I've included the manual change even though it's for a different
board, just to illustrate the similarity to the circled change in the
HV board ...  even down to the 1µF tantalum(?)
-- I've overlaid the schematic plan on the actual board to show the
substantial changes, not limited to the circled area, that are not in
my SM.


I'm still hoping that the two low rails do not involve the
transformer. The transistor pictured seems to be open circuit.

If anyone reads this who's worked on a 606, any hints might be good. I
can probably just go ahead and replace the transistor although the
markings are not very googleable (and not in Tek Xref that I can see).

Markings appear to be:
  F01
  9000
  740


--Toby



Thanks for any hints.

--Toby








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? At the moment I would plan to check the rectifiers CR756, CR760 on those secondary taps and their smoothing capacitors C756, C758 and C760.
Hoping the transformer itself isn't toast...
I eventually realised that my HV board is modified from the manual. There is a manual update page at the back of the manual that describes a similar change to the Z amplifier board, but not the cluster of components on the HV board that look like a similar rail splitting circuit. I wonder if there is a later HV board change? My SN is B0116xx.


Pics: https://imgur.com/a/njNQwj4

-- I've included the manual change even though it's for a different board, just to illustrate the similarity to the circled change in the HV board ... even down to the 1µF tantalum(?)
-- I've overlaid the schematic plan on the actual board to show the substantial changes, not limited to the circled area, that are not in my SM.


I'm still hoping that the two low rails do not involve the transformer. The transistor pictured seems to be open circuit.

If anyone reads this who's worked on a 606, any hints might be good. I can probably just go ahead and replace the transistor although the markings are not very googleable (and not in Tek Xref that I can see).

Markings appear to be:
F01
9000
740


--Toby


Thanks for any hints.
--Toby


Re: FS: Leigh Turner's (VK5LT) RF lab

Mark Vincent
 

Paul,

I looked up gdiwriter as the seller.

Mark


Re: FS: Leigh Turner's (VK5LT) RF lab

Paul McClay
 

Hi Mark,
That seems to get the same results.

Did this link not work: ebay.com/sch/gdiwriter/m.html ?


Re: FS: Leigh Turner's (VK5LT) RF lab

Mark Vincent
 

Paul,

Is this auction you are talking about? www.ebay.com/sch/i.html?_nkw=&_in_kw=1&_ex_kw=&_sacat=0&_udlo=&_udhi=&_ftrt=901&_ftrv=1&_sabdlo=&_sabdhi=&_samilow=&_samihi=&_sadis=15&_stpos=23236&_sargn=-1%26saslc%3D1&_salic=1&_fss=1&_fsradio=%26LH_SpecificSeller%3D1&_saslop=1&_sasl=gdiwriter&_sop=12&_dmd=1&_ipg=50&_fosrp=1

Mark


Re: 492BP fuzzy trace on left side of crt - any ideas on what to look for?

Jim Ford
 

Great find, Chuck!  I'm envious.    Jim FordSent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: ChuckA <chuck@...> Date: 10/19/21 1:34 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] 492BP fuzzy trace on left side of crt - any ideas on what to look for? A couple years ago I bought an HP 8753B Network Analyzer with test set that was cheap (under $400) as it was listed not working, bad CRT. I took a chance on it. Got it home and just had to clean the black soot off the face of the CRT, CRT was bright and sharp, everything worked perfectly.ChuckOn 10/19/2021 3:58 PM, Edward Prest wrote:> Nobody figured this out yet?>> It was just a dirty explosion shield. The shield was stuck to the CRT glass and I originally thought that it was the CRT.>>-- See Early TV at:www.myvintagetv.com


Re: 492BP fuzzy trace on left side of crt - any ideas on what to look for?

Tom Lee
 

A happy ending, for sure.

I was going to suggest looking at it with one eye at a time to see if that made a difference. ;)

--Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 10/19/2021 12:58, Edward Prest wrote:
Nobody figured this out yet?

It was just a dirty explosion shield. The shield was stuck to the CRT glass and I originally thought that it was the CRT.



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